The aim of the current study was to assess temporal trends in incidence of anal squamous cell carcinomas (SCC) and high-grade anal intraepithelial lesions (AIN2/3), and estimate survival from anal cancer and factors related to 5-year mortality in Denmark.
We analyzed anal SCC and AIN2/3 cases in the period of 1998–2018 from the Danish Cancer Register and the Danish Registry of Pathology, respectively. Overall, period, gender, and histology specific age-standardized incidence rates, average annual percentage change (AAPC), and 5-year relative survival were estimated. Cox proportional hazards models were applied to evaluate the effect on 5-year mortality of period, age, gender, and stage of disease.
Altogether 2580 anal cancers and 871 AIN2/3 were identified. The AIN2/3 incidence increased for women 1998–2007 (AAPC: 3.5% (95% CI −0.7, 8.0)) and then tended to decrease during 2008–2018(AAPC: −5.2% (95% CI −9.6, −0.6)). A similar pattern was observed for men, although at a lower incidence with the decrease starting later (2008–2012) and the trend not reaching statistical significance. The anal SCC incidence increased over the whole study period for both women and men (women AAPC: 4.0% (95% CI 3.2%, 4.9%) and men AAPC: 3.6% (95% CI 2.3%, 4.9%)). The relative survival improved over time (from 61% to 72%). Being older and male was associated with a higher risk of dying within 5 years.
There is a need to focus attention on anal cancer and its precursor lesions, as the cancer incidence continues to increase. Actions could include screening and gender-neutral HPV vaccination.
- • Incidence of anal precancers in women increased until 2007, and then tended to decrease.
- • Incidence of anal squamous cell carcinoma increased during the period 1998–2018.
- • Male sex and older age were associated with higher risk of dying from anal cancer.
Worldwide, nearly 50,000 anal cancer cases were diagnosed in 2018 and around 19,000 died of anal cancer . Anal cancer is preceded by precancerous lesions (anal intraepithelial neoplasia grade 2 and 3 (AIN2/3)). Anal cancer is most often squamous cell carcinoma (SCC) followed by adenocarcinoma (AC) . Anal SCC is associated with high-risk human papillomavirus (HPV). It is estimated that 88% of anal cancers and 95% of AIN2/3 lesions are associated with HPV .
The incidence of anal cancer has been increasing in high-income countries including USA, Northern and Western Europe and Australia, whereas incidence has been more stable in Asia, Central/Eastern Europe and Spain . It is suggested that anal SCC “may surpass cervical cancer over the next 10–15 years to become the leading HPV-associated cancer in elderly US women” . Increasing trends of anal cancer incidence until 2011 have been reported also in the Danish population . Previously, incidence of precancerous lesions has been reported only in USA and in Denmark until 2008 , showing increasing trends. However, a recent study from US showed that incidence of anal carcinoma in situ (CIS) decreased from 2010 .
During the last decades, survival after anal cancer has improved . In a recent study from Norway , the authors reported that survival was better for women compared to men but to our knowledge, no previous study has examined survival from anal cancer over time in Denmark.
The aim of this study was to examine the temporal trends in incidence of AIN2/3 and anal cancer in Denmark during 1998–2018. In addition, we assessed the 5-year relative survival after anal SCC and examined the effect of age, calendar year, gender, and stage of disease on anal cancer mortality.