After surgery, some cancer patients can safely avoid treatments such as radiation or chemotherapy, say two recent studies that explore shorter, gentler cancer care.

Researchers are looking for ways to predict which cancer patients can avoid unneeded treatment to cut down on costs and bad side effects.

One new study used a blood test to study which colon cancer patients could skip, or not have, chemotherapy after surgery. Another study suggests some low-risk breast cancer patients might not need radiation after the surgical removal of a mass or lump, a surgery known as a lumpectomy.

The research was discussed recently at the yearly meeting of the American Society of Clinical Oncology (ASCO). The colon cancer study, financed by the Australian and U.S. governments and nonprofit groups, was recently published by the New England Journal of Medicine.

The findings let doctors pay careful attention to "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 the Fred Hutchinson Cancer Center. Cohen reviewed the colon cancer findings and was not involved in the research.

Colon cancer study

Many colon cancer patients are given chemotherapy after surgery, even though they may be cured. The drugs can come with bad side effects such as nausea, anemia and memory problems.

But deciding which patients might not need further treatment has been difficult. So, the scientists studied whether a blood test could help doctors make the decision.

The study involved 455 patients who had surgery because cancer had spread into the colon wall. After surgery, one group received a blood test specially made for the tumor's genetic information to find any remaining bits of cancer DNA.

Their care was guided by the blood test. If the test showed no signs of remaining cancer, the patients did not get chemotherapy. Meanwhile, doctors made chemotherapy decisions for the rest of the patients in the usual way, guided by careful study of the tumor and nearby tissue.

Fewer patients in the blood test group got chemotherapy — 15 percent in comparison to 28 percent. But about 93 percent of both groups were still free of cancer after two years. In other words, the blood test group did equally well with less chemotherapy.

Dr. Jeanne Tie of the Peter MacCallum Cancer Center in Melbourne, Australia, led the research. Tie described the findings in terms of cancer relapse - the return of a cancer after a period of improvement.

"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," Tie said.

ASCO president Dr. Everett Vokes said that not having chemo makes "a big difference in a person's quality of life if that can be done without having to put them" at risk of the disease coming back.

Breast cancer

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, a common treatment for this type of cancer. But the women did not get radiation treatment.

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

Dr. Timothy Whelan of McMaster University in Hamilton, Ontario, led the study.

"We estimate the benefits of radiation would be very small in this population compared to the side effects," Whelan said.

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

Dr. Deborah Axelrod of NYU Langone Health was not involved in the research.

Axelrod described the study as a "feel-good" message for patients with low-risk tumors. Axelrod added that the data will help doctors understand which of their patients they "can comfortably, with confidence" not give radiation to.

I'm John Russell.

Carla K. Johnson reported on this story for the Associated Press. John Russell adapted it for VOA Learning English.

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chemotherapy – n. medical: the use of chemicals to treat or control a disease (such as cancer)

benefit—v. to be useful or helpful to (someone or something)

nausea – n. the feeling you have in your stomach when you think you are going to vomit

anemia – n. medical: a condition in which a person has fewer red blood cells than normal and feels very weak and tired

tumor – n. a mass of tissue found in or on the body that is made up of abnormal cells

hormone – n. a natural substance that is produced in the body and that influences the way the body grows or develops

detect -- v. to discover or notice the presence of (something that is hidden or hard to see, hear, taste, etc.)