New NGS based approach scores high in diagnosing retinoblastoma, says study

Strand Life Sciences, a genomic profiling company and leader in precision medicine diagnostics in India, along with its collaborators, announced the publication of a key study in the journal Molecular Vision. The study highlights the clinical utility of Next-Generation Sequencing (NGS) based tests for increased mutation detection sensitivity in an Indian Retinoblastoma (Rb) cohort.

Retinoblastoma, a malignant tumor of the eye and the most common primary intraocular cancer of childhood, causes major blindness in children. Mutations in the RB1 gene are the primary cause of Rb. Around 20 percent of the global Rb patients reside in India, making it the largest Rb population in the world.1In developed countries, children with Rb have a disease-free survival rate greater than 90 percent, compared to 10-30 percent in developing countries like India.2 The reasons for poor outcomes in developing countries are late diagnosis, lack of awareness, prohibitively high costs of diagnostic procedures, and inaccessibility to quality medical care.

In this particular study, 50 unrelated patients were screened for the Rb gene. Pathogenic (harmful) mutations were detected in 66 percent of the cases, out of which 12 were novel. In bilateral Rb cases, the mutation detection rate was 100 percent, while in unilateral Rb cases, the rate was 30 percent. This is consistent with the predominantly hereditary nature of bilateral disease as compared to the largely sporadic nature of unilateral disease. Previously, several Indian studies conducted screening of the RB1 gene in Rb patients and reported mutation detection rates in the range of 33 percent to 85 percent. These studies highlight the limitations of the techniques used in these studies because, in principle, close to 100 percent of bilateral Rb patients carry germline (inherited) mutations in the RB1 gene. This new study suggests that NGS-based approaches increase the sensitivity of mutation detection in the RB1gene, making it fast and cost-effective, compared to the conventional tests performed in a reflex-testing mode.

The burden of Rb on the Indian health care system has been steadily increasing, thus stressing the need for cost-effective methods for early detection, surveillance, and disease management. Due to its early age of occurrence and the risk of second cancers (soft tissue sarcomas, osteosarcomas, and melanomas) at later stages of life, early molecular diagnosis and treatment options must be considered for better management of the disease.

Dr. Vijay Chandru, Chairman and Managing Director, Strand Life Sciences, said, "In India, there is a pressing need for a cost-effective and comprehensive genetic testing method for the early diagnosis of Rb. In the current study, we report a 100 percent mutation detection rate in patients with bilateral Rb. Our study suggests that an NGS-based approach increases the sensitivity of mutation detection in the RB1 gene, and helps in the confirmation of a genetic diagnosis in patients and at-risk family members compared to conventional tests performed in reflex testing mode. Our finding strongly supports the incorporation of a NGS-based approach for the routine genetic testing of Rb in India, as it is highly sensitive, accurate, fast, and affordable."

Dr. Ramesh Hariharan, PhD, FASc, Co-founder and Chief Technology Officer, Strand Life Sciences, said, "In the RB1 gene, mutations are distributed throughout the entire length of the gene and can vary from very small to very large, possibly comprising even the entire gene. Traditionally, identifying these heterogeneous mutations has required a combination of tests, which is time-consuming and costly. By incorporating sophisticated bioinformatics into the analysis of our tests, we are able to use a single leading test based on NGS to derive most of the results, occasionally followed by MLPA for negative cases or ambiguous cases requiring confirmation."

Dr. Ashwin C Mallipatna, MBBS, MS, DNB a Pediatric Ophthalmologist from Bangalore, Co-Author of this study, said, "Retinoblastoma is the most common eye cancer in children, affecting hundreds of children in India and thousands of children worldwide each year, which can be fatal when diagnosed late. About half of the children suffering from this cancer carry a mutation in the RB1 gene that may run in their family (heritable mutation), with potentially fatal consequences to those affected. The American Joint Committee on Cancer has acknowledged the importance of this heritable trait in predicting patient survival, making it essential to consider while evaluating retinoblastoma."

Dr. Mallipatna added, "The importance of sensitive testing to detect an abnormal RB1 gene cannot be understated. NGS is cost-effective in detecting RB1 mutations. This study demonstrates a bio-informatics strategy that makes standard NGS-based testing more sensitive. Interpreting these laboratory results by doctors, and communicating that to the family is essential through proper genetic counselling.