Maximum standardized uptake value on FDG-PET predicts survival in stage I non-small cell lung cancer following carbon ion radiotherapy

The present study (University Hospital Medical Information Network study no. UMIN000003797) aimed to evaluate whether the maximum standardized uptake value (SUVmax) of pretreatment 18F‑fluorodeoxyglucose‑positron emission tomography (FDG‑PET) is prognostic factor for stage I non‑small cell lung cancer (NSCLC) treated with carbon ion radiotherapy (C‑ion RT). Patients treated between June 2010 and June 2013 at Gunma University Heavy Ion Medical Center (Maebashi, Japan) on a prospective protocol were included in the present study. Patients with T1a‑b and T2a NSCLC were treated with C‑ion RT at a dose of 52.8 Gy [relative biological effectiveness (RBE)] and 60.0 Gy (RBE), respectively, in four fractions. Prior to treatment, all patients underwent FDG‑PET, in which the SUVmax of primary tumors was evaluated. Local control, progression‑free survival (PFS), and overall survival (OS) were calculated. A total of 45 patients were analyzed and the median follow‑up period was 28.9 months. The 2‑year local control, PFS and OS rates for all patients were 93, 78 and 89%, respectively. The mean SUVmax of primary tumors was 5.5, and patients were divided into higher (≥5.5) and lower (<5.5) SUVmax groups. The 2‑year PFS rates were 61 and 89% for the higher and lower SUVmax groups, respectively (P=0.01), and the 2‑year OS rates for the higher and lower SUVmax groups were 76 and 96%, respectively (P=0.01). The higher SUVmax group exhibited a significantly worse PFS and OS compared with the lower SUVmax group; however, the SUVmax was not associated with the local control rate. In total, 2 patients (4%) experienced grade 2 or 3 radiation pneumonitis, with their symptoms improved through conservative treatment. No patients experienced any grade 4 or 5 toxicities. The results of the present study indicate that pretreatment SUVmax is a prognostic indicator for outcomes in patients with stage I NSCLC treated with C‑ion RT.