Metastasis directed therapy of metastatic colorectal cancer (mCRC) includes resection, radiofrequency ablation (RFA) and stereotactic radiotherapy (SBRT) of liver and/or lung metastases. The location of the primary tumor may influence survival in advanced disease. The aim of this study was to analyse the prognostic value of the primary tumors sidedness after local treatment of oligometastatic CRC in a national population based study.
Data was retrieved from the Danish Cancer Registry and the Danish National Patient Registry (DNPR) from all patients who underwent surgery for CRC between 2000-2013. Additional data from the DNPR included liver and/or lung metastasectomy, RFA or SBRT. Based on the surgical codes for primary tumor resection in DNPR, patients were grouped as right or left sided (including rectal cancer). Survival was calculated from the date of last recorded local treatment until death from any cause or end of follow-up. A Cox proportional hazard model was used to compute hazard ratios (HRs) for mortality between groups adjusting for age, gender, co-morbidity, nodal stage and site of local treatment.
A total of 38131 patients had surgery for a primary CRC and 2912 patients underwent a total of 3602 metastasis directed procedures. The median age was 64.9 years (range 20-92 years) and 59% were male. Local treatment modalities comprised liver surgery (n = 1616), lung surgery (n = 1075), liver RFA (n = 705), liver SBRT (n = 124) and lung SBRT (n = 82). In the locally treated cohort 590 and 2264 patients were resected for a right and left sided primary tumor, respectively, (unknown primary location n = 58). For all patients (n = 2912), the median survival was 3.8 years (95% CI 3.6-4.0). For patients with a right and left sided tumor, the median survival reached 3.2 years (95% CI 2.7-3.5) and 4.0 years (95% CI 3.8-4.2), respectively. With left sided as the reference the adjusted HR 1.20(95%CI 1.07-1.38, p = 0.003).
In this national population based study, we report a longer median survival for CRC patients with a left sided primary as compared to right sided primary tumor after local treatment for liver and lung metastasis.
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Department of Epidemiology, Aarhus University Hospital
A. Boysen: Advisory board: Bayer. All other authors have declared no conflicts of interest.