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

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.

Endometrial cells as a predictor of uterine cancer.

BACKGROUND: With the recent cervix screening national guidelines recommending against reporting of benign endometrial cells, we examined South Australian data to see what impact this would have on detecting uterine cancers. AIMS: To test whether benign endometrial cells detected in cervical cytology testing confer an increased risk of uterine cancer, and to ascertain what percentage of uterine cancers will be missed in cervical screening programs if these cells are not reported. METHODS: The study was a retrospective cohort design of 1585 women with shed endometrial cells, each matched with three women without shed cells. All were linked with cancer registry data to check for uterine cancer diagnosis. Cox proportional hazards regression was used to check for any increase in cancer risk with shed endometrial cells. Using the calculated relative risks for uterine cancer diagnosis, we estimated the number of uterine cancers in South Australia associated with benign endometrial cells. RESULTS: The presence of benign endometrial cells in a cervical cytology test increases the risk of uterine cancer sixfold. However, screening women with benign cells would involve a major increase in pathology work for only an 18% increase in uterine cancers detected. CONCLUSIONS: Until cytology systems have a higher sensitivity in detecting which benign endometrial cells are associated with uterine cancer, pathology laboratories are unlikely to be required to report these cells on tests. Inability to adjust for symptomatic status may have reduced the relevance of the results in this study.

Effects of variations in hysterectomy status on population coverage by cervical screening.

OBJECTIVES: To investigate geographic differences in hysterectomy rates and effects on estimated screening coverage in South Australia. METHODS: Hysterectomy data from South Australian hospitals for 1992-2000 were used to calculate age-specific hysterectomy rates for 20-69 year old women by residential subregion and postcode. Regional variations in rates were used to estimate variations in proportions of women with an intact uterus. Effects on estimates of screening coverage were investigated. RESULTS: About 66% of South Australian women were estimated to have an intact uterus at 70 years of age, based on hysterectomy rates for 1992-2000. The proportion was smaller in lower than upper socio-economic areas, and in country areas than the State capital (Adelaide). Estimates varied from 49% to 73% across 20 subregions. About 67% of 20-69 year olds with an intact uterus were estimated to have been screened in the 24-month period from 2000 to 2001. Similar estimates applied to Adelaide and country areas, irrespective of whether adjustments were made for differences in hysterectomy rates. A lower screening coverage applied to lower than upper socio-economic areas of Adelaide, irrespective of whether these adjustments were made. While adjusting for variations in hysterectomy rates generally had little effect on estimated screening coverage, there were notable exceptions. For example, in one subregion, coverage increased among 50-69 year olds from 53% to 66%. CONCLUSIONS: Adjustments for variations in hysterectomy rates can affect estimated screening coverage in some localities. Such adjustments should be undertaken to better define areas of under-screening for targeting in screening promotion.