Use of tumor site as a prognosticator: Population-based analysis of rectosigmoid and rectum cancers

Abstract

4123 Background: The study examines the prognostic significance of tumor location exclusively in rectosigmoid and rectal cancers. Although tumor location has traditionally been regarded as a prognostic determinant, data in support of this claim are lacking. We set out to determine this using data from a large population-based California Cancer Registry (CCR). Methods: A retrospective analysis of surgically treated cancer cases involving the rectum and rectosigmoid from 1994–2006 with a follow-up until January 2008 in CCR was conducted. Sub-site tumor location of the cancers involving the rectum was either defined as rectosigmoid or mid/distal rectum. Site-specific survival analyses were conducted by Kaplan-Meier method and hazard ratio calculated using Cox proportional hazard ratios (HR). Results: A total of 33,418 rectal cancer cases were identified, including 12,407 (37.1%) rectosigmoid cancers and 21,011 (62.9%) mid/distal rectum cancers. No significant differences by tumor location were noticed for age, gender, stage, histological type, grade or socioeconomic status. Fewer rectosigmoid cancers received radiation (81.9% vs. 62.3% p=<0.0001)) compared to mid/distal rectum cancers. After adjustment for treatment and relevant clinical factors, an improved rate of CRC-specific survival was noticed in non-metastatic rectosigmoid cancers when compared to cancers involving the mid/distal rectum. A significant decrease in mortality was observed in Stage-I [HR- 0.74(0.63–0.86)], Stage-II [HR-0.76(0.69–0.85)] and Stage-III [HR- 0.90 (0.83–0.98)] rectosigmoid cancers when compared to mid/distal rectum cancers. Number of lymph nodes examined (>12 vs. <12) was an independent prognostic factor for survival in Stage-II patients [HR-0.74 (0.63–0.87)]. Conclusions: Among locoregional cases, rectosigmoid cancers were found to have an improved CRC-specific survival compared to mid/distal rectum cancers, which was independent of other relevant clinical factors. [Table: see text] No significant financial relationships to disclose.