ORLANDO — A therapeutic, investigational vaccine given in combination with chemoradiotherapy after surgery was associated with improved survival in patients with resected pancreatic adenocarcinoma, according to a phase II trial presented at a symposium on gastrointestinal cancers sponsored by the American Society of Clinical Oncology.
The median overall survival for patients who received the vaccine was 26.8 months, compared with 20 months for historic controls, said Dr. Daniel A. Laheru of the department of oncology at Johns Hopkins University, Baltimore.
Of the 60 patients who received the vaccine, 88% survived for 1 year and 76% survived for 2 years. These results compare very favorably with those of previous studies, in which patients treated with surgery alone had an average 1-year survival rate of 63% and a 2-year survival rate of 42%, Dr. Laheru said at the symposium, which was also sponsored by the AGA Institute, the American Society for Therapeutic Radiology and Oncology, and the Society of Surgical Oncology.
Most of the participants (52 of 60) were considered to be at high risk because their cancer had spread to the regional lymph nodes.
The vaccine, known as GVAX immunotherapy, boosts the patient's own immune system to help it recognize cancer cells throughout the body and destroy them. GVAX is made up of lethally irradiated lines of pancreatic cancer cells that were engineered to secrete granulocyte macrophage colony stimulating factor (GM-CSF).
“The GM-CSF molecule attracts immune cells to the vaccine site, where the immune cells encounter pancreas cancer antigens. They then patrol the rest of the patient's body in a kind of seek and destroy mission, to destroy pancreas tumor cells possessing the same antigen profile,” Dr. Laheru explained. The vaccine does not prevent cancer, he added.
Patients who were deemed to be free of cancer 30 days after their surgery were eligible to receive the vaccine. The first infusion was given 8–10 weeks after pancreatic resection.
This was followed by treatment with a standard regimen of 5-fluorouracil-based chemotherapy plus radiation.
Patients who were disease free 1 month after chemoradiotherapy received three additional vaccine doses, 1 month apart, followed by a fifth booster 6 months later.
The vaccine immunotherapy was well tolerated. Side effects included transient vaccine injection site reactions, such as itching, redness, and swelling. These typically resolved within 10 days.
“Pancreatic cancer is the fourth leading cause of cancer-related death [in the United States]. Surgery is the only known cure for early pancreatic cancer, but most patients [have a recurrence] even after optimal resection. We are optimistic about the results from this study, which suggest that the vaccine could provide additional benefit over chemoradiotherapy, but prospective randomized trials are needed to confirm this observation,” Dr. Laheru said.
He and the Johns Hopkins investigators also plan to study whether the vaccine is most effective in combination with chemotherapy alone or with chemotherapy plus radiation.
Dr. Laheru disclosed that he received research funding from Cell Genesys Inc., which developed the vaccine.