Palliative resection of the primary tumor actually extends survival in patients with metastatic colorectal adenocarcinoma, according to a report published online Nov. 4 in Annals of Surgery.

In what the investigators described as the first population-based study to assess trends in cancer-specific and overall survival among U.S. patients who did or did not undergo palliative removal of the primary tumor, the resection consistently conferred statistically significant and clinically meaningful survival benefits among 37,793 patients treated during a 12-year period.

“There is a heated debate in the medical and surgical oncology community regarding whether or not an asymptomatic primary tumor should be removed in patients with unresectable, synchronous cancer metastases,” wrote Dr. Ignazio Tarantino of the department of surgery, Kantonsspital St. Gallen (Switzerland) and the department of general, abdominal, and transplant surgery, University of Heidelberg (Germany) and his associates.

Current National Comprehensive Cancer Network guidelines recommend against palliative surgery in this setting, primarily because of evidence that leaving the primary tumor in situ seldom leads to life-threatening complications such as bleeding or bowel obstruction, while resection can cause complications and is not strictly necessary in terminally ill patients. But given these new findings of a significant survival benefit, “the dogma that [such tumors] never should be resected … must be questioned,” the investigators wrote.

Dr. Tarantino and his associates analyzed Surveillance, Epidemiology, and End Results (SEER) data for 23,004 patients (60.9% of the total study population) who underwent primary tumor resection and 14,789 (39.1%) who did not. The percentage of patients who had the surgery steadily declined throughout the study period.

Palliative removal of the primary tumor was a significant protective factor for overall survival (HR of death, 0.49) and for cancer-specific survival (HR of cancer death, 0.49) in both the primary data analysis and a proportional hazard regression analysis.

Patients undergoing resection tended to be younger and healthier than those who did not have the procedure, so the researchers performed a propensity-score matching analysis to account for baseline differences between the two study groups. After adjustment for numerous potential confounders, palliative primary tumor resection continued to exert a significant protective effect for overall and cancer-specific survival, with HRs of 0.40 and 0.39, respectively. The survival benefit also persisted, with identical hazard ratios, in two further sensitivity analyses of the data, Dr. Tarantino and his associates noted (Ann. Surg. 2014 Nov. 4 [doi: 10.1097/SLA.0000000000000860]).

The mechanism by which palliative resection imparts a survival benefit is not yet known, they added.

Major advances in systemic treatment of metastatic colorectal cancer were achieved during the study period, and survival improved accordingly across both groups of patients over time. “Because of the improvement in systemic treatment, we anticipated that the differences in survival between the subsets of patients who did and who did not undergo palliative primary tumor resection would decrease over time. However – against our a priori hypothesis – our analysis demonstrates the contrary,” the investigators noted.

No financial or material support was provided for this study. Dr. Tarantino and his associates reported having no financial disclosures.