A major study could change care for many of the hundreds of thousands of people each year who have cancer that spreads to the brain from other sites, study leaders said on Sunday.

The study, one of three discussed at an American Society of Clinical Oncology conference in Chicago, found that contrary to conventional wisdom, radiation therapy to the whole brain did not improve survival, and harmed memory, speech and thinking skills.

“This is the classic question: Which is worse, the disease or the treatment?” said one study leader, Dr Jan Buckner of the Mayo Clinic in Rochester, Minnesota. Radiation helped control the cancer, Dr Buckner said, “but at the cost of cognitive decline”.

For patients, the study is not necessarily the bad news it may seem. It shows that in this case, quality of life is better with less treatment, and many people can be spared the expense and side effects of futile care.

The two other studies discussed on Sunday also questioned longstanding ways in which patients are treated. One found that removing lymph nodes when oral cancers are first diagnosed – not routinely done now – dramatically improves survival. Another found the opposite was true for people with the skin cancer melanoma that had spread to a few lymph nodes.

The first study affects the most patients by far. An estimated 400,000 patients in the US alone each year have cancer that spreads to the brain, usually from the lungs, breast or other sites.

That is different from tumors that start in the brain, like the one that on Saturday claimed the life of Joseph “Beau” Biden, the son of vice-president Joe Biden.

Cancer that spreads to the brain is usually treated with radiosurgery – highly focused radiation with a tool such as the Gamma Knife, followed by less intense radiation to the whole brain. The latter treatment can cause hair loss, dry mouth, fatigue and thinking problems.

Dr Paul Brown of the University of Texas MD Anderson Cancer in Houston led a study of 213 patients with one to three tumors in the brain to see whether the risks of whole brain radiation were worth its help in controlling cancer.

Half of the patients had the usual radiosurgery and the rest had that followed by whole brain radiation. Three months later, 92% of patients who got both treatments had cognitive decline versus 64% of those given just radiosurgery.

“The negative effects far outweigh any benefits” of the combination treatment, Brown said.

Doctors probably will use the combination less frequently because of this study, but certain patients still may benefit from it, said Dr Andrew Lassman of Columbia University and New York-Presbyterian Hospital. The work should spur research on different ways to give radiation that may not harm thinking skills as much.

The other two studies involved when to remove lymph nodes, a place where cancer often spreads. Nodes help drain fluid throughout the body, and removing them leaves patients vulnerable to a host of complications, including painfully swollen limbs, infections and nerve damage.

Dr AK D’Cruz of Tata Memorial Hospital in Mumbai, India, led a study of 500 patients with oral cancer, usually tumors of the lips, tongue or mouth. They are very common in the United States as well as India and other countries where alcohol and tobacco use is high.

Half of the patients in the study had neck lymph nodes removed at the same time as they had surgery to remove the oral cancer. The rest had the cancer removed but not their nodes. Nine months later, on average, researchers saw that removing the nodes cut the risk of death during the study by 36% and the risk of having cancer come back by 55%.

For every eight patients whose nodes were removed, two cancer recurrences and one death were prevented.

“This one-and-done approach” to surgery should be done for all patients, said Dr. Jyoti Patel, a spokeswoman for the oncology society.

In the melanoma study, about 500 people in Germany with skin cancers on the legs, arms or trunk that had spread minimally to nearby lymph nodes were either given additional surgery to remove lymph nodes or just observed. Survival rates were comparable three years later, meaning the additional surgery was not worth the risk of its side effects.

Some doctors predicted the study would change care; others said they would wait to see if a second study underway now reaches the same conclusion. In any case, it’s worth a discussion between patients considering the operation, doctors said.