Overall survival and breast cancer–specific survival were consistently better for women with early breast cancer who were treated with breast conservation surgery (BCS) followed by radiotherapy (RT) compared to women who were treated with mastectomy (Mx) with or without RT, a large Swedish cohort study indicates.
“Women should be strongly advised to not get more extensive surgery than necessary to excise the tumor ― we need to excise the tumor with clear margins, but [patients] do not benefit from further removal of noncancerous tissues,” commented lead author Jana de Boniface, PhD, Capio St. Göran’s Hospital, Stockholm, Sweden.
“Women may experience a feeling of safety from having the whole breast removed, but they should be counseled that a mastectomy does not result in a better prognosis — probably rather the opposite,” she told Medscape Medical News in an email.
There are also “benefits for quality of life, body image, and social functioning that are reported by many women if they keep as much of their own body intact as possible,” she added.
The study was published online on May 5 in JAMA Surgery
“The most important message from this study is that BCS is safe for our cancer patients, and this confirms data from many prospective randomized trials that it yields outcomes that are at least as good as mastectomy,” commented Lisa Newman, MD, MPH, Weill Cornell Medicine, New York City, who authored an accompanying commentary.
Breast Cancer Register
For this study, de Boniface and colleagues collected data prospectively from the Swedish National Breast Cancer Register on a total of 48,986 patients.
“We included all patients diagnosed as having primary invasive breast cancer from January 1, 2008, until December 31, 2017, who underwent breast surgery,” the investigators explain.
The team took into account comorbidities and the patients’ education, income, and country of birth, as identified from several databases across the study interval.
Women underwent surgery as follows:
59.9% underwent locoregional treatment with BCS with RT (BCS+RT);
25.3% underwent a mastectomy followed by RT (Mx+RT);
4.7% underwent mastectomy without RT (Mx-RT).
The median follow-up was 6.28 years.
Slightly more than one third (35.2%) of deaths that occurred during follow-up were due to breast cancer, the authors note. At 5 years, 91.1% of patients were still alive; the breast cancer–specific survival rate was 96.3%.
However, the breast cancer–specific survival rate was 66% worse among the women who had MX+RT compared to those who had BCS+RT (hazard ratio [HR], 1.66).
The overall survival was 79% worse following MX-RT compared to BCS+RT (HR, 1.79), after adjustment for tumor characteristics, treatment, demographics, comorbidity, and socioeconomic background. (It is well established that mastectomy is more commonly performed in women of lower socioeconomic status as well as in women with comorbidities, de Boniface commented.)
“Honestly, we would have expected that comorbidity and socioeconomic status, being factors that affect treatment choice, would have abrogated any survival differences between the surgical groups, but seeing that this is actually not the case is puzzling and highly interesting, although we have not found any clear causal relationship yet,” de Boniface noted.
Seeing that this is actually not the case is puzzling and highly interesting.
She also noted that most women have the option of undergoing BCS, even women with large tumors; it has been shown that they, too, can be safely treated with BCS.
“It is striking that extensive breast surgery is more prevalent in node-positive disease despite suitability for breast conservation, indicating a misconception of safety, probably both from a patient and a physician perspective,” the authors observe.
“This report casts additional doubt on the practice to offer mastectomy to patients who are suitable candidates for breast conservation,” they conclude.
Role of RT
In her commentary, Newman writes that these “fascinating results…challenge the wisdom of prematurely abandoning radiation after BCS for clinically early-stage disease.”
Commenting further to Medscape Medical News, she pointed out that postmastectomy RT was given routinely to the highest-risk mastectomy patients (namely, patients with node-positive disease), so outcomes among these high-risk patients cannot be compared on the basis of whether or not RT was given.
“Similarly, radiation was typically not given to the mastectomy patients with favorable biology — only 3.5% of T1N0 mastectomy patients received RT — so we cannot compare outcomes in these early-stage mastectomy patients based upon whether or not radiation was delivered,” she added.
Moreover, patients who underwent BCS were excluded from the analysis if they did not receive RT, suggesting that physicians may speculate that RT contributed to the survival advantage seen in the BCS group.
However, this does not mean that RT definitively explained the survival advantage in this cohort, she said.
“Ongoing studies evaluating omission of RT as another strategy to deescalate breast cancer treatment will need to be evaluated in the context of these data [that] suggest a possible survival benefit from radiation,” Newman acknowledged.
De Boniface and coauthors and Newman have disclosed no relevant financial relationships.