Treatment of Malignant Melanoma
Malignant melanoma is the most common cause of death due to skin disease and is one of the most common cancers in the USA, Australia and Europe. Although the incidence rates of skin cancer are increasing worldwide, mortality from the disease is not rising as fast due to early detection and treatment.
Treatment of melanoma consists primarily of surgical removal or excision of the tumor. Depending on the stage of the disease, involvement of other organs and the age and general health of the patient, surgery may also be accompanied by radiation therapy and chemotherapy.
The risk of death from melanoma depends on the stage and tumor depth in the skin. Spread of cancer cells occurs through the lymphatics to the lymph nodes and other organs. This is why traditionally melanomas were removed with wide skin margins (up to four centimeters from the border of the lesion). However over the past decades malignant melanoma resection margins have become narrower (one to two centimeters) due to increased morbidities (negative effects) associated with wide excisions and insufficient evidence of its greater benefits. Furthermore, several trials with conflicting results comparing wide versus narrow margins of excision have been done with no conclusive support as to which choice will prevent recurrence and increase survival rates. It is agreed therefore that more trials involving more subjects and longer follow up have to be done to determine the safest margins of resection that will give optimum benefits regarding recurrence and survival rates.
Melanoma Resection Margins
At present, guidelines that are being followed regarding the extent of excision depend mainly on the depth of the tumor, thus the resection margins of normal skin around the tumor borders are:
- For in situ melanomas (earliest form of the disease with no local invasion, just abnormal cells flat on the skin present) - half a centimeter margin
- For melanomas less than one millimeter (mm) thick – one centimeter (cm) horizontal and vertical margins
- For melanomas one to two mm thick - one centimeter (cm) margins
- For melanomas at least two mm thick – for some a two cm margin is recommended, others recommend three to four cm margins.
A multicenter clinical trial to investigate the effect of the margin of excision on the outcome in patients with high-risk malignant melanoma was performed under the auspices of the United Kingdom Melanoma Study Group, the British Association of Plastic Surgeons, and the Scottish Cancer Therapy Network. Their findings showed that for melanomas that are at least two mm thick a wider excision (at least two to three cm) should be done to prevent local and regional recurrences, and for melanomas that run deeper or are more than four mm thick, a three cm margin will be more prudent. Deeper involvement of the skin gives a greater risk of cancer cell invasion to the lymphatics and other organs, and this can be prevented by wider margins of excision.
As previously mentioned, depending on the stage of the skin cancer, meaning tumor size and spread to lymph nodes and other organs, treatment of melanomas may also involve radiation and chemotherapy aside from surgical excision. The patient should be adequately informed about the risks and benefits of the different choices of treatment corresponding to his skin cancer staging.
Dermatology Information System, “Melanoma Treatment Information for Professionals”, https://skincancer.dermis.net/content/e04typesof/e154/e156/index_eng.html
NEJM, “Excision Margins in High-Risk Malignant Melanoma”, https://www.nejm.org/doi/full/10.1056/NEJMoa030681#t=articleTop