Abstract P2-11-10: Toxicity analysis of elderly breast cancer patients using different accelerated partial breast irradiation techniques
Authors: Jacobs DHM , Marijnen CAM , Speijer G , Straver M , Marinelli A , Merkus J , Roelofzzen EMA , Zwanenburg LAG , Fisscher U , Petoukhova AL , Mast ME , Koper P 
Published: February 2018

PURPOSE We investigated the acute toxicity of Accelerated Partial Breast Irradiation using external beam (EB-APBI) and intraoperative radiotherapy (IORT) technique.

MATERIALS AND METHODS Women ≥60 years with unifocal breast tumors of ≤30 mm undergoing breast conserving therapy were eligible for this prospective multi-centre cohort study. After informed consent, patients were treated with IORT in one institute, EB-APBI was applied in other institutes. IORT was applied with electrons directly on the tumor bed following lumpectomy (21 Gy at 90% isodose). EB-APBI was delivered using 3D-conformal radiotherapy or IMRT in 10 daily fractions of 3.85 Gy. Acute toxicity was scored using the CTCAE v.3, initially by the treating physician and retrospectively by blinded researchers. The highest reported toxicity until 3 months after treatment was used. Patient reported symptoms were analysed using Visual Analogue Scales (VAS) for pain and fatigue (scale 0-10), and single items from the EORTC QLQ-C30 and Breast Cancer module questionnaires at different time points up till 3 months. P&lt;0.01 was deemed significant.

RESULTS Between January 2011 and August 2016, 622 patients were eligible, eventually 268 patients underwent IORT and 207 underwent EB-APBI. Of those, 267 (IORT) and 206 (EB-APBI) were available for toxicity analysis. Patient characteristics are shown in table 1. Although more patients experienced &gt;grade 2 acute toxicity in the IORT group (10.4% IORT and 4.9% EB-APBI; p=0.027), grade 3 toxicity was low and did not significantly differ between groups (3.3% IORT and 1.5% EB-APBI). No grade 4 toxicity occurred. After IORT more wound infections requiring oral antibiotics (5.2% versus 1.5%) and more seroma requiring aspiration (2.2% versus 0.5%) were observed.

Results for EORTC symptoms and VAS scores are displayed in table 2. Patients treated with EB-APBI experienced significantly less fatigue direct postoperatively (EORTC p=0.003, VAS p&lt;0.001). After 3 months, this difference dissolved, and only pain according to the VAS scale was significantly worse in the EB-APBI group (p=0.003).

Table 1. Patient characteristics  IORT, n=267EB-APBI, n=206p-valueAge(median; range) 68; 59-9067; 59-860.683pT stagepTis7%13%0.020 pT184%74%  pT29%13% pN stagepN093%97%0.092 pN17%3% ER statusPositive93%93%0.122Systemic therapyNo59%62%0.509

Table 2. EORTC and VAS scores BaselinePostoperativeAfter EB-APBI3 months after treatment IORTEB-APBIIORTEB-APBIEB-APBIIORTEB-APBIPain771920111013Fatigue1192916241723Breast pain4425211068Swollen breast122516554Oversensitive breast33362715811Skin side effects1147835VAS pain(median)  3.03.02.02.03.0VAS fatigue(median)  4.03.04.03.04.0EORTC: Scores of “quite a bit” and “very much” were scored positive. Percentage of patients that scored positive is shown.

CONCLUSION Even though more clinically relevant toxicity is seen in IORT treatment direct postoperatively, acute toxicity in both IORT and EB-APBI treatment is acceptable. IORT patients seem to recover more rapidly regarding fatigue than EB-APBI patients. This may be explained by the fact that IORT treatment is completed in one day.

Citation Format: Jacobs DHM, Marijnen CAM, Speijer G, Straver M, Marinelli A, Merkus J, Roelofzzen EMA, Zwanenburg LAG, Fisscher U, Petoukhova AL, Mast ME, Koper P. Toxicity analysis of elderly breast cancer patients using different accelerated partial breast irradiation techniques [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-10.