Isaac Garcia-Murillas and his colleagues look for tumor DNA in the blood of patients treated for breast cancer, to determine whether the patients are at risk of having their cancer return. | The Institute of Cancer Research, London
A blood test that picks up traces of tumor DNA in the bloodstream can accurately predict relapse in early-stage breast cancer patients about eight months before recurring tumors can be visually detected in the clinic, according to a new study. The non-invasive technique may give clinicians a new window of opportunity to tailor a patient's therapy before her cancer returns and spreads throughout the body.
"This is the first study to show that we could use a blood test in this way — to predict relapse," said Nicholas Turner from The Institute of Cancer Research and Royal Marsden Hospital, UK, who is senior author of the study. Although the blood test is not yet ready for clinical use, he said, "the hope is that we can identify residual cancer early enough to prevent relapse or substantially defer relapse."
The findings appear in the 26 August issue of Science Translational Medicine.
Genomic sequencing technologies have made it possible to scan blood for fragments of DNA shed by tumors, which may provide early signs of relapse. "Detection of disease progression earlier might have a plethora of benefits for patients," said Isaac Garcia-Murillas, also from The Institute of Cancer Research. This could help guide treatment of patients based on their mutational make-up, he noted.
Applying the sequencing approaches to early-stage cancers, from which circulating tumor DNA in the blood is often scarce, has remained a challenge. This is particularly true for breast cancer, where 95% of women are diagnosed at a very early stage of the disease, when chances of beating cancer are greatest.
While chemotherapy and surgery are effective against early-stage breast tumors, cancer cells that survive treatment can return and invade other organs as metastatic disease. Circulating tumor DNA may offer "a very advanced marker, a very sensitive marker [for] cancer cells that are left behind" after treatment, said Turner.
"The key challenge is figuring out which women are cured and which women are at further risk of relapse," said Turner. "Women who had completed surgery but still had tumor DNA in the blood have a high risk of developing relapse."
Identifying these patients earlier could help prevent their further relapse, while also helping patients who have been cured by surgery to avoid unnecessary further treatment.
The researchers studied 55 early-stage breast cancer patients who had received a standard treatment of chemotherapy followed by surgery. Using sequencing technologies, they tracked tumor-specific mutations in their blood drawn regularly for the next two years.
The technique accurately predicted relapse in 12 of 15 patients about eight months before tumors were spotted by conventional imaging in the clinic. By monitoring circulating tumor DNA, the researchers were able to uncover metastatic tumors throughout the body, except in the brain.
For some patients, analysis of circulating tumor DNA uncovered mutations potentially driving metastatic growth or drug resistance, which could help doctors select drugs that specifically target those mutations. Turner's team is planning to study a larger group of breast cancer patients to determine whether the blood test can direct personalized treatment strategies for patients at risk of relapse.
[Credit for associated teaser image: Flickr/Steven Kenny, East Kent Hospitals University NHS Trust, Wellcome Images/ CC BY-NC-ND 2.0]