The importance of pathological downstaging and the circumferential margin in rectal carcinomas treated with neoadjuvant chemoradiation

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3642 Introduction: Chemoradiation prior to surgery is now a common approach in the treatment of locally advanced rectal cancer. This report describes the resection, survival and local relapse rates of patients treated over an 8-year period at Mount Vernon Hospital and highlights the importance of pathological downstaging. Methods: Between 1994 and 2002, 155 patients with a locally advanced adenocarcinoma of the rectum were treated, with a median follow-up of 25 months. T stages were: T2:2, T3:59, T4:94. Median age 67 years, male: female ratio 73:27%. The radiotherapy dose was 45Gy in 25 fractions over 5 weeks. 5-FU was given as a 60 minutes infusion on days 1–5 and 29–33, at 350mg/m2, following low dose folinic acid. Surgery was performed in 122 patients. Actuarial survival, local control, resection margins and toxicity rates, according to CTC criteria were assessed. Results: Overall median survival (OS) was 37 months with a 34% 5-year OS. Median disease-free Survival (DFS) was 28 months with a 31% 5-year DFS. Resected specimens revealed 12% had had a complete pathological response (CPR) and pathological downstaging (PS) to pT0/1/2 was achieved in 28%. The 3-year DFS in PS was 52% compared to 9% in no PS (p<0.001), the 3-year OS was 64% versus 25% (p=0.0001). An overall R0 resection rate of 63% (98/155) was achieved. The 5-year DFS in R0 was 68% compared to 25% in R1/2 (p=0.0032). The 5-year OS was 72% versus 30% (p=0.020). 93% of patients achieved 100% compliance. Local recurrence (LR) rates were higher in the R1/2 group at 62% versus 10% in R0 and distant metastases rates were also higher in R1/2 75% versus 29% in R0. 93% of patients achieved 100% compliance. Conclusion: Survival is poor in patients with locally advanced rectal carcinoma. However, chemoradiation with 5-FU can produce effective downstaging and toxicity is manageable. This study highlights that improving the rates of pathological downstaging and R0 resections will lead to lower LR and DM rates, ultimately leading to an improved survival. No significant financial relationships to disclose.