Anal cancer in high-income countries: Increasing burden of disease

BACKGROUND: Previous studies have reported that anal cancer incidence has increased in individual countries; however, age-specific trends were not examined in detail. This study describes pooled and country-specific anal cancer incidence trends by sex, age (all ages, <60 and 60+ years) and histological subtype (all subtypes, squamous cell carcinoma [SCC] and adenocarcinoma [ADC]). METHODS: Five-year incidence and population-at-risk data were obtained from IARC’s Cancer Incidence in Five Continents for the years 1988–1992 to 2008–2012. The standardised rate ratios (SRRs) for 2008–2012 vs 1988–1992 and the 5-year average percent change (AvPC) during the period were used to assess changes in the age-standardised incidence rates. RESULTS: During the study period, there were significant increases in the incidence of SCC in both men and women of all age groups with significant increasing trend, and these increases were highest in those aged <60 years (SRR = 2.34 [95% CI:2.11–2.58] in men and SRR = 2.76 [95% CI:2.54–3.00] in women). By contrast, there were significant decreases in the incidence of ADC in men and women of all ages (SRR = 0.60 [95% CI:0.54–0.67]) and (SRR = 0.63 [95% CI:0.56–0.71], respectively), with similar decreases in those aged <60 years and 60+ years. These competing trends still resulted in significant increases in the overall incidence of anal cancer in men and women of all ages groups with significant increasing trend. The SRRs in men of all ages, <60 years and 60+ years were 1.35 (95% CI:1.28–1.42), 1.77 (95% CI:1.62–1.92) and 1.08 (95% CI:1.00–1.15), respectively. The corresponding SRRs in women were 1.75 (95% CI:1.67–1.83), 2.31 (95% CI:2.14–2.48) and 1.38 (95% CI 1.31–1.46), respectively. CONCLUSION: Increases in the incidence of anal SCC has driven an overall increase in anal cancer incidence; this may be associated with changing sexual behaviours and increasing levels of HPV exposure in younger cohorts. The findings further reinforce the importance of HPV vaccination.