Researchers say they may have discovered a new drug for the treatment of metastatic melanoma, one that uses the patient's own tumor cells to customize the therapy. The findings are published in the March issue of the journal Clinical Cancer Research.
The drug is sunitinib, which has already been approved by the FDA for the treatment of kidney cancer and gastrointestinal stromal cancer. In this Phase II clinical trial sunitinib proved effective against rare forms of melanoma that occur on parts of the body that the sun doesn't hit -- such as the mucosal surfaces of the mouth, the soles of the feet, and the palms of the hand.
"This form of skin cancer is particularly difficult to treat because it is resistant to chemotherapy, one of the standard therapies for most forms of cancer," says David Minor, MD, Director of Inpatient Oncology at California Pacific Medical Center -- part of the Sutter Health network -- and the co-author of the article. "Studies show that single-agent chemotherapy only produces a response rate of between 5 to 20 percent in patients with this form of cancer. So having one that produces a response of more than 50 percent is a big advance."
The forms of melanoma that were targeted in this study all have mutations in a gene called KIT, the tyrosine kinase receptor gene. The mutation makes an abnormal protein which then drives the growth of the tumor cell. Sunitinib works by turning off that protein and slowing down the cancer growth.
The researchers tested sunitinib in ten patients with advanced stage 4 metastatic melanoma who had the KIT mutation. Of those ten, four were able to complete the trial. Three of the four responded positively to the medication; one had a complete disappearance of her liver metastases for 15 months; the other two had remissions of seven months and one month.
"We need to be cautious because of the small number of patients involved in this trial," says Mohammed Kashani-Sabet, MD, a senior researcher at the CPMC Research Institute, Medical Director of CPMC's Center for Melanoma Research and Treatment, and the co-author of the study. "However, these results are encouraging because they are far better than we would expect to see with chemotherapy for this form of melanoma, and for this stage of the disease."
The researchers say that melanoma, like all cancers, is different in different people and that there are different gene mutations depending on the form. By identifying those who have the KIT mutation -- and sunitinib would not help a patient unless they had that mutation -- they are able to personalize the cancer therapy.
Because it has already been approved for the treatment of other cancers sunitinib has been well studied in larger patient populations. Side effects can include fatigue, low blood counts and a rash, but it is otherwise well tolerated by most people taking it.
The next step is to test the drug in a larger multi-center trial, possibly even involving patients at an earlier stage of the disease.
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