Resistance to chemotherapy is a major cause of treatment failure in patients with breast cancer. A study reported in the June issue of The Journal of Nuclear Medicine found that scintigraphic imaging with 99mTc-sestamibi accurately predicted which breast tumors would be chemoresistant. Scintigraphy is an imaging technique that uses radioisotopes and a gamma camera.

The researchers from the Regina Elena Cancer Institute in Rome, Italy wrote that they were able to predict 100% of the time that patients would respond to chemotherapy, and 83% of the time that patients would not respond. Physicians in this phase II clinical trial studied 30 patients with untreated locally advanced breast cancer for whom a cycle of chemotherapy followed by surgery was planned.

The patients received an injection of 99mTc-sestamibi and were scanned before treatment and again before surgery. Those who were likely to respond had a low wash-out rate, or WOR (<45%) of the 99mTc-sestamibi. That means a higher amount of it remained in the body after injection, and showed up in the scan. Those unlikely to respond had a higher WOR (>45%). The authors pointed out that knowing a tumor was likely to be chemoresistant would allow physicians to prescribe specific drugs to boost the body's ability to respond to chemotherapy.

Results of the first test were analyzed to determine the amount of radiotracer uptake in the tumor at 10 minutes and 240 minutes, and the washout rate was calculated. The second scan was used diagnostically to confirm tumor response to treatment and the pre-therapy result. Results were also confirmed pathologically by the subsequent surgery.

SOURCES:
The Journal of Nuclear Medicine, June 2002
Society of Nuclear Medicine (http://www.snm.org)