18F-FDG PET/CT for the Early Evaluation of Response to Neoadjuvant Treatment in Triple-Negative Breast Cancer: Influence of the Chemotherapy Regimen

Patients with triple-negative breast cancer (TNBC) have poor outcome when pathologic complete response (pCR) is not reached after neoadjuvant chemotherapy. Early prediction would be helpful. We evaluated the association between metabolic response after 2 cycles of neoadjuvant chemotherapy, pCR, and outcome in patients receiving 2 different anthracycline-based regimens (conventional and intensified). Methods: Of 77 consecutive TNBC patients, 23 received EC-D (4 cycles of epirubicin + cyclophosphamide followed by 4 cycles of docetaxel at conventional doses) and 55 received a dose-intensified, dose-dense concomitant regimen of epirubicin + cyclophosphamide (historically called SIM) for 6 cycles. PET/CT with F-18-FDG was performed at baseline and after 2 cycles of neoadjuvant chemotherapy. The associations between clinical factors, biologic factors, early metabolic change, pCR, and event-free survival (EFS) were examined (log-rank test). Results: Of the 78 patients, 29 (37%) achieved pCR. The change in SUVmax (Delta SUVmax) after 2 cycles was more pronounced in patients who achieved pCR (-72% vs. -42%; P < 0.0001). Delta SUVmax was more pronounced under SIM than under EC-D (-68% vs. -35%, P = 0.009), and there was a trend for a higher pCR rate (44% vs. 22%, P = 0.078). Twenty-two patients relapsed and 10 of them died (median follow-up, 34 mo). pCR was associated with EFS (log-rank, P = 0.001). Delta SUVmax was also significantly associated with EFS both in patients receiving SIM (P = 0.028) and in those receiving EC-D (P = 0.021). The optimal Delta SUVmax for predicting pCR and EFS was, however, specific to the treatment regimen. EFS was not associated with tumor grade (P = 0.98), histologic subtype (P = 0.17), or clinical stage (P = 0.097). Conclusion: Early metabolic change during neoadjuvant chemotherapy can predict pathologic response and EFS in TNBC patients under different chemotherapy regimens. However, the metabolic response varies with the type of chemotherapy.