Clinical complete response (cCR) after neoadjuvant chemoradiotherapy and conservative treatment in rectal cancer. Findings from the ACCORD 12/PRODIGE 2 randomized trial.

Background: During the ACCORD 12 randomized trial, an evaluation of the clinical tumor response was prospectively performed after neoadjuvant chemoradiotherapy. The correlations between clinical complete response and patient characteristics and treatment outcomes are reported.

Material And Methods: Between 2005 and 2008 the Accord 12 trial accrued 598 patients with locally advanced rectal cancer and compared two different neoadjuvant chemoradiotherapies (Capox 50: capecitabine+oxaliplatin+50Gy vs Cap 45: capecitabine+45Gy). An evaluation of the clinical tumor response with rectoscopy and digital rectal examination was planned before surgery. A score to classify tumor response was used adapted from the RECIST definition: complete response: no visible or palpable tumor; partial response, stable and progressive disease.

Results: The clinical tumor response was evaluable in 201 patients. Score was: complete response: 8% (16 patients); partial response: 68% (137 patients); stable: 21%; progression: 3%. There was a trend toward more complete response in the Capox 50 group (9.3% vs 6.7% with Cap 45). In the whole cohort of 201 pts complete response was significantly more frequent in T2 tumors (28%; p=0.025); tumors <4cm in diameter (14%; p=0.017), less than half rectal circumference and with a normal CEA level. Clinical complete response observed in 16 patients was associated with more conservative treatment (p=0.008): 2 patients required an abdomino-perineal resection, 11 an anterior resection and 3 patients benefited from organ preservation (2 local excision, 1 "watch and wait". A complete response was associated with more ypT0 (73%; p<0.001); ypNO (92%); R0 circumferential margin (100%).

Conclusion: These data support the hypothesis that a clinical complete response assessed using rectoscopy and digital rectal examination after neoadjuvant therapy may increase the chance of a sphincter or organ preservation in selected rectal cancers.