Partial Breast Irradiation Sufficient in Early Disease

APBI was shown to be just as effective WBI in early-stage breast cancer.

Accelerated partial breast irradiation (APBI) was shown to be just as effective and safe as whole breast irradiation (WBI), according to the results of a randomized phase III clinical trial conducted in Italy. There was no difference between APBI, delivered as intensity-modulated radiation therapy (IMRT), and WBI after a 5-year median follow-up. APBI also resulted in significantly better safety and cosmetic outcomes for patients. The results were presented by the study’s principal investigator, Lorenzo Livi, MD, of the radiotherapy-oncology unit at Florence University Hospital in Florence, Italy, at the 2014 San Antonio Breast Cancer Symposium (SABCS), held December 9–13 in San Antonio, Texas.

The mean time to ipsilateral breast tumor recurrence (IBTR) was 2.9 years. There was no statistically significant difference in the 5-year IBTR rate (1.4% and 1.5% in the WBI and APBI arms, respectively; P = .86) or the 5-year overall survival rate (96.6% and 99.4% in the WBI and APBI arms, respectively; P = .057). Because of the low IBTR rate, a longer follow-up is still needed.

“Our results showed a very low recurrence rate [for APBI] and no differences in terms of distant metastases and overall survival rate. Partial breast [irradiation] certainly will be an effective option for treatment in selected breast cancer patients,” Livi told Cancer Network via e-mail.

The trial (NCT02104895) examined whether efficacy and safety outcomes of APBI administered as IMRT were similar to standard WBI in early breast cancer patients after breast-conserving surgery. All patients were older than 40 years, had tumors less than 25 mm in size, and had a wide excision or quadrantectomy with clear margins of greater than 5 mm.

Five-hundred and twenty patients were randomized 1:1 to receive either accelerated IMRT delivered as 30 Gy in 5 fractions or WBI as 50 Gy plus a 10-Gy boost in 30 fractions. The primary endpoint was IBTR, and secondary endpoints were toxicity and overall survival.

APBI is an alternative treatment to WBI, used in certain early-stage breast cancer patients who typically have small tumors, clear margins after surgery, and cancer with no involvement of the lymph nodes. IMRT is a technique that uses 3-D CT images to deliver radiation doses that can better conform to the 3-D shape of the tumor and may minimize exposure of healthy tissue to radiation.

Three patients in the WBI arm and no patients in the APBI arm experienced local relapse (P = .11). Zero and three patients had new ipsilateral breast cancer in the WBI and APBI treatment arms, respectively (P = .063). Contralateral breast cancer occurred in seven and three patients in the WBI and APBI treatment arms, respectively (P = .31).

The APBI group showed a significantly better safety profile in any grade of skin toxicity (P = .0001). There were no grade 3 toxicities observed in either group. The cosmetic result was rated as excellent or good for more than 90% of patients in both groups. In terms of cosmesis, the APBI group showed better outcomes compared with the WBI group (P = .045).

The phase III National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39 trial is currently ongoing and is asking a similar question, but in a large 4,000-patient study-does APBI limited to the region of the tumor bed after a lumpectomy provide equivalent local tumor control compared with conventional WBI in the management of early-stage breast cancer?

According to Livi, the trial will read out next year.

Still, Livi emphasized that WBI “will remain a key point of treatment for a large [portion] of breast cancer [patients who] underwent breast-conserving surgery.”

“While waiting for the results of NSABP B-39, partial breast irradiation represents an attractive alternative for early breast cancer patients at low risk of recurrence,” said Livi. “IMRT represents a safe and relatively simple technique that allows us to deliver APBI without any increase in acute and late skin toxicity.”

Reference

1. Livi L, Meattini I, Marrazzo L, et al. Accelerated partial breast irradiation using intensity modulated radiotherapy versus whole breast irradiation: 5-year survival results of a phase 3 randomized trial. Presented at 2014 San Antonio Breast Cancer Symposium; December 9-13, 2014; San Antonio, Texas. Abstract S5-03.