Patterns of adjuvant therapy use and survival outcomes in patients with rectal cancer not receiving neoadjuvant therapy in an Australian cohort.

675Background: Consensus international guidelines recommend the use of neoadjuvant chemo-radiotherapy in patients with stage II-III rectal cancer. Despite this, due to factors including inaccurate/under-staging, patient co-morbidities and acute presentations, a proportion will undergo up-front surgical resection. The survival benefit of adjuvant therapy is unclear in this real world, non-trial population. Methods: A retrospective analysis of patients presenting with stage II-III rectal adenocarcinoma in South Western Sydney and Illawarra Shoalhaven Health Districts, Australia, between 2006 to 2015 was performed. Data was extracted from electronic health records, with institutional ethics approval. Treatment modalities, clinicopathological, recurrence and survival data were analyzed. The primary endpoint was overall survival (OS) by treatment modality. Results: 549 patients were identified, of which 295 (54%) underwent up-front surgical resection without neoadjuvant therapy. Of this cohort, 137 (46%) had n...