Differential impact of age on survival in head and neck cancer according to classic Cox regression and decision tree analysis

Abstract

Objectives: To assess the impact of age on the survival of patients with head and neck squamous cell carcinoma (HNSCC) using different statistical methods.

Design: A retrospective population-based study.

Setting: Surveillance, Epidemiology, and End Results database.

Subjects and methods: A total of 28 639 patients with newly diagnosed HNSCC were enrolled between 1 January 2007 and 31 December 2013. The effect of age on 5-year disease-specific survival was calculated using a Kaplan-Meier method and compared using log-rank tests. A Cox proportional hazards model was used for a multivariate analysis. A classification and regression tree (CART) analysis that partitioned patients with significantly different Kaplan-Meier curves was introduced to identify the important cancer-related parameters influencing survival.

Results: Uni- and multivariate analyses indicated that patients who were older than 60 years had poorer 5-year disease-specific survival regardless of tumour subsite and tumor-node-metastasis (TNM) stage. However, the CART analysis determined that age played only a minor role in survival after comparing with other prognosticators. The relative importance of age using the Gini index was as follows: 3.21% for oral cancer, 8.32% for oropharyngeal cancer, 2.56% for hypopharyngeal cancer and 16.51% for laryngeal cancer.

Conclusions: Different to traditional statistical methods, the CART analysis which was used to identify homogeneous populations revealed that the impact of age varied for different patient groups according to the presence or absence of other prognosticators. This important information could help to guide our clinical decisions and future researches.

Keywords: age; classification and regression tree; head and neck squamous cell carcinoma; regression analysis; survival.