Researchers from the National Cancer Institute announced Thursday that two cancer patients with rapidly growing melanoma were successfully treated with gene therapy. The patients -- both men -- were given immune system cells from their own blood that were engineered to attack their tumors. This took place 18 months ago -- and they are still surviving with no evidence of cancer. This success comes after a three-decade effort by surgeon Steven Rosenberg to find ways to use the immune system to fight cancer. This approach is not always successful, however, and 15 other patients who got this same treatment did not survive. Still, Rosenberg believes this small-scale success is proof that the principle of gene therapy can work. And others agree -- calling his work an important landmark, even though the response rate of two out of 17 is not ideal.

Rosenberg does not claim the two surviving patients are cured. If they survive for five years, he might classify them as possibly cured -- but even after five years, cancer can come back. He does consider this a huge breakthrough for these two men who are still alive and well. And he says he has every expectation that he can get the process to work even better in the future.