Some cancer patients can safely skip chemo treatments, 2 studies find

After surgery, some cancer patients can safely skip radiation or chemotherapy, according to two new studies exploring shorter, gentler cancer care.

The findings — presented at the yearly meeting of the American Society of Clinical Oncology in Chicago — could allow doctors to “focus on the patients we think would truly benefit from chemotherapy and avoid the side effects for patients for whom it’s likely unnecessary,” said Dr. Stacey Cohen of Fred Hutchinson Cancer Center in Seattle, who wasn’t involved in the research.

Many colon cancer patients are given chemotherapy after surgery even though they might already be cured. The drugs can cause side effects including nausea, anemia and memory problems. But pinpointing which patients might not need further treatment has been tricky.

For this study — funded by the Australian and U.S. governments and nonprofit groups and published in the New England Journal of Medicine — scientists looked at whether a blood test could help doctors determine which patients should get more treatment. It involved 455 patients who had surgery because cancer had spread to the colon wall. After surgery, one group had a blood test, customized to their tumor’s genetic profile, to detect any remaining cancer DNA.

If the blood test showed no signs of remaining cancer, the patients didn’t get chemo. For the others, doctors made chemo decisions the usual way, guided by analysis of the tumor and nearby tissue.

Fewer patients in the blood test group got chemo — 15% vs. 28%. But about 93% of both groups were still cancer-free after two years. So the blood test group fared equally well with less chemotherapy.

“In patients where cancer DNA is not detected after surgery, the chance of cancer relapse is very low, suggesting that chemotherapy is very unlikely to benefit these patients,” said Dr. Jeanne Tie of the Peter MacCallum Cancer Centre in Melbourne, Australia, who led the research.

Skipping chemo makes “a big difference in a person’s quality of life if that can be done without having to put them at jeopardy for recurrence,” said ASCO president Dr. Everett Vokes, who specializes in head and neck and lung cancer at University of Chicago Medicine.

The other study followed 500 older women with a common form of early-stage breast cancer and low levels of a protein known as Ki67, a marker for fast-growing cancer. After surgery, the women took hormone-blocking pills — standard treatment for this type of cancer. But they didn’t get radiation treatment.

After five years, 10 of the women had cancer return in the same breast, and there was one breast cancer death. There was no comparison group, but the researchers said the results compare favorably to historical data for similar patients who had radiation.

“We estimate the benefits of radiation would be very small in this population compared to the side effects,” said Dr. Timothy Whelan of McMaster University in Hamilton, Ontario, who led the study.

Radiation can cause skin problems, fatigue and, less commonly, long-term heart problems and second cancers.

The study will help doctors understand which patients “can comfortably, with confidence” omit radiation, said Dr. Deborah Axelrod of NYU Langone Health, who wasn’t involved in the research.