Interruptions of high-dose radiation therapy decrease long-term survival of favorable patients with unresectable non-small cell carcinoma of the lung: analysis of 1244 cases from 3 Radiation Therapy Oncology Group (RTOG) trials

Abstract

Purpose: To determine if prolonged treatment time adversely affects survival for patients with inoperable non-small cell carcinoma of the lung.

Methods and materials: Patients enrolled on three randomized studies (RTOG 8311, 8321, 8403) between 1983-1989 formed the database. Previous analyses found that the addition of thymosin (8321) or prophylactic cranial irradiation (8403) failed to prolong survival: both studies used thoracic irradiation with standard fractionation to 55-60 Gy in 30 fractions. In 8311, patients were treated by hyperfractionated radiation therapy to randomly assigned total doses of 60.0 Gy, 64.8 Gy, 69.6 Gy, 74.4 Gy or 79.2 Gy, 1.2 Gy twice daily, 5 days per week. Patients analyzed received +/- 4% of the assigned total dose and lived > 90 days (to ensure that all patients would have completed treatment). Completion < 5 days beyond protocol specifications was classified as "per protocol." Elapsed treatment time exceeding specifications by 5-9 days was a minor deviation, 10-13 days was a major deviation-acceptable, and > or = 14 days was a major deviation-unacceptable. Absolute survival was the endpoint to evaluate the effect of delays. The log rank statistic was used to test for survival differences in the univariate setting, the Cox regression model was used in the multivariate setting.

Results: Of 293 patients treated with standard fractionation, eight (2.7%) had deviations from the specified treatment time (six minor, two major-acceptable). With hyperfractionation, 90 (15%) patients had deviations (40 minor, 21 major-acceptable, 29 major-unacceptable). As the assigned dose increased, the deviation rate increased (9.7% for 60.0 Gy vs. 20.8% for 79.2 Gy). Survivals for hyperfractionation patients with any deviations in treatment time were significantly shorter than those treated "per protocol" (p = 0.16): estimated 2- and 5-years rates were 24% and 10% versus 13% and 3%, respectively. Multivariate analyses showed the delay effect to be entirely in patients treated with 69.6 Gy or higher; there was also dependence upon the patients' prognosis. In patients with favorable prognosis (KPS 90-100, weight loss < or = 5%, no N3), the difference in survival was pronounced (33% and 15% vs. 14% and 0% at 2- and 5-years, respectively). Such differences were not found in patients with unfavorable prognostic factors.

Conclusions: Interruptions delaying completion of planned radiation therapy were more frequent with higher total doses (> or = 69.6 Gy). Favorable patients (high KPS, little weight loss, < N3 nodal metastasis) had markedly adverse effects on long-term survival associated with delays to completion of the planned total dose.