Purpose: To determine the risk factors contributing to development of radiation pneumonitis (RP) in patients with lung cancer who undergo radiation therapy to the thorax.
Methods and materials: Development and severity of RP were retrospectively analyzed for 89 patients with lung cancer who underwent radiation therapy with or without chemotherapy at the National Shikoku Cancer Center Hospital between 1991 and 1995. The severity of RP was determined using a modified grading scale based on that of the Radiation Therapy Oncology Group and the European Organization for the Research and Treatment of Cancer.
Results: Fifty-two (58%) patients developed RP: 34 patients with Grade 1, 5 with Grade 2, 8 with Grade 3, and 5 with Grade 5 RP. Severe RP tended to develop earlier than less severe RP, but not to a significant extent (p = 0.151). On logistic regression analysis including both patient condition and treatment factors, development of Grade 1 or more severe RP was most frequently observed for Stage I-II disease (p = 0.011). The use of chemotherapy, large daily radiation dose, and once-daily fractionation (vs. twice-daily fractionation) were possibly related to the development of RP (p = 0.057, p = 0.069, and p = 0.092, respectively). For the group of 48 patients who underwent chemoradiation therapy, the use of large daily radiation dose was a significant risk factor for RP (p = 0.014). In addition, the use of once-daily fractionation was a marginally significant risk factor (p = 0.052). Among chemotherapy drugs administered, cisplatin was a favorable factor (p = 0.011), while adriamycin was a risk factor (p = 0.061).
Conclusions: In radiation therapy for lung cancer, administration of a large daily dose should be avoided in order to prevent RP, particularly when radiation therapy is combined with chemotherapy.