Background: Management of asymptomatic stage IV colorectal cancer (CRC) with irresectable metastases remains controversial.

Objective: The study compared treatment outcomes between primary tumor resection (PTR) and no primary tumor resection (no PTR) in asymptomatic stage IV CRC patients with irresectable metastases.

Materials and Methods: Retrospective cohort study of asymptomatic stage IV CRC patients between 1 September 2006 and 31 August 2016. The inclusion criteria were asymptomatic stage IV CRC, histologically confirmed adenocarcinoma from primary tumor, patients age ≥18 years old, no primary tumor-related symptoms, and Eastern Cooperative Oncology Group (ECOG) performance status 2 or below. The exclusion criteria were symptomatic primary tumors such as bleeding, obstruction, and perforation that required surgery, resectable metastases, and patients with secondary cancer that was diagnosed within 5 years. Primary outcomes were complications that related to primary tumor, such as obstruction, perforation, bleeding, and severe tenesmus, and metastatic complications of cancer. Secondary outcome was median survival time.

Results: There are 135 asymptomatic stage IV CRC patients with irresectable metastases in this study. Complications from primary tumor occurred in 9 (10.98%) and 26 (49.06%) patients in PTR and no PTR groups (p<0.001), respectively. Metastatic complications of cancer occurred in 33 (40.24%) and 19 (35.85%) patients in PTR and no PTR groups (p=0.718), respectively. The median survival time in asymptomatic stage IV colorectal cancer with irresectable metastases was 46.45 months.

Conclusion: The data of no PTR group shows statistically significant complications from primary tumor compared with PTR group. However, there is no statistically significant difference in metastatic complications of cancer in both groups.

Keywords: Stage IV colorectal cancer; Primary tumor resection; Metastases; Colectomy; Synchronous metastases