Trends and determinants of the incidence and mortality of cervical cancer in South Africa (1994-2012)
Cervical cancer (CC) is the leading cause of female cancer morbidity and mortality in South Africa, despite the introduction of preventive programs. However, there is a paucity of information on current CC rates and trends in South Africa. This study aimed to evaluate the national trends and determinants of CC over a 19 year period (1994-2012). We conducted temporal analyses of age-standardised incidence rates (ASIR) from 1994 to 2009 and age-standardised mortality rates (ASMR) from 2004 to 2012 using data from the National Cancer Registry and Statistics South Africa, respectively. We also evaluated a novel surrogate measure (complement of MR: IR ratio) to calculate five-year relative survival rates of CC (2004-2009). Temporal analyses were stratified by the province of residence, histological type, population- and age-groups, while linear regression models were fitted to determine the average annual percent change (AAPC) of the time trends. Spatial distribution was conducted by utilising the GIS coordinates of SA to map the provincial ASMR. Unconditional logistic regression analyses were carried out for three casecontrol studies using data from the hospital-based Johannesburg Cancer Case-Control Study (JCCCS) (1995-2010), to evaluate the effect of HIV infection; tobacco smoking and alcohol abuse and sexual and reproductive behaviours on the risk CC in Black South Africans. The cases were participants with CC while controls were other female cancer participants that had no known association with CC and its risk factors. There were 75,099 incident cases and 25,101 mortalities from CC in the periods studied with women below 50 years accounting for 43.1% of the cases and 35.7% deaths. The ASIR was 22.1/100,000 in 1994 and 23.3/100,000 in 2009 and there was an average annual decrease in incidence of 0.9% (AAPC=-0.9%, P-value<0.001). The ASMR decreased slightly from 13.9/100,000 in 2004 to 13.1/100,000 in 2012 (AAPC = -0.6%, P-value < 0.001). Based on current trends, the ASIR and ASMR were predicted to increase to 26.3/100,000 and 14.6/100,000 in 2030, respectively. From 2004 to 2012, five provinces had increased mortality rates (AAPC: 1.2 – 8.3, P-value<0.001) while four provinces had decreased mortality rates (AAPC: -16.6 - -1.0, P-value<0.001). In 2012, the ASMR in Black population group was 5.7-fold higher than in the White population group. The highest mortality was recorded in Mpumalanga Province (19.8/100,000) and the least in the Eastern Cape Province (8.9/100,000). From 2000 to 2009, the ASIR of adenocarcinoma of the cervix was relatively low (2.00 to 2.6 per 100,000 women) and stable, while the incidence of squamous cell carcinoma was high (17.0 to19.0 per 100,000 women) and the rate increased by 1.4% annually. The relative survival rates were higher in White and Indians/Asian women (60-80%) than in Blacks and Coloureds (40- 50%). The results of the JCCCS studies showed that the association between CC and HIV infection increased from two-fold (adjusted odds ratio, (adjOR) =1.98; 95% CI: 1.34-2.92) during the pre-anti-retroviral therapy (ART) era (1995-2003) to three-fold (adjOR=2.94 95%CI: 2.26- 3.83) in the ART era (2004-2010). Current tobacco smoking (adjOR=2.1, 95%CI: 1.10-4.01) and snuff use (adjOR=1.3, CI: 1.08-1.61) increased the likelihood of CC among Black women in South Africa. The risk of CC increased with prolonged use of hormonal contraceptives (P-value for trend = 0.003) and high parity (>6) (adjOR=4.5, 95%CI: 2.85- 7.25). The incidence and mortality of CC are probably underestimated due to underreporting of cancer in the country. South Africa had minimal changes in overall CC rates between 1994 and 2012, despite the initiation of a population-based CC screening program in 2000 and the nationwide roll out of ART in 2004. There was a marked disparity in CC rates by population group, age and province. HIV-infected women and those who use tobacco are more likely to develop CC, therefore targeted programs should be introduced to inform women about risk factors for CC. Maternal and child health initiatives should also involve CC control activities since a considerable number of women of the reproductive age (15 – 49 years) were affected.
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in the field of Epidemiology and Biostatistics. Johannesburg, June 2017
Olorunfemi, Gbenga (2017) Trends and determinants of the incidence and mortality of cervical cancer in South Africa (1994-2012), University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/23075>