Intraoperative Electron Radiotherapy (IOERT) in the Treatment of Primary Breast Cancer

Abstract

IOERT (intraoperative electron radiotherapy) in breast cancer is used either as a boost (10-12 Gy) followed by whole breast irradiation (WBI) or as full-dose partial breast irradiation (PBI, 20-24 Gy) during breast-conserving surgery. IOERT has the longest evidence of all IORT techniques. When administered as a boost, excellent low local recurrence rates were observed in long-term follow-up >5 years. Even in high-risk groups like triple-negative or locally advanced breast cancers, IOERT contributes to long-term local control rates of more than 90%. For selected low-risk groups, IOERT as PBI with 21 Gy seems to be a viable treatment alternative to standard WBI. IOERT has been shown to be advantageous for several reasons: Geographic misses are avoided due to direct visualization of the tumor bed; thus, a high single dose is delivered with utmost precision to small volumes, completely sparing the skin and ensuring good long-term cosmetic outcome. Furthermore, high single doses seem to induce biological mechanisms with verifiable antitumor capability in in-vitro cell-line studies. In addition, IOERT markedly shortens the overall treatment time both in combination with (now mostly hypofractionated) WBI or as a PBI in selected low-risk constellations.

The Composition of Surgical Wound Fluids from Breast Cancer Patients is Affected by Intraoperative Radiotherapy Treatment and Depends on the Molecular Subtype of Breast Cancer

“…IORT makes tumor microenvironment less favorable for tumor recurrence due to decreased concentration of tumor-facilitating cytokines, especially in luminal A subtype of BC. By correlating the long-term results of IOERT as a boost in the breast cancer [19] and results presented in this study, we can speculate, that changes in tumor microenvironment due to different cytokine concentration may have an impact on metastasis-free survival of BC patients after IORT. In relation to this, we also confirmed the decreased concentration of cytokines connected to EMT and CSC in IORT treated patients, which confirms our previously published results of in vitro experiments showing lower EMT and CSC phenotype in BC cells treated with SWF from IORT [14].…”

“…Due to breast cancer cell density (highest at up to 4 cm from the tumor edge), the probability of local recurrence is highest in the tumor bed. Therefore an additional single boost dose delivered directly to the tumor bed during the surgery, such as IORT, can significantly reduce local recurrence rates and the time of therapy comparing to standard EBRT [18,19]. This firstly is due to direct killing of residual cancer cells and also due to radiation-induced inflammation, which in turn can enhance the immunologic elimination of cancer cells.…”

Advances in Breast Radiotherapy: Brachytherapy, Intraoperative Electron Therapy, Protons, and Nodal Irradiation

“…All four papers exemplify the common aim of further reducing adverse effects by further confining the radiation dose to the area that has to be treated [1,2,3] or by discussing the use of radiotherapy instead of surgery in the treatment of regional lymph nodes [4]. …”

“…The two main options for reducing both the irradiated volume and the treatment duration when the bed of the surgically removed tumor needs to be irradiated, either alone - as partial breast irradiation - or as a boost dose, are discussed in the articles on interstitial brachytherapy [1] and on intraoperative radiotherapy [2], respectively. Brachytherapy arguably is the most conformal method to administer radiation, meaning that the radiation dose targeting the volume to be treated is maximally confined, therewith optimally sparing surrounding non-affected breast and connective tissues and organs (heart, lung, ribs).…”

“…This treatment technique only slightly prolongs the duration of surgery and as such does not require an extra course of radiotherapy. Kaiser et al [2] discuss ongoing trials of intraoperative radiotherapy both as partial breast treatment and as a method to deliver a booster dose.…”