BOSTON – Cosmetic results were significantly worse after 3 years for women who had accelerated partial-breast irradiation than for women treated with whole-breast irradiation in a randomized clinical trial, investigators found.
Nearly a third (32%) of women who underwent accelerated partial breast irradiation (APBI) with a 3-D conformal technique had cosmetic results rated as fair or poor by a nurse, compared with 19% of women who had undergone whole-breast irradiation (WBI), Dr. Timothy J. Whelan reported at the annual meeting of the American Society for Radiation Oncology.
APBI was also associated with more grade 1 and 2 toxicities than WBI, but there were few grade 3 toxicities with either technique and no grade 4 toxicities, said Dr. Whelan, a radiation oncologist at the Juravinski Cancer Centre in Hamilton, Ont.
"This increase in toxicity may have resulted from limited conformality of the 3-D conformal approach, the short time between the fractions – radiation with APBI was given twice a day with 6 hours between the fractions, which may not have been adequate – and maybe due to the asymmetric nature of partial breast irradiation itself, given that it’s only given to part of the breast," he said at a press briefing.
Trading Convenience for Toxicity?
APBI – in which a large dose per fraction of external beam radiation is given only to the surgical cavity with an additional safety margin – allows radiation therapy to be delivered in 1 week or less, making it an attractive alternative to multifraction therapy that can stretch over many weeks.
But it is still not clear whether APBI trades poorer outcomes for convenience, Dr. Whelan said. He and colleagues in Canada, Australia, and New Zealand conducted the RAPID trial (Randomized Trial of Accelerated Partial-Breast Irradiation Using 3-D Conformal External Beam Radiation Therapy) to find out. The study compared the efficacy and safety of the two modalities in women over 40 years of age with invasive or noninvasive breast cancers smaller than 3 cm.
Investigators enrolled 2,135 patients and randomized them to receive either WBI (1,065 patients) at 50 Gy in 25 fractions or 42.5 Gy in 16 fractions given once daily with or without boost irradiation or 3-D conformal APBI at 38.5 Gy in 10 fractions twice daily (1,070 patients). Cosmetic results were rated by a trained nurse on a global assessment using the European Organisation for Research and Treatment of Cancer (EORTC) Cosmetic Rating System for Breast Cancer, and for toxicity using the National Cancer Institute Common Terminology Criteria for Adverse Events 3.0. Radiologists blinded to treatment type also rated results on digital photographs.
Immediately after radiation, cosmetic results were similar between the groups, with nurse-assessed appearance rated as fair or poor in 17% of women who had WBI, and 19% who had APBI (P = .35). However, an interim toxicity analysis among 850 evaluable patients, showed that at 3 years (2.3 years median follow-up) 13% more of the patients who had undergone APBI had fair or poor cosmesis.
The Jury Is Out
Dr. Whelan noted that the between-group differences were about the same at 5 years, but did not provide data.
"The evidence for partial-breast irradiation is still not very clear. We don’t have very robust evidence about its efficacy, and we just now have recent evidence about its potential toxicities, he said.
Dr. Bruce Haffty, chair of radiation oncology at the Cancer Institute of New Jersey in New Brunswick, commented that "the results from the RAPID trial shed further light on the use of accelerated partial-breast irradiation, and emphasize the need to further investigate these fractionation schemes and sort out whether in fact the toxicity from partial-breast irradiation may be slightly worse than with whole-breast irradiation."
Dr. Haffty moderated a briefing where the data were presented, but was not involved in the RAPID trial.
The RAPID trial is supported by the Canadian Institutes of Health Research and Canadian Breast Cancer Research Alliance. Dr. Whelan has received honoraria from AstraZeneca and Novartis. Dr. Haffty reported no relevant disclosures.