Press "Enter" to skip to content

Study Confirms Role of RT in Early HR+ Breast Cancer

Action Points

  • A woman is receiving radiation therapy.

Adjuvant radiation plus hormonal therapy after breast-conserving surgery led to a 10-year local recurrence-free survival (lRFS) approaching 100%, a large randomized trial showed.

The results showed that 97.5% of women with average-risk hormone receptor-positive (HR+) breast cancer remained free of in-breast recurrence at 10 years with whole-breast irradiation (WBI) plus hormonal therapy. Women who only received hormonal therapy had a 10-year lRFS of 92.4%. Three times as many women had local recurrences when radiation therapy was omitted.

A similar benefit for radiation therapy emerged from an analysis of disease-free survival (DFS), which took into account any type of disease recurrence, Gerd Fastner, MD, of Paracelsus Medical University and University Hospital Salzburg in Austria, reported at the European Society for Radiotherapy and Oncology congress in Barcelona.

“We believe that the additional benefits of postoperative radiotherapy have been confirmed in hormone receptor-positive patients, regardless of whether or not they are at high risk of breast cancer recurrence,” Fastner said in a statement. “In light of current knowledge, this does not necessarily mean that [patients] have to have whole-breast irradiation nowadays, since partial breast irradiation (PBI) has proved to be competitive.”

He added that total omission of radiotherapy “should only be considered in frail, elderly patients who would not be able to tolerate such treatment.”

The findings validated the current guideline-supported standard of care in North America (radiation plus hormonal therapy), but the importance of the study extended beyond that confirmation, said Thomas Buchholz, MD, of Scripps MD Anderson Cancer Center in San Diego.

“Years, even decades, of study have tried to address whether radiation is necessary after breast-conserving surgery,” Buchholz told MedPage Today. “Initially those studies involved high-risk patients intermixed with low-risk patients, and they showed that radiation is beneficial. After those trials we attempted to identify a low-risk group in whom radiation potentially might not be beneficial. This study looked at the very favorable end of the spectrum, and even though it was a low-risk population, they confirmed the benefit.”

“This study is really good news for breast cancer patients,” he added. “In this appropriately treated low-risk cohort with hormone receptor-positive breast cancer, the risk of recurrence in the breast at 10 years was 2.5%. It’s just amazing how good the results are. If you say that you have a 97.5% chance of not having recurrence in the breast, you can’t get much better than that.”

Buchholz agreed with Fastner that most patients can have PBI protocols with hypofractionation that reduce the total treatment time.

Conducted by the Austrian Breast and Colorectal Cancer Study Group, the trial involved 869 patients with newly diagnosed, early-stage HR+/HER2-negative breast cancer. Eligible patients had low-risk tumors, defined as grade 1 or 2, tumor size <3 cm, and no lymph node involvement.

All patients had lumpectomy and were randomized to receive hormonal therapy alone or with WBI. The total radiation dose was 50 Gy, delivered via conventional fractionation protocols. Additionally, 71% of patients randomized to WBI received a 10-Gy boost to the tumor bed. The primary endpoint was in-breast recurrence.

After a median follow-up of 10 years, 10 patients in the WBI group had in-breast recurrences as compared with 31 among patients treated only with adjuvant hormonal therapy. In a multivariable analysis, WBI was associated with a 73% reduction in the risk of in-breast recurrence (P<0.01). The 10-year DFS was 94.5% with WBI versus 88.4% among those who did not have radiation therapy (P=0.01).

Metastasis-free and overall survival did not differ significantly between treatment groups, which could indicate that “improving control of the tumor at the primary site may translate into better survival in future years,” said Fastner.

A biomarker analysis showed a nonsignificant trend toward increased risk of in-breast recurrence in patients whose tumors carried high-risk characteristics (Ki-67 >20% or HER2 positivity). Fastner said longer follow-up in the cohort is needed to determine whether the findings occurred by chance.

The study was supported by AstraZeneca.

The investigators did not report financial disclosures.