Today skin cancer is more prevalent than all other human cancers combined. Is the weather to blame? Yes and no. UV radiation is undoubtedly a major trigger of skin cancer. But equal blame goes to a change in contemporary human behaviour, as more leisure time and the desire for a tan lead to more radiation exposure.
Despite education and early detection programmes, numbers of skin cancer patients are rapidly increasing everywhere. Fortunately, an average of about 95% of diagnoses is of the less lethal non-melanoma type. The sun-soaked Australians hold the infamous world record for the highest melanoma rate, at 9.6% of total national cancer cases against just 2.1% in Europe. Numbers of melanoma cases in the US are halfway between the Australian and European rates.
Two types of non-melanoma skin cancer are common: basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Both are seldom a threat to life. If removed at an early stage and with good medical care, the mortality rate is less than 1%. Nevertheless, they can severely damage the skin. Because both occur mostly on the visible sun-exposed body parts, in particular the head and neck, the cancers can disfigure a person’s appearance.
BCC is the least aggressive of the two. It rarely spreads to other body sites. Though almost always curable, the cancer is recurring. SCC is slightly more aggressive and has the potential to spread. BCC often appears as shiny, waxy red bumps. SCC shows itself more likely as red and scaly bumps. But both cancers can take many forms. At times, they become non-healing open sores.
Less common but more dangerous is melanoma. It usually develops on sun-exposed body parts but can appear in different forms anywhere on the body, even in the eye. Unfortunately, it very often looks like a benign mole somewhere on the skin (see ‘Non-cancerous growth’). The cancer readily spreads via lymph and blood vessels to other body tissue or organs. In almost a quarter of melanoma cases, the survival rate is low.
Both cancer types, non-melanoma and melanoma, can arise from sun damage. You read earlier that UV radiation scrambles the chemical code of skin cells – the DNA. The skin’s repair system can no longer read the code and generates an out-of-control malignant growth. In some cases, UV radiation is only the trigger and the repair system could have inherited a genetic fault that prevents it from properly reading the code. Other possible causes are a suppressed or defective immune system and certain toxic substances.
Fair-skinned and light-haired people lack the amount of skin pigments, melanin, that provide a protective shield against UV radiation. Skin cancer is, therefore, much more prominent in such populations, although not exclusively. Other genetic factors that are related to an increased risk are a tendency to sunburn instead of tanning, and a high number of moles.
Accumulated UV radiation is the main cause of non-melanoma type skin cancer in the elderly. A lifetime of excessive sun exposure, however, does not explain why melanoma grows very often on unexposed skin areas, such as the legs and the trunk. One theory is that short, frequent and intense exposure of non-acclimatized skin, especially at childhood, is likely to blame. Playing or sunbathing at the beach are examples. The figures from Australia show that the risk further increases if a person lives and works in a sunny country.
Treatment depends on the stage of the cancer and the health of the patient. In the early stages, surgery best prevents further growth but advanced skin cancer requires additional treatment, the most common being chemotherapy, despite its unwelcome side effects. Unfortunately, chemotherapy is not a cure. It can at best shrink the cancer or at worst slow the growth for a few months. Radiating the cancer is another common therapy. The procedure also tries to shrink or destroy the growth. Non-melanoma type skin cancer often responds quite well, but melanoma cells are more resistant.
Since the body has its own defences against cancerous growth, it seems logical that dcotors work on a way to support a patient’s immune system. First trials show that once a person responds to the experimental drug treatment, the benefits last much longer than they do with chemotherapy. Several natural products, such as herbal supplements, also aim to support the immune system, but their long-term benefits are so far unknown. Gene therapy has a similar purpose: like reloading a corrupt computer program, the right genes replace the faulty inherited material.
Skin cancer research is of national importance to many countries. Government agencies and industry both frantically search for cancer cures. Regardless of whether the motive is to save money in national health programmes or to make money by selling the cancer-curing ‘wonder drug’, we all will benefit eventually. In the meantime, the public can either blame the weather or follow the many preventative measures as published by health agencies.