Indian doctors are on the brink of a medical breakthrough: Diagnosing eye cancer in children through a simple blood test.
The cancer, known as retinoblastoma, affects the retina of the eye. While it is a rare form of cancer, affecting only about 2,000 people in India per year, among the cancers of the eye in children under the age of five it is the most common.
Usually, an abnormal white reflex in the child’s eye—which is often mistaken for a cat’s eyeshine—triggers detection.
“Parents will notice something funny in the child’s eye. In rural India, such an abnormal white reflex is considered good luck,” Krishnakumar Subramanian, head of ocular pathology department at Chennai-based Vision Research Foundation, told Quartz. “Sometimes when the child is photographed, someone notices the white reflex in the eye, and finally gets referred to an eye doctor.”
In the case of retinoblastoma, biopsy—a common way to diagnose cancer by removing a sample of tissue from the suspected site—is not possible. In fact, attempting a biopsy could make things worse, because the needle track can cause the cancer to spread outside the eye. So ancillary testing through ultrasound and MRI (magnetic resonance imaging) scan of the eyes and brain is used for diagnosis.
When the tumour is in its early stage, doctors can try to save the child’s eye using treatments such as chemotherapy (a cocktail of drugs) or radiotherapy (various doses of X-ray). However, most tumours are detected only in advanced stages, forcing doctors to enucleate the eye—that is, surgically remove the tumour and thus the eye.
Work in progress
To develop an easier method to detect the presence of retinoblastoma early on, scientists at Vision Research Foundation, a part of Sankara Nethralaya, looked to human blood. Cancer is difficult to treat because its cells are very slightly different from normal cells. However, that slight difference can be caught in the form of markers found in the blood.
After testing the blood for many such markers, Krishnakumar and his team came across the presence of specific microRNA, or miRNA, found only in children with the cancer. The usual role of RNA is to translate the genetic code in DNA into proteins. However, microRNA do not directly take part in this translation. Instead, they help regulate the expression of genes, deciding when to turn on and turn off certain translations.
The tests performed on blood serum samples so far are only a proof of concept. “If we can come up with a point-of-care device (that can detect such miRNA with precision), we plan to have the clinicians use it,” he said.
However, it could be sometime before these serum miRNA biomarkers come to clinical practice, because Krishnakumar’s results will first need to be validated in a large number of patients. Right now they’ve tested only 10 such patients. Fortunately, newer technologies are coming for identifying serum miRNAs, which will further enhance this research work.
“If the point-of-care devices work, the easiest way to screen children would be at the time of polio or other vaccination schedule,” Krishnakumar said.