Effects of proton and combined proton/photon beam radiation on pulmonary function in patients with resectable but medically inoperable non-small cell lung cancer.

Study Objectives: We evaluated the effects on pulmonary function of irradiating lung cancer with protons alone or protons combined with photons.

Design: Prospective phase I/II study.

Setting: University medical center.

Patients And Interventions: Ten patients with stage I-II non-small cell lung cancer (NSCLC) and FEV(1) < or = 1.0 L were irradiated with protons to areas of gross disease only, using 51 cobalt gray equivalents (CGE) in 10 fractions (protocol 1). Fifteen patients with stage I-IIIA NSCLC and FEV(1) > 1.0 L received 45-Gy photon irradiation to the primary lung tumor and the mediastinum, plus a 28.8-CGE proton boost to the gross tumor volume (protocol 2).

Measurements: Pulmonary function was evaluated prior to treatment and 1 month, 3 months, and 6 to 12 months following irradiation.

Results: In patients receiving protocol 1, no significant changes in pulmonary function occurred. In patients receiving protocol 2, at 6 to 12 months, the diffusion capacity of the lung for carbon monoxide had declined from 61% of predicted to 45% of predicted (p < 0.05), total lung capacity had declined from 114% of predicted to 95% of predicted (p < 0.05), and residual volume had declined from 160% of predicted to 132% of predicted (p < 0.05). Airway resistance increased from 3.8 to 5.2 cm H(2)O/L/s (p < 0.05). No statistically significant changes occurred in vital capacity, FEV(1), or PaO(2).

Conclusions: Our observations indicate that it is feasible to apply higher-than-conventional doses of radiation at a higher-than-conventional dose per fraction without excess pulmonary toxicity when conformal radiation techniques with protons are used.