Histology of non-small cell lung cancer predicts the response to stereotactic body radiotherapy

To investigate the prognostic impact of different histological subtypes of non-small cell lung cancer (NSCLC) on outcome following stereotactic body radiotherapy (SBRT) for NSCLC patients. We analyzed 126 consecutive patients with early-stage adenocarcinoma or squamous cell carcinoma treated with SBRT from 2004 to 2016. Adenocarcinoma patients were further sub-classified as high-risk or low-risk tumors. With a median follow-up time of 22months, 2-year overall survival (OS), local (LC), and distant control (DC) were 68%, 90% and 79%, respectively. For LC, histologic subtype was identified as major independent prognostic factor (p=0.033): while LC was 81% for squamous cell carcinoma patients, LC was significantly improved for high-risk and even more non-high-risk adenocarcinoma patients with 96% and 100%, respectively (p=0.026). The negative prognostic impact of the histologic subtype “squamous cell carcinoma” was not evident when patients received SBRT with higher total doses in EQD2 (2Gy equivalent dose): if patients were treated with a total dose in EQD2≥150Gy, no significant difference in LC for histologic subtypes was detected anymore (p=0.355). In the current study, histologic subtypes of NSCLC predicted local control probabilities following SBRT. Prospective, multi-center studies are needed to evaluate the prognostic impact of histology and consecutively the need for SBRT dose adaptation.