Evaluation of sex inequity in lung-cancer-specific survival

Abstract

Background: Whether sex is an independent prognostic factor in lung cancer survival is the subject of ongoing debate. Both large national registries and single hospital studies have shown conflicting findings. In this study, we explore the impact of sex on lung-cancer-specific survival in an unselected population that is well-characterized with respect to stage and other covariates.

Material and methods: All patients diagnosed with lung cancer at a single hospital serving a whole and defined region in Southern Norway during the 10 years 2007-2016 were included. Follow-up data were available for at least 56 months for all patients. Analyses were adjusted for stage, treatment, performance status, smoking, age, histology, epidermal growth factor receptor/anaplastic lymphoma kinase/immunotherapy treatment and period. Differences in lung-cancer-specific survival by sex were explored using restricted mean survival times (RMST).

Results: Of the 1,261 patients diagnosed with lung cancer, 596 (47%) were females and 665 (53%) males, with mean ages of 68.5 and 69.5 years, respectively. The observed 5-year lung-cancer-specific survival rate was 27.4% (95% CI 23.7, 31.2) in females and 21.4% (95% CI 18.2, 24.8) in males. However, after adjustment for covariates, no significant differences by sex were observed. The 5-year RMST was 0.9 months shorter (95% CI -2.1, 0.31, p = 0.26) in males compared to females.

Interpretation: In this cohort, sex was not associated with a difference in lung-cancer-specific survival after adjusting for clinical and biological factors. Imbalance in stage at diagnosis was the main contributor to the observed difference in lung-cancer-specific survival by sex.

Figure 1

Cumulative mortality and RMST with 95% confidence interval by sex in cohort of lung cancer patients during 5 years of follow-up after start of treatment. (a) Cumulative mortality of lung cancer and other deaths for females and males. (b) Difference in lung-cancer-specific cumulative mortality by sex. (c) RMST of lung cancer death and other death for females and males. (d) Difference in RMST of lung cancer death by sex. RMST: restricted mean survival time.