Two new drugs can significantly increase survival in patients with metastatic melanoma, the advanced and generally lethal form of skin cancer, researchers reported. Results were so dramatic in a trial of one of the drugs that the study was halted early, researchers reported Sunday at a Chicago meeting of the American Society of Clinical Oncology. Studies on both drugs were published online by the New England Journal of Medicine. Melanoma is among the most common cancers in the United States. An estimated 68,000 new cases are diagnosed each year, with 8,700 deaths. The shortened trial is notable because the experimental agent called PLX4032, or vemurafenib, is the first chemotherapy agent directed at a specific mutation involved in the formation of skin tumors.