Researchers have made significant advances in the treatment of metastatic malignant melanoma — one of the most difficult cancers to treat successfully — according to a new study. In the phase I extension study, researchers have seen rapid and dramatic shrinking of metastatic tumors in patients treated with a new compound that blocks the activity of the cancer-causing mutation of the BRAF gene, which is implicated in about 50 percent melanomas and 5 percent of colorectal cancers.