LBA 28 - Retrospective Cohort Study Evaluating Outcomes in Patients with and without Implants prior to Diagnosis of Early-Stage Breast Cancer Receiving APBI in 25 Gy in 5 Fractions vs. 21.9 Gy in 3 Fractions

Purpose/Objective(s):

To compare differences in toxicity between patients with and without implants/reconstruction receiving accelerated partial breast irradiation delivered in 21.9 Gy in 3 fractions.

Materials/Methods:

This retrospective cohort study evaluated all patients who received APBI to 21.9 Gy in 3 fractions for early-stage breast cancer at Mayo Clinic Arizona. Patients were separated into the implant/reconstruction and non-implant groups. Toxicities such as fatigue, radiation dermatitis, pain, erythema, hyperpigmentation, fibrosis, lymphedema, and the duration of follow-up were recorded.

Results:

A total of 79 patients received APBI with 21.9 Gy in 3 fractions. After the exclusion of 6 male patients and 6 patients with metastatic disease, the final cohort included 67 patients: 60 without implants and 7 with implants/reconstruction. Between the two groups toxicity was proportionally higher in the patients with implants, 85.7% in patients with implants vs 68.3% in patients without implants (p=0.163). Ipsilateral breast tumor recurrence was overall uncommon, 3.3% without implants and 14.3% in patients with implants (p=0.004). Other notable characteristics were higher observed rates of fatigue (42.9% vs 16.7%, p=0.051), pain (71.4% vs 25%, p=0.006), erythema (57.1% vs 30.0%, p=0.074), and fibrosis (57.1% vs 13.3%, p=0.001) amongst the implant group compared to the non-implants group.

Conclusion:

APBI delivered to 21.9 Gy in 3 fractions was generally well tolerated in both the implant group as well as the non-implant group. Proportionally patients with implants/reconstruction had higher reported toxicity when compared with the non-implant group. However, toxicity grade was not available for all patients, as some degree of low-grade toxicity is to be expected after radiation therapy (RT). None of the patients within the implant group experienced implant failure. One implant patient did experience recurrent painful cysts within the lumpectomy bed that did require medical intervention, two years after receiving APBI. IBTR was uncommon in both groups, and the single IBTR event in the implant group occurred prior to APBI, suggesting it may not be due to treatment failure.