Researchers have called for urgent intervention after their recent study found melanoma rates, now among the top 10 cancers in South Africa annually, alarmingly high among white South Africans, compared with countries like Australia, the Netherlands and England.
Melanoma, an aggressive cancer that is potentially fatal if not treated early, remains a public health challenge in several countries worldwide, write Caradee Wright of the South African Medical Research Council, Thandi Kapwata and Patricia Albers in the SA Medical Journal, saying exposure to solar ultraviolet radiation (UVR) was a modifiable risk factor for melanoma among lightly pigmented people.
However, behavioural changes are required to reduce excessive sun exposure, and infrastructure and policy support are needed, particularly in high solar UVR environments. Large, multi-component skin cancer awareness campaigns and interventions, like those implemented in Australia, have shown some success.
Such activities are generally less expensive than melanoma treatment, which is costly to the patient and the country, especially a middle-income country like South Africa.
Using previously unpublished historical data and data from the SA National Cancer Registry (NCR), the crude incidence per 100 000 population for melanoma was compared with three other countries at different latitudes with significant melonoma burdens.
This study sought to describe trends in melanoma incidence in white South Africans, among whom melanoma is more common than in other population groups, to inform skin cancer prevention efforts. While melanoma also occurs in black South Africans, it has a lower prevalence.
However, in this population group, factors such as presence of scar tissue, and lack of early self-screening rather than excessive sun exposure play a role in its causation.
The analyses, therefore, focused on white South Africans, for whom avoiding excess sun exposure is critical to melanoma prevention.
The NVC is a pathology-based registry that receives reports on patients diagnosed with cancer from all public and private sector histology, cytology and haematology laboratories in SA. NCR crude melanoma incidence data from 2001 to 2017 were downloaded from the internet and data for 1991 to 2000 were provided as digital photocopies of archived hard-copy reports (data for 1991 included 1990; 1995 included 1993 and 1994).
Crude melanoma incidence data for the Netherlands, England and Australia were downloaded from online cancer registry repositories, namely the National Cancer Registry of the Netherlands, the UK Statistics Authority and the Australian Cancer Database, respectively.
Joinpoint regression analysis determined changes in incidence trends by gender. Analysis entailed fitting the incidence data into a joinpoint model using log-linear regression that fits a series of straight lines joined at “joinpoints” where changes in incidence trends are observed.
The trend of each segment was expressed as the annual percentage change (APC), and the significance of each slope was determined using the Monte Carlo permutation technique. These analyses were carried out for SA and the three chosen comparison countries, and trends were compared.
Overall, between 1991 and 2017, SA, the Netherlands, England and Australia all showed an increasing trend in melanoma incidence. The crude incidence of melanoma among white South Africans ranged between 11 and 42 per 100 000 population. Between 1990 and 2017, white SA males had a higher crude melanoma incidence per 100 000 population than white females.
The Netherlands showed a more steady rise in crude melanoma incidence, ranging between 12 and 40 per 100 000 population.
England showed an increasing crude melanoma incidence ranging between 11 and 29 per 100 000 population. Australia had a higher overall incidence than the other countries, ranging from 37 to 72 per 100 000 population.
The Netherlands and Australia presented one statistically significant joinpoint for all study years for both males and females, indicating an overall statistically significant increase in APC .
The APCs for both genders in the Netherlands were higher than those for Australian males and females. There were two statistically significant joinpoints in trends for males in England, between 2002 and 2010 at a 4% APC and between 2010 and 2013 at an 18% APC.
For SA, two periods of decline in crude melanoma incidence were observed, between 1990 and 1996 and between 1999 and 2010, with males and females showing similar reductions in incidence.
However, the statistically significant APCs for early reporting years may reflect inaccuracies in historical data. Notably, data withholding occurred between 2005 and 2007, reducing overall numbers and probably skewing those results.
Despite these limitations, crude incidence data for white South Africans indicate increasing trends at incidence rates similar to Australia and the Netherlands, the former a high solar UVR environment and the latter home to a populace among whom intermittent sun exposure is associated with melanoma.[
The study highlights three important points for SA. First, the incidence of melanoma among white South Africans is high, given its comparability with melanoma incidence in countries such as Australia, the Netherlands and England.
In fact, the SA NCR reports show that melanoma is among the top 10 cancers in SA each year. Is enough being done to prevent melanoma in SA?
Second, since this study used only the melanoma incidence for white South Africans and excluded other population groups, it is striking that the incidence rates were similar to those of other countries.
This finding demonstrates the magnitude of the problem facing white South Africans. Melanoma incidence tends to be higher among white SA males compared with females.
Nevertheless, the difference in crude melanoma incidence between the genders is not that significant. Are white South Africans being targeted from an early age with skin cancer awareness information and prevention advice?
Third, cancer data collection, including of melanoma, by the NCR, has faced several challenges, such as the data withholding period and a lack of capacity and funding to ensure quality data for long-term trend analysis.
Although this was the first ~30-year study of crude melanoma incidence per 100 000, its accuracy is limited by the availability and quality of NCR data. The Cancer Association of South Africa is one of a few organisations promoting melanoma prevention in the country.
However, additional efforts targeting white South Africans, among whom melanoma incidence is significantly higher than in other population groups, are urgently required to curb melanoma incidence and embed positive behavioural change (such as using photoprotection and avoiding peak solar UVR periods during the middle of the day) in relation to excess sun exposure from an early age to help prevent melanoma.
No abstract was prepared for this study, said the authors.
See more from MedicalBrief archives:
Skin care campaign may have reduced melanoma in Australians
South Africa’s black population also faces significant melanoma risk
Blistering sunburns before 20 years increases melanoma risk