Tumour regression grading after chemoradiotherapy for locally advanced rectal cancer: A near pathologic complete response does not translate into good clinical outcome

Abstract

BackgroundAfter preoperative chemoradiotherapy (CRT) for rectal cancer, clinically undetectable residual tumour deposits or pathologic lymph nodes may remain in the mesorectum. AimThe aim of this study was to report histopathological effects of CRT and factors affecting outcome in a uniformly treated series of locally advanced rectal cancer (LARC) patients. MethodsBetween 2004 and 2008, 107 patients with cT3 (threatening the mesorectal fascia or <5cm from the anal verge), cT4 or cN2 rectal cancer were treated with preoperative CRT (25×2Gy with capecitabine) and TME 6–8weeks later. Central histopathological review followed. Tumour regression grade (TRG) was scored in pCR, near-pCR, response and no response. Cox regression was performed to identify prognosticators. ResultsThe 3-year distant metastasis-free interval, disease-free rate and overall survival rate were 82%, 73% and 87% (median 44months follow-up). TRG consisted of 20% pCR, 11% near-pCR, 55% response and 14% no response. 6/21 pCR patients harboured nodal metastases. 5/12 near-pCR had ypT3 disease, while 6 harboured node metastases. 5/12 near-PCR patients developed distant metastases. ypN and TRG were powerful outcome discriminators. ConclusionThe high number of near-pCR with ypT3 or ypN1/2 and their poor outcome demonstrates that “watch-and-wait” in LARC patients should be applied with care.