Prognostic value of molecular and radiologic characteristics on dedicated breast [<SUP>18</SUP>F]FDG PET/MRI in breast cancer patients treated with neoadjuvant chemo(targeted) therapy: a retrospective cohort study

Background This study aimed to investigate the prognostic value of molecular and radiologic characteristics of the primary tumour and axillary lymph nodes (ALNs) on dedicated breast [F-18]FDG PET/MRI in terms of event-free survival (EFS; recurrence and/or death) in breast cancer patients treated with neoadjuvant chemotherapy (NAC). Patients diagnosed with cT2-4N0 or cT1-4N + breast cancer underwent dedicated breast [F-18]FDG PET/MRI pre-, mid-, and post-NAC for response assessment between 2015-2017. Follow-up data per patient on recurrence and death were collected up to July 2025. To evaluate the prognostic value of variables for EFS, time-to-event analyses were used. P-values < 0.10 were considered to indicate statistical significance. Results 41 patients with 42 breast tumours underwent dedicated breast [F-18]FDG PET/MRI pre-, mid- and post-NAC for response assessment. Median follow-up time was almost nine years. Univariate Cox regression showed no significant association between pre- and mid-NAC PET- and MRI-derived parameters and EFS. Post-NAC, a higher maximum standardized uptake value (SUVmax; HR 1.41 [90% CI 1.04-1.92], p = 0.029), SUVpeak (HR 1.79 [90% CI 1.04-3.09], p = 0.035), SUVmean (HR 1.80 [90% CI 1.01-3.22], p = 0.046), tumour size (HR 1.04 [90% CI 0.99-1.09], p = 0.087) and signal enhancement ratio (SER; HR 6.46 [90% CI 0.79-52.55], p = 0.081) of the primary tumour were significantly (p < 0.10) associated with recurrence and/or death. Conclusions For PET- and MRI-derived parameters, several post-NAC values were predictive of EFS, but no significant association between pre- and mid-NAC values and EFS was found.