EAU 2019: Survival Differences Between Men and Women with Bladder Cancer Depend Strongly On Time Since Diagnosis

Barcelona, Spain (UroToday.com) It has consistently been shown that women diagnosed with bladder cancer have lower survival than men, partly because of worse stage at diagnosis1, but also secondary to diagnostic delay. Most studies assume that the sex-specific hazard ratio is constant over time, but a recent Norwegian study showed that this assumption is probably invalid2. Among 15,129 new cases of urothelial carcinoma in the Cancer Registry of Norway, Andreassen et al. found that risk rates were significantly higher for women than men up to 2 years after bladder cancer diagnosis, particularly for muscle-invasive cancers. Thereafter, risk rates appeared to be higher in men. Adverse T-Stage distribution in women explained half of the unfavorable survival difference in female patients two years after diagnosis. With this context in mind, Dr. Richters et al. presented results of their study from the Netherlands at today’s Novel Technology and Techniques in Urothelial Cancer Diagnosis session at EAU 2019. The aim of the study was to assess how the survival difference between men and women diagnosed with bladder cancer varied over time since diagnosis.

This study was an observational cohort study of data from the Netherlands Cancer Registry. The authors identified 24,169 patients diagnosed with histologically confirmed T≥1 bladder cancer in the period 2003-2012. Age, sex and period-matched life tables were utilized from the Dutch general population. Flexible parametric relative survival analysis was used to model excess mortality in each gender, to estimate the excess mortality ratio for male: female, and to explore the effect of covariates on these functions.

The male: female ratio in the cohort was 3:1. Female patients had worse clinical T, N and M-stage at diagnosis and had more often non-urothelial tumor histology compared with male patients. Overall 5 and 10-year survival probabilities were 43.3% and 29.8% in men and 37.4% and 26.6% in women. The excess mortality ratio for males versus females was highest in the first year with an approximate two-fold risk in women, and returned to 1 after 2 years. Adjustment for baseline differences in tumor characteristics slightly decreased the excess mortality ratio but did not change the time effect.

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This study validated the Norwegian study suggesting that the excess hazard ratio is considerably higher for women in the first 2 years after diagnosis. Whether this association is also true in the United States has yet to be determined.
The authors concluded with several concluding statements:
  • The association between sex and excess mortality was not stable over time since diagnosis
  • Excess mortality was higher among women than among men in the first 2 years after diagnosis and became approximately equal after that, also after taking baseline clinical differences into account.
  • Clinicians should incorporate knowledge on this time-varying pattern in their considerations regarding prognosis and treatment options for female patients.

Presented by: Anke Richters, Netherlands Comprehensive Cancer Organisation, Dept. of Research, Utrecht, The Netherlands 

Written by: Zachary Klaassen, MD, MSc, Assistant Professor of Urology, Georgia Cancer Center, Augusta University - Medical College of Georgia, Twitter: @zklaassen_md at the 34th European Association of Urology (EAU 2019) #EAU19 conference in Barcelona, Spain, March 15-19, 2019.

References:
  1. Klaassen Z, DiBianco JM, Jen RP, et al. Female, black and unmarried patients are more likely to present with metastatic bladder urothelial carcinoma. Clin Genitourin Cancer 2016;14(5):e489-492.
  2. Andreassen BK, Grimsrud TK, Haug ES. Bladder cancer survival: Women better off in the long run. Eur J Cancer 2018 May;95:52-58. 
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