- Genetic tests now accurately predict which breast cancer cases are most likely to benefit from oestrogen-lowering drugs and which don’t
- This means many women can get breast-conserving surgery rather than full mastectomy, depending on their genetic markers
- Indian genetic markers have shown that 30 per cent of breast or ovarian cancer cases are hereditary. That’s thrice the prevalence in the West.
- In Indians, most breast cancers are caused by faults in BRCA1 gene, while in the West, it is equally caused by markers both in BRCA1 and BRCA2 (These genes are present in every body)
- This has resulted in more targeted treatment
- Early results have also shown that certain ethnicities, rather than inheritance alone, like that of Konkani, Gujarati and Maharashtrian women, are more prone
- It’s now possible to tell which women need not undergo radiotherapy after mastectomy
Myeloid Leukaemia: The Gleevec Example
- In 2001, the discovery of imatinib mesylate (Gleevec) was a breakthrough for myeloid leukaemia
- It silences a protein called BCR-ABL that causes this type of leukaemia
- BCR-ABL results from an abnormal gene due to merger of chromosomes 9 and 22
- Before this drug was discovered, only one in three patients survived beyond five years post diagnosis. Gleevec improved survival rates to 90 per cent.
- Genetic tests to locate BCR-ABL can be done in India now
- Crizotinib (Pfizer discovery, sold as Xalkori) effectively tames lung cancer caused by a rogue copy of ALK gene
- Tests in India can now identify ALK
- Roche’s vemurafenib (sold as Zelboraf) pinpointedly attacks a rogue protein released by a mutated form of BRAF gene, which instructs skin cells to replicate endlessly
- BRAF test is available in India
- Since the sample is blood, it’s called liquid biopsy.
- Helps targeted therapy in breast, colorectal and bladder cancer
Why Hereditary Testing
- Current generalised screening approaches may not completely capture the risk for hereditary cancers