Comparable Results From Three Forms of Accelerated Partial-Breast Irradiation

[Hopeful]

Elsevier Global Medical News. 2009 Oct 21, S Boschert

SAN FRANCISCO (EGMN) - A comparison of three forms of accelerated partial-breast irradiation in 373 carefully selected patients with breast cancer found comparable rates of local control, survival, and acceptable cosmesis over a median 6 years of follow-up.

The 5-year actuarial rates for local recurrence were 1.6% in 199 patients who were treated with low-dose or high-dose interstitial brachytherapy (LDR/HDR), 1.1% in 94 patients who were treated with three-dimensional conformal external-beam radiation therapy (3-D CRT), and 2.6% in 80 patients who underwent Hologic Inc.'s MammoSite targeted-radiation therapy (MS).
The study found no statistically significant differences among the groups in any of the outcomes measured, Dr. Peter Y. Chen and his associates reported at a breast cancer symposium sponsored by the American Society of Clinical Oncology.

The 5-year actuarial rates of distant metastases were 3.2% for LDR/HDR, 6.6% for 3-D CRT, and 1.3% for MS. Disease-free survival rates were 96%, 92%, and 96%, respectively. Overall survival rates were 87%, 92%, and 91%, respectively. Cosmetic results were considered excellent or good in 99%, 89%, and 94%, respectively, said Dr. Chen of William Beaumont Hospital, Royal Oak, Mich.

Patients in the LDR/HDR group had considerably longer follow-up (27-113 months), compared with the 3-D CRT group (10-36 months) and the MS group (2-66 months), he noted. "Additional, continued follow-up will be needed of the 3-D CRT and MS patients to assess the long-term efficacy and equivalence of these three" modalities, he said.

Five phase III clinical trials are underway involving these modalities. Dr. Chen and his associates try to place all candidates for accelerated partial-breast irradiation in study protocols, he said, and they treat off-protocol candidates based on recent consensus panel guidelines issued by the American Society for Radiation Oncology (ASTRO).

All patients in the current study were treated at Beaumont between 1993 and 2006. Patients were eligible if they were older than 40 years, had invasive ductal carcinoma no larger than 3 cm, had lobular carcinoma or - in patients since 2003 - ductal carcinoma in situ, and had a partial mastectomy with negative margins of at least 2 mm. Until 1997, patients with up to three positive axillary nodes were included; after that, only node-negative patients were eligible.

The study excluded patients with an extensive intraductal component, skin involvement, or Paget disease.

The median age of patients was 64 years, and 94% had T1 lesions. Axillary nodes were negative in 92% of patients. Estrogen receptor positivity, which was present in 86% of patients, was the only factor associated with an increased risk for local recurrence in multivariate analyses.

Historically, interstitial multicatheter brachytherapy was the first of the three modalities to be used, starting with trials in 1987. Since 2000, several institutions, including Beaumont, have employed 3-D RCT. The MammoSite system was approved in 2002 initially to treat brain cancer, after which clinicians at Beaumont helped the company adapt it for use in breast cancer, he said.

Dr. Chen has received honoraria from Hologic Inc.

Hopeful