SAN ANTONIO (AP) ― Tens of thousands of women each year might be able to skip at least some of the grueling treatments for breast cancer ― which can include surgery, heavy chemo and radiation ― without greatly harming their odds of survival, new research suggests.

The research is aimed at curbing overtreatment, a big problem in cancer care. Treatments help many women beat the disease, but giving too many or ones that aren’t really needed causes unnecessary expense, trauma and lifelong side effects, such as arm swelling and heart troubles. Radiation can even raise the risk of new cancers.

Several studies presented Wednesday at the San Antonio Breast Cancer Symposium, an international conference on the disease, identify groups of patients who might be able to safely forgo certain treatments.

One found that many older women can skip radiation after surgery for early-stage tumors. Two others suggest that surgery may not help patients whose cancer has already spread widely. A fourth study tested a “light chemo” combination that could become a new standard of care.

The trend is “less and less therapy” for certain cancer types, said one conference leader, Dr. C. Kent Osborne of Baylor College of Medicine.

The highlights:

Surgery: Breast cancer is already widely spread in 5 to 20 percent of newly diagnosed patients, and at that point is usually incurable. The main treatment is chemotherapy or hormone treatments that attack cancer throughout the body. Sometimes doctors also remove the breast tumor in hope of prolonging survival, but this has not been put to a hard test.

Dr. Rajendra Badwe, director of the Tata Memorial Hospital in Mumbai, India, led a study of 350 women with widely spread cancers that had shrunk after initial chemotherapy. Half were given surgery to remove the breast or the lump plus any cancerous lymph nodes. The rest did not have surgery.

After about two years, 40 percent of both groups were alive, suggesting that medicines are enough and that these women can be spared the ordeal of having all or part of a breast removed.

A second study by Dr. Atilla Soran of the University of Pittsburgh Medical Center of nearly 300 women in Turkey also suggests surgery is not helping, though there were hints that some groups did better or worse. Surgery seemed to help if cancer had spread just to bone, and it appeared to do harm if it had spread to the liver or lungs.

“These are incredibly important, big-deal studies,” said Dr. Claudine Isaacs, a breast specialist at Georgetown University’s Lombardi Comprehensive Cancer Center. Many doctors jumped on earlier, less rigorous studies and advised women to have surgery, and this should be a warning against that, she said.

The results also may spur interest in a U.S. study on the topic. Dr. Seema Khan of Northwestern University in Chicago has had so much trouble recruiting participants that she lowered her goal and may not be able to answer the question.

“There’s a huge amount of bias” among doctors and patients about what is best, she said.

Radiation: Most breast cancers are found at an early stage, and many women are treated with surgery followed by hormones or chemotherapy, plus radiation. But cancer medicines have gotten so good at lowering the risk of a recurrence that doctors wonder whether the radiation is still needed. It can cause heart and other problems, especially in older women, and three or four weeks of daily treatments can be a burden.

Dr. Ian Kunkler of the University of Edinburgh in Scotland led a study of 1,326 patients 65 or older with early-stage cancers whose growth was driven by hormones. This is the most common form of the disease and the age group that accounts for most cases. Half were given radiation and half skipped it.

After five years, roughly 96 percent of both groups were alive, and most deaths were not from breast cancer. About 1 percent of those given radiation had cancer recur in the treated breast versus 4 percent of those who skipped radiation.

For every 100 women given radiation, “one will have a recurrence anyway, four will have a recurrence prevented, but 95 will have had unnecessary treatment,” Kunkler said. Since radiation did not affect survival or the risk of cancer spreading, skipping it “is a reasonable option.”

“Light” chemo

“Light” chemo: Doctors are unsure how to treat women with small tumors involving the gene that the drug Herceptin targets. Those tumors are low risk because they’re still confined to the breast, but high risk because the gene is thought to make them more aggressive. Some women get heavy-duty chemo, including drugs that can damage the heart.

Dr. Eric Winer of the Dana-Farber Cancer Institute in Boston led a study of 406 women given “light chemo” ― paclitaxel plus Herceptin for 12 weeks, followed by nine months of Herceptin alone. More than three years later, only four had cancer recur in the same breast, and two had recurrences in other places.

“This is likely to become a new standard,” Winer said.

The cancer conference is sponsored by the American Association for Cancer Research, Baylor and the UT Health Science Center.