Palliative Thoracic Radiotherapy for Lung Cancer: What Is the Impact of Total Radiation Dose on Survival?

Abstract

BACKGROUND: Effective symptom palliation can be achieved with low-dose palliative thoracic radiotherapy. In several studies, median survival was not improved with higher doses of radiation. More controversy exists regarding the impact of higher doses on 1- and 2-year survival rates. Therefore, a comparison of survival outcomes after radiotherapy with different biologically equivalent doses (equivalent dose in 2-Gy fractions, EQD2) was performed. METHODS: This was a retrospective single-institution study of 232 patients with small or non-small cell lung cancer. Most commonly 2 fractions of 8.5 Gy were prescribed (34%), followed by 10 fractions of 3 Gy or equivalent regimens (30%, EQD2 circa 33 Gy). The highest EQD2 consisted of 45 Gy. Intention-to-treat analyses were performed. RESULTS: Survival was significantly shorter with regimens of intended EQD2 < 33 Gy, e.g., 2 fractions of 8.5 Gy (median 2.5 months compared to 5.0 and 7.5 months with EQD2 of circa 33 and 45 Gy, respectively). The 2-year survival rates were 0%, 7% and 11%, respectively. In 128 prognostically favorable patients, median survival was comparable for the three different dose levels (6 - 8.3 months). The 2-year survival rates were 0%, 10%, and 13%, respectively (not statistically significant). CONCLUSION: Although most of the observed survival differences diminished after exclusion of poor prognosis patients with reduced performance status and/or progressive extrathoracic disease, a slight increase in 2-year survival rates with higher EQD2 cannot be excluded. Because of relatively small improvements, a confirmatory randomized trial in this subgroup would have to include a large number of patients.