December 12, 2019—San Antonio, Texas—A 10-year follow-up study of patients with breast cancer who had been treated with accelerated partial breast irradiation after surgery showed that their rates of recurrence were similar to those of patients who had received whole breast irradiation.
This outcome of the randomized, phase III Accelerated Partial Breast Irradiation Intensity Modulated Radiotherapy (APBI IMRT) trial was reported at the 2019 San Antonio Breast Cancer Symposium (SABCS), from December 10 – 14.
Icro Meattini, MD, of the University of Florence, Italy, explained that there were no differences in patient outcomes among selected cases, whether they were treated with whole breast irradiation or accelerated partial breast irradiation. Improved quality of life, reduced toxicity, and potential reductions in overall treatment times may result from a once-daily regimen of external accelerated partial breast irradiation.
According to Dr. Meattini, accelerated partial breast irradiation is less expensive and may be less likely to contribute to cosmetic changes compared with whole breast irradiation. Partial breast irradiation is an effective method for de-escalation of breast cancer treatment. Dr. Meattini suggested that partial breast irradiation provides a cost-effective, safe, and efficacious treatment option for many patients.
Dr. Meattini and colleagues examined 10-year follow-up data for women enrolled in APBI IMRT. The 5-year follow-up showed no significant difference in tumor recurrence or survival rates. APBI IMRT enrolled 520 women >40 years of age who suffered from either stage I or II breast cancer. Between 2005 and 2013, patients were randomized 1:1 to either accelerated partial breast irradiation or whole breast irradiation.
Patients in the accelerated partial breast irradiation arm received a total of 30 Gray (Gy) of radiation to the tumor bed in five daily fractions. Those in the whole breast irradiation arm received a total of 50 Gy in 25 daily fractions to the whole breast, plus a boost of 10 Gy to the tumor bed in five daily fractions.
Both treatment arms were comparable in terms of age, tumor size, tumor type, and adjuvant endocrine treatment, and both achieved a median 10-year follow-up.
The majority of patients harbored hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer, and most were over age 50 years.
After 10 years, 3.3% of patients in the accelerated partial breast irradiation group had experienced a recurrence of breast cancer vs 2.6% in the whole breast irradiation group. These results were comparable to the 5-year results, in which the group who received accelerated partial breast irradiation experienced a 2.4% recurrence rate, and patients who received whole breast irradiation, a 1.2% recurrence rate.
Differences were not statistically significant for either. Overall survival at the 10-year mark was also very similar between the two groups: 92.7% among women who had received accelerated partial breast irradiation and 93.3% among women who received whole breast irradiation.
Breast cancer-specific survival was 97.6% among patients who received accelerated partial breast irradiation; 97.5% among those who received whole breast irradiation. The rate of distant metastasis-free survival was 96.9% among both women who received accelerated partial breast irradiation and those who received whole breast irradiation.
Although the results were close, whole breast irradiation proved slightly more effective in reducing recurrence rates. The results suggested that the less invasive partial breast procedure may be an acceptable choice for patients with early breast cancer.
Dr. Meattini explained that many patients diagnosed with early breast cancer undergo lumpectomy followed by a course of radiation. He noted that postoperative radiation remains a primary adjuvant treatment for breast cancer that leads to significant reductions in the rate of local relapse occurrence.
Partial vs whole breast radiation has been a topic of multiple clinical trials. In recent years, researchers have sought to determine whether accelerated partial breast irradiation might be as effective as whole breast irradiation in preventing recurrence.
The growing body of research may help clinicians recommend that patients at lower risk of recurrence choose accelerated partial breast irradiation, whereas those at a higher risk of recurrence be recommended for whole breast irradiation.
Dr. Meattini concluded that these findings support promising results from prior studies demonstrating excellent disease control following accelerated partial breast irradiation.
The study’s chief limitation is its relatively small size.
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Rodrigo Arrangoiz MS, MD, FACS, FSSO 