Outcomes of Carbon-Ion Radiation Therapy Versus Photon Therapy for Isolated Paraortic Lymph Node Recurrence From Colorectal Cancer.

Abstract

To assess the effectiveness of carbon-ion radiation therapy (CIRT) versus that of photon radiation therapy (RT) in patients with isolated paraortic lymph node metastasis from colorectal cancer postcurative surgery. A retrospective analysis was conducted on 116 patients, including 53 treated with CIRT and 63 with photon RT. The primary endpoint was local control (LC), with progression-free survival (PFS) and overall survival (OS) as secondary endpoints. Kaplan-Meier and Cox regression analyses were used to evaluate outcomes. A propensity score matching analysis was also performed to adjust for baseline imbalances. At a median follow-up of 54.8 months for surviving patients, CIRT was associated with higher 2-year LC than photon RT (78.9% vs 68.1%, P = .028). Cox regression analysis identified CIRT (hazard ratio, 2.152; 95% confidence interval, 1.082-4.279) and a smaller gross tumor volume at RT as significant independent predictors of improved LC. The difference in LC remained significant after propensity score matching (2-year 78.9% vs 63.3%, P = .036). No significant differences in PFS or OS were observed between the groups. Grade 2 or higher acute gastrointestinal toxicity occurred in 17.4% of the photon RT group but was absent in the CIRT group. Acute hematologic toxicity of grade 2 or higher occurred in 22.6% of the CIRT group and 17.5% of the photon RT group. Late toxicity, reported only in the photon RT group (11.1%), consisted of mild gastrointestinal symptoms. CIRT demonstrated superior LC to photon RT in the treatment of isolated paraortic lymph node metastases, with a more favorable toxicity profile. Although no significant differences were observed in PFS or OS, careful patient selection and integration of systemic therapies may further optimize outcomes.