Abstract
Malignant melanoma is an aggressive cancer of pigment-producing cells, derivates of the neural crest. Surgical resection is the most effective form of treatment during initial phases of the disease.
Advanced stages are usually treated by adjuvant immunotherapy (interferon a) or dacarbazine + multiferon. Response and survival rates are extremely poor.
The emerging approach of personalized medicine brings about significant advances in the treatment of melanoma. Apart from administration of imatinib for a small subgroup of melanomas harbouring KIT mutations, the most promising approach is the use of B-RAF kinase inhibitors.
The previously tested RAF inhibitors (e. g. sorafenib) did not perform better compared to conventional chemotherapy or immunotherapy. However, the results are much more promising with the recently developed inhibitor PLX4032 (Plexxikon; RG7204, Roche Pharmaceuticals; vemurafenib).
This inhibitor targets tumours harbouring B-RAFV600E of B-RAF V600K activating mutations, which are present in 40-70% of malignant melanomas. An absence of the above mentioned activating mutations or parallel presence of activating RAS mutations (e. g.
RASG12D) should be used as contraindications. The use of PLX4032 provides better outcome than any of the currently used therapies, including partial or complete response recorded in 81% of patients, and prolonged median survival.
Currently, this drug is being tested in phase II and III trials. The incidence of PLX4032-related adverse effects is relatively high; acquired resistance repeatedly occurring within several months of treatment may also represent a significant problem.
Combined therapy is probably needed to further increase the complete response rate and to prolong survival. This should either include some of the currently used chemotherapeutics, or alternatively it may employ inhibitors of some of the kinases capable of stimulating the MEK and ERK kinases independently of B-RAF (e.g.
COT). Nevertheless, even PLX4032 monotherapy should be viewed as a significant improvement of the current state-of-the-art treatment of malignant melanoma.