From 2014 a clear increase in cervical cancer incidence was observed in Sweden. Using recently available data (June 2017) from the National Cancer Regiister (NCR) and the National Cancer Screening Register (NKCx) the objective of this study was to investigate this increase by histology, age, and clinical stage at diagnosis.
Incidence rate ratios (IRR) with 95% confidence intervals (CI) by calendar time were estimated in multivariate Poisson regression models, with interaction terms for histology, age and clinical stage at diagnosis as mediators.
There was an increase in cervical cancer incidence by around 20% (IRR=1.20, CI 1.06-1.36) from 2012 to 2015. This increase was mostly pronounced for adenocarcinoma with a 42% increase in incidence from the period 2012-2013 to 2014-2015 (IRR=1.42, CI 1.18-1.72), while for squamous, adeno-squamous and more rare types of cervical only small, statistically non-significant changes were seen in overall incidence. The increase of adenocarcinoma was mainly concentrated to FIGO stages IA and IB, with a more than 40% increase (IRR=1.45, CI 0.96-2.19 and IRR=1.48 CI 1.15-1.92, respectively). For squamous cancer there was a corresponding increase with around 20% for stage IB cancers only (IRR=1.20, CI 1.01-1.46). For adenocarcinoma the increase in incidence was more pronounced in women below age 50, and for those in stage IB cancers. For squamous cell cancer no statistically significant changes with age could be discerned for the comparison between the two time periods.
The main changes in incidence were seen for early clinical stages, and for adenocarcinoma for women below age 50. Whether these changes in incidence are due to an increase in the underlying risk of cervical cancer or failures of the screening organization still needs to be investigated.