Benchmarking epidemiological characteristics of cervical cancer in advance of change in screening practice and commencement of vaccination

Abstract

Objectives: To investigate trends in cervical cancer incidence, mortality and survival by histology for benchmarking purposes ahead of practice change and the introduction of Human Papilloma Virus (HPV) vaccine.

Methods: Using data from the South Australian Cancer Registry, age-standardised rates are presented for four-year periods from 1977 to 2004. Socio-demographic and secular predictors of glandular as opposed to squamous cancers are investigated, using multivariable logistic regression. Disease-specific survivals are analysed using Kaplan-Meier product-limit estimates and Cox proportional hazards regression.

Results: Incidence and mortality rates reduced by 55.1% and 59.3% respectively between 1977-80 and 2001-04, with larger reductions for squamous than glandular cancers. The ratio of squamous to glandular cancer incidence reduced from 5.4:1 in 1977-88 to 2.8:1 in 1993-2004, with a corresponding reduction from 5.2:1 to 3.0:1 for mortality. Compared with squamous cancers, glandular lesions were more common in patients from higher socio-economic areas, but less common in those over 70 years of age, Aboriginal patients, and those born in Southern Europe.

Conclusion: The proportion of cancers comprising glandular lesions has increased, possibly reflecting prevention of squamous cancers through treatment of screen-detected preinvasive lesions. Additional mortality reductions from screening may be limited where the proportion of glandular lesions is high, with vaccination offering the best prospects for gains in the long term. Priority should be given to Aboriginal and Torres Strait Islander women in vaccination programs in view of their high death rate from cervical cancer.