A new genetic test may help determine which people with breast cancer can safely skip radiation after breast-conserving surgery to remove their tumor.
Individuals with invasive breast cancer who had low scores on an investigational gene panel were just as likely to experience a recurrence if they received radiation therapy after breast-conserving surgery or not, Swedish researchers report.
As it stands, people with this type of breast cancer typically have surgery to remove the cancer followed by radiation, to reduce the risk that their breast cancer will return in the same spot.
“For the first time, a genetic screening test can predict which patients can omit radiation,” said study author Dr. Per Karlsson. He is a professor of oncology at the Sahlgrenska Comprehensive Cancer Center and the University of Gothenburg in Sweden.
More research is needed before this gene test is ready for prime time, Karlsson said.
“We will confirm the findings in new cohorts, and we will also start prospective trials to be sure that this is correct, but it looks really promising,” he added.
For the study, researchers evaluated the predictive power of POLAR (Profile for the Omission of Local Adjuvant Radiotherapy), a 16-gene panel that was developed based on differences between people with and without local recurrence following breast-conserving surgery.
The study included 623 people from three trials whose cancer had not spread to their lymph nodes. Their breast cancers were also estrogen receptor-positive and HER2-negative. Their tumors were analyzed after surgery to see which genes were expressed.
Each person received a POLAR score based on this analysis, and then the researchers looked at the benefits of radiation therapy among those people with high and low scores.
The main finding? People with a high POLAR score can benefit from radiation therapy, while those with lower scores can likely skip it, the study findings showed.
People with high POLAR scores who received radiation therapy after breast-conserving surgery had a 63% lower risk of local recurrence compared with those who didn't receive radiation. By contrast, there was no difference in recurrence rates seen among people with low POLAR scores, regardless of whether they received radiation or not. After 10 years, 5% of people with low scores who received radiation had a local recurrence, compared with 7% of those who didn't, the investigators found.
It's a win anytime a person can avoid radiation without risking a cancer recurrence, Karlsson said. “There are side effects for a small percentage of people, and if in the future we can omit radiation for some patients, it will be good for the quality of life,” he noted.
Besides being time-consuming, radiation may cause fatigue as well as skin side effects such as rashes, pain, redness and swelling.
The findings were scheduled for presentation Friday at the San Antonio Breast Cancer Symposium. Research presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.
Breast cancer experts who reviewed the new study agreed that doctors are entering a new era in the diagnosis and treatment of breast cancer.
This type of genetic profiling of breast tumors is the future, said Dr. Julia Smith, a medical oncologist at NYU Langone Perlmutter Cancer Center in New York City. “We are trying to minimize the number of treatments that we are giving in certain subgroups based on molecular and genetic profiles of their cancer.”
This study helps define a subgroup of people who may not need radiation, she said.
“People with this type of breast cancer tend to do well to begin with,” Smith noted. “We need a larger group of women who we can follow for a longer time as people with these types of breast cancer usually don't recur until more than 10 to 15 years later.”
Doctors don't want to overtreat people, agreed Dr. Katherina Zabicki Calvillo, a breast surgeon and founder of New England Breast and Wellness in Wellesley, Mass. “We are really focusing on getting the best outcomes for patients with minimal toxicity and risk," she said.
“It can be safe to omit radiation in certain populations. Although well-tolerated, radiation still has untoward side effects and affects the quality of life and return to work,” Calvillo explained. There may also be cost savings, she noted.
Calling the new study “interesting and important,” Dr. Marisa Weiss said the results can help tailor treatment recommendations about radiation. She is the chief medical officer and founder of Breastcancer.org in Ardmore, Pa.
“The POLAR 16-gene genomic test seems very promising in Swedish women,” Weiss said. “It will be important to test its validity in the much more heterogenous population within the U.S. before we can apply it to diverse populations with confidence.”
Breastcancer.org offers more on the genetic profiling of breast cancers.
SOURCES: Per Karlsson, MD, professor, oncology, Sahlgrenska Comprehensive Cancer Center, University of Gothenburg, Sweden; Julia Smith, MD, medical oncologist, NYU Langone Perlmutter Cancer Center, New York City; Katherina Zabicki Calvillo, MD, founder, New England Breast and Wellness, Wellesley, Mass.; Marisa Weiss, MD, chief medical officer, founder, Breastcancer.org, Ardmore, Pa.; presentation, San Antonio Breast Cancer Symposium, Dec. 9, 2022