An interim 18F-FDG PET/CT exam after two cycles of neoadjuvant chemotherapy was predictive of pathologic response and disease-free survival in patients with triple-negative breast cancer, an aggressive subtype of breast cancer, according to a prospective study published online Jan. 12 in the Journal of Nuclear Medicine.
Triple-negative breast cancer, an aggressive subtype, represents 15 percent of invasive breast tumors and is characterized by the lack of estrogen and progesterone receptors and the absence of HER2 overexpression. While patients with triple-negative breast cancer have a relatively poor outcome, with higher relapse rates than for other breast tumor types, these aggressive tumors have more intrinsic responsiveness to neoadjuvant chemotherapy than estrogen receptor–positive tumors, according to the study authors.
David Groheux, MD, of the department of nuclear medicine at Saint-Louis Hospital in Paris, and colleagues conducted this prospective study to investigate whether early changes in 18F-FDG tumor uptake during neoadjuvant chemotherapy can predict outcomes.
In the 30-month study, the researchers evaluated 20 consecutive patients with stage II or III breast carcinoma and a triple-negative phenotype with 18F-FDG PET/CT at baseline and after the second cycle. Neoadjuvant chemotherapy was continued irrespective of PET results. Four patients with distant metastases identified at initial staging were not included.
After completion of neoadjuvant chemotherapy, all patients underwent breast-conserving surgery or mastectomy and dissection of axillary lymph nodes.
At surgery, six patients had a pathologic complete response, whereas 14 had residual tumor. Four patients showed early relapse (in the two years after surgery), according to the authors. There were 11 metabolic responders and nine non-responders using a 42 percent decrease in maximum standardized uptake value as a cutoff. In non-responding patients, the risk of residual tumor at surgery was 100 percent (vs. 45 percent in responders), and the risk of early relapse was 44 percent (vs. 0 percent).
Groheux et al found that a less than 42 percent decrease in 18F-FDG uptake at two cycles means residual tumor at the end of neoadjuvant chemotherapy and a high risk of early relapse.
Thus, the authors concluded that in patients with triple-negative breast cancer, the change in 18F-FDG tumor uptake after two cycles of neoadjuvant chemotherapy “offers powerful stratification of patient outcomes. It early identifies poor metabolic responders who would end up with residual tumor at the end of the planned neoadjuvant chemotherapy regimen and who have a high risk of early relapse.”