Diabetes mellitus is a predictive factor for radiation pneumonitis after thoracic radiotherapy in patients with lung cancer.

Purpose: We evaluated the effects of diabetes mellitus (DM) and DM-related serologic factors (HbA1c and fasting glucose) on the development of radiation pneumonitis in patients with lung cancer. Methods: We retrospectively analyzed the clinical data of 123 patients with lung cancer treated with radiotherapy. Radiation pneumonitis was scored according to the toxicity criteria of the Radiation Therapy Oncology Group. We used binary logistic regression analysis to find significant predictive factors for the development of grade >= 3 radiation pneumonitis. Results: On univariable analysis, V20, mean lung dose, DM, HbA1c, and fasting glucose level were significantly associated with the development of grade >= 3 radiation pneumonitis. On multivariable analysis, V20, mean lung dose, DM, HbA1c, and fasting glucose level remained significant predictive factors for grade >= 3 radiation pneumonitis. The incidence of grade >= 3 radiation pneumonitis was 44.4% in patients with DM and 20.7% in patients without DM. The incidence of grade >= 3 radiation pneumonitis was 12.7% for HbA1c level <= 6.15% and 41.5% for HbA1c level >6.15%. The incidence of grade >= 3 radiation pneumonitis was 17.2% for fasting glucose level <= 121 mg/dL and 35.5% for fasting glucose level 121 mg/dL. Conclusion: DM, HbA1c, and fasting glucose level are significant predictive factors for the development of grade >= 3 radiation pneumonitis in patients with lung cancer. Patients with DM, patients who have HbA1c >6.15%, and patients who have fasting glucose >121 mg/dL should be treated with greater caution.