Comorbidity indexing for prediction of the clinical outcome after stereotactic body radiation therapy in non-small cell lung cancer

PURPOSE: To determine the prognostic impact of comorbidity and age in medically inoperable early-stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT) using the age-adjusted Charlson Comorbidity Index (aCCI). PATIENTS AND METHODS: Between November 2008 and January 2015, 196 consecutive patients with medically inoperable NSCLC were treated with SBRT at a single institution. The prescribed isocenter dose was either 60.0 Gray (Gy) in six fractions for central lung cancer or 56.25 Gy in three fractions for peripheral lung cancer. Baseline comorbidities were retrospectively retrieved according to available outclinic medical records as well as the hospital information system. The aCCI was scored for each patient and subjected according to outcome and toxicity as well as all of the single items of the aCCI and other clinical parameters using univariate and multivariate analysis. RESULTS: Thirty-one point 6 % (62/196) of patients were deceased, of whom 17.3% (34/196) died due to lung cancer and 14.3% (28/196) due to comorbidities. The median overall survival (OS) was 15.0 months (95% CI [11.9–18.1]), whereas the median cancer-specific survival (CSS) was not reached. An aCCI ≥7 compared with an aCCI ≤6 was significantly associated with an increased risk of death (HR 1.79, 95% CI [1.02–2.80], p = 0.04) and cancer-specific death (HR 9.26, 95% CI [4.83–24.39], p < 0.001), respectively. Neither OS nor CCS were significantly associated with age, sex, side (left vs. right), lobe, localization (central vs. peripheral), packyears, TNM, or any item of the aCCI. Considering the 14.3% (28/196) of deceased patients who died due to comorbidities, aCCI ≥9 was significantly associated with non-cancer-related death (HR 3.12, 95% CI [1.22–8.33], p = 0.02). The observed cumulative rate of radiation pneumonitis (RP) ≥2 was 12.7% (25/196). The aCCI had no statistical association with RP. CONCLUSION: Advanced age and numerous comorbidities characterizing this patient population were successfully assessed using the aCCI in terms of survival. Therefore, we recommend that age and comorbidity be indexed using the aCCI as a simple scoring system for all patients treated with SBRT for lung cancer.