Social class dictates cancer risk

Cervical and lung cancer are more common in poor people while rates of breast cancer and melanoma are higher in the wealthy. A detailed analysis of the incidence of these four different kinds of cancer, carried out on more than 300,000 English cancer patients and published today in the open access journal BMC Cancer, describes the effects of socioeconomic group, region and age.

Lorraine Shack at the North West Cancer Intelligence Service and a team of researchers working on behalf of the United Kingdom Association of Cancer Registries used information from all eight English cancer registries from 1998 to 2003. They compared the rates of these four cancers with variations in deprivation. The data were further categorised by the person's age.

As Shack describes, "We looked at all invasive cases of lung cancer, cervical cancer, malignant melanoma of the skin and female breast cancer. The deprivation statistics were based on average levels of socioeconomic status in the patient's local area."

Malignant melanoma and breast cancer were most common in more affluent groups. According to the authors, the variations in breast cancer rates may be because "Women from affluent socioeconomic groups are more likely to have their first child at a later age, have fewer children in their lifetime and take hormone replacement therapy. Each of these factors is associated with a slightly higher incidence of breast cancer."

The higher incidence of melanoma in the more wealthy groups may be partially explained by holidays abroad and the resulting exposure to UV. However, the authors highlight that sun bed use may have an impact across all socioeconomic groups, particularly in the young, "It is difficult to estimate sun bed use as most salons are private and poorly regulated. However, anecdotal evidence suggests that sun bed use is increasing in England, particularly for teenagers and young adults. Sun parlours tend to be clustered in areas of deprivation."

The study also found that the highest rates of lung and cervical cancer occurred in the most deprived groups. The higher incidence of lung cancer in the deprived groups is squarely blamed on smoking, "Smoking is strongly associated with socioeconomic status and over 80% of lung cancer cases can be estimated to be attributable to smoking."

Worryingly, the authors found the greatest difference in lung cancer rates between socioeconomic groups in people under the age of 65, possibly suggesting that the more deprived groups continue to smoke while the wealthier groups have quit smoking.

The study provides further evidence of the link between wealth and cancer risk. Research such as this has a crucial role to play in tailoring government screening programmes, and other preventative measures, to local needs.