Researchers say cancer vaccines hold promise

12.00 pm

SAN FRANCISCO - Early results from clinical trials of experimental cancer vaccines show they can halt, or even reverse, tumour growth in very sick patients who have failed other treatment, researchers said today.

"We may be entering a new era in vaccination therapy," Dr. John Nemunaitis, lead investigator on a lung cancer vaccine study selected for presentation at a meeting of the American Society of Clinical Oncology.

Cancer vaccines seek to trigger the body's own immune system to kill cancer cells.

Nemunaitis presented data from 30 patients - 22 with advanced lung cancer and 8 in early stages of the disease - in a trial of a "GVAX" vaccine against non-small cell lung cancer in which 18 per cent of the patients with advanced cancer saw their tumours disappear or shrink by more than half.

The cells of each type of lung cancer - small cell and non-small cell - grow and spread in different ways, and they are treated differently. Non-small cell lung cancer is usually associated with smoking.

In a second trial, researchers at Stanford University used modified immune cells to attack colorectal cancer. In a small initial study of 12 patients with end-stage cancer, their vaccine produced clinical benefits in four patients.

Both researchers suggested cancer vaccines may also be effective when patients are first diagnosed with cancer or in combination with anti-cancer treatments like surgery and chemotherapy.

"We might even be able to use them like any vaccine to prevent disease rather than treat it," said Dr. Lawrence Fong, lead author of the Stanford study.

Nemunaitis said the GVAX preliminary findings are particularly noteworthy since lung cancer patients who failed chemotherapy have little chance of responding to further chemo or other treatment.

The GVAX vaccine being developed by Cell Genesys Inc. . The study results were from a Phase I/II trial of the company's vaccine - an early stage of the research.

The company's cancer vaccines are composed of tumour cells taken from individual patients that have been irradiated and genetically modified to secrete a hormone that helps stimulate the immune system. Cell Genesys company is also working to develop a standardised lung cancer vaccine that can be mixed with the patients' own tumour cells to make the vaccine.

Of 22 patients with advanced-stage lung cancer, three patients, two who failed chemotherapy and one who failed radiation therapy, showed a complete disappearance of metastatic tumours following treatment with the vaccine.

Another patient who failed radiation and chemotherapy had a more than 50 percent reduction in his tumour. In addition to these major responses, four patients have seen their disease stabilise, according to study results.

All the responses have been maintained for a median follow-up time of five months, and researchers are giving second vaccinations to the patients with partial responses, Nemunaitis said.

"We had one 72-year-old woman with refractory non-small cell lung cancer with multiple lesions. We dissected one tumor to make the vaccine and were very impressed with her complete remission," Nemunaitis said.

In addition, out of the eight patients in the trial with early-stage lung cancer, seven received GVAX vaccine following surgery and they are all free of disease after an average of 7 months.

Cell Genesys is testing its GVAX vaccines in a range of cancers, including pancreatic, kidney and skin cancer, but its most advanced vaccine program is in prostate cancer.

The GVAX vaccines don't have serious side effects, especially compared to the harsh ones caused by chemotherapy, chief executive Stephen Sherwin told Reuters.

Side effects mimic the fever and injection site redness seen with other types of vaccination, Nemunaitis said.

The Stanford researchers took a different approach, using patients' own dendritic cells as a platform to fight cancer.

Dendritic cells are the cells that instruct T-cells to find and kill foreign cells. The body's own immune system, however, does not normally attack cancer cells because they are not foreign.

In the Stanford study, two out of the 12 patients saw their tumours shrink, two were stable for six months and one patient had a mixed response, with some tumours shrinking while others grew, the researcher said.

- REUTERS