Ten-Year Results Support Partial Breast Irradiation

Will Pass

December 12, 2019

SAN ANTONIO — For patients with early, low-risk breast cancer, accelerated partial breast irradiation (APBI) may be considered a standard alternative to whole breast irradiation, according to investigators.

This conclusion was based on 10-year follow-up results from the APBI IMRT Florence phase III trial, which showed that APBI was associated with significantly fewer adverse events and better cosmetic results than whole breast irradiation without increasing risks of tumor recurrence or mortality, reported lead author Irco Meattini, MD, of the University of Florence, Italy, and colleagues.

"As we well know, recent developments in radiation oncology...show a move toward a deescalation strategy for early breast cancer, including accelerated and nonaccelerated partial breast irradiation," Dr. Meattini said during a presentation at the San Antonio Breast Cancer Symposium. "What we have learned from [previous] phase 3 trials [is that with adequate patient selection for] partial breast irradiation, safety profile and cosmetic outcome are strongly associated with technique — the approach, the dose, the number of fractions per day, and the total dose."

The current phase 3 trial, which enrolled 520 patients with early breast cancer, aimed to determine long-term efficacy, safety, and cosmetic outcomes for partial versus whole breast irradiation. All patients enrolled were at least 40 years of age and had a maximum pathological tumor size of 25 mm. Patients were randomized in a 1:1 ratio to receive either whole breast irradiation (WBI) at a dose of 50 Gy in 25 fractions, followed by 10 Gy in five fractions delivered to the tumor bed; or APBI, which was delivered to the tumor bed at a dose of 30 Gy in five daily fractions.

The primary endpoint was ipsilateral breast tumor recurrence (IBTR). Secondary endpoints were overall survival, breast cancer–specific survival, distant metastasis-free survival, locoregional recurrences, and contralateral breast cancer. Adverse events and cosmesis also were evaluated.

Five-year results, previously reported, revealed no significant difference in survival rates or IBTR between treatment techniques, and results of the present 10-year analysis maintained these findings. Between groups, no significant differences were observed in any of the primary or secondary endpoints, suggesting that major efficacy outcomes were unaffected by type of irradiation delivered.

While major efficacy endpoints were comparable between groups, safety profiles and cosmetic results differed significantly.

Adverse events of all levels of severity were significantly more common with WBI than APBI. Grade 2 or higher acute adverse events occurred in 37.7% of patients treated with WBI, compared with just 2.0% of patients treated with APBI (P = .0001). The rate of grade 2 or higher adverse events was also significantly higher in the WBI group than in the APBI group in the late setting, albeit with a narrower margin than in the acute setting (2.7% vs 0%; P = .015). Skin toxicity rates followed a similar pattern, favoring APBI both in the acute phase (66.5% vs. 21.1%; P = .0001) and the late phase (30.0% vs. 4.5%; P = .0001).

In further support of APBI, cosmetic results, as measured by the Harvard Breast Cosmesis Scale, were significantly better in the APBI group than in the WBI group. Both physicians and patients were significantly more likely to report good or excellent cosmetic results with APBI than WBI.

"APBI might be considered a standard alternative to WBI in low risk and very low risk early breast cancer patients," Dr. Meattini concluded.

The investigators reported no disclosures.

Source: Meattini et al. SABCS. 2019 Dec 12. Abstract GS4-06.

This story first appeared on MDEdge.com.

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