NATIONAL HARBOR, Md. – Breast irradiation with 3-D conformal external beam therapy produced no significant toxicity in early results from more than 1,000 breast cancer patients with 3 years’ follow-up in a phase III trial.
Recent small studies have shown significant short-term toxicity related to the use of 3-D conformal external beam therapy (CEBT), with a 10%-20% incidence of unacceptable fibrosis or poor cosmesis, said Dr. Thomas Julian of the West Penn Allegheny Cancer Institute based in Pittsburgh.
The primary objective of the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39/Radiation Therapy Oncology Group (RTOG) 0413 study is to compare partial-breast irradiation vs. whole-breast irradiation for local tumor control after lumpectomy in patients with early-stage breast cancer. The study includes 3-D CEBT.
In light of the toxicity findings from other studies, Dr. Julian and colleagues reviewed toxicity data from 1,339 women in the NSABP B-39/RTOG 0413 study who were randomized to 3-D CEBT for partial-breast irradiation and who had been followed for an average of 37 months, including 1,004 women with at least 36 months of follow-up. Approximately two-thirds of the women were postmenopausal. A total of 68% had noninvasive breast cancer, 24% had ductal carcinoma in situ, and 8% had invasive stage I breast cancer.
No grade 4 or 5 toxicities were reported, and grade 3 side effects were rare in results presented at the Breast Cancer Symposium, which was sponsored by the American Society of Clinical Oncology.
Virtually all patients (97%) were free of chemoradiation dermatitis. Just 2% had grade 1 of this toxicity, 1% had grade 2, and fewer than 1% had grade 3.
The highest toxicity rates were related to radiation dermatitis. In all, 36% of patients had no toxicity, 52% had grade 1 toxicity, 11% had grade 2, and 1% had grade 3.
No hyperpigmentation occurred in 52% of patients; 42% had grade 1 toxicity, and 6% had grade 2. Induration also was uncommon, with 67% of patients having none, whereas 25% had grade 1, 7% had grade 2, and 1% had grade 3. And telangiectasia was rare, with 89% having none, 9% having grade 1, 2% having grade 2, and fewer than 1% having grade 3.
Similarly, 71% of the patients had no fibrosis-cosmesis toxicity; 16% had grade 1, 10% had grade 2, and 3% grade 3. Deep connective tissue fibrosis was not a problem for 72% of the patients; another 16% had grade 1, 11% grade 2, and 1% had grade 3.
“Contrary to findings in recent published reports, the 3-D conformal APBI [accelerated partial breast irradiation] toxicity rates in our trial are acceptably low,” said Dr. Julian.
“Our trial surpasses others reported in patient number and length of follow-up, emphasizing the important of large, phase III, randomized trials with vigorous quality assurance to determine treatment outcomes and avoid the bias that can arise from small, single-institution series,” he said.
The whole-breast irradiation group protocol was 50 Gy (2.0 Gy per fraction) or 50.4 Gy (1.8 Gy per fraction) to the whole breast, followed by an optional boost to 60.0 -66.6 Gy. The partial-breast irradiation protocol involved one of three options: 34 Gy in 3.4-Gy fractions using multicatheter brachytherapy, 34 Gy in 3.4-Gy fractions using a MammoSite balloon catheter, or 38.5 Gy in 3.85-Gy fractions using 3-D conformal external beam radiation.
The study was supported in part by Nucletron.