Excluding non-melanoma skin cancer,(1) melanoma is the fourth most common cancer in Australia, which along with New Zealand has the world’s highest incidence rate for melanoma.
Incidence and mortality
Melanoma represents 9.5% of all cancers, with more than 10,300 cases diagnosed annually. The risk of being diagnosed by age 85 is 1 in 15 for men and 1 in 24 for women.
In 2008, there were 1430 deaths from melanoma.
Screening
Individuals at high risk of melanoma (see risk factors below) should be taught to check their skin for irregular or changing lesions, and have annual checks by a dermatologist.
Symptoms and diagnosis
Often melanoma has no symptoms, however it can be associated with changes that relate to ‘ABCDE’ - Asymmetry, irregular Border, uneven Colour, Diameter (usually over 6mm), Evolving (changing and growing). Other symptoms include dark areas under nails or on membranes lining the mouth, vagina or anus.
Diagnosis is by biopsy to remove the whole lesion.
Staging
If the excised lesion is thick, a biopsy of the first draining lymph node (sentinel node) is performed. The most important feature of a melanoma in predicting its outcome is its thickness (stage 0 is less than 0.1mm, stage I less than 2mm, stage II greater than 2mm, stage III spread to lymph nodes and stage IV distant spread). The presence of ulceration also predicts a poor outcome. If distant spread is suspected, CT scans of the chest, abdomen and pelvis are performed. The blood test LDH can sometimes be useful to assess metastatic disease.
Causes
Melanoma risk increases with exposure to UV radiation, particularly with episodes of sunburn (especially during childhood).
Melanoma risk is increased for people who have:
- increased numbers of unusual moles (dysplastic naevi)
- depressed immune systems
- a family history of melanoma in a first degree relative
- fair skin, a tendency to burn rather than tan, freckles, light eye colour, light or red hair colour
- had a previous melanoma or non-melanoma skin cancer.
Prevention
Avoid sunburn by minimising sun exposure when the SunSmart UV Alert exceeds 3 and especially between the hours of 10am and 3pm when UV levels reach their peak. Seek shade, wear a hat that covers the head, neck and ears, wear sun protective clothing and close-fitting sunglasses, and wear an SPF30+ sunscreen. Avoid using solariums (tanning salons).
Treatment
Surgery can be curative for thin melanomas and requires that the melanoma be removed with at least 1–2cm of normal skin around it. If the draining lymph nodes are involved they are removed.
For thick melanomas some cancer centres offer high dose interferon after surgery, however many offer clinical trials of vaccines because there is no routine therapy mandated. Surgery should be the mainstay of treating relapsed melanoma if it is possible to remove all of the disease.
For widespread disease, chemotherapy is borderline effective and drugs such as dacarbazine can palliate symptoms, as can biologicals like interferon or interleukin 2. Radiotherapy may palliate local symptoms.
Prognosis
An individual’s prognosis depends on the type and stage of cancer, as well as their age and general health at the time of diagnosis. Five year survival for people diagnosed with melanoma is 92%, rising to 99% if the melanoma is detected before it has spread. If spread is within the region of the primary melanoma, the five year survival is 65%, dropping to 15% if the disease is widespread.
For more information, contact Cancer Council Helpline on 13 11 20 (cost of a local call).
(1) Non-melanoma skin cancer is the most commonly diagnosed cancer according to general practice and hospitals data, however there is no reporting of cases to cancer registries.