Boost IORT in Breast Cancer: Body of Evidence

Abstract

The term IORT (intraoperative radiotherapy) is currently used for various techniques that show decisive differences in dose delivery. The largest evidence for boost IORT preceding whole breast irradiation (WBI) originates from intraoperative electron treatments with single doses around 10 Gy, providing outstandingly low local recurrence rates in any risk constellation also at long term analyses. Compared to other boost methods, an intraoperative treatment has evident advantages as follows. Precision. Direct visualisation of the tumour bed during surgery guarantees an accurate dose delivery. This fact has additionally gained importance in times of primary reconstruction techniques after lumpectomy to optimise cosmetic outcome. IORT is performed before breast tissue is mobilised for plastic purposes. Cosmesis. As a consequence of direct tissue exposure without distension by hematoma/seroma, IORT allows for small treatment volumes and complete skin sparing, both having a positive effect on late tissue tolerance and, hence, cosmetic appearance. Patient Comfort. Boost IORT marginally prolongs the surgical procedure, while significantly shortening postoperative radiotherapy. Its combination with a 3-week hypofractionated external beam radiotherapy to the whole breast (WBI) is presently tested in the HIOB trial (hypofractionated WBI preceded by IORT electron boost), a prospective multicenter trial of the International Society of Intraoperative Radiotherapy (ISIORT).

Comparison of seroma production in breast conserving surgery with or without intraoperative radiotherapy as tumour bed boost

“…Even though data from the TARGIT-A and ELIOT trial suggest that IORT may be an oncological reliable alternative to conventional postoperative fractionated irradiation in a low to medium risk collective [12], IORT is routinely used only as a boost followed by whole breast radiation in our hospital. IORT can be considered a safe treatment modality [13][14][15][16][17][18] but only a few authors have published data on IORT and seroma production [19].…”

Techniques for Intraoperative Radiation Therapy for Early-Stage Breast Carcinoma

“…Of note, the risk of fat necrosis after APBI increases with lower dose homogeneity and higher volumes of tissue exposes to 150 and 200% of the prescription dose [39,40]. Although cosmesis would theoretically be improved with IORT because there is less irradiation of normal tissue [41,42], there is also the potential for worse cosmesis because of a lack of symmetry within the irradiated breast [43]. Careful patient selection, future science group www.futuremedicine.com considering tumor-to-breast ratio and distance to skin is critical.…”

Therapeutic analysis of Intrabeam‐based intraoperative radiation therapy in the treatment of unicentric breast cancer lesions utilizing a spherical target volume model

“…An alternative to standard EBRT is intraoperative radiation therapy (IORT) in which at the time of breast conserving surgery a single dose of radiation is delivered 3. Unlike other types of radiotherapy, intraoperative radiotherapy (IORT) delivers a high single dose of radiation to the area around the tumor bed.…”

“…This shorter treatment option has been hypothesized to improve patient compliance, cost, and overall experience 9. Since the 20 Gy dose of IB‐IORT is biologically much greater than the fractional doses of EBRT, initially there was concern for an increase in toxicity, but studies have shown no treatment related mortality or excess morbidity including problems with wound healing, infection, or cosmetics 3, 9. One major difference between IB‐IORT and EBRT is breast changes such as fat necrosis and other distinct mammographic changes, which can complicate future diagnostic mammography, although usually, these changes are easily discernible from recurrent tumors 9.…”