Evaluation of clinical practice over time for patients with stage II and III rectal cancer: a collaborative study of Newfoundland and Labrador and Ontario

Short, Ian P. B. (2021) Evaluation of clinical practice over time for patients with stage II and III rectal cancer: a collaborative study of Newfoundland and Labrador and Ontario. Masters thesis, Memorial University of Newfoundland.

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Abstract

Background: In 1990, the National Institutes of Health released the first published guidelines for the treatment of rectal cancer, which recommended chemo-radiation therapy in the postoperative setting for patients with stage II and III of the disease. Since then, numerous studies have suggested the superiority of neoadjuvant chemo-radiation therapy in terms of local control, acute and long-term toxic effects, patient compliance, and sphincter preservation. As a result, the current standard of care for patients with stage II and III rectal cancer has become neoadjuvant chemo-radiation therapy followed by surgery with curative intent. The objective of this research is to evaluate the changes made to the clinical practice of rectal cancer over time by comparing the effects of neoadjuvant chemo-radiation therapy to standard therapy on patient survival and disease recurrence. Methods: We examined the clinicopathological data for a sample of 757 confirmed cases of rectal adenocarcinoma collected from 1 of 3 cohorts: the Newfoundland Colorectal Cancer Registry from 1997 to 2003, the Ontario Familial Colorectal Cancer Registry from 1997 to 2000, and the single practice of a general surgeon working in Newfoundland and Labrador from 1993 – 2014. The primary outcome of our study was overall survival in patients with stage II and III of the disease, which was measured from the date of diagnosis to the date of death. We investigated the effect of neoadjuvant chemo-radiation therapy on overall survival for these patients. Results: For patients with stage I-IV rectal cancer, age, anterior resection surgery, complete excision, grade, vascular and perineural invasion, and stage were independent predictors of overall survival (p < 0.05). For patients with stage II and III of the disease, age, anterior resection surgery, complete excision, grade, stage, and the presence of perineural invasion were independently associated with overall survival (p < 0.05). Again, no significant association between neoadjuvant therapy and patient survival was observed independent of these variables. The rate of neoadjuvant chemo-radiation therapy was significantly higher for stage II and III patients diagnosed after December 2003 (5% vs. 41%, p < 0.001). For this cohort, age, sex, stage, and vascular invasion were independent significant predictors of overall survival (p < 0.05). Again, neoadjuvant chemo-radiation therapy had no significant effect on survival. However, the relative risk for neoadjuvant chemo-radiation therapy was 0.428 (p= 0.107). Conclusions: In the cohort with stage II and III rectal cancer diagnosed after 2003, the magnitude of the relative risk for neoadjuvant chemo-radiation suggested benefit, but it did not achieve statistical significance because of the inadequate power caused by the small study size.

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