Age-dependent changes in the prognostic advantage of papillary thyroid cancer in women: A SEER-based study

Papillary thyroid cancer (PTC) is more prevalent in women, and women show a better prognosis than men; however, the factors contributing to this prognostic difference are confounding. Therefore, we aimed to investigate the effect of the interaction between sex and age on the prognosis of PTC.

A total of 108,459 patients with PTC were retrospectively analysed, and Cox-regression models were used to assess differences in disease specific survival (DSS) by sex, with inverse probability of treatment weighting (IPTW) to control for between-group differences in prognosis by sex due to age change. Restricted cubic splines were used to analyse prognostic differences between sexes for papillary thyroid microcarcinoma (PTMC) and PTC. Multiple mediation analyses were used to assess the direct or indirect effect of sex on DSS.

The DSS was higher for women than men (98.6% vs. 95.4%, χ²  = 458.57, p < .001). After IPTW adjustment, the DSS of women was better than that of men (HR = 0.67, 0.60-0.76). In the subgroup analysis, women had an advantage in DSS across most age intervals (crude HR = 0.166 [0.082-0.337], p < .001, IPTW-adjusted HR = 0.331 [0.161-0.681], p < .001). The difference between the two gradually narrowed with increasing age, and the prognosis of women was better than that of men in PTMC, while this advantage was not obvious in PTC.

The overall PTC prognosis of women is better than that of men, but the prognostic advantage of women diminishes with age and tumour growth. These differences in prognosis may be due to some indirect factors caused by different sexes.