18F-FDG-PET metabolic tumour volume as a predictor of early response to neo-adjuvant chemotherapy in locally advanced breast cancer patients

Objectives The objective of the present study was to see whether the metabolic tumour volume (MTV) could serve as an early predictor in the assessment of response after 2-cycles of neo-adjuvant chemotherapy (NACT) in breast cancer.

Methods 17 females in the age of 49.6 ± 6.8 (mean, SD), with locally advanced breast cancer (LABC) underwent PET-CT scan before start and after 2-cycles of NACT. The MTV was segmented using RT Image, open source code package in the Interactive Data Language. The tumour foci were identified by the user on the maximum intensity projection image and then volume were segmented automatically by the region growing algorithm. Final histopathology following surgery after 6 cycles of NACT served as reference.

Results The Baseline PET tumour volume ranged from 6.8 –375cc, SUV_max ranged from 1.2–25, SUV_mean ranged from 0.8- 10.4 and the MTV ranged from 5.3-2051ml. The 2-cycle post NACT PET tumour volume ranged from 3.4 –122 cc, SUV_max ranged from 1.1 – 8.9, SUV_mean ranged from 0.6- 3.8 and the MTV ranged from 2.6-344 ml. The percentage reduction in the MTV after 2-cycles of NCAT as compared with the baseline MTV ranged from 2-98 %. The percent reduction in MTV post NCAT shows good correlation with the histopathology response following surgery after 6 cycles of NCAT in all patients except for one.

Conclusions Metabolic tumour burden can serve, as an early predictor of response to NACT. The ¹⁸F-FDG PET-CT can differentiate responders from non-responder after two cycles of NACT in patients with LABC