For the study, researchers surveyed 1,945 women diagnosed with early-stage breast cancer about the severity of seven treatment side effects: nausea and vomiting, diarrhea, constipation, pain, arm swelling, shortness of breath and breast skin irritation.

Overall, 45 percent of participants reported severe or very severe forms of at least one of these side effects. When women got chemotherapy, the odds of severe side effects were twice as high, though the side effects were just 30 percent more likely when chemo was paired with radiation.

“We did know that some of these side effects were associated with these treatments, but we did not know how severe or how common these side effects were,” said study co-author Dr. Allison Kurian, a researcher at Stanford University School of Medicine in California.

“I found it striking that nearly half of all women treated for early-stage breast cancer reported suffering toxicity that they considered severe or very severe,” Kurian added by email. “This emphasizes the prevalence and seriousness of the problem.”

Early-stage breast cancer is the most common type of invasive breast cancer diagnosed in the U.S, and it involves smaller tumors that may have spread to nearby lymph nodes but not other parts of the body.

Most early-stage breast cancer patients have surgery – either a lumpectomy that removes malignant tissue while sparing the rest of the breast or a mastectomy that removes the entire breast. After surgery, they may also get chemotherapy or radiation to destroy any remaining abnormal cells and reduce the risk of cancer coming back.

Overall, 93 percent of the women in the study experienced at least one of the seven side effects, researchers report in the journal Cancer.

Nearly one in 10 women surveyed said they made at least one unscheduled clinic visit because of side effects, and 5 percent said they went to an emergency department or hospital.

Severe swelling in the arm or skin irritation were the most common reasons for unscheduled clinic visits. Severe breathing difficulties, arm swelling, pain or diarrhea were the most common side effects that brought women to the hospital.

Most patients in the study got some type of surgery and about half of them had radiation. There were 736 women who had chemotherapy, including 217 who received this in addition to radiation.

About 29 percent of chemotherapy patients reported severe or very severe pain, compared with 19 percent of women who didn’t receive chemo.

Women who had both chemotherapy and radiation treatment were 30 percent more likely to report a severe side effect, compared to women who had only one of those treatments.

Women who had double mastectomy were twice as likely as those who had lumpectomy to report severe or very severe pain.

Severe side effects were also more common for Latina women, who were 30 percent more likely than white women to report a severe or very severe side effect.

The study wasn’t a controlled experiment designed to prove that certain treatments directly cause specific severe side effects, the authors note. Researchers also lacked data on the timing or dosing of chemotherapy and radiation, both of which can influence the severity of side effects.

“It is intuitive that patients who have worse disease, and who therefore require more therapy, experience worse toxicity,” said Dr. Anees Chagpar, a researcher at Yale University in New Haven, Connecticut, who wasn’t involved in the study.

Still, the results should encourage doctors to consider when patients treatment regimens might be to achieve the same survival benefit with side effects, Chagpar added by email.

“The treatments we have for cancer are very effective, but there is a growing recognition of the ‘collateral damage’ that can accompany these treatments,” said Dr. Shelley Hwang, a researcher at Duke University in Durham, North Carolina, who wasn’t involved in the study.

“Patients should recognize two things: first, that cancer treatments involve trade-offs; second, that some toxicities can be long-lasting,” Hwang added by email.