Canadian research that led to the discovery of a specific gene mutation -- Neurotrophic Tyrosine Receptor Kinase or NTRK gene fusion -- has allowed a first-of-its kind cancer treatment to be created by pharmaceutical company Bayer and approved for use by Health Canada.
A gene mutation is the result of a mistake or alteration in a normal DNA sequence or gene structure that can cause myriad of health problems.
“NTRK gene fusion is a mutation that occurs when a ‘break’ happens in DNA and the NTRK gene is relocated to another part of the DNA molecule, finding itself ‘fused’ to another gene that would not normally be beside it,” said Dr. David Malkin, an oncologist at Toronto’s SickKids hospital, in an email to CTV News.ca Tuesday.
“The new NTRK fusion gene then does not function properly and the cell grows and divides uncontrollably…which can lead to cancer,” Malkin said.
Dr. Poul Sorensen, a B.C. pathologist, is credited with the discovery of the molecular and cellular pathways characterizing NTRK genes in the late ‘90s that allowed further development into a brand new cancer treatment.
"By using a molecular-based approach to studying a cancerous tumour, we were able to identify the NTRK gene fusion as the driver of what is now known as TRK fusion cancer," said Sorensen in a release. "This validated the idea of studying rare tumours and represented a new approach to cancer drugs and their regulation with the drug intended for a wide variety of cancers."
NTRK gene fusion is found in both children and adults with many kinds of cancers, such as thyroid, lung and sarcoma, but the cause of the mutation is not known, said Malkin.
“Approximately 1 per cent of human cancers overall have NTRK fusions…the tumours that harbor NTRK gene fusion can be treated with a combination of chemotherapy, surgery and/or radiation,” said Malkin, adding that a new development to target the NTRK gene fusion directly has had promising results.
Pharmaceutical giant Bayer announced at the end of July that Health Canada had approved Vitrakvi, a “first-in class oral and highly selective TRK inhibitor that may shrink the tumour or may slow or stop it from growing” in adult and pediatric patients with solid tumours that present the NTRK gene fusion mutation.
It is the first time that Health Canada has approved a treatment like this, the release says.
The release states that in the clinical trials leading up to the approval of the Vitrakvi treatment by Health Canada, the overall positive response rate was 75 per cent, with 22 per cent of patients experiencing a complete response to treatment.
In addition, the overall response rate for pediatric patients was 90 per cent and 69 per cent in adult patients, with “responses…rapid and durable,” the release said.
It’s an important step for Canadian families like Kayley and Shayne Leeds from Claresholm, Alta, whose son Ashton was diagnosed with Stage 4 thyroid cancer in 2015, just before his fifth birthday.
After years of treatment at SickKids and the children’s hospital in Calgary, which included surgeries and radiation treatment for the tumours in his thyroid, neck and chest, by 2017 Ashton was getting worse.
“Over the span of a few months and a series of tests Ashton’s doctors found that the cancer was spreading in his lungs and was no longer responding to radioactive iodine treatments,” Kayley Leeds told CTV News.ca in an email Wednesday.
Doctors asked to test Ashton’s tumours for their sequencing database of pediatric cancers, known as the KiCS program, and discovered that Ashton’s cancer was caused by the NTRK gene fusion.
Ashton was enrolled in a Seattle clinical trial for Vitrakvi, as it was only available in trials at the time, and had a “dramatic” response, his mother said.
“We watched his health improve dramatically, his breathing, colour, appetite and energy level all returned to normal,” Kayley Leeds said. “He has stayed stable ever since, with no side effects.”
Leeds said 2019 marks the two-year anniversary of the medication giving now 9-year-old Ashton “his life back.”
The family still flies to Seattle every month for check-ups, but now that Health Canada has approved Vitrakvi for use in Canada, the Leeds say they have a message for families affected by pediatric NTRK gene fusion cancers.
“I want people to know there is hope, I want them to know that everyday new possibilities and new treatment options are becoming available,” Leeds said.
