Hypofractionated Proton Beam Therapy for Centrally Located Lung Cancer

Introduction To clarify the efficacy and safety of hypofractionated proton beam therapy ( PBT ) for centrally located lung cancer. Methods We retrospectively reviewed 39 patients who received hypofractionated [≧3 Gy (relative biological effectiveness: RBE )/fraction] PBT for centrally located cT 1‐2N0M0 (8th edition) lung cancer between 1999 and 2015. A tumour within 2 cm of the proximal bronchial tree was defined as a centrally located tumour. Results Twenty‐four patients (62%) were treated with 80 Gy ( RBE ) in 20 fractions (112 Gy 10 ), whereas eight (21%) were treated with 66 Gy ( RBE ) in 10 fractions (109.56 Gy 10 ). The median follow‐up period for censored patients was 48 months (range: 4–140). The 2‐year progression‐free survival ( PFS ) and overall survival ( OS ) rates were 86 and 100% for T1 disease and 56 and 94% for T2 disease, respectively. Patients who received 110 Gy 10 or higher showed significantly better PFS than those who received less than 110 Gy 10 , while no significant difference was noted in OS between the two groups. The sites of the first progression were local in six patients (27%), regional in seven (32%), distant in seven (32%), and local and distant in two (9%). Among the 13 patients with loco‐regional recurrence, only two (15%) received treatments with curative intent. Dyspnoea of grade 3 was noted in one patient (3%), and pneumonitis of grade 2 was noted in four patients (10%). Conclusion Hypofractionated PBT may be a very safe and effective treatment option for centrally located early lung cancer.