Monte Carlo dose calculations of shielding disks with different material combinations in intraoperative electron radiation therapy (IOERT).

PURPOSE: Shielding disks play an important role in intraoperative electron radiation therapy, and different designs are currently used in clinical practice. This paper investigates the dosimetric impact of the shielding disk used during intraoperative electron radiation therapy (IOERT). MATERIALS AND METHODS: This paper focuses on the study of four shielding disks types that have been used in our clinic: Aluminum (Al)/Lead (Pb), PMMA/Copper(Cu)/PMMA, Aluminum (Al)/Copper (Cu) and Aluminum (Al)/Steel with their specific thicknesses. The theoretical study was conducted with the EGSnrc Monte Carlo (MC) code. On the other hand, the measurements were carried out with gafchromic films for the four shielding disks for the same setup inside the water phantom. Finally, a comparison of the simulated and measured PDD curves was performed for the four material combinations. RESULTS: MC simulation and gafchromic measurements illustrated that dose values under the four shielding disks types were close to 0, whereas the backscattering enhancement of the disks were 103% with Al/Pb shielding disk, 102% with Al/Steel shielding disk, 102% with Al/Cu shielding disk, 95% with PMMA/Cu/PMMA shielding disk. The PDDs values of the gafchromic films in front of the disks were: 107%, 105%, 104%, and 94% for the Al/Pb, Al/Steel, Al/Cu, and PMMA/Cu/PMMA disks respectively. CONCLUSIONS: The dose values above and under the shielding disks were acceptable for the four studied shielding types. Demonstrated it is possible to use any of them clinically, while the best shielding disk was the Al/Pb since it has minimum thickness and a small backscatter enhancement.

Early invasive cancer and partial intraoperative electron radiation therapy of the breast: experience of the jules bordet institute.

Objectives. The aim of this prospective phase II study is to evaluate the treatment of early-stage breast cancer (T1 N0) with intraoperative electron radiation therapy (IOERT) in terms of local control, early complications, and cosmesis. Patients and Methods. From February 2010 to February 2012, 200 patients underwent partial IOERT of the breast. Inclusion criteria were unifocal invasive ductal carcinoma, age ≥40 years, histological tumour size ≤20 mm, and no lymph node involvement. A 21 Gy dose was prescribed over the 90% isodose line in the tumour bed. Median follow-up is 23.3 months (7-37). Results. Acute toxicity was not frequent (Grade 1: 4.5%, Grade 2: 1%). The cosmetic result was considered to be very good or good in 92.5%. One ipsi lateral out-quadrant recurrence at 18 months was observed. The crude and actuarial local recurrence rates after median follow-up were 0.5% and 0.9%, respectively. Conclusion. The preoperative diagnostic work-up must be comprehensive and the selection process must be rigorous for this therapeutic approach reserved for small ductal unifocal cancers. After a 23.3-month median follow-up time, the clinical results of IOERT for selected patients are encouraging for the locoregional recurrence and the toxicity rates. The satisfaction of our patients in terms of quality of life was extremely high.