Gene tests to detect cancer get thumbs down from doctors

MUMBAI: Senior doctors have raised the red flag against targeting consumers directly for gene-based blood tests to detect the presence of cancer and its various stages.
Dr B Krishna, a senior nuclear medicine specialist, said patients had started demanding that their doctors use genetic tests as they are non-invasive and painless to detect cancer. “Patients don’t seem to realize that these blood tests are still in an investigational stage.The established tests, on the other hand, are 100% right ,” he said.
Medical oncologist Dr Sandeep Goyle concurred, saying these gene-based tests for cancer are new and still not widely used across the world.
The one that has, in particular, riled specialists is the circulatory tumour cell test that, as the name suggests, gives a result based on the volume of circulating cancer cells found in a blood sample. “Circulating cell evaluation for cancer, the so-called liquid biopsy, will eventually become more widespread,” said radiologist Dr Bhavin Jhankaria, adding, “but currently there aren’t enough studies that help us understand their utility.”
Gene tests are widely viewed as an evolution of diagnostic methods in every medical specialty. In 2004, the US FDA approved blood-based gene testing for colon, breast and prostate cancers.
The entire genome testing made its debut in India two years ago, with specific tests offering a total lifetime risk analysis of various diseases such as diabetes, cancer, hypertension and so on becoming available. Now, gene testing companies have begun offering CTC testing as well, forcing associations such as the Society of Nuclear Medicine India to react.
“In 2007, the American Society of Clinical Oncology advised against CTC testing for the diagnosis of advanced breast cancer,” said a letter by the Society of Nuclear Medicine India. The association’s letter signed by Dr Anshu R Sharma and Dr Basant Malpani pointed out that, in 2010, the American Joint Committee on Cancer did not include CTC tests in its cancer staging system.
“Direct-to-customer circulating cell advertisements mislead patients into believing that there is now some new magic method of evaluating cancer, as compared to the traditional, well-established methods of tissue biopsies, histopathology and radiologic investigations, including PET/CT,” said Dr Jhankaria. He said such marketing methods could jeopardize the future use of these technologies and, more importantly, prevent patients from taking correct decisions.
Dr Krishna said some patients had already voiced their concern about undergoing PET scans that uses a nuclear isotope to detect cancer when gene-based blood tests were available. “Benefits from PET-CT studies far outweigh radiation risks. Radiation exposure from medical imaging is a very small fraction of the total radiation received in an individual’s lifetime,” he said.
However, gene testing companies insist it’s not an “either or” question. Gene testing is complementary to present testing systems. “Over the past decade, advances in genetic technologies have allowed researchers to characterize the genetic mutations in a wide range of cancers, providing researchers and clinicians with a comprehensive view of cancer development and offered unique pharmacogenetic opportunities to target specific genetic mutations that are key drivers of the disease process,” Sumit Jamuar of the Global Gene Corporation said.
Identification of genetic mutations in a patient allows testing to be offered to other family members to determine if they too are at an increased risk for cancer.