ORLANDO, May 31 — A vaccine approach that trains immune cells and sends them marching into battle has shown promise in advanced melanoma, a researcher said here.

• Explain to interested patients that metastatic melanoma is a difficult disease to treat.
• Note that this study is the first late-stage clinical trial to show a benefit for a therapeutic vaccine approach to the disease.
• Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

The vaccine, used along with a powerful stimulant of the immune system, shrank melanoma metastases and prolonged the time before the disease resumed progression, according to Patrick Hwu, M.D., of M.D. Anderson Cancer Center in Houston.

In the phase III controlled trial, there was also a trend to longer overall survival that did not reach statistical significance, Dr. Hwu said at the annual meeting of the American Society of Clinical Oncology.

The vaccine consists of part of a molecule — dubbed gp100 — that is on the surface of melanoma cells. It’s delivered along with interleukin-2, a powerful immune system stimulant.

The vaccine, Dr. Hwu said, “takes T cells to boot camp” and trains them to attack the tumor. The interleukin-2 multiplies the killer cells into a “large army that can then attack the tumors to kill them.”

The approach is not new — a 1998 early stage trial in 31 patients showed good response — but this is the first phase III trial to show positive results, Dr. Hwu said.

The researchers randomized 185 patients with metastatic melanoma in 21 centers to get either interleukin-2 alone or interleukin-2 with the gp100 vaccine.

The primary endpoint was clinical response, but the researchers also measured time to relapse.

The overall response rate was 22.1% in the vaccine arm, compared with 9.7% in the patients who got interleukin-2 alone, Dr. Hwu said.

Progression-free survival also favored the vaccine, at 2.9 months compared with 1.6 months for interleukin-2 alone — a difference that was significant at P=0.0101.

The median overall survival favored the vaccine — at 17.6 months compared with 12.8 — but the difference did not reach statistical significance, Dr. Hwu said.

The finding is very preliminary, according to Len Lichtenfeld, M.D., of the American Cancer Society, who was not part of the study.

“There’s a long way to go before it can be generally applied,” he said.

But he said much of the progress in cancer care has been composed of small steps and this study is part of the pattern.

“A lot of our advances in cancer treatment take years if not decades,” he said, “and those years and decades are made up of small changes over a very long time.”

The findings are “definitely very promising for a very poor-prognosis group of patients,” said Sonali Smith, M.D., of the University of Chicago Medical Center, who moderated a press conference at which the research was presented.

She said the approach might act as a “platform” for more refined and potent vaccines.

Indeed, Dr. Hwu noted, the results mean that about 80% of patients did not respond. “We have to do better and I think we can” by employing different immune stimulants, he said.

The study was sponsored by the NIH. Some of the researchers reported financial links with Novartis. Dr. Lichtenfeld is an employee of the American Cancer Society. Dr. Smith said she had no disclosures to report.

Primary source: Journal of Clinical Oncology

Source reference:

Schwartzentrube SJ et al. “A phase III multi-institutional randomized study of immunization with the gp100: 209-217(210M) peptide followed by high dose IL-2 compared with high dose IL-2 alone in patients with metastatic melanoma” J Clin Oncol 2009; 27(15S): Abstract CRA9011.

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