Several new drugs are showing great promise in treating kidney cancer, a dif-ficult-to-treat form of cancer. The drugs are “targeted” to attack certain molecular mechanisms that spur cancer growth.
The disease is usually resistant to chemotherapy. Only one drug has been approved for kidney cancer, interleukin-2 (IL-2). IL-2 can bring about complete remissions in 3% to 10% of patients, but it is overly toxic and most patients do not receive it.
Because the new data, presented at the American Society of Clinical Oncology meeting in June 2004, were mainly from small trials without placebo controls, doctors cautioned that the results might not hold up in larger, randomized trials and that the drugs might not prolong lives. Overall, however, the medications either shrank tumors or at least stopped them from growing in most patients.
SU 11248 (Sugen/Pharmacia, Pfizer) shrank tumors by at least 50% in 21 of 63 patients and stopped tumor growth in 23 others. The Pfizer-sponsored trial involved 63 patients whose tumors had continued to worsen despite previous treatment with IL-2 or interferon.
BAY 43-9006 (Bayer/Onyx) caused tumor shrinkage or stopped tumor growth in 82 of 106 patients. Most of these patients had undergone earlier unsuccessful treatment. Tumors shrank by 50% in 13 of those patients.
The two drugs used in concert were bevacizumab (Avastin™, Genentech), which is approved to treat colon cancer, and erlotinib (Tarceva™, Genentech), which has extended the lives of lung cancer patients. Avastin™ blocks the flow of blood to tumors, and Tarceva™ blocks epidermal growth factor receptor. In that trial, tumors shrank by at least half in 12 of 58 patients and shrank by a lesser amount or stopped growing in 38 others.
The newer targeted therapies generally have fewer side effects than older chemotherapy drugs.