Sex-Based Differences in Medullary Thyroid Cancer Survival: A Matched Analysis of 4602 Patients.

Abstract

Background: Whereas medullary thyroid cancer (MTC) is more common in female patients, studies have indicated that MTC is more aggressive in males. It is unknown whether sex-based differences in MTC outcomes are due to inherent tumor behavior or factors such as care characteristics.

Methods: Patients with MTC stages I to IV were identified using the National Cancer Database (2004-2020). Male patients were matched one-to-one with females based on pathologic staging. Overall survival (OS) was estimated using the Kaplan-Meier method. A Cox proportional hazards model was used to estimate the association of biologic sex with OS.

Results: The study matched 4062 patients (2031 females and 2031 males). The median age was 55 years (interquartile range, 43-66 years). Age, race, comorbidity score, and care characteristics such as time to diagnosis and surgery type did not differ by sex (all p > 0.05). Pathologic stage was primarily stage IVA (35.5%), followed by stages I (24.7%) and III (18.9%). The unadjusted 10-year OS for the female patients was 81.1% (95% confidence interval [CI], 78.7-83.2%) versus 69.6% (95% CI 66.8-72.3%) for the male patients (p < 0.001, log-rank). Survival for the male patients with stages II, III, and IVA disease was significantly worse (all p < 0.05). After multivariable adjustment, the male patients showed an 81% higher mortality risk than the female patients (hazard ratio [HR], 1.81, 95% CI 1.50-2.20; p < 0.001).

Conclusions: Despite patient-matching and adjustment for several factors, the male patients with MTC demonstrate worse survival than the matched female patients. These findings indicate that MTC behavior differs by sex.