Use of a new pancreatic cancer vaccine can improve the 2-year survival of patients with resectable disease from about 42% to 76%, according to the results of a phase II trial presented Tuesday at a cancer meeting in Philadelphia. Still, the authors emphasize that the findings are preliminary and further follow-up is needed.
The vaccine, which had shown encouraging results in a phase I trial, consists of pancreatic cancer cells, rendered inactive through irradiation and genetically modified to express GM-CSF. After intradermal injection of the vaccine, the GM-CSF attracts immune cells that recognize the antigens on the irradiated cells and then seek out and destroy the patient’s own circulating pancreatic cancer cells. Pancreatic cancer is known to be an aggressive malignancy with few treatment options. In 2003, researchers presented a chemoradiotherapy protocol that substantially improved survival. Unfortunately, this protocol, which involved 5-fluorouracil, weekly cisplatin, and every other day interferon-alpha with radiotherapy, was also fairly toxic. “The 1- and 2-year survival rates achieved with that protocol were similar to what we obtained with the vaccine,” but with less toxicity, lead author Dr. Daniel Laheru, from Johns Hopkins Kimmel Cancer Center in Baltimore, told Reuters Health. “A little under half of the patients in that study were admitted to the hospital for GI-related complications.”The present study involved 60 patients with resected pancreatic adenocarcinoma. The first dose of the vaccine was given 8 to 10 weeks after surgery and then a standard chemoradiotherapy regimen was administered. If no disease was apparent one month later, the patient was given three more doses of the vaccine on a monthly basis. The fifth and final dose was given 6 months after the fourth dose. Dr. Laheru presented his team’s findings in a press briefing at a joint meeting of the American Association for Cancer Research, National Cancer Institute, and the European Organization for Research and Treatment of Cancer. The vaccine was associated with 1- and 2-year survival rates of 88% and 76%, respectively. Previous studies have typically yielded corresponding rates of 63% and 42%. Immune analysis showed that GM-CSF levels decreased in amplitude with subsequent monthly injections of the vaccine, suggesting a drop in potency. However, with the fifth dose, the timing of the GM-CSF peak and the amplitude had returned to what was seen after the first dose. While the findings are potentially good news for patients with early stage disease, Dr. Laheru was quick to point out that “only about 15% to 20%” of patients with the malignancy fit into this category.”Clearly, the majority of patients have advanced disease at presentation,” he said. “We completed a study last year using a similar vaccine in patients with advanced pancreatic cancer and we’ve just submitted the results for publication.”(Source: Reuters Health: Anthony J. Brown, MD: Oncolink: November 2005.)