Development and validation of a nomogram for predicting cancer‐specific survival of surgical resected stage I‐II adenosquamous carcinoma of the lung

OBJECTIVES: Primary lung adenosquamous carcinoma (ASC) is a rare cancer subtype and has a poor prognosis. The prognostic factors for resected early-stage ASC remain unclear. We aimed to develop a nomogram to predict lung cancer-specific survival (LCSS) of patients undergoing surgical resection for stage I-II ASC. METHODS: Data of patients undergoing resection for stage I-II ASC and diagnosed between 2004-2015 were identified from the Surveillance, Epidemiology, and End Results (SEER) database. All the included patients were randomized at a 7:3 ratio into a training and a validation cohort. We selected and integrated significant prognostic factors based on competing for risk regression to build a nomogram. The performance of the nomogram was evaluated using Harrell's concordance index (C-index) and calibration plots. RESULTS: A total of 988 patients (530 men and 458 women) undergoing surgical resection for stage I-II ASC were identified and randomized into a training (692, 70%) cohort and a validation cohort (296, 30%). The baseline characteristics were similar in the training and validation cohorts. Age, T stage, N stage, and the number of examined lymph nodes were independent prognostic factors for LCSS and were used in the nomogram. The calibration plots showed that the 3- and 5-year LCSS probabilities were consistent between the nomogram prediction and the actual observation. The C-index of the nomogram was 0.671 (95%CI: 0.618-0.724) and 0.635 (95%CI: 0.557-0.713) in the training cohort and validation cohort, respectively. We developed a risk classification system based on the nomogram to stratify patients into high- and low-risk of cancer-specific death groups. Patients with a similar risk shared similar prognostic prediction regardless of the stage category and patients with the same risk shared similar prognoses despite the different stage category. CONCLUSIONS: We developed a competing risk nomogram to reliably predict cancer-specific survival of patients undergoing surgical resection for stage I-II ASC. The nomogram might be a useful tool to identify patients undergoing surgical resection for ASC who could be suitable candidates for adjuvant chemotherapy.