Novel test can detect circulating tumor DNA to determine if a patient has metastatic melanoma.
Blood tests, in addition to standard genetic tests, may be able to identify cases of aggressive skin cancer that previously avoided detection, according to a new study presented at the American Association for Cancer Research annual meeting.
The study authors believe that rapid and accurate diagnostic tools for types of metastatic melanoma may lead to earlier identification of cancer recurrence. The experimental blood tests are able to identify melanoma DNA within 48 hours, and may lead to speedy treatment.
The tests are the first to identify melanoma DNA in the blood of patients with metastatic disease who lack BRAF or NRAS genes, which are known to increase cancer growth, according to the study.
The authors project that when these tests become widely available, a majority of melanomas will be identifiable.
“Our goal is to use these tests to make more informed treatment decisions and, specifically, to identify as early as possible when a treatment has stopped working, cancer growth has resumed, and the patient needs to switch therapy,” said senior study investigator David Polsky, MD, PhD.
The tests work by monitoring blood levels of circulating tumor DNA (ctDNA), which are released in the blood when cancer cells die and fragment. The tests specifically search for mutations of a gene that controls telomerase reverse transcriptase (TERT), which maintains the physical structure of cancer cells’ chromosomes, according to the study.
These changes occur in mutated building blocks, where a cytidine molecule in the switch for the TERT gene is replaced by thymidine. Both C228T and C250T mutations causes the TERT switch to be turned on, which promotes cancer cell growth.
In the ongoing study, the authors checked test results against 10 tumor samples from patients with and without metastatic melanoma. They also tested 4 blood plasma samples from the patients.
The authors found that the blood test results were correct in all cases, and successful detection only required as little as 1% of mutated ctDNA, according to the study. The authors noted that TERT mutations were absent in samples of blood plasma and tonsil samples.
The authors believe that the new blood tests may have advantages over standard methods, since the tests avoid radiation exposure from CT scans, and can be performed easily, according to the study.
Once validated and approved for use, the blood tests are expected to be widely implemented. Previous studies indicate that similar blood tests for BRAF and NRAS mutations are able to better identify new tumor growth compared with established tests that look for the lactate dehydrogenase. While lactate dehydrogenase expression can increase during tumor growth, it can also indicate other diseases or biological functions, making it a less reliable biomarker.
The authors plan to continue assessing the use of the blood tests to monitor cancer progression, and to determine if an alternative treatment is necessary. They also intend to explore whether the test could be used to detect other TERT mutation-driven cancers, such as brain tumors, the study concluded.