According to a recent article published in the Journal of Nuclear Medicine, an imaging scan utilizing 99mTc-Sestamibi may help predict how a patient with locally advanced breast cancer will respond to neoadjuvant chemotherapy.
1 Locally advanced breast cancer refers to stages II or III breast cancer. Stage II breast cancer is a primary cancer less than two inches that involves the axillary (under the arm) lymph nodes, or is greater than ¾ inch and does not involve any lymph nodes. Stage III breast cancer is a primary cancer that is greater than two inches and involves the axillary lymph nodes, a primary cancer that is less than two inches and causes axillary lymph nodes to be attached to each other or another structure or a primary cancer that is attached to the chest wall or skin. Clinical studies have demonstrated that neoadjuvant (prior to surgery) chemotherapy for locally advanced breast cancer may help to shrink cancer prior to surgery and allow for more complete surgical removal of the cancer. Some patients respond much better to chemotherapy than others; however, it is unclear which patient or disease characteristics are associated with improved anti-cancer responses.
One type of imaging scan used in different fields of medicine utilizes the radioisotope, technetium99 (99mTc).
99mTC is linked to a protein called sestamibi.
99mTc-sestamibi is injected into a patient’s vein and tends to accumulate in cancer cells.
99mTc spontaneously emits radiation and can be viewed in the body with a gamma camera. Previous studies have suggested that cancer cells that rapidly “wash out”
99mTc may have higher levels of a protein system referred to as the multi-drug-resistant energy dependent P-glycoprotein pump system.
2 This system pumps out certain agents from the cell, including many chemotherapy agents, making the cancer resistant to anti-cancer effects of chemotherapy. This prompted researchers to evaluate the association between “wash-out” time of
99mTc and resistance to chemotherapy.
Researchers from Italy recently conducted a clinical trial to determine if a correlation existed between wash-out times of
99mTc and anti-cancer responses to neoadjuvant chemotherapy in 30 patients with locally advanced breast cancer. Patients received
99mTc before and after chemotherapy. Scans were done at 10 minutes and 240 minutes following injection to determine wash-out time of
99mTc. Surgery included a mastectomy (removal of the entire breast), during which time a laboratory analysis was performed on the residual cancer.
According to analysis, 12 patients had an anti-cancer response to neoadjuvant chemotherapy and 18 patients were resistant to neoadjuvant chemotherapy. According to wash-out times of
99mTc, 100% of patients with a slow wash-out time responded to the chemotherapy, whereas only approximately 20% of patients with a rapid wash-out time responded to chemotherapy. Furthermore,
99mTc studies following therapy confirmed the findings established prior to therapy in 29 of the 30 patients.
These researchers concluded that wash-out times of
99mTc may indicate if a patient with locally advanced breast cancer is at risk for not responding to neoadjuvant chemotherapy and help to guide patients and physicians in determining more appropriate treatment options. This technique is still in investigative stages, but further studies are warranted using different chemotherapy combinations in various types of cancer. Patients with locally advanced breast cancer may wish to speak with their physician regarding the risks and benefits of participating in a clinical trial further evaluating
1.Sciuto R, Pasqualoni R, Bergomi S, et al. Prognostic value of 99mTc-Sestamibi washout in predicting response of locally advanced breast cancer to neoadjuvant chemotherapy.
Journal of Nuclear Medicine. 2002;43:745-751.
2.Kostakoglu L, Elahi N, Kiratli P, et al. Clinical validation of the influence of P-glycoprotein on Tc-99m-sestamibi uptake in malignant tumors.
Journal of Nuclear Medicine. 1997;38:1003-1008.