Blood Tests May Be Able to Detect Eye Cancer

Is that a freckle or eye cancer? Good question. Here’s another question – did you know that you can get both freckles and melanomas in the eye? And because freckles are cute but melanomas are not, this brings us back to the all-important first question.

The uvea is a part of the eye that encompasses several bits of anatomy. The iris is the well-known colored part of the eye visible from the front; the ciliary body is the part no one has heard of but it plays several important roles; and the choroid is a layer of tissue lining the inside of the eyeball, rich in blood vessels that provide oxygen to the outer layers of the light-sensing retina. A harmless freckle (or nevus, as doctors like to call it; nevi being the plural) can present in any part of the uvea; 6 out of 10 people have iris nevi and about 1 in 10 have a choroidal nevus. Unfortunately, a harmful melanoma can also present in any part of the uvea as well, with a particular preference for the parts of the eye not so easily visible in a mirror – the ciliary body and the choroid.


Ocular Melanoma

Ocular melanoma, while a relatively rare disease, is still considered the most common primary cancer of the eye (meaning it originated in the eye rather than metastasizing, or traveling, from elsewhere). About 2,000 people are diagnosed with this cancer every year in the US and although it can occur in any age group and any race, it appears to have a higher prevalence in fair complexioned individuals with a median age around 55 years.

Uveal melanomas may cause fatality if not promptly treated. Although you can live without an eye, if cancerous cells metastasize to the liver or lung and begin to destroy healthy tissues there, those organs can be much harder to live without. The American Society of Clinical Oncology lists the 5-year survival rate of choroidal melanomas as:

  • 84% for small melanomas
  • 68% for medium melanomas
  • 47% for large melanomas

This indicates the percentage of patients likely to survive at least 5 years after having been diagnosed with a choroidal melanoma.
Treatment of a uveal melanoma will depend on various factors, such as its exact location and its size. There are two broad categories of treatment – radiation treatments or surgical treatments. The most drastic of these may be considered enucleation, which involves surgical removal of the entire affected eyeball and eventual insertion of a prosthetic.
But we’re getting ahead of ourselves. Before we enucleate the eyeball let’s make sure we got the diagnosis correct.


Diagnosis of Uveal Melanoma

Because nevi are common but benign and melanomas are rare but cancerous, it is important to be able to distinguish the two. In addition to this, what once was may not be anymore – that is to say, it may have started as a cute little eye freckle but about 1 in 9,000 of these transforms into a raging uveal melanoma with time and so needs to be monitored by an experienced eye doctor.

Uveal melanomas demonstrate a few characteristics that may be helpful to differentiate them from harmless nevi. These include size, distance from the optic nerve, thickness, color, and visual symptoms such as vision loss or flashing lights. Traditionally, these observable traits of the suspect spot in question have been combined with additional clinical testing, such as ultrasound or angiography, and close monitoring. However, these methods may still leave some doubt in the mind – to enucleate or not to enucleate? Then enters a tumor biopsy, but this comes with its own risks, including potentially causing the tumor cells to spread more rapidly or causing some other sight-threatening complication.

So then enters a plain and simple blood test.

Researchers in Australia recently discovered a highly accurate blood test for detecting not only the presence of a uveal melanoma, distinguishing the spot from a nevus, but also its metastatic potential.

Tiny chains of molecules known as miRNA are expressed in varying levels during cancer and have been found to be easily detectible in the bloodstream and certain tissues. In cases of other types of cancer, such as skin melanomas, some of these miRNA molecules have also been noted to provide some valuable diagnostic information. The medical researchers found that 6 specific types of miRNA were associated with the presence of uveal melanoma but not nevi. Additionally, analyzing the levels of certain miRNA molecules was found to be associated with survival rate due to a correlation between localized (staying put) versus metastatic (going for a ride) melanoma, allowing some degree of prediction of the prognosis.

The blood test analysis showed a high sensitivity (able to detect a melanoma if present) and specificity (didn’t get confused with a nevus). However, as the test may not be mainstream just yet, the current best advice is to continue monitoring any suspect spots with your eye doctor as recommended. But as research continues and the test develops, one day we will hopefully find a straightforward, easily accessible blood test that can provide the confidence we need to decide between cute little freckle or raging melanoma monster.