Survival benefits of asymptomatic primary tumor resection after bevacizumab plus FOLFIRI as first-line therapy for patients with metastatic colorectal cancer with synchronous unresectable metastasis.

56 Background: Metastatic colorectal cancer (mCRC) poses a clinical challenge and requires a combination of systemic therapy and conversion surgery. Although first-line chemotherapy and target therapy are considered the standard treatments for mCRC, the role of primary tumor resection (PTR) in asymptomatic synchronous mCRC with unresectable metastatic lesion after initial therapy remains relatively underexplored. Methods: A retrospective observational study was conducted from January 2015 to January 2021, involving 74 patients with synchronous mCRC who received bevacizumab plus FOLFIRI as first-line systemic therapy. All 74 patients had unresectable metastatic lesions confirmed through multidisciplinary team (MDT) discussion. Patients' characteristics, PTR data, and radiotherapy (RT) and overall survival (OS) outcomes were analyzed. The patients were categorized into a "PTR" group and a "No PTR" group and then further stratified into IVA, IVB, and IVC subgroups based on the initial mCRC stage. Additionally, four subgroups - namely "PTR(+)/RT(+)", "PTR(+)/RT(-)", "PTR(-)/RT(+)", and "PTR(-)/RT(-)" were formed to assess the combined effects of PTR and RT. Results: The median OS for all the patients was 23.8 months (20.5 - 27.1 months). The "PTR" group exhibited a significantly higher median OS of 25.9 months (21.3 - 30.5 months) compared with 21.4 months (15.8 - 27.1 months) in the "No PTR" group ( P = 0.048). Subgroup analyses revealed a trend of improved survival with PTR in patients with stage IVA and IVB; however, the results were not statistically significant ( P = 0.116 and 0.493, respectively). A subgroup analysis of PTR and RT combinations revealed no significant difference in median OS rates. Conclusions: For asymptomatic mCRC with synchronous unresectable distant metastasis. PTR following first-line therapy with bevacizumab plus FOLFIRI can provide a survival benefit, particularly in stage IVA/IVB patients compared with stage IVC patients. Additionally, RT for primary tumor did not provide an additional OS benefit in mCRC with unresectable metastasis. A prospective randomized trial with a larger sample size is essential to further elucidate the role of PTR in this context.