¹⁸F-Fluorodeoxyglucose PET-CT evaluation after one course of neoadjuvant therapy fails to predict pCR in HER2 + BC...

¹⁸F-FDG PET-CT has emerged as a powerful imaging tool for initial staging and prognosis evaluation of patients with Breast Cancer (BC). However, previous studies are inconsistent on attributing a predictive value to the pathological Complete Response (pCR) determined by PET-CT. Our objective was to assess the association between pCR and ¹⁸F-FDG PET-CT findings in patients with HER2+ BC in neoadjuvant setting.

We collected data from patients enrolled in the prospective and multicentric French clinical trial NeoTOP (NCT02339532) who underwent ¹⁸F-FDG PET-CT before and after their first course of neoadjuvant treatment (depending on topoisomerase 2-α amplification status: 3 cycles of FEC 100 followed by 3 cycles of Docetaxel + Trastuzumab + Pertuzumab or 6 cycles of Docetaxel + Carboplatin + Trastuzumab + Pertuzumab). PET response was evaluated with visual and quantitative methods, by measuring tumor uptake parameters (SUV and SUL maximal and mean values), then compared to the pCR established according to Chevallier's classification. \ RESULTS: Out of 86 patients, 45 had fully analysable PET and pathological data. pCR rate was 73.3%. Sensitivity and specificity of PET visual analysis for pCR diagnosis were 14.0-83.0% respectively. SUVmax baseline value was 12.0±7.2 and decreased by 55.0±21.0% after one cycle of treatment. Quantitative PET parameters and their variations were not significantly different between pCR and non-pCR patients (p>0.05 in all cases).

¹⁸F-FDG PET-CT before and after the first cycle of neoadjuvant treatment does not appear to be an effective tool to predict pCR in patients with HER2+ BC.