Objective: The incidence and long-term survival analysis for vulvar cancer, due to its rarity, has not been fully described in Asian population. The objective of the study is to determine the trends in incidence and long-term survival for vulvar cancer in a Japanese population, using a population-based cancer registry data in Osaka, Japan.
Methods: The age-standardized incidence rate of 389 cases of vulvar squamous cell carcinoma (SCC) diagnosed between 1976 and 2010 was calculated, using the 1985 model population of Japan. The annual percentage change (APC) of the age-standardized incidence was estimated by the joinpoint regression models. The 5- and 10-year relative survival of 290 cases with vulvar SCC diagnosed between 1976 and 2008 were analyzed, using a cohort or period approach. Using the 10-year relative survival, the conditional 5-year survival for patients who lived for some years after diagnosis was also calculated.
Results: We have found that the age-standardized incidence rate for vulvar cancer trended downward during the period of 1979-1992 (APC - 6.3%; 95% confidence interval (CI) [- 11.3% to - 1.0%]), whereas it trended upward from 1993 to 2010 (APC 1.9%; 95% CI [- 0.7% to 4.6%]). There was no statistically significant difference for the 5- and 10-year relative survival between the two periods of 1976-2000 and 2001-2008. A statistically significant increase in the conditional 5-year survival at 2 years after diagnosis was observed (48.4%; 95% CI [41.1-55.3] versus 75.6%; 95% CI [64.0-83.9]).
Conclusion: Despite an increasing trend in vulvar cancer incidence among Japanese population, the relative survival rate for vulvar cancer did not change over the 35 years of this study. We found that the conditional 5-year survival for vulvar cancer, as patients survived additional years, approached within reach of 100%. These data can provide valuable information for both patients and clinicians.
Keywords: Cancer registry; Conditional survival; Relative survival; Squamous cell carcinoma; Vulvar cancer.