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

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.

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.

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).

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.