The files provided here are were related to manuscript, entitled "Primary Tumor Resection with or without Metastasectomy for Left- and Right-sided Stage IV Colorectal Cancer: An Instrumental Variable Analysis", submitted for publication in BMC Gastroenterology.

There is still no clear evidence regarding survival with primary tumor resection plus metastasectomy (PMTR) or primary tumor resection alone (PTR) in Stage IV Colorectal Cancer patients. It is also unclear whether primary tumor location is predictive of the survival benefits of PMTR or PTR. In this population-level study, we evaluated the therapuetic value of PMTR and PTR in left- and right-sided stage IV colorectal cancer, using intrumental variable analysis to adjust for measured and unmeasured confounders, and estimate the effects of PMTR or PTR on overall survival. We demonstrate that increased use of PMTR benefits patients with left-sided tumors but not those with right-sided tumors, whereas increased use of PTR does not improve survival in either group. Thus, when selecting patients for PMTR, primary tumor location should be taken into consideration. In addition, routine use of palliative PTR in asymptomatic patients should be avoided.

The files include: crc4_cust_2016.zip crc5_cust_2016.zip crc9_cust_2016.zip crclo_cust_2016.csv R_code.R

The data cleaning and cleansing, and models building for using the R packages “tidyr”, “dplyr”, “tibble”, “data.table”, “tableone”, “caret”; verification and correction of analysis for using the R package “rms”; survival analysis and Cox analysis for using the R package “survival”, “survminer”; figure drawing for using R package “ggplot2”.