Patients with early breast cancer with small, node-negative tumors can safely be treated with accelerated partial-breast irradiation using intensity-modulated radiotherapy. According to the 10-year median follow-up of the randomized phase III APBI IMRT Florence trial, recurrence rates were low and comparable to those achieved with whole-breast irradiation, and cosmesis was better.1
APBI IMRT Florence Trial
Icro Meattini, MD
Ipsilateral breast cancer recurrence rates at a median follow-up of 10 years were 3.9% in the accelerated partial-breast irradiation arm and 2.6% in the whole-breast irradiation arm (hazard ratio [HR] = 1.57; P = .39). These rates reflected a very low number of events: nine in the partial-breast irradiation arm and six with whole-breast irradiation. Locoregional recurrence rates were also similar: 3.9% in the partial-breast irradiation arm and 3.0% in the whole-breast irradiation arm, reflecting nine and seven events, respectively, according to Icro Meattini, MD, Associate Professor at the University of Florence in Italy, who reported the findings at the 2019 San Antonio Breast Cancer Symposium.
“[Accelerated partial-breast irradiation] might be considered a standard alternative to [whole-breast irradiation] in patients with low-risk, early breast cancer. In well-selected cases, there is no difference in patients’ outcomes whether they are treated with [accelerated partial-breast irradiation] or [whole-breast irradiation],” Dr. Meattini said. “A once-daily regimen of external [accelerated partial-breast irradiation] might also produce an improved quality of life, with less toxicity, and can potentially reduce the overall treatment time.”
Dr. Meattini noted that the approach fits with other recent developments in radiation oncology, “a move toward a de-escalation strategy for early breast cancer.”
The phase III trial enrolled 520 patients with early breast cancer. Patients were at least 40 years old and had a maximum pathologic tumor size of 25 mm. Patients were randomly assigned in a 1:1 ratio to receive either whole-breast irradiation at a dose of 50 Gy in 25 fractions, followed by 10 Gy in 5 fractions delivered to the tumor bed, or accelerated partial-breast irradiation delivered to the tumor bed at a dose of 30 Gy in 5 daily fractions.
The primary endpoint was ipsilateral breast tumor recurrence. Secondary endpoints were overall survival, breast cancer–specific survival, distant metastasis–free survival, locoregional recurrence, contralateral breast cancer, cosmesis, and adverse events.
KEY POINTS
- In the phase III APBI IMRT Florence trial, 10-year median follow-up showed similar recurrence rates for accelerated partial-breast irradiation and whole-breast irradiation.
- Ipsilateral recurrence rates were 3.9% and 2.6%, respectively (P = .39).
- Patients and physicians were more likely to report good or excellent cosmetic results with partial-breast irradiation.
Cosmesis and Adverse Events
As previously reported, after 5 years of follow-up, there were no significant differences in survival rates or ipsilateral recurrence between treatment techniques.2 The current analysis reported in San Antonio showed maintenance of these findings, demonstrating that major efficacy outcomes were not affected by the radiation approach. That said, although major efficacy endpoints were comparable between the arms, the safety profiles and cosmetic results differed significantly, he reported.
Adverse events of all levels of severity were significantly more common with whole-breast irradiation than accelerated partial-breast irradiation, including acute and late adverse events, grade ≥ 2 skin toxicity, and cosmesis. Of importance to patients, cosmesis (as measured by the Harvard Breast Cosmesis Scale) was significantly better after accelerated partial-breast irradiation. Both physicians and patients were significantly more likely to report good or excellent cosmetic results with partial-breast than whole-breast irradiation, he said.
DISCLOSURE: Dr. Meattini reported no conflicts of interest.
REFERENCES
1. Meattini I, Saieva C, Lucidi S, et al: Accelerated partial breast or whole breast irradiation after breast conservation surgery for patients with early breast cancer: 10-year follow up results of the APBI IMRT Florence randomized phase III trial. 2019 San Antonio Breast Cancer Symposium. Abstract GS4-06. Presented December 12, 2019.
2. Livi L, Meattini I, Marrazzo L, et al: Accelerated partial breast irradiation using intensity-modulated radiotherapy vs whole breast irradiation: 5-year survival analysis of a phase III randomised controlled trial. Eur J Cancer 51:451-463, 2015.
