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A new study validated a prognostic nomogram for retroperitoneal sarcoma (RPS) using a large, external cohort. The nomogram incorporates six variables, and provided strong concordance with observed disease-free survival (DFS) and overall survival (OS).
RPS account for about 15% of all soft-tissue sarcomas, and their unique characteristics make traditional staging difficult, according to study authors led by Chandrajit P. Raut, MD, of Brigham and Women’s Hospital in Boston. A multi-institutional nomogram was developed previously based on a 523-patient cohort who underwent surgical resection for RPS between 1999 and 2009.
The nomogram included six clinical characteristics and variables: age at the time of diagnosis; tumor size; FNCLCC tumor grade; histologic subtype; multifocality at the time of initial presentation; and extent of surgical resection. Because the American Joint Committee on Cancer (AJCC) is considering including this tool in its forthcoming revised staging system, the study authors decided to validate it in an external cohort of 631 RPS patients who underwent surgery at one of six centers. The results were published online ahead of print in Cancer.
The 7-year DFS rate in the validation cohort was 38.4%, and the 7-year OS rate was 58%. This was similar to the development cohort’s outcomes, at 35.7% and 50.5%, respectively. All six of the nomogram’s included variables were found to be independently prognostic.
The researchers used a Harrell C-statistic to measure the nomogram’s discriminative ability. For DFS, the result was 0.69, while for OS it was 0.73. These were very similar to the concordance rates found in the development cohort (0.71 and 0.74, respectively).
“Correlation between observed and nomogram-predicted DFS and OS rates suggest good calibration of the multi-institutional RPS nomogram in a larger, independent validation cohort,” the authors wrote. “External validation of the…nomogram established its broad applicability in predicting outcomes in patients with primary RPS who were treated at experienced centers, and supports its inclusion in the 8th edition of the AJCC classification.”
Study Details
The median age in the validation cohort was 59 years, and the median tumor size was 21 cm. There were similar numbers of patients with FNCLCC grade 1 (32.7%), 2 (39.8%), and 3 (27.5%) tumors.
The most common histologic subtype was dedifferentiated liposarcoma (36.6%), followed by well-differentiated liposarcoma (25%), leiomyosarcoma (21.7%), and other subtypes. Almost all patients (94.8%) had a complete resection. Most patients (91%) did not receive chemotherapy or radiotherapy (68.3%).
Panobinostat Shows Promise in Phase I Sarcoma Trial
A phase I trial found that panobinostat combined with epirubicin is well tolerated and could offer benefit in patients with refractory sarcoma.
“More than half of patients treated for localized soft tissue sarcoma will experience relapse,” wrote study authors led by Pamela N. Munster, MD, of the University of California, San Francisco. Histone deacetylase (HDAC) inhibitors have shown some promise in other early phase I studies with anthracyclines. “Furthermore, HDAC inhibition was shown to promote differentiation and apoptosis in sarcoma.”
The new phase I trial combined the HDAC inhibitor panobinostat—which was approved in February 2015 for the treatment of multiple myeloma—with epirubicin. It began as a 3 + 3 dose escalation trial in patients with advanced solid tumors, followed by an expansion cohort at the maximum tolerated dose in 20 sarcoma patients. The results were published in Annals of Oncology.
In total, 40 patients received 20- to 60-mg panobinostat; 17 patients had previous exposure to topoisomerase II inhibitors. The study drug was administered on days 1, 3, and 5, followed by 75-mg/m2 epirubicin on day 5, in 21-day cycles. Dose-limiting toxicities were seen at 50 mg (one patient) and 60 mg (two patients); these included atrial fibrillation, grade 4 thrombocytopenia and febrile neutropenia, and grade 3 fatigue. The recommended phase II dose was set at 50 mg, and the 20 sarcoma patients in the expansion cohort received this dose.
Of 37 total evaluable patients, a partial response was seen in four of them (11%), and 17 patients (46%) had stable disease.
In only the 20-patient sarcoma expansion cohort, 12 patients were deemed to have received benefit from panobinostat. There was one response in those patients, and 11 patients had stable disease for longer than 3 months. The median progression-free survival in these patients was 3.4 months, and the median overall survival was 8.3 months. The authors noted that acquired topoisomerase resistance was reversed in 8 of 14 patients.
“A major challenge in HDAC inhibitor therapy is the absence of biomarkers,” wrote the authors. In this study, they showed that patients with a “pronounced degree” of peripheral blood mononucleocyte histone acetylation were more likely to derive benefit from the therapy. A decrease in neutrophil count over the first 5 days of the first cycle of therapy also was correlated with clinical benefit.
“This study suggests that further investigation of HDAC inhibition in combination with DNA-damaging agents in defined advanced sarcoma subtypes to validate these preliminary findings is warranted,” concluded the authors.
For several decades, research efforts have focused on targeting progression of cancer cells in primary tumors. Primary tumor cell targeting strategies include standard chemotherapy and immunotherapy and modulation of host microenvironment including tumor vasculature. However, cancer progression is comprised of both primary tumor growth and secondary metastasis (Langley RR and Fidler IJ. Tumor cell-organ microenvironment interactions in the pathogenesis of cancer metastasis. Endocr Rev. 2007 May;28(3):297-321; http://www.ncbi.nlm.nih.gov/pubmed/17409287). Owing to the property of unilimited cell division, cells in primary tumor increase rapidly in number and density and are able to favorably influence their microenvironment. Metastasis, on the other hand, depends on the ability of cancer cells to disseminate, circulate, adapt to the harsh environment and seed in different organs to establish secondary tumors. Although tumor cells are shed into the circulation in large numbers since early stages of tumor formation, few tumor cells can survive and proceed to overt metastasis. (Husemann Y et al. Systemic spread is an early step in breast cancer. Cancer Cell. 2008 Jan;13(1):58-68; http://www.ncbi.nlm.nih.gov/pubmed/18167340). Tight vascular wall barriers, unfavorable conditions for survival in distant organs, and a rate-limiting acquisition of organ colonization functions are just some of the impediments to the formation of distant metastasis (Chiang AC and Massagué J. Molecular basis of metastasis. N Engl J Med. 2008 Dec 25;359(26):2814-23; http://www.ncbi.nlm.nih.gov/pubmed/19109576).
It has been hypothesized that metastasis is initiated by a subpopulation of circulating tumor cells (CTC) found in the blood of patients. Therefore, understanding the function of CTC and targeting the CTC is gaining attention as a possible therapeutic avenue in carcinoma treatment.
Figure: Circulating tumor cells in the metastatic cascade
Initial methods relied on the difference in physical properties of cells. When spun in a centrifuge, different cells in the blood sample settle in separate layers based on their byoyancy, and CTC are found in the white blood cell fraction. Because CTC are generally larger than white blood cells, a size-based filter could be used to separate the cell types (Vona G, et al, Isolation by size of epithelial tumor cells : a new method for the immunomorphological and molecular characterization of circulating tumor cells. Am J Pathol, 2000 Jan;156(1):57-63; http://www.ncbi.nlm.nih.gov/pubmed/10623654).
Herbert A Fritsche, PhD, Professor and Chief, Clinical Chemistry, Department of Laboratory Medicine, The University of Texas, MD Anderson Cancer Center, demonstrated that the CTC can be captured using antibody labeled magnetic beads, either in positive or negative selection schema. After the circulating tumor cells are isolated, they may be characterized by immunohistochemistry and counted. Alternatively, these cells may be characterized by gene expression analysis using RT-PCR. One of the CTC detection methods, Veridex Inc, Cell Search Assay, has been cleared by the US FDA for use as a prognostic test in patients with metastatic cancers of the breast, prostate and colon. This technology relies on the expression of epithelial cellular adhesion molecular (EpCAM) by epithelial cells and the isolation of these cells by immunomagnetic capture using anti-EpCAM antibodies. Enriched CTC are identified by immunofluorescence. Martin Fleisher, PhD, Chair, Department of Clinical Laboratories, Memorial Sloan-Kettering Cancer Center discussed in a webinar at the biomarker symposia, Cambridge Healthtech Institute, that every new technology has shortcomings, and the reliance on cancer cells to express sufficient EpCAM to enable capture may affect the role of this technology in future clinical use. Heterogeneous downregulation of epithelial surface antigen in invasive tumor cells has been reported. Thus, alternative methods to detect CTC are being developed. These new methods include-
Flow cytometry that sorts cells by size and surface antigen expression.
CTC microchips that are designed to capture CTC as whole blood flows past EpCAM-coated mirco-posts.
Enrichment by filtration using filters with a pore size of 7-8 µm, that permits smaller red blood cell, leukocytes, and platelets to pass, but captures CTC that have diameters of about 12-15 µm.
Better identification of CTC
Baccelli et al (2013) developed a xenograft assay and demonstrated that the primary human luminal breast cancer CTC contain metastasis-initiated cells (MICs) that give rise to bone, lung and liver metastases in mice. These MIC-containing CTC populations expressed EPCAM, CD44, CD47 and MET. It was observed that in a small cohort of patients with metastases, the number of CTC expressing markers EPCAM,CD44, CD47 and MET, but not of bulk EPCAM+ CTC, correlated with lower overall survival and increased number of metastasic sites. These data describe functional circulating MICs and associated markers, which may aid the design of better tools to diagnose and treat metastatic breast cancer. The findings were published in the Nature Biotechnology journal recently (Baccelli I, et al. Identification of a population of blood circulating tumor cells from breast cancer patients that initiates metastasis in a xenograft assay. Nature Biotechnology 2013 31, 539–544; http://www.ncbi.nlm.nih.gov/pubmed/23609047).
CTC as prognostic and predictive factor for cancer progression
Martin Fleisher, PhD states “detecting CTC in peripheral blood of patients with cancer has become a clinically relevant and important prognostic biomarker and has been shown to be a predictive biomarker post-therapy. But, key to the use of CTC as a biomarker is the technology designed to enrich cancer cells from peripheral blood.”
Since CTC isolation methods started being established, correlation studies between the cells and a patient’s disease emerged. In 2004, investigators at the Department of Breast Medical Oncology, University of Texas MD Anderson Cancer Center (Houston, TX) discovered that the CTC were associated with disease progression and survival in metastatic breast cancer. The clinical trial recruited 177 patients with measurable metastatic breast cancer for levels of CTC both before the patients were to start a new line of treatment and at the first follow-up visit. The progression of the disease or the response to treatment was determined with the use of standard imaging studies at the participating centers. Patients in a training set with levels of CTC equal to or higher than 5 per 7.5 ml of whole blood, as compared with the group with fewer than 5 CTC per 7.5 ml, had a shorter median progression-free survival (2.7 months vs. 7.0 months, P<0.001) and shorter overall survival (10.1 months vs. >18 months, P<0.001). At the first follow-up visit after the initiation of therapy, this difference between the groups persisted (progression-free survival, 2.1 months vs. 7.0 months; P<0.001; overall survival, 8.2 months vs. >18 months; P<0.001), and the reduced proportion of patients (from 49 percent to 30 percent) in the group with an unfavorable prognosis suggested that there was a benefit from therapy. Thus, the number of CTC was found to be an independent predictor of progression-free survival and overall survival in patients with metastatic breast cancer (Cristofanilli M, et al, Circulating tumor cells, disease progression, and survival in metastatic breast cancer. N Engl J Med. 2004 Aug 19;351(8):781-91; http://www.ncbi.nlm.nih.gov/pubmed/15317891).
Similar results have been observed in other cancer types, including prostate and colorectal cancer. The Cell Search System developed by Veridex LLC (Huntingdon Valley, PA) enumerated CTC from 7.5 mL of venous blood and was used to compare the outcomes from three prospective multicenter studies investigating the use of CTC to monitor patients undergoing treatment for metastatic breast, colorectal, or prostate cancer. Evaluation of CTC at anytime during the course of disease allowed assessment of patient prognosis and is predictive of overall survival (Miller MC, et al. Significance of Circulating Tumor Cells Detected by the CellSearch System in Patients with Metastatic Breast Colorectal and Prostate Cancer. J Oncol. 2010; http://www.ncbi.nlm.nih.gov/pubmed/20016752). In addition, the CTC test may permit the oncologist to make an early decision to discontinue first line therapy for metastatic breast cancer and pursue more aggressive alternative treatments.
Genetic analysis of CTC
Additional studies have analyzed the genetic mutations that the cells carry, comparing the mutations to those in a primary tumor or correlating the findings to a patient’s disease severity or spread. In one study, lung cancer patients whose CTC carried a mutation known to cause drug resistance had faster disease progression than those whose CTC lacked the mutation. The investigators analyzed the evolutionary aspect of cancer progression and studied the precursor cells of metastases directly for the identification of prognostic and therapeutic markers. Single disseminated cancer cells isolated from lymph nodes and bone marrow of 107 consecutive esophageal cancer patients were analyzed by whole-genome screening which revealed that primary tumors and lymphatically and hematogenously disseminated cancer cells diverged for most genetic aberrations. Chromosome 17q12-21, the region comprising HER2, was identified as the most frequent gain in disseminated tumor cells that were isolated from both ectopic sites. Furthermore, survival analysis demonstrated that HER2 gain in a single disseminated tumor cell but not in primary tumors conferred high risk for early death (Stoecklein NH, et al. Direct genetic analysis of single disseminated cancer cells for prediction of outcome and therapy selection in esophageal cancer. Cancer Cell. 2008 May;13(5):441-53; http://www.ncbi.nlm.nih.gov/pubmed/18455127).
The abovementioned studies indicate that CTC blood tests have been successfully used to track the severity of a cancer or efficacy of a treatment. In conclusion, the evolution of the CTC technology will be critical in the emerging area of targeted therapy. With the development and use of new technologies, the links between the genomic information and CTC could be explored and established for targeted therapy.
Challenges in CTC research
Potential clinical significance of CTC has been demonstrated as early detection, diagnostic, prognostic, predictive, surrogate, stratification, and pharmacodynamic biomarkers. Hong B and Zu Y (2013) discuss that “the role of CTC as a disease marker may be unique in different clinical conditions and should be carefully interpreted. A good example is the comparison between the prognostic and predictive biomarkers. Both biomarkers employ progression-free survival and overall survival for data interpretation; however, the prognostic biomarker is independent of specific drug treatment or therapy, and used for the determination of outcomes before treatment, while the predictive biomarker is related to a particular treatment to predict the response. Furthermore, inconsistent results are increasingly reported among the various CTC assay methods, specifically pertaining to results for the CTC detection rate, patient positivity rate, and the correlation between the presence of CTC and survival rate (Hong B and Zu Y. Detecting circulating tumor cells: current challenges and new trends. Source. Theranostics. 2013 Apr 23;3(6):377-94; http://www.ncbi.nlm.nih.gov/pubmed/23781285).
Heterogeneity in CTC along with several other technical factors contribute to discordance, including the changes in methodology, lack of reference standard, spectrum and selection bias, operator variability and bias, sample size, blurred clinical impact with known clinical/pathologic data, use of diverse capture antibodies from different sources, lack of awareness of the pre-analytical phase, oversimplification of the cytopathology process, use of dichotomous decision criteria, etc (Sturgeon C. Limitations of assay techniques for tumor markers. In: (ed.) Diamandis EP, Fritsche HA, Lilja H, Chan DW, Schwartz MK. Tumor markers: physiology, pathobiology, technology, and clinical applications. Washington, DC: AACC Press. 2002:65-82; Gion M and Daidone MG. Circulating biomarkers from tumour bulk to tumour machinery: promises and pitfalls. Eur J Cancer. 2004;40(17):2613-2622; http://www.ncbi.nlm.nih.gov/pubmed/15541962). Therefore, employing a standard protocol is essential in order to minimize a lot of inconsistencies and technical errors.
CTC in a small amount of blood sample might not represent the actual CTC count in the whole blood. In fact, it has been reported that the Cell Search system might undercount the number of CTC. Nagrath et al (2007) have demonstrated that the average CTC number per mL of whole blood is approximately 79-155 in various cancers (Nagrath S, et al. Isolation of rare circulating tumous cells in cancer patients by microchip technology. Nature. 2007;450(7173):1235-1239; http://www.ncbi.nlm.nih.gov/pubmed/18097410). In addition, an investigative CellSearch Profile approach (for research use only) detected an approximately 30-fold higher number of the median CTC in the same paired blood samples (Flores LM, et al. Improving the yield of circulating tumour cells facilitates molecular characterisation and recognition of discordant HER2 amplification in breast cancer. Br J Cancer. 2010;102(10):1495-502; http://www.ncbi.nlm.nih.gov/pubmed/20461092). Such measurement discrepancies indicate that the actual CTC numbers in the blood of patients could be at least 30-100 fold higher than that currently reported by the only FDA-cleared CellSearch system.
Thus, although promising, the CTC technology faces several challenges both in detection and interpretation, which has resulted in its limited clinical acceptance and use. In order to prepare the CTC technology for future widespread clinical acceptance, a comprehensive guideline for all phases of CTC technology development was published by the Foundation for the National Institutes of Health (FNIH) Biomarkers Consortium. The guidelines describe methods for interactive comparisons of proprietary new technologies, clinical trial designs, a clinical validation qualification strategy, and an approach for effectively carrying out this work through a public-private partnership that includes test developers, drug developers, clinical trialists, the FDA and the National Cancer Institute (NCI) (Parkinson DR, et al. Considerations in the development of circulating tumor cell technology for clinical use. J Transl Med. 2012;10(1):138; http://www.ncbi.nlm.nih.gov/pubmed/22747748).
Reference:
Langley RR and Fidler IJ. Tumor cell-organ microenvironment interactions in the pathogenesis of cancer metastasis. Endocr Rev. 2007 May;28(3):297-321; http://www.ncbi.nlm.nih.gov/pubmed/17409287
Vona G, et al, Isolation by size of epithelial tumor cells : a new method for the immunomorphological and molecular characterization of circulating tumor cells. Am J Pathol, 2000 Jan;156(1):57-63; http://www.ncbi.nlm.nih.gov/pubmed/10623654
Baccelli I, et al. Identification of a population of blood circulating tumor cells from breast cancer patients that initiates metastasis in a xenograft assay. Nature Biotechnology 2013 31, 539–544; http://www.ncbi.nlm.nih.gov/pubmed/23609047
Cristofanilli M, et al, Circulating tumor cells, disease progression, and survival in metastatic breast cancer. N Engl J Med. 2004 Aug 19;351(8):781-91; http://www.ncbi.nlm.nih.gov/pubmed/15317891
Miller MC, et al. Significance of Circulating Tumor Cells Detected by the CellSearch System in Patients with Metastatic Breast Colorectal and Prostate Cancer. J Oncol. 2010; http://www.ncbi.nlm.nih.gov/pubmed/20016752
Stoecklein NH, et al. Direct genetic analysis of single disseminated cancer cells for prediction of outcome and therapy selection in esophageal cancer. Cancer Cell. 2008 May;13(5):441-53; http://www.ncbi.nlm.nih.gov/pubmed/18455127
Hong B and Zu Y. Detecting circulating tumor cells: current challenges and new trends. Source. Theranostics. 2013 Apr 23;3(6):377-94; http://www.ncbi.nlm.nih.gov/pubmed/23781285
10. Sturgeon C. Limitations of assay techniques for tumor markers. In: (ed.) Diamandis EP, Fritsche HA, Lilja H, Chan DW, Schwartz MK. Tumor markers: physiology, pathobiology, technology, and clinical applications. Washington, DC: AACC Press. 2002:65-82
Gion M and Daidone MG. Circulating biomarkers from tumour bulk to tumour machinery: promises and pitfalls. Eur J Cancer. 2004;40(17):2613-2622; http://www.ncbi.nlm.nih.gov/pubmed/15541962
Nagrath S, et al. Isolation of rare circulating tumous cells in cancer patients by microchip technology. Nature. 2007;450(7173):1235-1239; http://www.ncbi.nlm.nih.gov/pubmed/18097410
Flores LM, et al. Improving the yield of circulating tumour cells facilitates molecular characterisation and recognition of discordant HER2 amplification in breast cancer. Br J Cancer. 2010;102(10):1495-502; http://www.ncbi.nlm.nih.gov/pubmed/20461092
In the last post of Melanoma titled “In focus: Melanoma Genetics”, I discussed the clinical characteristics and the genetics involved in Melanoma. This post would discuss melanoma therapeutics, both current and novel.
According to the American Cancer Society, more than 76,000 new cases and more than 9100 deaths from melanoma were reported in the United States in 2012[1] Melanoma develops from the malignant transformation of melanocytes, the pigment-producing cells that reside in the basal epidermal layer in human skin. Although most melanomas arise in the skin, they may also arise from mucosal surfaces or at other sites to which neural crest cells migrate.
Melanoma therapeutics
Surgical treatment of cutaneous melanoma employs specific surgical margins depending on the depth of invasion of the tumor and there are specific surgical treatment guidelines of primary, nodal, and metastatic melanoma that surgeons adhere to while treatment. Melanoma researchers have been focusing on developing adjuvant therapies for that would increase the survival post-surgery.
Chemotherapy
Among traditional chemotherapeutic agents, only dacarbazine is FDA approved for the treatment of advanced melanoma (Eggermont AM and Kirkwood JM, Eur J Cancer, Aug 2004;40(12):1825-36). Dacarbazine is a triazene derivative and alkylates and cross-links DNA during all phases of the cell cycle, resulting in disruption of DNA function, cell cycle arrest, and apoptosis. Currently, 17 clinical trials are underway to test the efficacy and effectiveness of dacarbazine against melanoma as either a single agent or in combination chemotherapy regimens with other anti-cancer chemotherapeutic agents such as cisplatin, paclitaxel. Temozolomide is a triazene analog of dacarbazine and is approved for the treatment of malignant gliomas. At physiologic pH, it is converted to a short-lived active cytotoxic compound, monomethyl triazeno imidazole carboxamide (MTIC). MTIC methylates DNA at the O6 and N7 positions of guanine, resulting in inhibition of DNA replication. Unlike dacarbazine, which is metabolized to MITC only in the liver, temozolomide is metabolized to MITC at all sites. Temozolomide is administered orally and penetrates well into the central nervous system. Temozolomide is being tested in many combination regimens for patients with melanoma metastatic to the brain (Douglas JG and Margolin K, Semin Oncol, Oct 2002;29(5):518-24).
Immunotherapy
Melanoma and the immune system are closely related. Hence, immunotherapy has been explored in the treatment of the disease. The two most widely investigated immunotherapy drugs for melanoma are Interferon (IFN)-alpha and Interleukin-2 (IL-2).
The role of IFNalpha-2b in the adjuvant therapy of patients with localized melanoma at high risk for relapse was established by the results of three large randomized trials conducted by the US Intergroup; all three trials demonstrated an improvement in relapse-free survival and two in overall survival. One of these trials, a large randomized multicenter trial performed by the Eastern Cooperative Oncology Group (ECOG), in high-risk melanoma patients showed significant improvements in relapse-free and overall survival with adjuvant IFN-α-2b therapy, compared with standard observation (ECOG 1684). The results of the study led to FDA approval of IFN-α-2b for treatment of melanoma. This study was performed on patients with deep primary tumors without lymph node involvement and node-positive melanomas. In other studies, little antitumor activity has been demonstrated in IFN-α-2b–treated metastatic stage IV melanoma.
Recombinant IL-2 showed an overall response rate of 15-20% in metastatic melanoma and was capable of producing complete and durable remissions in about 6% of patients treated. Based upon these data, the US FDA has approved the use of high-dose IL-2 for the therapy of patients with metastatic melanoma. Aldesleukin (Brand name: Proleukin) is a recombinant analog of the endogenous cytokine interleukin-2 (IL-2). It binds to and activates the IL-2 receptor (IL-2R), followed by heterodimerization of the IL-2R beta and gamma(c) cytoplasmic chains; activation of Jak3; and phosphorylation of tyrosine residues on the IL-2R beta chain, resulting in an activated receptor complex (NCI). The activated complex recruits several signaling molecules that act as substrates for regulatory enzymes associated with the complex. It is administered intravenously and stimulates lymphokine-activating killer (LAK) cells, natural killer (NK) cells and the production of cytokines such as gamma interferon (nm|OK). Several clinical trials are currently underway using Aldesleukin to determine the efficacy of combination treatment in melanoma patients.
Another anti-cancer immunotherapeuty-based mechanism involved inhibition of inhibitory signal of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), a molecule on T-cells that plays a critical role in regulating natural immune responses. Ipilimumab (Brand name: Yervoy) was by FDA for melanoma treatment. It is a human monoclonal antibody (MAb) T-cell potentiator that specifically blocks CTLA-4. It is approved for inoperable advanced (Stage III) or metastatic (Stage IV) melanoma in newly diagnosed or previously treated patients (nm|OK). The approval, March 25, 2011, was based on a randomized (3:1:1) double-blind double-dummy clinical trial (MDX010-20) in patients with unresectable or metastatic melanoma who had received at least one prior systemic treatment for melanoma. Patients were randomly assigned to receive either ipilimumab, 3 mg/kg intravenously, in combination with the tumor vaccine (n=403); ipilimumab plus vaccine placebo (n=137); or tumor vaccine with placebo (n=136). Patients treated with ipilimumab alone had a median overall survival (OS) of 10 months while those treated with tumor vaccine had a median OS of 6 months. The trial also demonstrated a statistically significant improvement in OS for patients treated with the combination of ipilimumab plus tumor vaccine compared with patients treated with tumor vaccine alone. For more information on the trial, check the clinical trials website, www.clinicaltrials.gov
Signaling pathway inhibitors
Approximately 90% of BRAF gene mutations involve valine (V) to glutamic acid (E) mutation at number 600 residue (V600E). The resulting oncogene product, BRAF (V600E) kinase is highly active and exhibits elevated MAPK pathway. The BRAF(V600E) gene mutation occurs in approximately 60% of melanomas indicating that it could be therapeutically relevant.Vemurafenib (Brand name: Zelboraf) is a novel small-molecule inhibitor of BRAF (V600E) kinase. It selectively binds to the ATP-binding site and inhibits the activity of BRAF (V600E) kinase. Vemurafebib inhibits over active MAPK pathway by inhibiting the mutated BRAF kinase, thereby reducing tumor cell proliferation (NCI). Encouraging results of phase III randomized, open-label, multicenter trial were reported recently at the 2011 ASCO meeting (Chapman PB, et al, ASCO 2011, Abstract LBA4). The trial compared the novel BRAF inhibitor vemurafenib with dacarbazine in patients with BRAF-mutated melanoma. Previously untreated, unresectable stage IIIC or stage IV melanoma that tested positive for BRAF mutation were randomized (1:1) to vemurafenib or dacarbazine. The response rate (RR) was significantly high (48.4%) in vemurafenib treated patients as compared to 5.5% in dacarbazine among the 65% of patients evaluable for RR to date. In addition, vemurafenib was associated with significantly improved OS and PFS compared to dacarbazine in patients with previously untreated BRAF (V600E) mutation bearing patients with metastatic melanoma.
Biochemotherapy
Biochemothreapy combine traditional chemotherapy with immunotherapies, such as IL-2 and IFN-α-2b. These combination therapies seemed promising in phase II trials, however, seven large studies failed to show statistically significant increased overall survival rates for various biochemotherapy regimens in patients with stage IV metastasis (Margolin KA, et al, Cancer, 1 Aug 2004;101(3):435-8). Owing to inconsistent results of the available studies with regard to benefit including RR, OS and progression time, and consistently high toxicity rates, clinical practice guideline do not recommend biochemotherapy for the treatment of metastatic melanoma (Verma S, et al, Curr Oncol, April 2008; 15(2): 85–89).
Vaccines
The use of therapeutic vaccines is an ongoing area of research, and clinical trials of several types of vaccines (whole cell, carbohydrate, peptide) are being conducted in patients with intermediate and late-stage melanoma. Vaccines are also being tested in patients with metastatic melanoma to determine their immune effects and to define their activity in combination with other immunotherapeutic agents such as IL-2 or IFNalpha (Agarwala S, Am J Clin Dermatol, 2003;4(5):333-46). In fact, recently investigators at the Indiana University Health Goshen Center for Cancer Care (Goshen, IN) conducted a randomized, multicenter phase III trial involving 185 patients with stage IV or locally advanced stage III cutaneous melanoma. The patients were assigned into treatment groups with IL-2 alone or with vaccine (gp100) followed by IL-2. The vaccine-IL-2 group had a significantly improved OR as compared to the IL-2-only group (16% Vs. 6%) and longer progression free survival (2.2 months Vs. 1.6 months). The median overall survival was also longer in the vaccine-interleukin-2 group than in the interleukin-2-only group (17.8 months Vs. 11.1 months). Thus, a combination of vaccine and immunotherapy showed a better response rate and longer progression-free survival than with interleukin-2 alone in patients with advanced melanoma (Schwartzentruber DJ, et al, N Engl J Med, 2 Jun 2011;364(22):2119-27).
Which Treatment When?
Earlier, there were essentially two main options for patients suffering from advanced melanoma, dacarbazine and IL-2. Dacarbazine, a chemotherapeutic agent produces modest improvements in survival or symptomatic benefits in most patients. Interleukin-2 -based drugs, on the other hand, induce long-term remissions in a small group of patients but are highly toxic. Recently, FDA approved ipilimumab and vemurafenib for patients with metastatic melanoma. Apart from these, therapies are also aiming at starving the tumor by inhibiting angiogenesis or depleting nutrients essential for cancer growth. Of the antiangiogenic compounds, VEGFR inhibitors SU5416 and AG-013736 demonstrated broad-spectrum antitumor activity in mice bearing xenografts of human cancer cell lines originating from various tissues, including melanoma. In addition, several trials are currently underway to test the efficacy of the drugs in combination. In the future, personalized medicine-based recommendations of novel and existing drugs for melanoma patients might be the way to go.
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