Can induction chemotherapy before concurrent chemoradiation impact circumferential resection margin positivity and survival in low rectal cancers?

BACKGROUND: Distance from anal verge and abdominoperineal resection are risk factors for circumferential resection margin (CRM) positivity in rectal cancer. Induction chemotherapy (IC) before concurrent chemoradiation (CRT) has emerged as a new treatment modification. Impact of IC before concurrent CRT on CRM positivity in low rectal cancer remains to be independently studied. The objective of this study was to determine CRM positivity in low rectal cancer, with and without prior IC, and to identify predictors of disease free and overall survival.
MATERIALS AND METHODS: Patients who underwent surgery for rectal cancer between 2005 and 2011 were retrospectively reviewed and divided into two groups. Group 1 received IC before CRT and Group 2 did not. Demographics, clinicopathological variables and CRM status were compared. Actuarial 5 year disease free survival (DFS), overall survival (OS) and independent predictors of survival were determined.
RESULTS: Patients in the IC group presented with advanced stage (Stage 3=89.2% versus 75.4%) (P=0.02) but a high rate of total mesorectal excision (TME) (100% versus 93.4%) (P=0.01) and sphincter preservation surgery (54.9 % versus 22.9%) (P=0.001). Patients with low rectal cancer who received IC had a significantly low positive CRM rate (9.2% versus 34%) (P=0.002). Actuarial 5 year DFS in IC and no IC groups were 39% and 43% (P=0.9) and 5 year OS were 70% and 47% (P=0.003). Pathological tumor size [HR: 2.2, CI: 1.1-4.5, P=0.01] and nodal involvement [HR: 2, CI: 1.08-4, P=0.02] were independent predictors of relapse while pathological nodal involvement [HR: 2.6, CI: 1.3-4.9, P=0.003] and IC [HR: 0.7, CI: 0.5-0.9, P=0.02] were independent predictors of death.
CONCLUSIONS: In low rectal cancer, induction chemotherapy before CRT may significantly decrease CRM positivity and improve 5 year overall survival.