Definitive Photon or Proton Radiotherapy for Oligo-recurrences at the Regional Lymph Nodes after Surgery in Patients with Non-Small Cell Lung Cancer

Abstract

To evaluate outcomes of definitive radiotherapy (RT) for oligo-recurrences at the regional lymph nodes after surgery in patients with non-small cell lung cancer (NSCLC). Between January 2003 and December 2016, 33 patients were selected from our database for this analysis. The selection criteria were as follows: a) lymph node recurrence at the hilar, the mediastinum, and the supraclavicular fossa after surgery, b) no recurrence/metastasis at other than the lymph nodes, and c) receiving photon or proton RT ≥ 60 Gy/GyE. Twenty-two patients were men, and the median age was 68 years (range, 51 – 80 years). The pathological stage according to UICC 7th classification was Stage I in 14, II in 5, III in 12, IV in 1, and unknown in 1. Twelve patients had squamous cell carcinoma, 15 had adenocarcinoma, and the remaining 6 had others. The median time from the surgery to the recurrence was 14.8 months (range, 2.2 – 61.0 months). Thirty (91%) patients underwent positron emission tomography/computed tomography before RT. Their rN stages were rN1 in 3, rN2 in 20, and rN3 in 10. The lymph node metastasis at the single and multiple stations were observed in 15 and 18 patients, respectively. The elective nodal irradiation was performed in 30 patients, and 17 received proton RT. Concurrent chemotherapy was administered in 10 patients. The median follow-up time from the first day of salvage RT was 35.2 months (range, 5.9 - 89.6 months) for all patients. The 3-year overall survival, progression-free survival, and distant metastasis-free survival rates after RT were 63.8%, 45.1%, and 53.6%, respectively. In 18 (54%) of 33 patients, disease recurrences occurred and initial failure sites were observed at regional lymph node in 10 (in-field: n = 4, out-field: n = 6), at distant organs in 6, and both of them in 2 patients. The 3-year control within the irradiated field and regional control rates were 79.7%, and 63.3%, respectively. Concurrent chemotherapy improved the 3-year regional control rate compared with RT alone (87.5% vs 53.9%, p = 0.039). Proton RT had a tendency to improve the 3-year regional control rate compared with photon RT (76.6% vs 50.0%, p = 0.084). No Grade 4 or severe acute and late non-hematologic toxicity developed, but Grade 3 esophagitis and esophageal stricture were observed in each patient. Definitive RT for NSCLC patients with oligo-recurrence at the regional lymph nodes after surgery is considered to be an effective treatment option with high local control rate.