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Nomograms for predicting disease progression in patients of Stage I non-small cell lung cancer treated with stereotactic body radiotherapy

Objective
Non-local progression is a major concern in non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT). Herein we aimed to create a pre-treatment prognostic nomogram for patients with Stage I NSCLC receiving SBRT.


Methods
We retrospectively studied 182 eligible patients. Patients were randomly divided into a model (70%) group and a validation (30%) group. In the model group, thirteen parameters consisting of patient, treatment, and tumor factors were studied and multivariate Cox proportional hazards regression was performed to identify independent predictors for survival outcome, based on which we developed clinical nomogram. The nomogram was externally validated in the validation group.


Results
Multivariate analysis showed that tumor size (P = 0.011) was the only factor correlated with 2-year overall survival, whereas 2-year locoregional control (LRC) was significantly related to tumor size (P = 0.024) and the maximum standardized uptake value (SUVmax) (P = 0.044), so does 2-year progression-free survival (PFS) (tumor size: P = 0.026; SUVmax: P = 0.038). Nomogram for 2-year LRC and 2-year PFS were created based on aforementioned results. The C-indexes for the nomograms to predict 2-year LRC and PFS were 0.816 and 0.804, respectively, in model group, and were 0.729 and 0.731, respectively, in the validation group. Calibration plots also showed that the model performed well.


Conclusions
Tumor of larger size and higher SUVmax predisposed patients to early onset of locoregional and distant progression. The nomogram developed in our study would be helpful in clinical decision-making and selection of patients who may benefit from more rigorous follow-up and aggressive systemic treatment plan.