Breast Tumor's Response to Chemotherapy Can Be Effectively Detected by PET Scans

In a study presented at the European Cancer Conference (ECCO 14) in Barcelona, Spain, In September 2007, an Australian researcher reported that when the scanning procedure was used to measure the accumulation of radioactive glucose fluorodeoxyglucose (FDG) in tumor tissue from patients with locally-advanced breast cancer before and after preoperative chemotherapy. Women who had the highest accumulation at the beginning and who then had the highest percentage decrease in accumulation after four cycles of chemotherapy were more likely to have a complete response to their treatment, i.e., no tumor cells remaining in the final tumor resection specimen. However, measurements taken utilizing mammography or ultrasound were not able to predict a pathologic response accurately.

FDG-PET works by injecting a glucose molecule (FDG), tagged with a radioactive tracer, into the patient. The molecule is metabolically active and concentrates in tumor tissues where it emits energy that PET scanning can detect. PET measures the standard uptake values (SUVs), meaning, how much FDG has accumulated in the tumor. If the SUVs decrease after chemotherapy, this shows that there are fewer, or no, cancer cells available where the FDG can accumulate. This study suggests that tumors with high initial SUVs seem to be more sensitive to chemotherapy, thereby giving a better chance of achieving a reduction or complete removal of the cancer.

Dr. Vinod Ganju, a medical oncologist for Monash Oncology Research Institute (MORI; Victoria, Australia) and Monash Breast Cancer Research Consortium, Monash Medical Centre (Melbourne, Australia), said, "In our study, we were able to show that patients who had higher baseline SUVs and a greater reduction in SUV at the second PET scan, were more likely to respond to the chemotherapy and achieve a complete pathological response. Patients who achieve a complete pathological response are more likely to survive and have a better prognosis.”

The researchers recruited 47 women with locally-advanced breast cancer to their study, and they were able to evaluate data from 44 of these women. The patients were randomly assigned to receive either fluorouracil, epirubicin, cyclophosphamide (FEC) followed by docetaxel, or docetaxel followed by FEC. The initial SUVs and the percentage reduction in SUVs after chemotherapy were correlated to pathologic response (complete, partial, or no response) as assessed by examination of biopsy samples.

Nine women had a complete pathologic response (pCR), 15 had a partial response (pPR), and 20 less than optimal pathologic response (NR) to chemotherapy. Women who had a pCR were significantly more likely to have higher SUVs before chemotherapy than NR women (an average of 9.7 versus 6.4 on the SUV measurement scale). The percentage reduction in SUVs after chemotherapy was also significant, with SUVs in pCR women reducing by an average of 83.3% compared to 50.4% in NR women.


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Monash Oncology Research Institute