Being able to diagnose early-stage cancer may no longer require an invasive biopsy, as scientists have developed a blood test that can give them an answer instead.
In trials scientists were able to detect 62% of cancers in a group of cancer patients using the new technique, as well as identify which stage it had reached.
Not only that, but their novel method did not identify a single healthy patient as having the disease (which can often happy because of non-problematic mutations in blood cells in the body), meaning no one was treated unnecessarily.
Blood tests for cancer are a growing part of clinical oncology but remain in the early stages of development as sometimes screening tests are not specific enough and flag genetic mistakes in the masses of DNA circulating in a blood sample.
For example, there is a chance cells will acquire mistakes or mutations and in a small fraction of people, these changes will spur a blood cell to multiply faster than its neighboring cells, potentially leading to pre-leukemic conditions.
But these are actually “false positive” results that often lead to unnecessary over testing and over-treatments.
Professor of Oncology Victor Velculescu said: “The challenge was to develop a blood test that could predict the probable presence of cancer without knowing the genetic mutations present in a person’s tumor.”
The blood test was designed by a team at the John Hopkins Kimmel Cancer Centre to look out for tiny quantities of tumour-derived DNA floating around in the blood, that signals someone might have the disease.
They say it is unique in that it can distinguish between DNA shed from tumours and other-altered DNA that can be mistaken for cancer biomarkers by other methods.
Velculescu said: “This study shows that identifying cancer early using DNA changes in the blood is feasible and that our high accuracy sequencing method is a promising approach to achieve this goal.”
The blood test was then performed on blood samples from 200 people with all stages of cancer in the USA, Denmark and Netherlands.
The test correctly predicted cancer in 50% of the colorectal patients with stage I disease, 89% with stage II disease, 90% with stage III and 93% with stage IV disease.
Of 71 people with lung cancer, the test found 45% with stage I disease, 72% with stage II disease, 75% with stage III disease and 83% with stage IV cancer.
For 42 patients with ovarian cancer, 67% with stage I disease were correctly identified, as well as 75% with stage II disease, 75% with stage III cancer and 83% with stage IV disease.
Among 45 breast cancer patients, the test spotted cancer-derived mutations in 67% patients with stage I disease, 59% with stage II disease and 46%with stage III cancers.
The team says that the populations who could benefit most from such a DNA-based blood test are those at high risk, such as women with BRCA1 and BRCA2 breast-cancer genes and smokers, for whom standard computed tomography scans often lead to false positives.