Some Older Women With Luminal A Breast Cancer May Be Able To Skip Radiation After Lumpectomy
Women ages 55 and older diagnosed with early-stage, estrogen receptor-positive, progesterone receptor-positive, HER2-negative breast cancer that had low levels of Ki67 protein and a low risk of recurrence were able to safely skip radiation after lumpectomy, according to the LUMINA study.
The research was presented on June 7, 2022, at the American Society for Clinical Oncology (ASCO) Annual Meeting. Read the abstract of “LUMINA: A prospective trial omitting radiotherapy (RT) following breast conserving surgery (BCS) in T1N0 luminal A breast cancer (BC).”
About luminal A breast cancer
Luminal A breast cancer is estrogen receptor- and progesterone receptor-positive, HER2-negative, and has low levels of the Ki67 protein — a protein that helps control how fast cancer cells grow. Luminal A cancers tend to grow more slowly than other breast cancers, have a lower grade, and have a good prognosis. Luminal A is the most common subtype of breast cancer; researchers estimate that it makes up at least half of all new breast cancer diagnoses.
About the study
Called LUMINA, this study included 500 women ages 55 and older diagnosed with early-stage luminal A ductal breast cancer who received treatment at 26 centers in Canada. In this study, luminal A breast cancer was defined as having:
estrogen receptors on 1% or more of the cancer cells
progesterone receptors on more than 20% of the cancer cells
no HER2 receptors, meaning the cancer was HER2-negative
Ki67 protein levels of 13.25% or lower
The researchers excluded women diagnosed with lobular breast cancer from the study.
All the women had lumpectomy surgery to remove the cancer followed by at least five years of hormonal therapy — either an aromatase inhibitor or tamoxifen. The women enrolled in the study between August 2013 and July 2017.
People commonly receive radiation therapy after lumpectomy because it reduces the risk of the cancer coming back (called recurrence by doctors). Research shows that lumpectomy plus radiation offers the same outcomes as mastectomy.
Still, radiation therapy can be inconvenient for many people because it usually involves daily trips to the treatment center for three to seven weeks. Radiation therapy also can cause several side effects, including fatigue and skin blistering and peeling.
In this study, the researchers wanted to know if women diagnosed with small, early-stage luminal A breast cancer that had a very low risk of recurrence could safely skip radiation after lumpectomy if they received hormonal therapy.
After five years of follow-up:
10 women were diagnosed with breast cancer in the same breast (local recurrence)
8 women were diagnosed with breast cancer in the opposite breast (contralateral breast cancer)
13 women died, but only one woman died of breast cancer
“Women greater than or equal to 55 years of age, with [low grade] luminal A breast cancer, following breast conserving surgery who were treated with endocrine therapy alone for five years, had a very low rate of local recurrence,” said presenter Timothy J. Whelan, MD, professor of oncology and Canada Research Chair in Health Services Research in Cancer at McMaster University. “The prospective and multicenter nature of this study supports that such patients are candidates for the omission of radiotherapy.
“Over 300,000 women are diagnosed yearly with invasive breast cancer in North America,” Dr. Whelan continued. “We estimate that these results could apply to 30,000 to 40,000 women per year who could avoid the morbidity, inconvenience, and cost of radiotherapy.”
What this means for you
If you’re at least 55 years old and have been diagnosed with early-stage, hormone receptor-positive, HER2-negative breast cancer that has a very low risk of recurrence and are deciding on treatments, you may want to talk to your doctor about this study.
It makes sense to ask if your oncologist requested Ki67 testing to be done on the cancer tumor. This test is not always done but is becoming more common.
If your doctor orders the test and the resulting Ki67 levels are very low, lumpectomy and hormonal therapy — without radiation therapy — may make sense for your unique situation.
Written by: Jamie DePolo, senior editor
— Last updated on June 21, 2022, 8:48 PM