Daniel Reinhorn, Yulia Kundel, Noa Gordon, Judit Prus, Sara Morgenstern, Nir Wasserberg, David Groshar, Hanna Bernstine, Baruch Brenner
This multicenter study provides preliminary real-world evidence on W&W after cCR in highly selected patients with pMMR/MSS LARC treated with immunotherapy-containing neoadjuvant regimens, but larger prospective comparative studies with longer follow-up are required before its feasibility and oncological safety can be established.
BACKGROUND: Early prediction of pathological response to neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer (LARC) may help guide individualized treatment strategies. This prospective clinical trial aimed to evaluate whether interim 18F-fluorodeoxyglucose (18FDG)-positron emission tomography (PET)-computed tomography (CT) performed after 2 weeks of nCRT predicts histological response, including pathological complete response (pCR) and tumor regression grade (TRG).
METHODS: Twenty-one LARC patients receiving nCRT followed by surgery were included. 18FDG-PET-CT was performed at baseline and after 2 weeks of nCRT. Maximum and mean standardized uptake values (SUV-max and SUV-mean) and metabolic tumor volume (MTV) were calculated at both time points. pCR and TRG were assessed, and correlations between PET parameters and histological response were analyzed.
RESULTS: No significant differences in ΔSUV-mean%, ΔSUV-max%, and ΔMTV% were found between pCR and non-pCR groups or between TRG I-II and TRG III-V groups. Absolute SUV-mean and SUV-max values at baseline, and SUV-max and MTV values at 2 weeks, differed significantly between pCR and non-pCR groups. ROC analyses demonstrated discriminatory ability for predicting pCR, with area under the curve (AUC) values of 0.79-0.82.
CONCLUSIONS: Early metabolic response after 2 weeks of nCRT did not correlate with pCR or TRG in LARC. Absolute SUV-mean and SUV-max values at baseline and absolute SUV-max and MTV values at 2 weeks showed predictive value for pCR.