The predictive role of baseline pulmonary function test in lung carcinoma patients for radiation-induced lung toxicity treated with conformal radiation therapy.

Introduction: Radiation-induced lung toxicity (RILT) is a major concern in patients who receive radiation to thorax. The purpose of the study was to evaluate the changes of pulmonary function tests (PFTs) in lung carcinoma patients treated with three-dimensional conformal radiation therapy (3-D CRT) and relation RILT with dosimetric and nondosimetric factors.

Methods: This was a prospective observational study which included 65 patients of lung carcinoma treated with 3-D CRT. PFTs were assessed before the radiotherapy and at third and sixth month post-radiation therapy. Radiation pneumonitis (RP) was graded according to National Cancer Institute Common Toxicity Criteria (CTCAE) version 4.0.

Results: Majority of patients already had poor lung function before commencing the radiotherapy. There was a modest decrease in pulmonary function after radiation therapy with (3-D CRT). Postradiotherapy, at third month, eight patients (12%) and at the sixth month, 16 patients (25%) were observed with Grade II RP. At the third month, the nondosimetric factors, age >65 years (P = 0.027) and pretreatment Diffusion capacity of the Lung for Carbon monoxide (DLCO) 60% (P = 0.03) were significantly related to grade ≥ II Radiation pneumonitis (RP). Among dosimetric factors, mean lung dose ≥20 Gy (P = 0.001) and volume receving 20Gy ≥35% (P = 0.05) were significantly related to grade ≥ II RP. These factors were also related to grade ≥ II RP at the sixth month with a significant P value.

Conclusion: There is a progressive decrease in pulmonary function after (3-D CRT) in lung carcinoma patients. The study suggested that the baseline PFT may be utilized for the identification of high-risk patients for RILT before starting the radiotherapy in lung carcinoma.