MRI used for breast cancer staging
The staging for breast cancer occurs when a pathology report confirms the presence of breast cancer. The main purpose of breast cancer staging is to determine the extent of the breast cancer, both locally and elsewhere in the body, and to find out as much as possible in order to predict the behavior and aggressiveness of the cancer.
Bone scans, PET scans, and sentinel node biopsies are already proven to be effective in determining any metastasis of the breast cancer. And, additional mammography and ultrasound are very effective tools to determine the local extent of the breast tumor and to plan for surgery.
That said, there is no question that MRI is the most sensitive of the imaging modalities used for breast cancer management, and it would naturally be given consideration as a staging technique for planning breast conserving surgeries. However, a real concern is that the use of MRI in breast cancer staging may result in over treatment of the breast cancer, i.e. by unnecessary mastectomy or bilateral mastectomy.
Don’t get me wrong, this page is still extremely useful, however, I have created a newer version with more up-to-date information on MRI used for breast cancer staging. Check it out!
MRI for breast cancer staging will frequently find additional disease
On average, the use of breast MRI for staging purposes identifies additional areas of breast cancer not previously detected on other imaging studies, about 16% of the time. More specifically, MRI used for staging detects about 16% more multi-focal and multi-centric breast cancer than conventional imaging.
The effect of MRI staging on treatment decisions is not insignificant. Conversion from wide local excision to mastectomy occurs about 8% of the time when multifocal or multicentric tumors are discovered. The use of MRI staging for uni focal breast tumors results in change from a planned wide local excision to a mastectomy about 1% of the time, and in about 5% of cases results in a more extensive surgical excision.
Small multifocal tumors missed on conventional imaging are usually controlled by radiation therapy and follow-up mammography
The arguments in favor of the use of breast MRI for staging will always demonstrate that MRI finds up to 4 times as much local and occult breast cancer as mammography and ultrasound, due to its increased sensitivity. Some studies even suggest that conventional mammography may miss up to 35% of malignant disease, perhaps due to dense breast tissue, but more likely due to the presence of small multifocal or multicentric breast tumors.
However, if you consider the overall contralateral breast cancer rates and local recurrence rates after longer interval, it can be suggested that undiscovered breast carcinoma in conventionally staged breast cancers is adequately controlled by radiation therapy.
The other issue to remember is that although MRI has extremely high sensitivity, the specificity of those results is somewhat lower. In other words, MRI will find more breast disease, but a biopsy will usually be required anyways to determine exactly what was found. There are difference of opinion here however. Not all studies find a significant increase in benign biopsies as a result of MRI in breast cancer staging.
MRI used for staging does not significantly reduce local recurrence rates
The rate of contralateral breast cancer after a period of 8 years has been shown to be about the same for MRI-staged vs. conventionally imaged breast tumors. It has been suggested that the use of MRI in staging for treatment will result in lower local recurrence rates because there will be fewer positive margins (more complete and effective surgical excisions).
But, when you really look at the follow-up statistics, the number of ‘re-excisions‘ due to positive margins (malignant cells found in the margins around a tumor removal site) is only about 1% lower than for breast cancers staged by conventional means. In terms of local recurrence of breast cancer, studies have shown that local recurrence for MRI-staged tumors treated by breast conserving surgeries and radiation therapy are, after 8 years, only 1% lower than for breast cancers staged by conventional means.
Local recurrence is mostly attributable to the biology of the carcinoma
With regard to the issue of local recurrence, most of the time this can be attributed simply to the biology of the breast carcinoma itself, rather than staging and treatment issues. Highly aggressive breast cancer is more likely to recur as this genetic tendency is present. Radiation therapy has proven to be the most effective treatment to control local recurrence, and whether or not the tumor was initially staged by MRI will not likely have any significant bearing on the biological predisposition for local recurrence in aggressive breast carcinomas.
MRI must be shared among all diseases
Once also has to consider practical issues such as the increased cost and time involved in breast MRI, relative to the overall benefit. Consideration must be given to the fact that MRI in a hospital setting is to be used for the benefit of all diseases, not just breast cancer.
MRI for breast cancer staging should be used on problem cases
MRI is often suggested as a follow-up procedure to assess the response to chemotherapy (or possibly to assess the response to neo-adjuvant chemotherapy), and MRI certainly gives the surgeon the clearest possible view of the tumor and potential surgical issues. Sometimes MRI is also used to guide needle-biopsies and vacuum-assisted biopsies, but ultrasound and mammography are usually adequate for this. Probably the main argument in favor of MRI in breast cancer staging is the early detection of contralateral breast tumors, but contralateral tumors will almost certainly be detected by follow-up mammography within the next 6 months to a year anyways.
So, while there will be differences in practices, MRI tends to be used in breast cancer staging only for problem solving purposes. For example, if there is some kind of discrepancy between the clinical and pathological and the results of mammography and ultrasound, then MRI should be used to resolve this discrepancy. MRI is also suggested for staging patients with metastases to the axillary lymph nodes, but with no evident breast tumor, and also for BRCA1 and BRCA2 mutation carriers who do not undergo bilateral mastectomy.
Here is a little quiz…
- What helps determine breast cancer staging? Your doctor determines your breast cancer stage by considering the size of your tumor, whether cancer cells have spread to the lymph nodes under your arm (axillary lymph nodes), or whether cancer cells have spread to other parts of your body.
- What are some tests and procedures used to stage breast cancer? Blood tests, breast imaging tests, and additional imaging tests.
- What does an MRI machine look like? Most MRI machine are large, tube-shaped magnets. When you lie inside an MRI machine, the magnetic field temporarily realigns hydrogen atoms in your body. Radio waves cause these aligned atoms to produce very faint signals, which are used to create cross-sectional MRI images, like slices in a loaf of bread for instance.
- When is MRI usually performed? It is performed after you have had a biopsy that’s positive for cancer, and your doctor needs more information about the extent of the disease. In certain situations, such as for women with high risk of breast cancer, breast MRI may be used with mammograms as a screening tool for detecting breast cancer.
- Why is MRI done? Breast MRI is most often used to screen for breast cancer in women thought to have a high risk of the disease. Your doctor may recommend a breast MRI if you’ve been diagnosed with breast cancer, and your doctor wants to determine the extent of the cancer, you have a suspected leak or rupture of a breast implant, you’re at a high risk of breast cancer (family history, etc), you have a strong family history of breast cancer, you have very dense breast tissue, and mammogram didn’t detect a prior breast cancer, and/or you have a history of precancerous breast changes such as atypical hyperplasia or lobular carcinoma in situ, a strong family history of breast cancer and dense breast tissue.
- What are some known risks for MRI? A breast MRI is a safe procedure that doesn’t expose you to radiation. But as with other tests, a breast MRI has risks such as a risk of false-positive results, or a risk of reaction to the contrast dye used.
- How do I prepare for my MRI appointment? Schedule your MRI for the beginning of your menstrual cycle, tell your doctor about any allergies you have, tell your doctor if you have kidney problems, tell your doctor if you’re pregnant or if you’re nursing, don’t wear anything metallic during the MRI, and tell your doctor about implanted medical devices.
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