Prognostic impact of radiation therapy to the primary tumor in patients with non-small cell lung cancer and oligometastasis at diagnosis

Purpose: We investigated prognostic factors associated with survival in patients with non-small cell lung cancer (NSCLC) and oligometastatic disease at diagnosis, particularly the influence of local treatment to the primary site on prognosis. Methods and Materials: From January 2000 through June 2011, 78 consecutive patients with oligometastatic NSCLC (<5 metastases) at diagnosis underwent definitive chemoradiation therapy (≥45 Gy) to the primary site. Forty-four of these patients also received definitive local treatment for the oligometastases. Survival outcomes were estimated using the Kaplan-Meier method, and risk factors were identified by univariate and multivariate analyses. Results: Univariate Cox proportional hazard analysis revealed better overall survival (OS) for those patients who received at least 63 Gy of radiation to the primary site (P=.002), received definitive local treatment for oligometastasis (P=.041), had a Karnofsky performance status (KPS) score >80 (P=.007), had a gross tumor volume ≤124 cm ³ (P=.002), had adenocarcinoma histology (P=.002), or had no history of respiratory disease (P=.016). On multivariate analysis, radiation dose, performance status, and tumor volume retained significance (P=.004, P=.006, and P<.001, respectively). The radiation dose also maintained significance when patients with and without brain metastases were analyzed separately. Conclusions: Tumor volume, KPS, and receipt of at least 63 Gy to the primary tumor are associated with improved OS in patients with oligometastatic NSCLC at diagnosis. Our results suggest that a subset of such patients may benefit from definitive local therapy.