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2019 ASCO: Partial- vs Whole-Breast Irradiation in Early-Stage Breast Cancer

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Key Points

  • When looking at the entire study population, women who received partial-breast irradiation experienced a 4.6% recurrence rate. Those who underwent whole-breast irradiation experienced a 3.9% rate of recurrence.
  • In subsegments of the study population, rates of recurrence were nearly identical for women with ductal carcinoma in situ, regardless of whether they received whole- or partial-breast irradiation. This was also true for women with breast cancer classified as low-risk based on the American Society for Radiation Oncology clinical guidelines.
  • Toxicity from treatment was similar, as well as the risk for secondary cancers.

Partial-breast irradiation produces similar long-term survival rates and risk for recurrence compared with whole-breast irradiation for many women with low-risk, early-stage breast cancer, according to new data from the NRG Oncology/NSABP B-39/RTOG 0413 trial. Results were presented by Ganz et al at the 2019 ASCO Annual Meeting (Abstract 508).

This randomized, phase III study compared whole-breast irradiation with partial breast-irradiation in a large group of women with stage 0, I, or II breast cancer. More than 4,200 patients were enrolled in the trial, which included a prospective quality of life substudy with patient-reported outcomes evaluation of breast cancer treatment outcomes (cosmesis, function, pain) and fatigue using BCTOS and SF-36 vitality scales. Secondary quality of life parameters included treatment-related symptoms, perceived convenience of care, and the BPI pain scale.

Results

Study results showed that while partial-breast irradiation does not produce equivalent cancer control for all patients with stage 0, I, and II breast cancer, it should still be considered as an alternative for women with ductal carcinoma in situ and early-stage breast cancers deemed “low-risk” based on other tumor characteristics.

When looking at the entire study population, women who received partial-breast irradiation experienced a 4.6% recurrence rate. Those who underwent whole-breast irradiation experienced a 3.9% rate of recurrence. Toxicity from treatment was similar, as well as the risk for secondary cancers.

However, researchers also looked at how this played out in subsegments of the population and found that rates of recurrence were nearly identical for women with ductal carcinoma in situ, regardless of whether they received whole- or partial-breast irradiation. This was also true for women with breast cancer classified as low-risk based on the American Society for Radiation Oncology clinical guidelines.

Researchers showed that in this subsegment of patients with breast cancer, the likelihood of recurrence 10-years posttreatment was very low overall and almost identical between women who received whole-breast irradiation (2.3%) and partial-breast irradiation (2.7%).

In patients not treated with chemotherapy, patients treated with partial-breast irradiation had less fatigue and did not meet criteria for cosmesis equivalence. In patients treated with chemotherapy, partial-breast irradiation had worse fatigue and equivalent cosmesis to whole-breast irradiation. In both groups, patients undergoing partial-breast irradiation reported less pain at end of treatment. In nonchemotherapy­-treated patients, those undergoing partial-breast irradiation had more pain at 36 months, but in chemotherapy-treated, there was no difference.

Julia White, MD, co-principal investigator of the national trial and Head of Breast Radiation Oncology at The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute, said this is very important because it reduces the burden of care for women who can still achieve cancer control with fewer treatments over a shorter period of time.

“A significant portion of the breast cancer patient population nationally—about 25,000 to 30,000 women—would qualify for partial-breast irradiation. This is tremendously important because it allows us to give women the right amount of treatment for her disease and potentially allows better access to effective breast conservation for those who live far from a radiation facility. Partial-breast irradiation can also be delivered in 5 consecutive days vs whole-breast [irradiation], which can involve 4 to 6 consecutive weeks of multiday treatment. There is no denying that the 5-day treatment is less costly and disruptive to life.”

Disclosure: For full disclosures of the study authors, visit coi.asco.org.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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