Fragments of cancer-related DNA circulating in the blood of patients with colorectal cancer can be used to determine whether their surgery should be followed by chemotherapy, new research has shown.

Scientists at the Walter and Eliza Hall Research Institute, with international partners from Ludwig Cancer Research and the Johns Hopkins Kimmel Cancer Center, have designed a blood-based screening test to determine a patient’s risk of colon cancer recurrence after surgery.

Accurate testing of this risk factor could end the arduous experience of chemotherapy following surgical tumour removal by accurately identifying those patients who don’t need the extra treatment.

Lead author of the study Dr Jeanne Tie, a clinical research fellow at the Institute, said most patients with stage 2 colon cancers would be cured of the disease after surgery alone.

She said stage 2 tumours had generally invaded through the bowel wall but did not spread to other organs and the majority of these cancers at this stage were cured by surgery alone.

“Because current methods of predicting recurrence are imprecise, doctors tend to err on the side of caution,” Dr Tie said.

The research, just published in the journal Science Translational Medicine, followed 230 stage 2 colon cancer patients in 13 hospitals in Australia over four years.

“Up to 40 per cent of these patients undergo the ordeal of chemotherapy even though we know only a small fraction of them are likely to experience a cancer relapse.

“By identifying who is likely to experience a relapse we can better target post-operative chemotherapy at those who actually need it, and spare those patients who will not benefit from this additional treatment.”

Cancer cells often shed their DNA into the blood when they die. Recent technology has allowed researchers to capture and profile these fragments of DNA and understand whether chemotherapy would be beneficial.

This work was supported by the National Health and Medical Research Council (NHMRC); the Victorian State Government Operational Infrastructure Support, the Victorian Cancer Agency, Ludwig Cancer Research, the Conrad N. Hilton Foundation, the Sol Goldman Sequencing Facility at Johns Hopkins and the National Institutes of Health.

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