Hypofractionated proton beam therapy for centrally located lung cancer

To clarify the efficacy and safety of hypofractionated proton beam therapy (PBT) for centrally located lung cancer.

We retrospectively reviewed 39 patients who received hypofractionated [≧3 Gy (relative biological effectiveness: RBE)/fraction] PBT for centrally located cT1-2N0M0 (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.

Twenty-four patients (62%) were treated with 80 Gy (RBE) in 20 fractions (112 Gy₁₀ ), whereas eight (21%) were treated with 66 Gy (RBE) in 10 fractions (109.56 Gy₁₀ ). 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 Gy₁₀ or higher showed significantly better PFS than those who received less than 110 Gy₁₀ , 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%).

Hypofractionated PBT may be a very safe and effective treatment option for centrally located early lung cancer.