Ocular melanoma is a rare form of cancer of the eye that diagnosed in approximately 2,500 adults in the U.S. each year. It is a malignant tumor that starts in the eyes and is most often found in fair-skinned individuals between 50 to 55 years of age. Of course, anyone of any age and race can get this disease. It causes vision loss, blindness, and can spread to the brain and liver. Sadly, by the time many people are diagnosed, the disease has spread and they die within a few years of the initial diagnosis.
Despite its name, ocular melanoma isn’t caused by exposure to the sun. While it is a rare form of cancer, there have been clusters of people with this disease in North Carolina and Alabama. (See blog entry Folks with Ocular Melanoma Cluster on Social Media and 2020 Ocular Melanoma News). The individuals in the Alabama group in all went to Auburn University, while those in the North Carolina group live in Huntersville, near Charlotte.
For many years, treatments were limited to radiation and enucleation, which is the surgical removal of the eye. However, recent medical research has led to new insights about the disease and possible treatments.
Predicting When Tumors Metastasize
Current monitoring to detect metastases or disease spread involves MRI, CT scan or ultrasound imaging of the lungs or liver. The trouble with this is that the imaging can go on for years and patients need more information to make informed treatment decisions.
Work at the Oregon Health & Science University (OHSU) found that circulating hybrid cells or CHCs in the blood of ocular melanoma patients. What’s important about these cells is that they can provide clues about disease progression and metastasis without requiring a tumor biopsy.
Researchers would like to see the CHCs used a diagnostic biomarker to help differentiate ocular melanoma from benign nevi (moles). The CHCs could also be used a tool to see how well treatment is working. CHCs have potential to improve diagnostic certainty in the future,” said ocular oncologist Alison Skalet, MD, PhD, who along with her colleagues at the OHSU Knight Cancer Institute, worked on this study.
New Drug to Treat Ocular Melanoma
As stated earlier, treatments for ocular melanoma were limited to radiation and surgical removal of the eye when the radiation failed to stop tumor growth. While drugs have been used to treat this disease, success has been limited, at best.
That changed in 2021 when researchers at Memorial Sloan Kettering Cancer Center presented their finding at the annual American Association for Cancer Research meeting. A new drug, tebentafusp, demonstrated promising results in a large phase III clinical trial. In the study, people receiving this drug had close to half the risk of death compared to those treated with a checkpoint inhibitor drug or chemotherapy.
How tebentafusp works is that it enables the body’s immune T cells to recognize and attack uveal melanoma cells by targeting a protein on the cancer cells known as gp100. T cells usually ignore this protein, but the tebentafusp is like a matchmaker that helps the T cells recognize the cancers cells as a threat.
Its weakness is that it only works in persons with a specific human leukocyte antigen (HLA) type. HLAs are proteins found on most cells in the body. Approximately 40 to 50 percent of people of Western European descent have the HLA type that tebentafusp targets. While this drug only helps half of ocular melanoma patients, it is the first therapy proven to extend survival for those with this disease.
From predicting when tumor will metastasize to treatments that help people live longer, medical research is paving the way for improved outcomes in ocular melanoma. Of course, there’s more on the research horizon. The next blog entry will explore efforts to make ocular melanoma respond to immunotherapy.
Sources:
https://ocularmelanoma.org/disease
https://www.ohsu.edu/casey-eye-institute/new-clues-metastasis-ocular-melanoma
https://www.mskcc.org/news/new-drug-shows-promise-treating-eye-cancer-called-uveal-melanoma