The women in this trial who skipped radiotherapy, and were treated with breast-conserving surgery followed by endocrine therapy, had an overall survival rate of 97.2%. The local recurrence rate was 2.3%, which was the study’s primary endpoint.
“Women 55 and over, with low-grade luminal A-type breast cancer, following breast conserving surgery and treated with endocrine therapy alone, had a very low rate of local recurrence at 5 years,” commented lead author Timothy Joseph Whelan, MD.
“The prospective and multicenter nature of this study supports that these patients are candidates for the omission of radiotherapy,” said Dr. Whelan, oncology professor and Canada Research Chair in Breast Cancer Research at McMaster University and a radiation oncologist at the Juravinski Cancer Centre, both in Hamilton, Ont.
“Over 300,000 [people] are diagnosed with invasive breast cancer in North America annually, the majority in the United States,” said Dr. Whelan. “We estimate that these results could apply to 10%-15% of them, so about 30,000-40,000 women per year who could avoid the morbidity, the cost, and inconvenience of radiotherapy.”
The results were presented at the annual meeting of the American Society of Clinical Oncology.
Dr. Whelan explained that adjuvant radiation therapy is generally prescribed following breast conservation therapy to lower the risk of local recurrence, but the treatment is also associated with acute and late toxicity. In addition, it can incur high costs and inconvenience for the patient.
Previous studies have found that among women older than 60 with low-grade, luminal A-type breast cancer who received only breast-conserving surgery, there was a low rate of local recurrence. In women aged older than 70 years, the risk of local recurrence was about 4%-5%.
This latest study focused on patients with breast cancer with a luminal A subtype combined with clinical pathological factors (defined as estrogen receptor ≥ 1%, progesterone receptor > 20%, HER2 negative, and Ki67 ≤ 13.25%).
This was a prospective, multicenter cohort study that included 501 patients aged 55 years and older who had undergone breast-conserving surgery for grade 1-2 T1N0 cancer.
The median patient age was 67, with 442 (88%) older than 75 years. The median tumor size was 1.1 cm.
Median follow-up was 5 years. The cohort was followed every 6 months for the first 2 years and then annually.
The primary outcome was local recurrence defined as time from enrollment to any invasive or noninvasive cancer in the ipsilateral breast, and secondary endpoints included contralateral breast cancer, relapse-free survival based on any recurrence, disease free survival, second cancer or death, and overall survival.
At five years, there were 10 events of local recurrence, for a rate of 2.3%. For secondary outcomes, there were eight events of contralateral breast cancer (1.9%); 12 relapses for a recurrence-free survival rate of 97.3%; 47 disease progression (23 second nonbreast cancers) for a disease-free survival rate of 89.9%; and 13 deaths, including 1 from breast cancer, for an overall survival of 97.2%.
Confirms earlier data
Penny R. Anderson, MD, professor in the department of radiation oncology at Fox Chase Cancer Center, Philadelphia, commented that this was an “extremely well-designed and important study.
“It has identified a specific subset of patients to be appropriate candidates for consideration of omission of adjuvant breast radiation therapy after breast-conserving surgery,” she added.
Although previously published trials have helped identify certain patient groups who have a low risk of local recurrence – and therefore, for whom it may be appropriate to omit radiation – they have been based on the traditional clinical and pathologic factors of tumor size, margin status, receptor status, and patient age.
“This LUMINA trial utilizes the molecular-defined intrinsic subtype of luminal A breast cancer to provide additional prognostic information,” she said. “This finding certainly suggests that this group of patients are ideal candidates for the omission of radiation, and that this should be discussed with these patients as a potential option in their treatment management.”
Overall, this trial is a “significant addition and a very relevant contribution to the literature demonstrating that adjuvant breast radiation may safely be omitted in this particular subgroup of breast cancer patients,” she said.
Unanswered questions
Commenting on the study, Julie Gralow, MD, chief medical officer and executive vice president of ASCO, told this news organization that she thinks the take-home message is that there is “clearly a population of early-stage breast cancer [patients] who after lumpectomy do not benefit from radiation.”
“I think where there will be discussion will be what is the optimal way of identifying that group,” she said, noting that in this study the patients were screened for Ki67, a marker of proliferation.
Testing for Ki67 is not the standard of care, Dr. Gralow pointed out, and there is also a problem with reproducibility since “every lab does it somewhat differently, because it is not a standard pathology approach.”
There are now many unanswered questions, she noted. “Do we need that central testing of Ki67? Do we need to develop guidelines for how to do this? Is this better than if you’ve already run an Oncotype or a MammaPrint test to see if the patient needs chemo, then would that suffice? That is where the discussion will be. We can reduce the number of patients who need radiation without an increase in local regional recurrence.”
In terms of clinical practice, Dr. Gralow explained that there are already some data supporting the omission of radiation therapy in an older population with ER-positive small low-grade tumors, and this has become a standard clinical practice. “It’s not based on solid data, but based on an accumulation of retrospective analyses,” she said. “So we have already been doing it for an older population. This would bring down the age group, and it would better define it, and test it prospectively.”
Limitations to note
Also commenting on the study, Deborah Axelrod, MD, director of clinical breast surgery at New York University Langone’s Perlmutter Cancer Center, explained that, in the last decade, knowledge about the behavior of breast cancers based on molecular subtyping has greatly increased. “Results of studies such as this have given us information on which cancers need more treatment and for which cancers we can de-escalate treatment,” she said. “Refining this more, it’s about reducing the morbidity and improving quality of life without compromising the oncological outcome.”
She noted that a big strength of this LUMINA study is that it is prospective and multicenter. “It has been supported by other past studies as well and will define for which patients with newly treated breast cancers can we omit radiation, which has been the standard of care,” said Dr. Axelrod. “It is based on the age and biology of breast cancer in defining which patient can forgo radiation and showed a low risk of recurrence in a specific population of women with a favorable breast cancer profile”
There were limitations to the study. “There is a 5-year follow-up and local recurrence for ER-positive cancers continues to rise after 5 years, so longer-term follow-up will be important,” she said. Also, she pointed out that it is a single-arm study so there is no radiation therapy comparison arm.
Other limitations were that the patients were older with smaller tumors, and all were committed to 5 years of endocrine therapy, although compliance with that has not been reported. There may be some older patients who prefer radiation therapy, especially a week of accelerated partial breast irradiation, rather than commit to 5 years of endocrine therapy as mandated in this study.
“Overall, the takeaway message for patients is that the omission of radiation therapy should be considered an option for older women with localized breast cancer with favorable features who receive endocrine therapies,” said Dr. Axelrod.
LUMINA was sponsored by the Canadian Breast Cancer Foundation and the Canadian Cancer Society. Dr. Whelan has reported research funding from Exact Sciences (Inst). Dr. Axelrod and Dr. Anderson reported no disclosures. Dr. Gralow reported relationships with Genentech, AstraZeneca, Hexal, Puma BioTechnology, Roche, Novartis, Seagen, and Genomic Health.
A version of this article first appeared on Medscape.com.