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 circumferentialresection margin (CRM) positivity in rectal cancer. Induction chemotherapy (IC) before concurrentchemoradiation (CRT) has emerged as a new treatment modification. Impact of IC before concurrent CRT onCRM positivity in low rectal cancer remains to be independently studied. The objective of this study was todetermine CRM positivity in low rectal cancer, with and without prior IC, and to identify predictors of diseasefree and overall survival. Materials and
Methods: Patients who underwent surgery for rectal cancer between2005 and 2011 were retrospectively reviewed and divided into two groups. Group 1 received IC before CRTand Group 2 did not. Demographics, clinicopathological variables and CRM status were compared. Actuarial 5year 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 ahigh 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 positiveCRM 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] andnodal involvement [HR: 2, CI: 1.08-4, P=0.02] were independent predictors of relapse while pathological nodalinvolvement [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 predictorsof death.
Conclusions: In low rectal cancer, induction chemotherapy before CRT may significantly decreaseCRM positivity and improve 5 year overall survival.