A supplemental radiation dose given concurrently with hypofractionated whole-breast irradiation (WBI) produces comparable results as a sequential supplemental dose given after conventional WBI in patients with high-risk early-stage breast cancer, according to a phase 3 trial.
The study showed that in-breast recurrence, cosmesis, and toxicity outcomes were similar with the concurrent radiation boost and the sequential boost. However, the concurrent boost reduced treatment time.
These results were presented at the 2022 ASTRO Annual Meeting by Frank A. Vicini, MD, of Michigan Healthcare Professionals in Farmington Hills.
Dr Vicini and colleagues conducted this phase 3 trial (NRG RTOG 1005; ClinicalTrials.gov Identifier: NCT01349322) in 2262 eligible patients with high-risk early breast cancer who had undergone lumpectomy.
The patients were randomly assigned to the 2 treatment arms. One arm received conventional WBI at 50 Gy in 25 fractions or 42.7 Gy in 16 fractions plus a sequential boost of 12 Gy in 6 fractions or 14 Gy in 7 fractions (n=1124).
The other arm received hypofractionated WBI at 40 Gy in 15 fractions plus a concurrent boost of 48 Gy (n=1138). In both arms, patients received either target-based 3-dimensional conformal radiation or intensity-modulated radiation therapy.
At baseline, there were no significant differences between the 2 arms. The median age in both arms was 55 years. About one-third of patients in each arm had stage II disease, and 52% in each arm had grade 3 histology. Roughly 60% of patients in each arm received adjuvant chemotherapy.
The primary endpoint was in-breast recurrence. At a median follow-up of 7.4 years, there were 56 in-breast recurrence events overall. The 5-year in-breast recurrence rate was 2.0% in the sequential boost arm and 1.9% in the concurrent boost arm. The 7-year rate was 2.2% and 2.6%, respectively. The threshold for noninferiority was met (hazard ratio, 1.32; 90% CI, 0.84-2.05; P =.039).
There were no significant differences in treatment-related adverse events (TRAEs) between the 2 arms. Grade 3 or higher TRAEs occurred in 3.3% of patients in the sequential boost arm and 3.5% of those in the concurrent boost arm.
The researchers also found no significant differences between the treatment arms for patient-assessed cosmesis (P <.0001 for non-inferiority) or physician-assessed cosmesis (P =.33 for superiority).
Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Vicini FA, Winter K, Freedman GM, et al. NRG RTOG 1005: A phase III trial of hypo fractionated whole breast irradiation with concurrent boost vs. conventional whole breast irradiation plus sequential boost following lumpectomy for high risk early-stage breast cancer. ASTRO 2022. October 23-26, 2022. Abstract 1.