Female sex is associated with a lower risk of bone metastases and favourable prognosis in non-sex-specific cancers

Background The objectives were to investigate the disparity in the prevalence of bone metastases (BM) between the sexes and to assess the effect of female sex on the development and prognosis of BM. Methods Cases of invasive non-sex-specific cancers diagnosed between 2010 and 2015 in the Surveillance, Epidemiology, and End Results (SEER) program were used. The prevalence of BM was calculated by combining the prevalence of BM among different cancers. Multivariable logistic regression and proportion hazard regression were conducted to investigate the effect of female sex, and the results were pooled by meta-analysis. Results The pooled prevalence of BM among male and female patients was 2.3% (95% CI: 1.6-3.2%) and 1.8% (95% CI: 1.2-2.6%), respectively. The pooled prevalence of BM dramatically decreased for patients aged 11-40 years old, plateaued for patients aged 41-90 years old and increased for patients aged > 90 years old in both male and female patients. Meta-analysis suggested that female sex had a protective effect on the development of BM (pooled OR = 0.80; 95% CI: 0.75-0.84; p < .001) and a favourable prognosis for respiratory system cancers (pooled HR = 0.81; 95% CI: 0.71-0.92; p < .001). However, no significant associations existed for other cancers. Male non-sex-specific cancer patients and those with male-leaning genetic variations or hormonal status have a greater likelihood of developing BM than female patients. Conclusions Female sex was associated with fewer BM in various non-sex-specific cancers, and the effect was constant with changes in age. Female sex showed a protective effect exclusively on the prognosis of respiratory system cancers.