People with melanoma skin cancer may benefit from surgery followed by an experimental cancer vaccine, according to a new report in the Journal of Clinical Oncology (Vol. 20, No. 20: 4549-4554).

Melanoma can be extremely hard to treat if it spreads to distant parts of the body.

Eddy C. Hsueh, MD, and colleagues from the John Wayne Cancer Institute in Santa Monica, Calif., reported on over 15 years of experience with the vaccine, known as Canvaxin, in patients with metastatic melanoma.

They found that patients who received the vaccine after surgery were about twice as likely be alive after five years, and lived about twice as long as those who had surgery without the vaccine.

Melanoma is different from most other cancers in several ways.

It is easily treated by surgery if it is detected early, when it hasn’t gone beyond the skin. But it can spread quickly. Survival drops dramatically once it reaches the lymph nodes or spreads to other parts of the body.

This is partly because it is not as responsive to chemotherapy or radiation therapy as are many other cancers.

But the differences between melanoma and other cancers are not all bad news, according to the study authors.

Melanoma is one of only a few cancers in which the immune system appears to play a prominent role. There have been medical reports of rare cases where advanced melanomas shrink on their own. These remissions have been credited to the patients’ own immune systems killing off the cancer cells.

Scientists have taken this cue and developed immune-boosting treatments for the disease, such as interferon-alfa (IFN-a) and interleukin-2 (IL-2). But these treatments are effective in shrinking only a small percentage of melanomas, do not usually result in cures, and can have major side effects. Because of this, new treatments for metastatic melanoma are needed.

There is another difference that appears to be related to the immune system as well. Once most types of cancer have spread to other parts of the body, surgery is not a helpful option. Even if visible tumors are removed, cancer cells continue to grow in other parts of the body.

But in some studies of cancers where the immune system appears to play a role (as in melanoma), patients seem to live longer when surgery can remove all detectable tumors.

One explanation, according to the study authors, is that removing the bulk of the cancer allows the person’s immune system to "mop up" the remaining cancer cells, or at least to keep them in check.

Further boosting the immune system at this point may provide significant gains in survival.

To test this theory, the researchers conducted five small studies over the course of several years. People with metastatic melanoma had surgery to remove all known cancer and then received Canvaxin. This vaccine is made up of melanoma cells that were first irradiated to make sure they could no longer grow in the body.

The idea was to expose the body’s immune system to parts of melanoma cells, which would cause it to attack other melanoma cells throughout the body, and hopefully prevent a recurrence of the disease.

During the five studies, 150 people were treated with surgery plus the vaccine. For the present analysis, the authors compared them to another group of 113 similar patients who received only surgery during the same time period who were not part of the original studies.

The researchers found that about 40% of the patients in the vaccine group were still alive after five years, compared to only about 20% of the people who did not get the vaccine. The average survival time for the vaccine group was 36 months. For the control group it was 18 months.

One potential drawback of the treatment is that most patients with metastatic melanoma cannot have all detectable tumors removed by surgery. Still, while this was not a formal study, the survival advantage noted in those who got the vaccine is encouraging, said the authors.

A similar study, recently reported in the Annals of Surgery (Vol. 236: 438-449), found the same vaccine appeared to confer a similar survival benefit following surgery in patients whose melanoma had spread to the lymph nodes.

Two large studies are now underway to confirm these findings. At the moment, however, the US Food and Drug Administration (FDA) has placed them on partial clinical hold, meaning they are not enrolling new patients.

The study results point to the potential promise of vaccines in treating melanoma, and perhaps other types of cancer as well. While no cancer vaccines have yet been approved by the FDA, several of the most promising are being used to combat melanoma.