Neoadjuvant radiotherapy and outcomes of rectal cancer – comparison of rectal cancer management and outcomes in the setting of standard intraoperative anatomic dissection of the rectum. Single centre study.

Background: Neoadjuvant radiotherapy (NRT) has become an integral part of the multidisciplinary management of locally advanced rectal cancer. Whilst there is an abundance of literature on its effect in reducing local recurrence and improving cancer-specific survival, the standard use of Kaplan-Meier and Cox-regression analyses does not account for non-cancer related deaths as a competing risk. This cohort study aimed to use competing risks statistical method to examine the association between NRT and recurrence and cancer-specific death after potentially curative rectal cancer resection. Methods: A hospital database of prospectively collected data on clinical, operative, pathology and follow-up information of at least 5 years for all surviving patients were examined. The data were analysed by competing risks methods and multivariable regression models. Results: Six hundred and sixty-two patients between January 1995 and December 2014 met the inclusion criteria of the study. Following examination of the resection specimen, 594 patients underwent potentially curative resections, of which 151 received NRT. There were no statistically significant bivariate association between NRT and overall survival (HR 1.21, CI 0.95-1.53, p = 0.120), disease-free survival (HR 1.18, CI 0.94-1.53, p = 0.202) or local-only recurrence (HR 1.07, CI 0.46-2.50, p = 0.868). Competing risk methods found significant association between NRT and cancer-specific deaths (HR 1.72, CI 1.21-2.45, p = 0.003) as well as tumour recurrence at any site (HR 1.61, CI 1.16-2.25, p = 0.005). However, their significant association was diminished in multivariable models. Multivariable models found tumour with direct spread beyond muscular propria and presence of nodal metastases may have independent effect on survival and recurrence outcomes. Conclusions: Competing risks findings in this study showed significant association between NRT and cancer-specific deaths as well as tumour recurrence at any site