Early prediction of histopathological response of rectal tumors after one week of preoperative radiochemotherapy using ¹⁸F-FDG PET-CT imaging. A prospective clinical study.

Goldberg, Natalia; Kundel, Yulia; Purim, Ofer; Bernstine, Hanna; Gordon, Noa; Morgenstern, Sara; Idelevich, Efraim; Wasserberg, Nir; Sulkes, Aaron; Groshar, David; Brenner, Baruch

Background: Preoperative radiochemotherapy (RCT) is standard in locally advanced rectal cancer (LARC). Initial data suggest that the tumor's metabolic response, i.e. reduction of its 18 F-FDG uptake compared with the baseline, observed after two weeks of RCT, may correlate with histopathological response. This prospective study evaluated the ability of a very early metabolic response, seen after only one week of RCT, to predict the histopathological response to treatment. Methods: Twenty patients with LARC who received standard RCT regimen followed by radical surgery participated in this study. Maximum standardized uptake value (SUV-MAX), measured by PET-CT imaging at baseline and on day 8 of RCT, and the changes in FDG uptake (ΔSUV-MAX), were compared with the histopathological response at surgery. Response was classified by tumor regression grade (TRG) and by achievement of pathological complete response (pCR). Results: Absolute SUV-MAX values at both time points did not correlate with histopathological response. However, patients with pCR had a larger drop in SUV-MAX after one week of RCT (median: -35.31% vs ?18.42%, p = 0.046). In contrast, TRG did not correlate with ΔSUV-MAX. The changes in FGD-uptake predicted accurately the achievement of pCR: only patients with a decrease of more than 32% in SUV-MAX had pCR while none of those whose tumors did not show any decrease in SUV-MAX had pCR. Conclusions: A decrease in ΔSUV-MAX after only one week of RCT for LARC may be able to predict the achievement of pCR in the post-RCT surgical specimen. Validation in a larger independent cohort is planned.

RADIOCHEMICAL analysis; CANCER patients; RADIOTHERAPY; PHOTOTHERAPY; MEDICAL electronics

Radiation Oncology, 2012, Vol 7, Issue 1, p124

1748-717X

Academic Journal

10.1186/1748-717X-7-124