A blood test that detects microscopic fragments of genetic material shed when cancer cells die allowed researchers to determine which patients with stage 2 colon cancer required follow-up chemotherapy after surgery and which could skip it, according to research presented June 4 at the 2022 annual American Society of Clinical Oncology meeting in Chicago.
About 151,030 new cases of colorectal cancer are expected to be diagnosed in the United States in 2022.
Pinpointing the best after-surgery strategy for people with stage 2 colon and rectal cancers remains a “clinical dilemma,” said lead researcher of the study Jeanne Tie, MD, an associate professor at the Walter and Eliza Hall Institute of Medical Research and Peter MacCallum Cancer Center in Victoria, Australia.
Currently, these patients are usually prescribed oxaliplatin (Eloxitan), followed by a fluoropyrimidine after surgery.
In the DYNAMIC trial, which tracked 455 patients in Australia and New Zealand, researchers used a blood test known as a “liquid biopsy” to detect evidence of circulating tumor DNA (ctDNA).
A positive result suggested that cancer cells still remained in the body, raising the risk for recurrent disease and marking those individuals as good candidates for chemotherapy after surgery. Those who tested negative, however, were allowed to opt for “watchful waiting” — a strategy that involves close tracking for signs of disease recurrence, or a round of chemotherapy,
Half the patients eligible to skip chemotherapy, based on liquid biopsy findings, decided to skip it, decreasing the number of patients to receive chemotherapy from 28 percent to 15 percent. There was no difference in disease outcome among those who eschewed more treatment and those who continued it.
All patients were initially followed every three months and then every six months to evaluate any evidence of a possible relapse. Those who chose “watchful waiting” rather than chemotherapy after receiving a negative ctDNA result had recurrence-free survival rates almost identical to those who opted for treatment.
“Using the blood tests can differentiate the two groups, allowing those without evidence of cancer to forgo additional treatment without relapse risk,’ says Dr. Tie.