Clinical Applications of Scintimammography
While mammography is still generally considered the best tool for breast cancer screening, scintimammography does have certain benefits. From a patient’s perspective perhaps the greatest benefit is the immediacy of the results. It is not necessary to wait for a six to twelve month follow-up. Scintimammography tends to be used when there is a palpable lesion greater than 1 cm in diameter, which is a relatively late discovery of a potentially malignant breast cancer mass. A confirmed negative reading via scintimammography can therefore be quite reassuring. Scintimammography is performed and read by nuclear medicine specialist, and not a radiologist. It is only possible to get a scintimammogram in a hospital or setting which has a nuclear medicine department.
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Other Scintimammography applications and considerations: Tumor response to chemotherapy
Scintimammography is often used when considering treatment options such as surgical removal or chemotherapy. Pronounced and late absorption of scintimammographic activity would tend to predict a positive clinical response to chemotherapy. However, if the Sestamibi molecules are rapidly cleared out of the area, this would tend to suggest a system that may be restive to chemical treatments.
Use of Scintimammographic screening to probe metastasis to the axillary lymph nodes
After a Sestamibi injection, a ‘hot spot‘ might be discovered around the axillary lymph node, which is highly indicative of metastasis of the breast cancer to the axilla. One way scintimammography works is by revealing lumps of tissue that are metabolically active, more-so than most normal tissue. Dye-injected Sestamibi molecules are taken up by metabolically active cells. Since cancers are made of rapidly dividing cells, which are therefore very metabolically active, scanning the progress of Sestamibi molecules can effectively reveal a lump if it is large enough. If there is no such ‘hot spot‘, this is a positive sign but should not be taken as the equivalent of a negative sentinel node biopsy or negative axillary dissection.
Follow up for high risk patients
Scintimammography will likely be employed for follow-up evaluations of ‘high risk‘ women, particularly those with BRCA1 and BRCA2 genetic variants. It is also a useful follow up for women who have had a prior lumpectomy or radiation therapy, atypical histology, or prior use of hormonal contraceptives. (Use of hormonal contraceptives may result in unusually dense breast tissue and a subsequently poor or inconclusive ultrasound image).
Scintimammography positive and false positive breast cancer indicators
The most probable reasons for a false positive scintimammographic reading are fibroadenoma and fibrocystic disease. This is because some fibroadenomas and fibrocystic changes can have metabolically active areas too. In order to avoid a false positive the scintimammography procedure is typically performed 8 or 9 days after a fine needle aspiration, 4-6 weeks after a large core breast biopsy, and 2-3 months following radiotherapy or breast surgery. As positive evidence of breast cancer the physicians and technologists will be looking for a unique, well-defined hot spot, and mild to intense uptake. Where there is found to be symmetrical, ill-defined, and somewhat bilateral uptake of the Sestamibi molecule, this tends to suggest a more benign condition.
Scintimammography has proven to be an accurate and clinically useful diagnostic method for the screening and staging evaluation of women with palpable breast masses when mammography is indeterminate. And, 99mTc-sestamibi scintimammography could be of considerable value in the staging and surgical work up of patients with breast cancer.
Below are some Q&A…
- Why is scintimammography done? Scintimammography is a nuclear medicine imaging test that uses a radioactive material (known as a radioactive isotope) and a special camera to take images of the breast. This test may also be called breast scintigraphy. Breast cancer cells attract more radioactive material than normal or benign (non-cancerous) cells. This is because cancer cells divide and grow more rapidly. The radioactive isotope gathers in larger amounts in cancer cells because of this rapid growth.
- How is scintimammography done? Scintimammography is not commonly used. It does not replace mammography. It may be done to check breast lumps that do not show up clearly on a mammogram because of either scar tissue from previous surgery or radiation therapy, dense breast tissue, or breast implants. Other reasons why scintimammography is done is when multiple tumors are seen in the breast, or to scan the lymph nodes in the armpit (axilla) to see if they contain cancer.
- What are some potential side effects of scintimammography? The doses of x-rays or radioactive materials used in nuclear medicine imaging an vary widely. Dose depends on the type of procedure and body part being examined. Some potential side effects that might occur include bleeding, soreness, swelling may develop at injection site, and allergic reactions to the radio pharmaceutical may occur, but are extremely rare.
- What are the limitations of scintimammography? Activity from other organs, such as the heart of liver, may interfere with the test and affect the scintimammography results. Scintimammography may not detect very small tumors, such as those less than 1 cm in diameter.
- Who is a candidate for scintimammography? Scintimammography may be appropriate for patients with dense breast tissue, large, palpable (able to be felt) abnormalities that cannot be imaged well with mammography or ultrasound, breast implants, when multiple tumors are suspected, a lump at the surgical site after mastecomy (breast removal) since scar tissue may be difficult to distinguish from other tumors with other breast imaging exams, and/or to check the axillary lymph nodes to determine whether they contain cancer cells (sentinal lymph node biopsy).
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