State of the art in oncologic imaging of breast.
Author-Writer: Dror Nir, PhD
Word Cloud By Danielle Smolyar
In the coming posts I will address the state of the art in oncologic imaging based on a review paper; Advances in oncologic imaging†‡ that provides updates on the latest approaches to imaging of 5 common cancers: breast, lung, prostate, colorectal cancers, and lymphoma. This paper is published at CA Cancer J Clin 2012. © 2012 American Cancer Society.
The paper gives a fair description of the use of imaging in interventional oncology based on literature review of more than 200 peer-reviewed publications.
In this post I summaries the chapter on breast cancer imaging.
Breast Cancer Imaging
As a start the authors describes the evolution in the ACS imaging guidelines for breast cancer screening. Most interesting to learn is how age limits are changing. The most recent: “In 2010, the Society of Breast Imaging and the Breast Imaging Commission of the ACS issued recommendations for breast cancer screening to provide guidance in light of the controversies and emerging technologies.5 These recommendations were based on multiple prospective randomized trials as well as population-based experience.
Recommendations for screening with non-mammographic imaging are based not on evidence showing mortality reduction but largely on surrogate indicators, i.e., tumor size and nodal status, suggesting improved survival compared with women who are not screened.” I have referred to these guidelines in my recent post: Not applying evidence-based medicine drives up the costs of screening for breast-cancer in the USA.
As long as imaging interpretation is based mainly on observations related to lesion morphology:
“The imaging characteristics of malignant lesions are nonspecific and usually do not allow a definitive diagnosis. When a biopsy is recommended based on mammography, it has a 25% to 45% likelihood of resulting in a diagnosis of carcinoma.11 Similar positive predictive values are reported for biopsies recommended based on MRI.”
It is worthwhile noting that these results do not reflect purely the specificity of the imaging device but rather the specificity of the whole workflow; i.e imaging, biopsy and histopathology. All imaging techniques have false negatives: Mammography screening of general population misses approximately 20% of the cancers. This rate increases as breast density increases. MRI is not applied to general population. When applied to highly suspicious cases MRI misses ~10% of the invasive cancers. Although ultrasound has proven to be useful in detecting cancer especially in women with dense breasts: Automated Breast Ultrasound System (‘ABUS’) for full breast scanning: The beginning of structuring a solution for an acute need! Based on the literature reviewed by the authors of this paper they do not recommend routine sonography for these women.
For women with locally advanced breast cancer (Fig. 2) who undergo neoadjuvant therapy before breast surgery, the authors recommends post-treatment staging using MRI, which has been found to predict complete response with sensitivity above 60% and specificity as high as 90%.26
A 27-year-old female with locally advanced poorly differentiated invasive ductal carcinoma underwent evaluation of extent of disease before starting neoadjuvant chemotherapy. Sagittal fat-suppressed T1-weighted postcontrast MR images demonstrate an almost 6-cm heterogeneously enhancing mass (A) involving the skin of the lower breast (arrow) with (B) right axillary (arrow) and (C) right internal mammary adenopathy (arrow).
Same is recommended for women who have undergone lumpectomy if the surgical margins are positive. As post therapy follow-up, a new baseline mammogram of the treated breast is recommended followed by annual mammography.
In regards to emerging technology the following are discussed: Mammographic tomosynthesis – see also Improving Mammography-based imaging for better treatment planning
Contrast-enhanced digital mammography – “involves the injection of iodinated contrast material, as is done for computed tomography (CT); this enables hypervascular lesions to be seen with modified mammography technology, potentially providing the same information obtained through MRI. Little has been published on the clinical application of this technology, but diagnostic accuracy better than that of mammography and approaching that of MRI has been reported.31, 32”
MR choline spectroscopy – has been shown to improve the positive predictive value of breast MRI and may be useful in reducing the number of lesions that require biopsy (Fig. 4).33 Studies of spectroscopy have reported sensitivities of 70% to 100% and specificities of 67% to 100% in the detection of breast cancer. Decreasing choline concentrations may also be a useful indication of tumor response to treatment before any change in tumor volume can be detected.34, 35 Technical factors have limited the use of spectroscopy to lesions 1 cm in size or larger.”
Sagittal fat-suppressed T1-weighted postcontrast MR image is shown (A) of the right breast of a 48-year-old female who was status post–contralateral mastectomy for DCIS with the spectroscopy voxel placed over an enhancing mass (arrow). The magnified spectrum (B) demonstrated no choline peak. Biopsy yielded fibroadenoma.
Diffusion-weighted MRI (DW-MRI) – “adding DW-MRI data to other imaging characteristics of lesions on breast MRI may increase the positive predictive value of the examination, in turn decreasing the number of benign lesions requiring biopsy for diagnosis.” See also Imaging: seeing or imagining? (Part 2).
Axial T1-weighted fat-suppressed postcontrast MR image is shown (A) of the left breast of a 42-year-old female with biopsy-proven contralateral cancer undergoing evaluation of disease extent. An enhancing mass (arrow) was seen in the left breast. This mass (arrow) was also demonstrated on the axial diffusion-weighted MR image (B). Biopsy yielded fibroadenoma with atypical ductal hyperplasia and lobular carcinoma in situ.
Ultrasound-elastography – “Ultrasound elastography has been reported to differentiate benign from malignant breast lesions with sensitivities of 78% to 100% and specificities of 21% to 98%.39 When added to other US techniques, it may improve radiologists’ performance in distinguishing malignant breast lesions.”
Positron emission tomography (PET) – “alone or combined with CT, allows noninvasive, quantitative assessment of biochemical and functional processes at the molecular level in the body. It is most often performed with the radiolabeled glucose analogue [18F] fluorodeoxyglucose ([18F]FDG) to detect the elevated glucose metabolism that is a hallmark of cancer. In breast cancer, its utility depends on the pretest probability for advanced disease, and thus the clinical stage.” The authors found that the use of [18F] FDG PET to patients with stage I and II disease is “limited”. Specifically, they claim that it is not sufficiently accurate for axillary nodal staging in this subset of patients.40 The did find enough evidence to recommend the use of FDG PET in patients with advanced disease: “where it accurately defines disease extent,41 and frequently eliminates the need for other imaging tests, and provides an early readout of treatment response as well as prognostic information.”
Combined PET/MRI is mentioned as a promising technology for predicting response to therapy “but this remains to be proven”.
Positron emission mammography (PEM) – “adapts full-body PET imaging to the breast. In a multicenter study, the interpretation of PEM in conjunction with mammographic and clinical findings yielded a sensitivity of 91% and a specificity of 93% for breast cancer.47 “. However, the authors mention that its use for screening (applying to healthy women) has been criticized because of the need to administer a radioactive tracer.
Lung Cancer Imaging
To be followed…
Other research papers related to the management of breast cancer were published on this Scientific Web site:
Introducing smart-imaging into radiologists’ daily practice.
Will Bio-Tech make Medical Imaging redundant?
Improving Mammography-based imaging for better treatment planning
Not applying evidence-based medicine drives up the costs of screening for breast-cancer in the USA.
New Imaging device bears a promise for better quality control of breast-cancer lumpectomies – considering the cost impact
Predicting Tumor Response, Progression, and Time to Recurrence
“The Molecular pathology of Breast Cancer Progression”
Personalized medicine gearing up to tackle cancer
Whole-body imaging as cancer screening tool; answering an unmet clinical need?
What could transform an underdog into a winner?
Mechanism involved in Breast Cancer Cell Growth: Function in Early Detection & Treatment
Nanotech Therapy for Breast Cancer
A Strategy to Handle the Most Aggressive Breast Cancer: Triple-negative Tumors
Optical Coherent Tomography – emerging technology in cancer patient management
Breakthrough Technique Images Breast Tumors in 3-D With Great Clarity, Reduced Radiation
Imaging: seeing or imagining? (Part 1)
Imaging: seeing or imagining? (Part 2)
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PUT IT IN CONTEXT OF CANCER CELL MOVEMENT
The contraction of skeletal muscle is triggered by nerve impulses, which stimulate the release of Ca2+ from the sarcoplasmic reticuluma specialized network of internal membranes, similar to the endoplasmic reticulum, that stores high concentrations of Ca2+ ions. The release of Ca2+ from the sarcoplasmic reticulum increases the concentration of Ca2+ in the cytosol from approximately 10-7 to 10-5 M. The increased Ca2+ concentration signals muscle contraction via the action of two accessory proteins bound to the actin filaments: tropomyosin and troponin (Figure 11.25). Tropomyosin is a fibrous protein that binds lengthwise along the groove of actin filaments. In striated muscle, each tropomyosin molecule is bound to troponin, which is a complex of three polypeptides: troponin C (Ca2+-binding), troponin I (inhibitory), and troponin T (tropomyosin-binding). When the concentration of Ca2+ is low, the complex of the troponins with tropomyosin blocks the interaction of actin and myosin, so the muscle does not contract. At high concentrations, Ca2+ binding to troponin C shifts the position of the complex, relieving this inhibition and allowing contraction to proceed.
Figure 11.25
Association of tropomyosin and troponins with actin filaments. (A) Tropomyosin binds lengthwise along actin filaments and, in striated muscle, is associated with a complex of three troponins: troponin I (TnI), troponin C (TnC), and troponin T (TnT). In (more ) Contractile Assemblies of Actin and Myosin in Nonmuscle Cells
Contractile assemblies of actin and myosin, resembling small-scale versions of muscle fibers, are present also in nonmuscle cells. As in muscle, the actin filaments in these contractile assemblies are interdigitated with bipolar filaments of myosin II, consisting of 15 to 20 myosin II molecules, which produce contraction by sliding the actin filaments relative to one another (Figure 11.26). The actin filaments in contractile bundles in nonmuscle cells are also associated with tropomyosin, which facilitates their interaction with myosin II, probably by competing with filamin for binding sites on actin.
Figure 11.26
Contractile assemblies in nonmuscle cells. Bipolar filaments of myosin II produce contraction by sliding actin filaments in opposite directions. Two examples of contractile assemblies in nonmuscle cells, stress fibers and adhesion belts, were discussed earlier with respect to attachment of the actin cytoskeleton to regions of cell-substrate and cell-cell contacts (see Figures 11.13 and 11.14). The contraction of stress fibers produces tension across the cell, allowing the cell to pull on a substrate (e.g., the extracellular matrix) to which it is anchored. The contraction of adhesion belts alters the shape of epithelial cell sheets: a process that is particularly important during embryonic development, when sheets of epithelial cells fold into structures such as tubes.
The most dramatic example of actin-myosin contraction in nonmuscle cells, however, is provided by cytokinesisthe division of a cell into two following mitosis (Figure 11.27). Toward the end of mitosis in animal cells, a contractile ring consisting of actin filaments and myosin II assembles just underneath the plasma membrane. Its contraction pulls the plasma membrane progressively inward, constricting the center of the cell and pinching it in two. Interestingly, the thickness of the contractile ring remains constant as it contracts, implying that actin filaments disassemble as contraction proceeds. The ring then disperses completely following cell division.
Figure 11.27
Cytokinesis. Following completion of mitosis (nuclear division), a contractile ring consisting of actin filaments and myosin II divides the cell in two.
http://www.ncbi.nlm.nih.gov/books/NBK9961/
This is good. I don’t recall seeing it in the original comment. I am very aware of the actin myosin troponin connection in heart and in skeletal muscle, and I did know about the nonmuscle work. I won’t deal with it now, and I have been working with Aviral now online for 2 hours.
I have had a considerable background from way back in atomic orbital theory, physical chemistry, organic chemistry, and the equilibrium necessary for cations and anions. Despite the calcium role in contraction, I would not discount hypomagnesemia in having a disease role because of the intracellular-extracellular connection. The description you pasted reminds me also of a lecture given a few years ago by the Nobel Laureate that year on the mechanism of cell division.
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