The impact of primary tumour resection and sidedness in patients with synchronous metastatic colorectal cancer (mCRC): Findings from the South Australian Metastatic Colorectal Cancer Registry (SAMCRC).

Abstract

739 Background: The benefit of primary tumour resection (PTR) in patients with synchronous mCRC is not clear. The influence of tumour location on PTR benefit is also uncertain. Methods: SAMCRC is a population based registry collating data from all patients in South Australia diagnosed with mCRC from February 2006. We examined outcomes according to whether the primary colorectal tumour was excised within 3 months of diagnosis or remained in situ; we also examined whether outcomes were affected by tumour side (right v left). Registry data was included for patients with synchronous metastic adenocarcinoma from colon or rectum. Exclusion criteria included metastasectomy, tumour resection within 7 days or death within 3 months of mCRC diagnosis. Kaplan Meier analysis was used for Survival. Tumour sidedness and PTR were analysed with a multivariate Cox proportional hazards model. Survival was measured from the landmark date (3 months from date of diagnosis). Results: 2575 patients with synchronous mCRC have entered the database, of which 1869 patients were eligible for the PTR analysis. 50.2% (n = 938) underwent PTR. 481 patients (51.3%) of the PTR analysis group had left-sided primary tumours whilst 436 had right sided tumours (46.5%) which was significant (p < 0.001). 63% of the PTR cohort were male (n = 1006). Site and age metastases were included in the multivariate analysis. PTR was associated with improved survival from landmark compared to no resection (15.0 mo vs 11.2 mo, 95% CI 15.0 – 16.3 vs 11.2 – 12.3, p = 0.031). In the entire synchronous mCRC group, left-sided tumours (62.1%) had a longer median survival (17.8 mo vs 10.4 mo, 95% CI 15.7 – 19.5 vs 10.4 – 11.7 p = < 0.001). An interaction test was performed for sidedness and was not significant. Conclusions: PTR was associated was associated with improvement in survival in this large population based registry. This finding did not differ signifcantly between right and left sided tumours. Survival was superior for patients with left sided tumours, in keeping with established data. Criteria for selection of patients with mCRC who benefit from PTR need to be defined.