Clinical characteristics and prognostic nomogram for patients with insular thyroid carcinoma: a population-based analysis

Insular thyroid carcinoma (ITC) is an uncommon poorly differentiated thyroid malignancy. Due to its rarity, its demographic and clinicopathological features and survival remains unclear. The present study aimed to describe the features and survival of ITC, determine its prognostic factors, and establish a prognostic nomogram.Patients with ITC were identified in the Surveillance, Epidemiology, and End Results database from 2004 to 2019. The features and survival of patients with ITC and other thyroid carcinomas were compared after balancing the baseline characteristics using propensity score matching (PSM). Univariate and multivariate Cox analyses were used to identify the prognostic factors for ITC. Moreover, overall survival (OS)- or cancer-specific survival (CSS)-specific nomograms were established to predict ITC prognosis.A total of 206 patients with ITCs were identified. The 1-, 2-, 5-, and 10-year OS rates of 206 patients with ITC were 90.3%, 82.0%, 62.2%, and 42.5%, respectively. The median OS was 93 months (95% CI, 73.0-140.0), while the median CSS was 141 months (95% CI, 93.0-173.0). After PSM analysis, the survival analysis of the matched cohort revealed that ITC had a worse clinical outcome than papillary thyroid cancer and follicular thyroid cancer, and better survival than anaplastic thyroid carcinoma. Multivariate Cox regression analysis demonstrated that age, N stage, M stage, and surgery were independent prognostic factors for both OS and CSS in ITC patients. The C-indices for the OS- and CSS-specific nomograms were 0.778 (95% CI, 0.724-0.832) and 0.808 (95% CI, 0.754-0.862), respectively. The calibration curve and ROC analysis indicated that the nomogram models exhibited a good discriminative ability. Decision curve analysis suggested that the nomogram models had a significant positive net benefit and were better than the traditional TNM staging system at predicting survival.ITC has distinct clinicopathological characteristics and survival compared to other thyroid carcinomas, and the established nomogram could predict the survival probability of patients with ITC accurately with a higher net benefit.