Blood biopsy reveals unique, targetable genetic alterations in patients with rare cancer

Using fragments of circulating tumour DNA in blood, University of California San Diego School of Medicine researchers were able to identify theoretically targetable genetic alterations in 66 percent of patients with cancer of unknown primary (CUP), a rare disease with seven to 12 cases per 100,000 people each year.
In order to plan treatment for cancer in general, physicians first attempt to pinpoint the primary cancer — where the tumour first developed. In CUP, despite its spread throughout the body, the origin remains unknown, making treatment more difficult. The current standard of care is platinum-based combination chemotherapies with a median survival time of six to eight months.
In a study, researchers report that by sequencing circulating tumour DNA (ctDNA) derived from blood samples in 442 patients with CUP, they were able to identify at least one genetic alteration linked to cancer in 290 — 66 percent — of patients. Researchers used a screening test developed by Guardant Health that evaluates up to 70 genes. Based on known carcinogenic mutations, 99.7 percent of the 290 patients who had detectable tumour DNA in their bloodstream had genomic alterations that could hypothetically be targeted using existing FDA-approved drugs (as off-label use) or with therapies currently under investigation in clinical trials.
“By definition, CUP does not have a definite anatomical diagnosis, but we believe genomics is the diagnosis,” said Razelle Kurzrock, MD, director of the Center for Personalized Cancer Therapy at Moores Cancer Center at UC San Diego Health and senior author. “Cancer is not simple and CUP makes finding the right therapy even more difficult. There are multiple genes and abnormalities involved in different areas of the body. Our research is the first to show that evaluating circulating tumour DNA from a tube of blood is possible in patients with CUP and that most patients harbour unique and targetable alterations.”
“Another advantage of the liquid biopsy is that the location of the cancer does not matter,” said Shumei Kato, MD, assistant professor of medicine at UC San Diego School of Medicine and first author. “With a blood sample, we can analyse the DNA of tumours throughout the body to find targetable alterations. With tissue biopsies, we can only see genomic changes that are in that one site and that may not be the same as what is in different sites not biopsied, such as the lung or bone.”
Moores Cancer Centerhttp://tinyurl.com/y9lffvh3