A scoring system for predicting the survival prognosis of patients receiving stereotactic body radiation therapy (SBRT) for 1–3 lung metastases

Introduction: The main goal of the present study was the development of a survival scoring system for patients treated with stereotactic body radiation therapy (SBRT) for very few lung metastases. Such an instrument would be of value when selecting the optimal dose for individual patients with a limited number of pulmonary lesions. Methods: Forty-six patients receiving SBRT for 1–3 lung metastases were retrospectively analyzed. The biologically effective dose plus nine characteristics [gender, age, performance score, interval from tumor diagnosis to SBRT, primary tumor type, additional (extra-pulmonary) metastases, major location of lung metastases, number of pulmonary lesions, and volume treated with SBRT] were evaluated. Characteristics significantly associated with the survival on Cox regression analysis were incorporated in the scoring system. Scoring points were received from 1-year survival rates divided by 10. Sums of these scoring points represented the scores for the individual patients. Results: Survival rates at 1 and 2 years were 66 and 56 %, respectively. On Cox regression analysis, performance score (p = 0.025), the type of primary tumor (p = 0.013) and the additional metastases (p = 0.032) had a significant impact on survival. Scores for patients ranged from 15 to 25 points. Three groups were designed: 15 points, 16–20 points, and 21–25 points. One-year survival rates were 0, 52, and 83 %, respectively (p = 0.005); 2-year survival rates were 0, 52, and 66 %, respectively. Conclusion: A survival scoring system for patients receiving SBRT for very few lung metastases was developed. This score allowed us to estimate the survival prognosis of these patients and can aid physicians when aiming to choose the optimal SBRT dose for individual patients.