Triple-negative breast cancer: Early assessment with 18F-FDG PET/CT during neoadjuvant chemotherapy identifies patients who are unlikely to achieve a pathological complete response

Objectives Triple-negative breast cancer (TNBC), characterized by negativity for estrogen and progesterone receptor and no HER2 over-expression, represents 15% of all invasive breast tumors. Patients with TNBC who do not achieve pathological complete response (pCR) with neoadjuvant chemotherapy (NAC) are at high risk of early relapse. We investigated whether changes in 18F-FDG tumor uptake can predict early such response to NAC.

Methods Twenty TNBC patients without distant metastases had 18F-FDG PET/CT at baseline and after the 2nd cycle of NAC. NAC was continued as planned, irrespective of PET results.

Results The change in 18F-FDG tumor uptake (SUVmax) between baseline and PET-2 ranged from 91% decrease to 13% increase (mean: -45%). At surgery, pCR was found in six (30%), and residual tumor (non-pCR) in 14 patients (70%). Four patients (20%) showed early relapse during follow-up; disease-free survival (DFS) was 77% at 3 years. Partition of patients with respect to a 42% decreases in FDG uptake formed two groups: metabolic responders (≥42% decrease) and non-responders (<42% decrease). Using this partition, pCR rate was 55% and 0% respectively (fisher exact test p-value = 0.014) and DFS at 3 years was 100% and 56% respectively (log-rank = 0.028).

Conclusions A less than 42% decrease in SUV after two cycles of NAC identifies a substantial fraction of patients in whom the probability of achieving pCR is very low and the risk of early relapse high. These patients can be entered trials involving novel therapeutic strategies (e.g., newer cytotoxic agents, PARP inhibitors +/- platinum salts, bevacizumab with chemotherapy, etc.)