Melanoma is a form of skin cancer that develops in the pigmenting skin cells, called melanocytes. The Skin Cancer Foundation estimates that last year, about 120,000 new cases of melanoma would be diagnosed in the U.S. Roughly 68,130 cases would be invasive melanoma. It’s the most common form of cancer among those 25 to 29.
Although melanoma accounts for only about five percent of all skin cancers, it’s the cause of about 75 percent of skin cancer deaths. Last year, 8,700 people in the U.S. were expected to die from melanoma. The reason for the poor survival rate is that many cases are diagnosed after the cancer has invaded to deep tissues and/or spread to distant areas of the body. For melanoma that has spread regionally, five year survival rates are only about 62 percent. Once the cancer reaches distant areas of the body, five-year survival rates drop to about 15 percent.
Treating the Cancer
The mainstay of treatment for melanoma is surgical removal of the tumor. Doctors may try to remove the tumor by taking one layer of tissue at a time, checking each slice to see if any cancer cells remain. However, even seemingly small melanomas can grow deeply and leave behind a large hole once they are removed. Depending on the location and spread of the cancer, surgeons may remove the nearby lymph nodes as well.
If the melanoma spreads, it can be very difficult to treat. It’s impossible to detect and remove all distant melanoma cells. Chemotherapy (anti-cancer medications) may be tried. Other options may include immunotherapy or radiation therapy.
Rose Bengal for Advanced Disease
Sanjiv Agarwala, M.D., Oncologist at St. Luke’s Hospital in Bethlehem, PA says treatment for stage 3 melanoma is very limited. Surgery doesn’t often work because the cancer comes back. Even though the cancer is still somewhat localized, radiation therapy has limited effectiveness. Thus, patients don’t really have any good treatment options.
Agarwala and a few colleagues across the world are testing a new treatment for advanced melanoma, called PV-10 (Rose Bengal). PV-10 is a rose-colored stain used more than 100 years ago to dye wool. Doctors found the stain could be used in diagnostic tests to detect eye abrasions and to assess liver function. Researchers also discovered the stain may be taken up by cancer cells. Inside a cancer cell, the drug accumulates in specialized structures, called lysosomes, often causing the cell to die. Surrounding healthy cells are unaffected because they don’t take up the PV-10.
PV-10 is injected directly into a melanoma tumor. Agarwala says that the injection can be very painful for some people, so an anesthetic agent is given prior to the treatment. Following the injection, the tumor turns red. Agarwala explains that response is simply the result of the tumor cells taking up the red stain and the color has no direct effect on the treatment. Over the next few days, as the cancer cells die, the tumor dries up, scabs and falls off. It can take two to three weeks to see the final effects of the treatment.
Not all melanomas respond to PV-10. In a phase II study, researchers found 60 percent of participants had at least a 30 percent shrinkage of their tumor. However, researchers saw another, very surprising effect of the treatment. About one-third of patients who responded to the injection also had shrinkage of nearby and distant melanoma tumors that were NOT injected. The reason for the so-called "bystander effect" isn’t known. However, Agarwala theorizes that when the target tumor dies, the cancer cells release proteins that the immune system learns to recognize, improving the body’s ability to attack other melanomas.
Agarwala says the PV-10 is best for patients who have advanced, but localized disease with external tumors. It would not be used for those with a significant number of internal tumors.
Researchers are designing a phase III trial to further study the effects and benefits of PV-10 for melanoma. Though the drug is not yet approved in the U.S., it is available to melanoma patients who have no other treatment options through a compassionate use program. For more information go to clinicaltrials.gov, and then type the trial identification number in the search box: NCT01260779
Research compiled and edited by Barbara J. Fister
For information about PV-10’s expanded access for compassionate use, go to clinicaltrials.gov, and then type the trial identification number in the search box: NCT01260779.
For general information on PV-10, go to the company’s website at pvct.com
For information about melanoma:
American Academy of Dermatology, http://www.aad.org
American Cancer Society, http://www.cancer.org
National Cancer Institute, http://www.cancer.gov
Skin Cancer Foundation, http://www.aad.org/for-the-public/home