Results from the analysis of the NRG Oncology RTOG 1005 clinical trial data concluded that treating patients with early-stage, high-risk breast cancer with a supplemental radiation boost to the surgical cavity concurrently during hypo-fractionated whole breast irradiation (H-WBI) for a 3-week treatment course was not considered inferior to treating patients over several weeks with conventional whole breast irradiation (C-WBI) and a sequential boost following lumpectomy.

These results were recently presented during the plenary session of the American Society for Radiation Oncology (ASTRO) Annual Meeting in October 2022.

The phase III study randomised 2,262 eligible patients with early-stage (0,I,II), high-risk breast cancer to receive either C-WBI at either 50 Gy in 25 fractions (F) or 42.7 Gy in 16 F plus a sequential boost of 12 Gy in 6 F or 14 Gy in 7 F (Arm 1); or to receive H-WBI at 40 Gy in 15 F plus a concomitant boost of 8 Gy in 15 F of 0.53 Gy per day (Arm 2).

Radiation treatment options on this trial were target based 3-dimensional conformal radiation therapy (3DCRT) or intensity modulated radiation therapy (IMRT).

The primary goal was to determine if H-WBI with concurrent boost (Arm 2) was not inferior in controlling in-breast recurrence (IBR) for this patient population.

Data from the analysis not only indicated that Arm 2 was not inferior to Arm 1 at controlling IBR for patients, but also that there were no differences in toxicity or cosmetic outcome between arms.

“This data is incredibly important because the current standard of a sequential boost after H-WBI or C-WBI - adds additional treatment time which directly impacts patients’ lives,” stated Frank A Vicini, MD, a radiation oncologist with GenesisCare and the lead author of the NRG-RTOG 1005 abstract. “By delivering H-WBI with a concurrent boost within 3 weeks - we have the ability to deliver a similarly efficacious treatment option but at a great convenience for our patients and with comparable toxicity outcomes.” 

Of the 2,262 randomised, eligible patients on NRG-RTOG 1005, Arm 1 included 1,124 and Arm 2 included 1,138.

Patients who received 3DCRT was 81% versus patients who received IMRT was 19%.

With a median follow-up of 7.3 years and 56 IBR events, the 5- and 7-year IBR were 2.0% and 2.2% on Arm 1 and 1.9% and 2.6% on Arm 2.

The hypothesised upper limit of the hazard ratio (HR) for non-inferiority was 2.12, with a 1-sided significance level of 0.05. 

The non-inferiority comparison (Arm 1 reference level) resulted in a HR (90% CI): 1.32 (0.84, 2.05) and p = 0.039, thus meeting non-inferiority.

No differences in AEs noted between arms, with low rates of ≥ grade 3 treatment-related AEs, 3.3% versus 3.5% for Arm 1 versus 2, respectively (p=0.79).

There was no difference in physician-reported 3-year excellent/good cosmesis by arm: 86% for Arm 1 vs 84% Arm 2 (p=0.61).

Source: NRG Oncology