A review of the association between baseline [18F] fluorodeoxyglucose uptake and axillary pathological complete response in node-positive breast cancer patients: focus on clinical subtypes

The objective is to assess whether the degree of metabolic uptake of the primary tumor and axillary lymph nodes (ALNs) on baseline [18F] fluorodeoxyglucose ([18F]FDG) PET/CT is associated with the probability to achieve axillary pathologic complete response (pCR) in clinically node-positive (cN+) breast cancer patients treated with neoadjuvant systemic therapy (NST), overall and per clinical subtype. Studies that assessed the maximum standardized uptake value (SUVmax) in the primary tumor and ALNs on baseline [18F]FDG PET/CT and reported axillary pCR rates in patients diagnosed with cN+ invasive breast cancer treated with NST, followed by surgery, were searched. Area under the curve (AUC) values were obtained. A total of seven studies (561 patients) were included. The mean baseline SUVmax of the primary tumor ranged from 8.1 (±4.3) to 9.8 (±7.2). Mean baseline axillary SUVmax ranged from 6.0 (±5.6) to 7.3 (±6.2). The axillary pCR rate ranged from 38.0% to 48.1%. Considering the primary tumor, no study reported on the association between baseline SUVmax and the axillary pCR rate. Considering the ALNs, the AUC value for baseline axillary SUVmax to predict axillary pCR ranged from 0.52 [95% confidence interval (CI): 0.39-0.65; all subtypes included] to 0.74 (95% CI: 0.53-0.95; only human epidermal growth factor receptor 2+ and triple negative). In conclusion, no association between the primary tumor SUVmax on baseline [18F]FDG PET/CT and axillary pCR was found. Concerning the axilla, based on limited scientific evidence, the axillary SUVmax on baseline [18F]FDG PET/CT may be associated with axillary pCR after NST in cN+ breast cancer patients, however, potential differences between clinical subtypes should be considered.