IORT with electrons as boost strategy during breast conserving therapy in limited stage breast cancer: long term results of an ISIORT pooled analysis

On the need of in vivo verifications as quality control for intraoperative electron radiotherapy in breast cancer

INTRODUCTION

Intraoperative electron radiotherapy (IOERT) is a technique aiming to deliver radiotherapy during oncological surgery. In breast IOERT, the applicator and shielding disc placement are correlated with organs at risk (OAR) irradiation, in vivo verification of these parameters is scarcely reported. The aim of our study is to report and analyze possible causes of the misalignment using radiochromic films and compare our results to others reported in the bibliography.

METHODS

From November 2019 to April 2023, in vivo verifications were performed for 33 patients. IOERT was performed using a LIAC 10 MeV (Sordina, Italy) electron accelerator. We attached a radiochromic film to the upper side of the polytetrafluoroethylene cover of the shielding disc. The percentage of the irradiation area outside the disc was recorded and various parameters (applicator angulations, prescription depth, tumor location and breast size) were analyzed to find possible correlations.

RESULTS

For 29 patients, 20 Gy were prescribed while 10 Gy were prescribed to 4 patients. The average irradiated area outside the disc was 19% (0-56%) corresponding to a surface of 4.5 cm2 (0-17.4 cm2). The applicator of 5 cm was used for most of the patients. The mean prescription depth was 1.4 cm (0.5-2.5 cm). We found no correlation between the analyzed parameters and misalignment.

CONCLUSION

This study confirms the presence and magnitude of the misalignments. We strongly recommend in vivo verifications as a quality check during IOERT procedures. The misalignment has no correlation with tumor localization parameters, so the solution could be based on technical improvements of the applicator.

Evaluating the induced photon contamination by different breast IOERT shields using Monte Carlo simulation

BACKGROUND AND OBJECTIVE

Avoiding the underlying healthy tissue over-exposure during breast intraoperative electron radiotherapy (IOERT) is owing to the use of some dedicated radioprotection disks during patient irradiation. The originated contaminant photons from some widely used double-layered shielding disks including PMMA+Cu, PTFE+steel, and Al+Pb configurations during the breast IOERT have been evaluated through a Monte Carlo (MC) simulation approach.

METHODS

Produced electron beam with energies of 6, 8, 10, and 12 MeV by a validated MC model of Liac12 dedicated IOERT accelerator was used for disk irradiations. Each of above-mentioned radioprotection disks was simulated inside a water phantom, so that the upper disk surface was positioned at R90 depth of each considered electron energy. Simulations were performed by MCNPX (version 2.6.0) MC code. Then, the energy spectra of the contaminant photons at different disk surfaces (upper, middle, and lower one) and relevant contaminant dose beneath the studied disks were determined and compared.

RESULTS

None of studied shielding disks show significant photon contamination up to 10 MeV electron energy, so that the induced photon dose by the contaminant X-rays was lower than those observed in the disk absence under the same conditions. In return, the induced photon dose at a close distance to the lower disk surface exceeded from calculated values in the disk absence at 12 MeV electron energy. The best performance in contaminant dose reduction at the energy range of 6-10 MeV belonged to the Al+Pb disk, while the PMMA+Cu configuration showed the best performance in this regard at 12 MeV energy.

CONCLUSION

Finally, it can be concluded that all studied shielding disks not only don't produce considerable photon contamination but also absorb the originated X-rays from electron interactions with water at the electron energy range of 6-10 MeV. The only concern is related to 12 MeV energy where the induced photon dose exceeds the dose values in the disk absence. Nevertheless, the administered dose by contaminant photons to underlying healthy tissues remains beneath the tolerance dose level by these organs at the entire range of studied electron energies.

Tumor Bed Boost Radiotherapy in the Conservative Treatment of Breast Cancer: A Review of Intra-Operative Techniques and Outcomes

Conservative surgery is the preferred treatment in the management of breast cancer followed by adjuvant whole-breast irradiation. Since the tumor bed is the main site of relapse, boost doses are conveniently administered according to risk factors for local relapse to increase the efficacy of the treatment. The benefit of a radiation boost is well established and it can be performed by several techniques like brachytherapy, external radiation or intraoperative radiotherapy. Greater precision in localizing the tumor cavity, immediacy and increased biological response are the main advantages of intraoperative boost irradiation. This modality of treatment can be performed by means of mobile electron accelerators or low-photon X-ray devices. There is a lot of research and some published series analyzing the results of the use of an intraoperative boost as an adjuvant treatment, after neoadjuvant systemic therapy and in combination with some reconstructive surgeries. This review discusses advantages of intraoperative radiotherapy and presents the main results of a boost in terms of local control, survival, tolerance and cosmesis.

The Efficacy of Low-Kilovoltage X-Rays Intraoperative Radiation as Boost for Breast Cancer: A Systematic Review and Meta-Analysis

Background

Intraoperative radiotherapy (IORT) is a novel promising technology that may replace external beam radiation therapy (EBRT) as boost for patients receiving breast-conserving surgery. To better evaluate the efficacy of IORT using low-kilovoltage (low-kV) X-rays as boost, we presented this meta-analysis according to the PRISMA checklist.

Methods

Studies reported survival outcomes of intraoperative radiation using low-kilovoltage X-rays system (Intrabeam®, Carl Zeiss Meditec, Dublin, CA, USA) as boost were identified through electronic bibliographic database: PUBMED. The meta-analysis module in Stata (16.0) is used to pool the studies. A Poisson regression model is used to predict a 5-year local recurrence rate.

Results

Twelve studies including 3006 cases were included in the final analysis, with a median follow-up of 55 months weighted by sample size. The pooled local recurrence rate is 0.39% per person-year (95% CI: 0.15%-0.71%), with a low degree of heterogeneity (I² = 0%). The predicted 5-year local recurrence rate was 3.45%. No difference in pooled local recurrence rate was found between non-neoadjuvant patients studies and neoadjuvant patients studies (0.41% per person-year vs. 0.58% per person-year, P = 0.580).

Conclusions

This study shows that low-kV IORT is an effective method as boost in breast cancer patients, with a low pooled local recurrence rate and low predicted 5-year local recurrence rate. Besides, no difference in the local recurrence rate was found between non-neoadjuvant patients studies and neoadjuvant patients studies. Low-kV IORT boost may be a promising alternative to EBRT boost in the future, which is being tested in the ongoing TARGIT-B trial.

The role of the radiation therapy breast boost in the 2020s

Given that most local relapses of breast cancer occur proximal to the original location of the primary, the delivery of additional radiation dose to breast tissue that contained the original primary cancer (known as a "boost") has been a standard of care for some decades. In the context of falling relapse rates, however, it is an appropriate time to re-evaluate the role of the boost. This article reviews the evolution of the radiotherapy boost in breast cancer, discussing who to boost and how to boost in the 2020s, and arguing that, in both cases, less is more.

Long-term results of breast cancer patients who received IOERT as boost during BCS: A single-institution retrospective analysis

Objectives

Intraoperative electron radiotherapy (IOERT) applied as boost to the tumor bed during breast conserving surgery is advantageous in terms of local recurrence in breast cancer patients. In addition, it has other advantages over the adjuvant boost RT such as no risk of tumor bed change, ease of sequencing radiotherapy chemotherapy, and reduced workload of the radiotherapy clinic. This study aimed to evaluate the long-term results of our patients who were treated with this method in our institution and are still being followed up.

Material and Methods

One hundred and three patients enrolled in this study received IOERT equivalent to 10 Gy as boost during BCS and were subsequently given adjuvant WBI according to the biological subtype of the tumor systemic therapy. These patients were analyzed using their files and hospital records. Patients were evaluated for overall survival, local recurrence, distant metastasis, and cosmetic outcome (using LENT-SOMA scale).

Results

Median age was 53,5 (27-74), mean follow-up time was 75 (48-106) months. Mean pathological tumor size was 18 mm (4-30), 90 of the patients had invasive ductal carcinoma, eight of them were lobular and five of them had mixed histological structure. Ninety-three of the patients presented histological grade II, 15 grade III; 74 patients were luminal A-like, 15 luminal B-like, eight HER2 positive and six triple negative breast cancer. According to the LENT-SOMA scale, 35 had grade 0, 42 each had grade I, 23 had grade II, and two had grade III. All patients underwent whole breast irradiation after surgery, 81 received chemotherapy and 90 endocrine therapy. There was one local recurrence, distant recurrence was seen in four patients and one patient died of non-breast cancer causes. Overall survival was %99, and event free survival %96.

Conclusion

IOERT for breast cancer treatment during BCS is a safe option with low chronic toxicity and the cosmetic outcome gets better over time.

Intraoperative radiation therapy in the management of early stage breast cancer

Adjuvant radiotherapy (RT) following breast conserving surgery (BCS) is associated with an improvement in local control and a reduction in breast cancer mortality. While traditionally delivered with whole breast irradiation (WBI), novel approaches have looked to reduce the duration, target volume, and toxicity of adjuvant RT. One such approach is intraoperative radiation therapy (IORT), which delivers radiation at the time of surgery with 80-90% of patients not requiring additional WBI. The current review presents IORT techniques and outcomes from modern series evaluating IORT as monotherapy or as a tumor bed boost. Based on two randomized trials (TARGIT-A and ELIOT) with recent updates, concern regarding higher rates of local recurrence with IORT exist, whether using electrons or low-energy techniques. In contrast, data is promising regarding IORT used as a boost, with ongoing studies evaluating its role prospectively. With respect to toxicity, the data suggest IORT is associated with comparable to slightly lower rates of toxicity though there may be a higher risk of seroma requiring aspiration and fat necrosis with IORT. Given current data and guidelines, WBI or other partial breast techniques should remain the standard of care in early stage breast cancer patients, while IORT should not be utilized outside of prospective clinical trials at this time.

Efficacy and Tolerance of IMRT Boost Compared to IORT Boost in Early Breast Cancer: A German Monocenter Study

The aim of this retrospective study is to compare the two boost subgroups, IORT or IMRT, in terms of overall survival (OS), progression-free survival (PFS), cosmesis, and acute and late toxicity. It shall be shown whether and which of the boost techniques offers better results with respect to the facial points, since there are already many studies on applying boost to the tumor bed after/during breast conserving surgery, and there are few which compare the different techniques. For this comparison, two subgroups of 76 patients each (n = 152), treated between 2002 and 2015, were enrolled in the study. In one subgroup, the 9 Gy boost was intraoperatively administered after complete removal of the primary tumor, while the other subgroup received the boost of 8.4 Gy percutaneously and simultaneously integrated into the tumor bed after breast conserving surgery. Both subgroups have subsequently undergone whole breast irradiation (WBI) of 50.4/50 Gy in 1.8−2 Gy per fraction. OS and the incidence of late toxicity did not differ between the two subgroups and no risk factor was found regarding PFS. Acute toxicities initially occurred significantly less (p < 0.001) in the IORT subgroup; however, after WBI took place, this difference vanished. Therefore, boost application by means of IORT or IMRT can be considered equivalent.

Early Outcome, Cosmetic Result and Tolerability of an IOERT-Boost Prior to Adjuvant Whole-Breast Irradiation

Background/Aims: Due to its favorable dose distribution and targeting of the region at highest risk of recurrence due to direct visualization of tumor bed, intraoperative electron radiation therapy (IOERT) is used as part of a breast-conserving treatment approach. The aim of this study was to analyze tumor control and survival, as well as the toxicity profile, and cosmetic outcomes in patients irradiated with an IOERT boost for breast cancer. Materials and Methods: 139 Patients treated at our institution between January 2010 and January 2015 with a single boost dose of 10 Gy to the tumor bed during breast-conserving surgery followed by whole-breast irradiation were retrospectively analyzed. Results: 139 patients were included in this analysis. The median age was 54 years (range 28−83 years). The preferred surgical strategy was segmental resection with sentinel lymphonodectomy (66.5%) or axillary dissection (23.1%). Regarding adjuvant radiotherapy, the vast majority received 5 × 1.8 Gy to 50.4 Gy. At a median follow-up of 33.6 months, recurrence-free and overall survival were 95.5% and 94.9%, respectively. No patient developed an in-field recurrence. Seven patients (5.0%) died during the follow-up period, including two patients due to disease recurrence (non-in-field). High-grade (CTCAE > 2) perioperative adverse events attributable to IOERT included wound healing disorder (N = 1) and hematoma (N = 1). High-grade late adverse events (LENT-SOMA grade III) were reported only in one patient with fat necrosis. Low-grade late adverse events (LENT-SOMA grade I-II) included pain (18.0%), edema (10.5%), fibrosis (21%), telangiectasia (4.5%) and pigmentation change (23.0%). The mean breast retraction assessment score was 1.66 (0−6). Both patients and specialists rated the cosmetic result “excellent/good” in 84.8% and 87.9%, respectively. Conclusion: Our study reports favorable data on the cosmetic outcome as well as the acute and early long-term tolerability for patients treated with an IOERT boost. Our oncologic control rates are comparable to the previous literature. However, prospective investigations on the role of IOERT in comparison to other boost procedures would be desirable.

Long-Term Outcomes of an International Cooperative Study of Intraoperative Radiotherapy Upfront Boost With Low Energy X-Rays in Breast Cancer

Purpose

The purpose of this study was to assess the effectivity of upfront kilovoltage intraoperative radiotherapy (IORT) as a boost in high-risk early-stage breast cancer patients from an international pooled cohort.

Materials/Methods

Patients from four centers in three different countries were retrospectively screened. Those with a minimum 1-year follow-up were included. Cumulative local (LR), regional (RR), and distant metastasis rates (DM) were analyzed. Additionally, the estimated overall survival (OS) was assessed. The Cox regression analysis was performed to identify failure predicting factors.

Results

A total of 653 patients from centers in Peru, Spain, and Germany were included. The median follow-up was 55 (12–180) months, and age was 58 (27–86) years. Clinical tumor (T) staging was T1 65.85%, T2 30.17%, and T3 3.98%. Positive margins were found in 7.9% and in-situ component in 20.06%. The median IORT dose was 20 (6–20). The median time from IORT to EBRT was 74.5 (13-364) days. An overall 3.4% (n = 22) of patients developed local recurrence at some point during follow-up. The 12-, 60-, and 120-month cumulative LR were 0.3%, 2.3%, and 7.9%, respectively. After multivariate analysis, only age <50 remained to be a significant prognostic factor for local recurrence (HR 0.19, 95% CI 0.08–0.47; p < 0.05). The 10-year estimated OS was 81.2%.

Conclusion

Upfront boost with IORT yields similar local control outcomes to those EBRT-based reports. Results from prospective trials, regarding toxicity, cosmesis, and effectivity are awaited to confirm these findings.

Intra-Operative Electron Radiation Therapy (IOERT) Anticipated Boost in Breast Cancer Treatment: An Italian Multicenter Experience

In breast cancer, the use of a boost to the tumor bed can improve local control. The aim of this research is to evaluate the safety and efficacy of the boost with intra-operative electron radiotherapy (IOERT) in patients with early-stage breast cancer undergoing conservative surgery and postoperative whole breast irradiation (WBI). The present retrospective multicenter large data were collected between January 2011 and March 2018 in 8 Italian Radiation Oncology Departments. Acute and late toxicity, objective (obj) and subjective (subj) cosmetic outcomes, in-field local control (LC), out-field LC, disease-free survival (DFS) and overall survival (OS) were evaluated. Overall, 797 patients were enrolled. IOERT-boost was performed in all patients during surgery, followed by WBI. Acute toxicity (≥G2) occurred in 179 patients (22.46%); one patient developed surgical wound infection (G3). No patients reported late toxicity ≥ G2. Obj-cosmetic result was excellent in 45%, good in 35%, fair in 20% and poor in 0% of cases. Subj-cosmetic result was excellent in 10%, good in 20%, fair in 69% and poor in 0.3% of cases. Median follow-up was 57 months (range 12-109 months). At 5 years, in-field LC was 99.2% (95% CI: 98-99.7); out-field LC 98.9% (95% CI: 97.4-99.6); DFS 96.2% (95% CI: 94.2-97.6); OS 98.6% (95% CI: 97.2-99.3). In conclusion, IOERT-boost appears to be safe, providing excellent local control for early-stage breast cancer. The safety and long-term efficacy&nbsp;should encourage use of this treatment, with the potential to reduce local recurrence.

Intraoperative irradiation in breast cancer: preliminary results in 80 patients as partial breast irradiation or anticipated boost prior to hypo-fractionated whole breast irradiation

Purpose

To present the first results of intraoperative irradiation (IORT) in breast cancer with a low-energy photon system used as partial breast irradiation (PBI) or as an anticipated boost before whole breast hypo-fractionated irradiation (IORT + WBI), concerning tolerance, side effects, quality of life, and patient-reported outcomes.

Materials and methods

Eighty patients treated with an Intrabeam^® system of 50 kV X-rays received a 20 Gy dose intraoperatively were included. Moderate daily hypofractionation of 2.7 Gy in 15 fractions up to 40.5 Gy was administered if high-risk factors were present. Acute post-operative toxicity, surgery complications, chronic toxicity, patient-reported cosmesis and Breast-Q questionnaire were performed at follow-up visits.

Results

Thirty-one patients were treated as PBI and the remaining 49 as IORT + WBI. Only the IORT + WBI group presented acute toxicity, mainly mild acute dermatitis (11 patients) and one subacute mastitis. A total of 20 patients presented fibrosis (18 patients grade I, 2 patients grade II), 15 (30.5%) patients in the IORT + WBI group and 3 (9.6%) patients in the group of PBI. The cosmesis evaluation in 73 patients resulted poor, fair, good or excellent in 2, 7, 38 and 26 patients, respectively. In PBI group Breast-Q scored higher, especially in terms of their psychosocial well-being (78 vs 65) and satisfaction with radiation-induced toxicity (77 vs 72, respectively) compared to IORT + WBI group.

Conclusion

IORT is a well-tolerated procedure with low toxicity, good cosmesis and favorable patient-reported outcomes mainly when administered as PBI.

Bystander effects induced by electron beam-irradiated MCF-7 cells: a potential mechanism of therapy resistance

PURPOSE

The distinct direct and non-targeting effects of electron beam radiation on MCF-7 cells remain obscure. We aimed to investigate the effect of electron beam irradiation (EBI) and conditioned media (CM) of the irradiated MCF-7 cells on MCF-7 cells. The cytotoxic effects of CM from irradiated MCF-7 cells on the mesenchymal stem cells and human umbilical vein endothelial cells (HUVECs) were also examined.

METHODS

Cell viability and apoptosis were assayed via MTT and flow cytometry analysis, respectively. The production of ROS (reactive oxygen species) was evaluated by the chemical fluorometric method, while the amount of extracellular vesicles was detected via acetylcholinesterase activity assay. Expression of genes involved in apoptosis, including caspase-3, -8, -9, and stemness such as Sox-2 and Oct-4, were calculated through qPCR. The wound healing rate of cells was monitored via in vitro scratch assay.

RESULTS

Compared to the control group, EBI groups showed decreased cell viability but increased apoptosis and ROS as well as acetylcholinesterase activity dose-dependently (P < 0.05). Concurrently with increasing the dose of the electron beam, the transcript levels of apoptotic genes (caspase-3, -8, -9) and stemness-related genes (Sox-2 and Oct-4) were up-regulated following EBI. The wound healing rate of irradiated MCF-7 cells increased dose-dependently (P < 0.05). Similar results were observed after treatment with CM from irradiated MCF-7 cells. Additionally, CM from irradiated MCF-7 cells decreased the viability of MCF-7 cells, mesenchymal stem cells, and HUVECs (P < 0.05).

CONCLUSION

MCF-7 cells treated with an electron beam and CMs from irradiated MCF-7 cells exhibit an up-regulation in both genes involved in the apoptosis pathway and stemness. As a result, EBI can affect apoptosis and stemness in MCF-7 cells in direct and bystander manners. However, specific signaling pathways require careful evaluation to provide an understanding of the mechanisms involved in the EBI-induced alternation in tumor cell dynamics.

State of the art in breast intraoperative electron radiation therapy after intraoperative ultrasound introduction

BACKGROUND

Breast intraoperative electron radiation therapy (B-IOERT) can be used in clinical practice both as elective irradiation (partial breast irradiation - APBI) in low risk breast cancer patients, and as an anticipated boost. The procedure generally includes the use of a shielding disk between the residual breast and the pectoralis fascia for the protection of the tissues underneath the target volume. The aim of the study was to evaluate the role of intraoperative ultrasound (IOUS) in improving the quality of B-IOERT.

PATIENTS AND METHODS

B-IOERT was introduced in Trieste in 2012 and its technique was improved in 2014 with IOUS. Both, needle and IOUS were used to measure target thickness and the latter was used even to check the correct position of the shielding disk. The primary endpoint of the study was the evaluation of the effectiveness of IOUS in reducing the risk of a disk misalignment related to B-IOERT and the secondary endpoint was the analysis of acute and late toxicity, by comparing two groups of patients treated with IOERT as a boost, either measured with IOUS and needle (Group 1) or with needle alone (Group 2). Acute and late toxicity were evaluated by validated scoring systems.

RESULTS

From the institutional patients who were treated between June 2012 and October 2019, 109 were eligible for this study (corresponding to 110 cases, as one patients underwent bilateral conservative surgery and bilateral B-IOERT). Of these, 38 were allocated to group 1 and 72 to group 2. The target thickness measured with the IOUS probe and with the needle were similar (mean difference of 0.1 mm, p = 0.38). The percentage of patients in which the shield was perfectly aligned after IOUS introduction increased from 23% to more than 70%. Moreover, patients treated after IOUS guidance had less acute toxicity (36.8% vs. 48.6%, p = 0.33) from radiation therapy, which reached no statistical significance. Late toxicity turned out to be similar regardless of the use of IOUS guidance: 39.5% vs. 37.5% (p = 0.99).

CONCLUSIONS

IOUS showed to be accurate in measuring the target depth and decrease the misalignment between collimator and disk. Furthermore there was an absolute decrease in acute toxicity, even though not statistically significant, in the group of women who underwent B-IOERT with IOUS guidance.

Intraoperative radiotherapy boost as part of breast-conservation therapy for breast cancer: a single-institution retrospective analysis

Background

There are currently no data from randomized controlled trials on the use of intraoperative radiotherapy (IORT) as a tumor bed boost as part of a breast-conservation approach for breast cancer. This study retrospectively reviewed the safety and efficacy of IORT as a boost treatment at a tertiary cancer center.

Methods

From 2015 to 2019, patients underwent breast-conserving surgery with axillary lymph node staging and a single dose of 20 Gy IORT with 50-kV photons, followed by whole-breast irradiation (WBI) and adjuvant systemic therapy (if applicable). Patients were followed for assessment of acute and late toxicities (using the Common Terminology Criteria for Adverse Events version 5.0) at 3–6-month intervals. Outcomes included ipsilateral (IBTR) and contralateral breast progression-free survival (CBE), distant metastasis-free survival (DMFS), and overall survival (OS).

Results

Median follow-up for the 214 patients was 28 (range 2–59) months. Most patients had T1 disease (n = 124) and were clinically node negative. Only few patients had high-grade and/or triple-negative disease. The vast majority of patients underwent sentinel node biopsy, and 32 (15%) required re-resection for initially positive margins. Finally, all tumor bed margins were clear. Nine (4.2%) and 48 (22.4%) patients underwent neoadjuvant and adjuvant chemotherapy, respectively. WBI was predominantly performed as conventionally fractionated WBI (n = 187, 87.4%), and the median time from BCS to WBI was 54.5 days. IORT was delivered with a single dose of 20 Gy. The median WBI dose was 50 Gy (range 29.4–50.4 Gy). No patients experienced grade 4 events; acute grade 3 toxicities were limited to 17 (8%) cases of radiation dermatitis. Postoperative toxicities were mild. After WBI only one case of late grade ≥ 2 events was reported. There were two recurrences in the tumor bed and one contralateral breast event.

Conclusion

This investigation provides additional preliminary data supporting the using of IORT in the boost setting and corroborates the existing literature. These encouraging results should be prospectively validated by the eventual publication of randomized studies such as TARGIT‑B.

Comparison of IORT (Radical and Boost Dose) and EBRT in Terms of Disease-Free Survival and Overall Survival according to Demographic, Pathologic, and Biological Factors in Patients with Breast Cancer

Background

The standard treatment for breast cancer is breast-conserving surgery (BCS) with radiotherapy. If external beam radiation therapy (EBRT) can be safely replaced with intraoperative radiotherapy (IORT), it will help patients to save their breast and to have equivocal or better results in DFS and overall survival (OS).

Methods

A total of 2022 patients with breast cancer treated during 6 years were enrolled in the current study. A total of 657, 376, and 989 patients received EBRT, radical, and boost dose by IORT, respectively, according to the IRIORT consensus protocol. The primary endpoint was recurrence and death. The secondary endpoint was the role of variables in recurrence and death.

Results

With a mean follow-up of 34.5 and 40.18 months for the IORT and EBRT groups, respectively, there was a significant difference in DFS between electron boost and X-ray boost groups (P=0.037) and the electron radical group compared with EBRT (P=0.025), but there was no significant difference between other boost and radical groups in DFS and OS.

Conclusions

IORT can be a preferred treatment modality because of its noninferior outcomes, and in some special conditions, it has superior outcomes compared to EBRT, particularly in delivering radical dose with IORT.

IOERT versus external beam electrons for boost radiotherapy in stage I/II breast cancer: 10-year results of a phase III randomized study

Background

Intraoperative radiotherapy with electrons (IOERT) boost could be not inferior to external beam radiotherapy (EBRT) boost in terms of local control and tissue tolerance. The aim of the study is to present the long-term follow-up results on local control, esthetic evaluation, and toxicity of a prospective study on early-stage breast cancer patients treated with breast-conserving surgery with an IOERT boost of 10 Gy (experimental group) versus 5 × 2 Gy EBRT boost (standard arm). Both arms received whole-breast irradiation (WBI) with 50 Gy (2 Gy single dose).

Methods

A single-institution phase III randomized study to compare IOERT versus EBRT boost in early-stage breast cancer was conducted as a non-inferiority trial. Primary endpoints were the evaluation of in-breast true recurrences (IBTR) and out-field local recurrences (LR) as well as toxicity and cosmetic results. Secondary endpoints were overall survival (OS), disease-free survival (DFS), and patient’s grade of satisfaction with cosmetic outcomes.

Results

Between 1999 and 2004, 245 patients were randomized: 133 for IOERT and 112 for EBRT. The median follow-up was 12 years (range 10–16 years). The cumulative risk of IBTR at 5–10 years was 0.8% and 4.3% after IOERT, compared to 4.2% and 5.3% after EBRT boost (p = 0.709). The cumulative risk of out-field LR at 5–10 years was 4.7% and 7.9% for IOERT versus 5.2% and 10.3% for EBRT (p = 0.762). All of the IOERT arm recurrences were observed at > 100 months’ follow-up, whereas the mean time to recurrence in the EBRT group was earlier (55.2 months) (p < 0.05). No late complications associated with IOERT were observed. The overall cosmetic results were scored as good or excellent in physician and patient evaluations for both IOERT and EBRT. There were significantly better scores for IOERT at all time points in physician and patient evaluations with the greatest difference at the end of EBRT (p = 0.006 objective and p = 0.0004 subjective) and most narrow difference at 12 months after the end of EBRT (p = 0.08 objective and p = 0.04 subjective analysis).

Conclusion

A 10-Gy IOERT boost during breast-conserving surgery provides high local control rates without significant morbidity. Although not significantly superior to external beam boosts, the median time to local recurrences after IOERT is prolonged by more than 4 years.

The Role of Intraoperative Radiation in Early-stage Breast Cancer

Intraoperative radiation therapy (IORT) is a specialized form of accelerated partial breast irradiation in which a single dose of radiation is delivered to the tumor bed at the time of breast conserving surgery. With completion of radiation to the tumor bed at the time of surgery, IORT promises improved patient convenience, compliance, and quality of life. In addition, with its potentially skin-sparing properties and ability to deliver a high biologically effective dose to the tumor bed while reducing dose to nontarget tissues, IORT results in different but overall less toxicities compared with other modalities of radiation for breast cancer. However, skepticism over the role of IORT in breast cancer exists, and the 2 randomized trials that have analyzed IORT as the definitive radiation component of breast conservation therapy have shown an increase in local recurrence rates with IORT compared with whole breast irradiation, but similar rates of overall survival. In this review, we discuss the practicalities of IORT, the prospective data supporting and negating the role of IORT in lieu of whole breast irradiation, and the toxicity after IORT in early-stage breast cancer. We also review the role of IORT as a radiation boost and specific strategies for successful implementation of IORT in breast cancer.

Post-lumpectomy radiation therapy boost in breast cancer patients: evidence revisited

Purpose

Radiation therapy is an integral part in the management of breast cancer after breast conservative surgery. In selected patients at high risk for local recurrence (LR), a boost radiation dose is commonly applied to the tumour bed.

Methods

We performed a review of the English literature using PubMed, Medline and Google Scholar for published manuscripts addressing the effect of boost radiation in breast cancer patients, focusing mainly on LR and overall survival (OS).

Results

A total of seven studies were included in our review. Most studies (6/7, 85.7%) showed a significant improvement in local control independent of age (hazard ratios ranging between 0.34 and 0.73), with the largest absolute benefit in younger patients. None of the studies, however, was able to demonstrate an improvement in OS.

Conclusions

With lack of sufficient studies addressing the role of boost radiation, individualised treatment decisions are recommended, taking into account the risk factors for LR, including tumour biology. Real-life data are sorely needed to better assess the role of tumour bed boost in the contemporary era.

Chronic toxicity and long-term outcome in intraoperative electron radiotherapy as boost followed by whole-breast irradiation

PURPOSE

The administration of a dose boost to the tumor bed after breast-conserving surgery has proven to reduce local recurrence. Intra-operative electron radiotherapy (IOERT) offers an alternative method to deliver a boost with several advantages, such as direct visualization of the tumor bed, less inter- and intrafraction motion and a reduction in the number of medical appointments. The objective of our study is to assess chronic toxicity and long-term outcome for our patients after IOERT boost.

MATERIAL AND METHODS

Forty-six patients treated at our institution between July 2013 and June 2020 with IOERT boost during Breast-Conserving Surgery and consecutive whole breast irradiation were prospectively analyzed. A 10-12 Gy boost was prescribed to 42 patients and 4 patients received a 20 Gy boost. An analysis for overall survival, local relapse and distant progression was performed. Acute and chronic toxicity was assessed by CTCAE 4.0.

RESULTS

The median age was 64.5 years (40-90). The median follow-up was 62 months (4-86). We had no local recurrences but 2 patients (4.3%) presented a distant recurrence. Mean pathological tumor size was 16 mm (6-52). 84.8% (39) of the patients had invasive ductal carcinoma. 52.2% (24) presented histological grade II. 52.2% (24) were Luminal A like, 21.7% (10) Luminal B like, 13% (6) HER2 positive, 13% (6) triple negative. No Grade 3-4 chronic toxicity was observed. Grade 1-2 fibrosis was evidenced in 13% (6) of the patients, 4.3% (2) patients presented fat necrosis, 6.5% (3) presented seroma, 4.3% (2) had localized pain, 2.2% (1) presented localized hematoma and 2.2% (1) presented localized edema.

CONCLUSIONS

IOERT boost in breast cancer treatment during BCS is a safe option with low chronic toxicity. The recurrence rates are comparable to published data and emphasize that IOERT as boost is an effective treatment.

Oncological outcome, postoperative complications, and mammographic changes after intraoperative radiotherapy with electrons (IOERT) as a boost in a large single-institution cohort of breast cancer patients

Advantages of using intraoperative radiotherapy with electrons (IOERT) as a boosting modality in breast-conserving therapy include the direct visualization of the tumor bed, a reduced skin dose, and patient convenience. We report oncological outcome, postoperative complication rate, and mammographic changes on follow-up imaging in women treated at our institution with IOERT as a boost modality in breast-conserving therapy for early-stage breast carcinoma. Between January 2007 and June 2018, 763 consecutive patients were enrolled. During breast-conserving surgery, an IOERT boost of 9 Gy was applied, followed by whole breast irradiation (WBI). At a median follow-up of 62.2 months (range: 0.5-135), 13 in-breast recurrences were observed, yielding a local tumor control rate of 98.4% at 5 years. In multivariable analysis, high tumor grading was predictive for local recurrence (HR = 5.6; 95%CI: 1.19-26.2). A total of 27 (3.5%) patients developed any kind of postoperative complication. None of the tumor characteristics nor any of the IOERT technical parameters were predictive for development of a postoperative complication. On follow-up imaging, 145 patients with mammographic changes BIRADS score ≥3 were found of which 50.3% required a biopsy. Only 17 patients had positive biopsies; none of the IOERT parameters were predictive for false-positive imaging. A 9 Gy IOERT boost combined with postoperative WBI provided outstanding local control rates, was well-tolerated, with limited postoperative complications. However, radiologists must be aware of a presumable higher prevalence of mammographic changes after IORT as a boost.

[Rib fracture following intra-operative radiotherapy for breast cancer. Case Report and local experience]

Intra-operative radiotherapy for breast cancer has been developed throughout the last two decades. It is already well-established regarding local control and toxicity for intra-operative radiotherapy using electrons as we now have the necessary background knowledge. However, very few data on later toxicity are available for intra-operative radiotherapy using low-energy photons. We report here the case of a 36-year-old woman who experienced rib fracture following intra-operative and external radiotherapy. This patient has been included in the Targit-boost trial. The intra-operative irradiation has been operated with an INTRABEAM device delivering low-energy photons of 50-kV.

Surgical Wound Fluids from Patients with Breast Cancer Reveal Similarities in the Biological Response Induced by Intraoperative Radiation Therapy and the Radiation-Induced Bystander Effect-Transcriptomic Approach

In patients with breast cancer who undergo breast-conserving surgery (BCS), more than 90% of local recurrences occur in the same quadrant as the primary cancer. Surgical wound fluids (SWF) are believed to play a role in this process by inducing an inflammatory process in the scar tissue area. Despite strong clinical data demonstrating the benefits of intraoperative radiotherapy (IORT), the biological basis underlying this process remains poorly understood. Ionizing radiation (IR) directly affects cells by damaging DNA, thereby altering the cell phenotype. IR directly affects cancer cells and also influences unirradiated cells located nearby, a phenomenon known as the radiation-induced bystander effect (RIBE), significantly modifying the tumor microenvironment. We hypothesized that SWF obtained from patients after BCS and IORT would induce a radiobiological response (due to RIBE) in unirradiated cells, thereby modifying their phenotype. To confirm this hypothesis, breast cancer cells were incubated with SWF collected from patients after BCS: (1) without IORT (wound fluid (WF) group), (2) with IORT (radiotherapy wound fluid (RT-WF) group), and (3) WF with conditioned medium from irradiated cells (WF+RIBE group) and then subjected to microarray analysis. We performed gene set enrichment analysis to determine the biological processes present in these cells. This analysis showed that the RT-WF and WF+RIBE groups shared common biological processes, including the enhancement of processes involved in cell-cycle regulation, DNA repair, and oxidative phosphorylation. The WF group was characterized by overrepresentation of pathways involved in the INF-α and INF-γ response, inflammatory response, and the IL6 JAK/STAT3 signaling pathway. These findings show that MDA-MB-468 cells stimulated with surgical wound fluids obtained from patients who underwent BCS plus IORT and from cells stimulated with SWF plus RIBE share common biological processes. This confirms the role of the radiation-induced bystander effect in altering the biological properties of wound fluids.

Long-term outcome after intraoperative radiotherapy as a boost in breast cancer

PURPOSE

To investigate long-term oncological outcome and incidence of chronic side effects in patients with breast cancer and intraoperative radiotherapy given as an upfront boost (IORT boost).

METHODS

Retrospective analysis of 400 patients with an IORT boost with low-energy X‑rays (20 Gy), subsequent whole-breast irradiation (46-50 Gy), and annual oncological follow-up. Side effects were prospectively evaluated (LENT-SOMA scales) over a period of up to 15 years. Side effects scored ≥grade 2 at least three times during follow-up were judged to be chronic.

RESULTS

The median age was 63 years (30-85) and the median follow-up was 78 months (2-180) after IORT boost. In 15 patients a local recurrence occurred, resulting in a local recurrence rate at 5, 10, and 15 years of 2.0%, 6.6%, and 10.1%, respectively. The overall survival rates at 5, 10, and 15 years were 92.1%, 81.8%, and 80.7%, respectively. The most common high-grade side effects were fibrosis (21%) and pain (8.6%). The majority of side effects occurred within the first 3 years. The actuarial rates of chronic fibrosis were 19.1% and 21.1% at 5 and ≥8 years, of chronic pain 8.6% at ≥4 years, of chronic edema of the breast 2.4% at ≥2 years, of chronic lymphedema 0.0% at 5 and 10 years, and of chronic hyperpigmentation 0.5% at ≥2 years. Side effects were similar or less than expected from an external beam boost.

CONCLUSION

IORT boost appears to be a highly efficient and safe method for upfront delivery of the tumor bed boost in high-risk breast cancer patients.

Acute Toxicity and Early Oncological Outcomes After Intraoperative Electron Radiotherapy (IOERT) as Boost Followed by Whole Breast Irradiation in 157 Early Stage Breast Cancer Patients-First Clinical Results From a Single Center

Introduction: Breast conserving surgery (BCS) followed by postoperative whole breast irradiation (WBI) is the current standard of care for early stage breast cancer patients. Boost to the tumor bed is recommended for patients with a higher risk of local recurrence and may be applied with different techniques. Intraoperative electron radiotherapy (IOERT) offers several advantages compared to other techniques, like direct visualization of the tumor bed, better skin sparing, less inter- and intrafractional motion, but also radiobiological effects may be beneficial. Objective of this retrospective analysis of IOERT as boost in breast cancer patients was to assess acute toxicity and early oncological outcomes. Material and Methods: All patients, who have been irradiated between 11/2014 and 01/2018 with IOERT during BCS were analyzed. IOERT was applied using the mobile linear accelerator Mobetron with a total dose of 10 Gy, prescribed to the 90% isodose. After ensured woundhealing, WBI followed with normofractionated or hypofractionated regimens. Patient reports, including diagnostic examinations and toxicity were analyzed after surgery and 6-8 weeks after WBI. Overall survival, distant progression-free survival, in-breast and contralateral breast local progression-free survival were calculated using the Kaplan-Meier method. Furthermore, recurrence patterns were assessed. Results: In total, 157 patients with a median age of 57 years were evaluated. Postoperative adverse events were mild with seroma and hematoma grade 1-2 in 26% and grade 3 in 0.6% of the patients. Wound infections grade 2-3 occurred in 2.2% and wound dehiscence grade 1-2 in 1.9% of the patients. Six to eight weeks after WBI radiotherapy-dependent acute dermatitis grade 1-2 was most common in 90.9% of the patients. Only 4.6% of the patients suffered from dermatitis grade 3. No grade 4 toxicities were documented after surgery or WBI. 2- and 3-year overall survival and distant progression-free survival, were 97.5 and 93.6, and 0.7 and 2.8%, respectively. In-breast recurrence and contralateral breast cancer rates after 3 years were 1.9 and 2.8%, respectively. Conclusion: IOERT boost during BCS is a safe treatment option with low acute toxicity. Short-term recurrence rates are comparable to previously published data and emphasize, that IOERT as boost is an effective treatment.

Breast intraoperative electron radiotherapy: Image-based setup verification and in-vivo dosimetry

INTRODUCTION

Single fraction nature of intraoperative radiotherapy highly demands a quality assurance procedure to qualify both beam setup and treatment delivery. The aim of this study is to evaluate the treatment setup during breast intraoperative electron radiotherapy (IOERT) and in-vivo dose delivery verification.

MATERIALS AND METHODS

Twenty-five breast cancer patients were enrolled and setup verification for each case was performed using C-arm imaging. The received dose by surface and distal end of target was measured by EBT2 film. The significance level of difference between obtained dosimetry results and predicted ones was evaluated by the T statistical test.

RESULTS

Acquired C-arm images in two different oblique views revealed any misalignment between the applicator and shielding disk. The mean difference between the measured surface dose and expected one was 1.8% ± 1.2 (p = 0.983) while a great disagreement, 11.1% ± 1.5 (p < 0.001), was observed between the measured distal end dose and expected one. This discrepancy is mainly correlated to the backscattering effect from the shielding disk. Target depth nonuniformities can also contribute to this remarkable difference.

CONCLUSION

Employing the intraoperative imaging for IOERT setup verification can considerably improve the treatment quality. Therefore, it is suggested to implement this imaging procedure as a part of treatment quality assurance. Favorable agreement between the predicted and measured surface doses demonstrates the applicability of EBT2 film for dose delivery verification. The results of in-vivo dosimetry showed that the electron backscattering from employed shielding disk can affect the received dose by the distal end of tumor bed.

Patient preferences regarding intraoperative versus external beam radiotherapy for early breast cancer and the impact of socio-demographic factors

PURPOSE

Patient comfort and preference have steadily gained attention in radio-oncologic treatment of breast cancer. Therefore, the purpose of this investigation was to further explore patient preferences in choosing between intraoperative radiotherapy (IORT) and external beam radiotherapy (EBRT).

METHODS

We prospectively analysed data of 101 women, who were candidates for breast-conserving surgery with adjuvant radiotherapy. A two-part video was shown to patients: an educational section about EBRT/IORT, followed by a preference elicitation section focusing on additional accepted risk (AAR) of recurrence after either treatment. Furthermore, participants completed a questionnaire to identify factors that influence patient preference of radiation modality.

RESULTS

The data demonstrate that 42.5% of patients would accept additional risk of recurrence for IORT versus 9% AAR for EBRT, while 48.5% of patients would not accept any additional risk, yet would choose IORT over EBRT if risks of recurrence were equivalent. When combining patient preferences and the results from the questionnaire, no single socio-economic/-demographic factor was found to significantly correlate with AAR of IORT.

CONCLUSION

Our study confirms the existence of subgroups of breast cancer patients who would accept an additional risk of recurrence associated with choice of radiation modality to receive a single dose of IORT as adjuvant radiotherapy for breast cancer instead of EBRT over several weeks; yet our data fail to identify a single factor significantly associated with these patient preferences and, therefore, helpful for individualised decision-making processes.

Surgical wound fluids from patients treated with intraoperative radiotherapy induce radiobiological response in breast cancer cells

Breast cancer is the most common cancer occurring in women. The standard of breast cancer treatment is based on breast-conserving surgery with administration of adjuvant whole breast radiotherapy. Research shows that in-breast relapse is most likely to occur in the tumour bed, i.e. around the scar. Intraoperative radiotherapy (IORT), in which radiation is delivered to the tumour bed, reduces the risk of local recurrence not only through direct cell killing, but also through modification of local microenvironment. Additionally IORT modifies the composition and biological activity of surgical wound fluid. Since many researchers show that radiation damage is mediated through factors secreted to the environment by irradiated cells, we hypothesized that this radiation-induced bystander effect is partly responsible for the change observed in surgical wound fluids. We collected conditioned medium from irradiated breast cancer cells (CM) and surgical wound fluids from patients who underwent IORT (RT-WF) and from patients after breast-conserving surgery alone (WF). We incubated two breast cancer cell lines (MCF-7 and MDA-MB-468) with WF, RT-WF, CM or WF + CM and measured radiobiological response of cells. We measured the level of double-strand breaks, induction of apoptosis and the changes in expression of genes related to DNA damage repair. We observed that stimulation with RT-WF and with WF + CM-induced double-strand breaks and increased expression of DNA damage repair-related genes, which was not observed after stimulation with WF. These results suggest that IOERT induces secretion of bystander factors mediating the genotoxic effect of ionizing radiation.

Optimise not compromise: The importance of a multidisciplinary breast cancer patient pathway in the era of oncoplastic and reconstructive surgery

Modern breast cancer care is a complex multidisciplinary undertaking in which the integrated function of multiple constituent parts is critical, and where changes to one therapeutic component may profoundly influence the delivery and outcomes of another. Oncoplastic and reconstructive breast surgery has evolved in the era of longer survival rates for women with breast cancer and aims to enhance oncological and cosmetic outcomes. However, concurrently there has been an expansion in the indications for post-mastectomy radiation therapy (Abdulkarim et al., 2011; Early Breast Cancer Trialists' Collaborative Group (EBCTCG), 2014; Poortmans et al., 2015; Wang et al., 2011), the recognition of several biologically distinct breast cancer subtypes (Perou et al., 2000; Sørlie et al., 2001, 2003; Cheang et al., 2008, 2009; Sotiriou et al., 2003; Millar et al., 2011; Blows et al., 2010; Schnitt, 2010; Haque et al., 2012; Dai et al., 2015) and the development of recommendations for prophylactic surgery for high-risk women, including BRCA-mutation carriers (James et al., 2006; Domchek et al., 2010). Primary systemic therapy is increasingly utilised yet has varying efficacy depending on tumour biology (Cortazar et al., 2014). In this paper we review the evidence which informs the multidisciplinary team opinion in the era of oncoplastic and reconstructive breast surgery. We aim to describe an optimal multidisciplinary approach which balances competing risks of multimodal therapies to optimise oncological and cosmetic outcomes.

Breast intraoperative radiotherapy: a review of available modalities, dedicated machines and treatment procedure

Background

Breast intraoperative radiotherapy (IORT) is a partial irradiation technique that delivers a single fraction of radiation dose to the tumour bed during surgery. The use of this technique is increasing (especially in the Middle East), and therefore, it is essential to have a comprehensive approach to this treatment modality. The aim of this study is to conduct a literature review on available IORT modalities during breast irradiation as well as dedicated IORT machines and associated treatment procedures. The main IORT trials and corresponding clinical outcomes are also studied.

Materials and Methods

A computerised search was performed through MEDLINE, PubMed, PubMed Central, ISI web of knowledge and reference list of related articles.

Results

IORT is now feasible through using two main modalities, including low-kilovolt IORT and intraoperative electron radiotherapy (IOERT). The dedicated machines employed and treatment procedure for mentioned modalities are quite different. The outcomes of implemented clinical trials showed that IORT is not inferior to external beam radiotherapy (EBRT) in specifically selected and well-informed patients and can be considered as an alternative to EBRT.

Conclusion

Although the clinical outcomes of introduced IORT methods are comparable, but based on the review results, it could be said that IOERT is the most effective technical method, in view of the treatment time and dose uniformity concepts. The popularity of IORT is mainly due to the distinguished obtained results during breast cancer treatment. Despite the presence of some technical challenges, it is expected that the IORT technique will become more widespread in the immediate future.

Intraoperative Radiation Therapy (IORT): A Series of 1000 Tumors

BACKGROUND

Two prospective, randomized trials, TARGIT-A and ELIOT, have shown intraoperative radiation therapy to be a safe alternative, with a low-risk of local recurrence, compared with whole breast radiation therapy, following breast-conserving surgery, for selected low-risk patients. We report the first 1000 tumors treated with this modality at our facility.

METHODS

A total of 1000 distinct breast cancers in 984 patients (16 bilateral) were treated with breast conserving surgery and X-ray IORT from June 2010 to August 2017. Patients were enrolled in an IORT registry trial. Local recurrence was the primary endpoint.

RESULTS

There have been 28 ipsilateral local recurrences, ten DCIS and 18 invasive. Four local recurrences were within the IORT field, 13 outside of the IORT field but within the same quadrant as the index cancer, and 11 were new cancers in different quadrants. There have been four regional nodal recurrences and one distant recurrence. There have been no breast cancer related deaths and 14 non-breast cancer deaths. With a median follow-up of 36 months, Kaplan-Meier analysis projects 3.9% of patients will recur locally at 4 years. This includes all ipsilateral events in all quadrants.

CONCLUSIONS

The local, regional, and distant recurrence rates observed in this trial were comparable to those of the prospective randomized TARGIT-A and ELIOT trials. The low complication rates previously reported by our group as well as the low recurrence rates reported in this study support the cautious use and continued study of X-ray IORT in women with low-risk breast cancer.

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

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.

Intraoperative Radiotherapy for Breast Cancer

Intraoperative radiotherapy (IORT) for early stage breast cancer is a technique for partial breast irradiation. There are several technologies in clinical use to perform breast IORT. Regardless of technique, IORT generally refers to the delivery of a single dose of radiation to the periphery of the tumor bed in the immediate intraoperative time frame, although some protocols have performed IORT as a second procedure. There are two large prospective randomized trials establishing the safety and efficacy of breast IORT in early stage breast cancer patients with sufficient follow-up time on thousands of women. The advantages of IORT for partial breast irradiation include: direct visualization of the target tissue ensuring treatment of the high-risk tissue and eliminating the risk of marginal miss; the use of a single dose coordinated with the necessary surgical excision thereby reducing omission of radiation and the selection of mastectomy for women without access to a radiotherapy facility or unable to undergo several weeks of daily radiation; favorable toxicity profiles; patient convenience and cost savings; radiobiological and tumor microenvironment conditions which lead to enhanced tumor control. The main disadvantage of IORT is the lack of final pathologic information on the tumor size, histology, margins, and nodal status. When unexpected findings on final pathology such as positive margins or positive sentinel nodes predict a higher risk of local or regional recurrence, additional whole breast radiation may be indicated, thereby reducing some of the convenience and low-toxicity advantages of sole IORT. However, IORT as a tumor bed boost has also been studied and appears to be safe with acceptable toxicity. IORT has potential efficacy advantages related to overall survival related to reduced cardiopulmonary radiation doses. It may also be very useful in specific situations, such as prior to oncoplastic reconstruction to improve accuracy of adjuvant radiation delivery, or when used as a boost in higher risk patients to improve tumor control. Ongoing international clinical trials are studying these uses and follow-up data are accumulating on completed studies.

A prospective phase I comparison of toxicity and cosmesis outcomes of single-fraction IORT and hypofractionated radiotherapy with IORT boost in early-stage breast cancer

PURPOSE

Radiation therapy is proven to reduce local recurrence in patients with early-stage breast cancer. To reduce toxicity, treatment time, and improve accuracy, intraoperative radiation therapy was used as definitive treatment or as a boost. The study's objective was to compare the short-term toxicity and cosmesis of single-fraction (SF) IORT and hypofractionated radiotherapy with IORT boost (HfB) given as definitive treatment.

METHODS AND MATERIALS

Between March 2011 and December 2013, 57 patients aged 45-91 years and 24 patients aged 43-83 years (total n = 81) with Stage 0-II were treated with SF or HfB (Mobetron, IntraOp Medical, Sunnyvale, CA). For SF treatment, 21 Gy was delivered using 4.5-6 cm applicators with electron energies from 6 to 12 MeV. For HfB, an intraoperative boost of 10 Gy was delivered using 4-7 cm applicators with energies from 4 to 12 MeV followed by whole-breast radiation with 40.5 Gy over 15 fractions. Toxicity was assessed at 2 weeks, 6 months, and 12 months per Radiation Therapy Oncology Group acute skin toxicity criteria and cosmesis.

RESULTS

At 12 months, SF and HfB were well tolerated by all patients with no Grade 3+ toxicity. At 1 year, Grade-2 toxicity was resolved. Ninety-eight percent of SF patients and ninety percent of HfB patients had 0-1 grade toxicity. In the SF and HfB groups, 100% of patients had excellent or good cosmesis at 12-month followup interval. The SF exhibited a more favorable cosmesis with a higher percentage of excellent scores compared with HfB (80.4% vs. 45%; p = 0.0033).

CONCLUSIONS

After breast conservation surgery, SF or HfB may be an option for patients with early-stage breast cancer compared to conventional external beam radiotherapy.

Commissioning, clinical implementation, and performance of the Mobetron 2000 for intraoperative radiation therapy

The Mobetron is a mobile electron accelerator designed to deliver therapeutic radiation dose intraoperatively while diseased tissue is exposed. Experience with the Mobetron 1000 has been reported extensively. However, since the time of those publications a new model, the Mobetron 2000, has become commercially available. Experience commissioning this new model and 3 years of data from historical use are reported here. Descriptions of differences between the models are emphasized, both in physical form and in dosimetric characteristics. Results from commissioning measurements including output factors, air gap factors, percent depth doses (PDDs), and 2D dose profiles are reported. Output factors are found to have changed considerably in the new model, with factors as high as 1.7 being measured. An example lookup table of appropriate accessory/energy combinations for a given target dimension is presented, and the method used to generate it described. Results from 3 years of daily QA measurements are outlined. Finally, practical considerations garnered from 3 years of use are presented.

FMECA Application to Intraoperative Electron Beam Radiotherapy Procedure As a Quality Method to Prevent and Reduce Patient's Risk in Conservative Surgery for Breast Cancer

INTRODUCTION

Failure Mode Effects and Criticalities Analysis (FMECA) represents a prospective method for risk assessment in complex medical practices. Our objective was to describe the application of FMECA approach to intraoperative electron beam radiotherapy (IOERT), delivered using a mobile linear accelerator, for the treatment of early breast cancer as an anticipated boost.

MATERIALS AND METHODS

A multidisciplinary Working Group, including several different professional profiles, was created before the beginning of clinical practice in 2012, with the purpose of writing the Flow Chart and applying the FMECA methodology to IOERT procedure. Several criticalities were identified a priori in the different steps of the procedure and a list of all potential failure modes (FMs) was drafted and ranked using the risk priority number (RPN) scoring system, based on the product of three parameters: severity, occurrence, and detectability (score between 1 and 5). The actions aimed at reducing the risk were then defined by the Working Group and the risk analysis was repeated in 2014 and in 2016, in order to assess the improvement achieved.

RESULTS

Fifty-one FMs were identified, which represented the issues prospectively investigated according to the FMECA methodology. Considering a set threshold of 30, the evaluated RPNs show that 33 out of 51 FMs are critical; 6 are included in the moderate risk class (RPN: 31-40); 16 in the intermediate risk class (RPN: 41-50), and 11 in the high risk class (RPN: >50).

DISCUSSION

The most critical steps concerned the surgical procedure and IOERT set-up. The introduction of the corrective actions into the clinical practice achieved the reduction of the RPNs in the re-analysis of the FMECA worksheet after 2 and 4 years, respectively.

CONCLUSION

FMECA proved to be a useful tool for prospective evaluation of potential failures in IOERT and contributed to optimize patient safety and to improve risk management culture among all the professionals of the Working Group.

Keynote Address at the American Society of Breast Surgeons 18th Annual Meeting : Current and Future Application of Intraoperative Radiotherapy (IORT) in the Curative and Palliative Treatment of Breast Cancer

Intraoperative radiotherapy (IORT) is increasingly used worldwide. Breast cancer is the most rapidly growing indication for IORT, approaching 70-80% of cases in most centers. This report reviews the theoretical background and clinical use of IORT for primary and metastasized breast cancer. There are established applications such as tumor bed boost during breast-conserving surgery followed by whole breast radiotherapy or IORT as a form of accelerated partial-breast irradiation (APBI) for selected patients. Novel applications such as IORT for vertebral or brain metastases are presented as well as technological developments, widening the spectrum of potential clinical applications for IORT.

Intraoperative radiotherapy: review of techniques and results

Intraoperative radiotherapy (IORT) is a technique that involves precise delivery of a large dose of ionising radiation to the tumour or tumour bed during surgery. Direct visualisation of the tumour bed and ability to space out the normal tissues from the tumour bed allows maximisation of the dose to the tumour while minimising the dose to normal tissues. This results in an improved therapeutic ratio with IORT. Although it was introduced in the 1960s, it has seen a resurgence of popularity with the introduction of self-shielding mobile linear accelerators and low-kV IORT devices, which by eliminating the logistical issues of transport of the patient during surgery for radiotherapy or building a shielded operating room, has enabled its wider use in the community.

Electrons, low-kV X-rays and HDR brachytherapy are all different methods of IORT in current clinical use. Each method has its own unique set of advantages and disadvantages, its own set of indications where one may be better suited than the other, and each requires a specific kind of expertise.

IORT has demonstrated its efficacy in a wide variety of intra-abdominal tumours, recurrent colorectal cancers, recurrent gynaecological cancers, and soft-tissue tumours. Recently, it has emerged as an attractive treatment option for selected, early-stage breast cancer, owing to the ability to complete the entire course of radiotherapy during surgery. IORT has been used in a multitude of roles across these sites, for dose escalation (retroperitoneal sarcoma), EBRT dose de-escalation (paediatric tumours), as sole radiation modality (early breast cancers) and as a re-irradiation modality (recurrent rectal and gynaecological cancers).

This article aims to provide a review of the rationale, techniques, and outcomes for IORT across different sites relevant to current clinical practice.

Biology of high single doses of IORT: RBE, 5 R's, and other biological aspects

Intraoperative radiotherapy differs from conventional, fractionated radiotherapy in several aspects that may influence its biological effect. The radiation quality influences the relative biologic effectiveness (RBE), and the role of the five R’s of radiotherapy (reassortment, repair, reoxygenation, repopulation, radiosensitivity) is different. Furthermore, putative special biological effects and the small volume receiving a high single dose may be important. The present review focuses on RBE, repair, and repopulation, and gives an overview of the other factors that potentially contribute to the efficacy. The increased RBE should be taken into account for low-energy X-rays while evidence of RBE < 1 for high-energy electrons at higher doses is presented. Various evidence supports a hypothesis that saturation of the primary DNA double-strand break (DSB) repair mechanisms leads to increasing use of an error-prone backup repair system leading to genomic instability that may contribute to inactivate tumour cells at high single doses. Furthermore, the elimination of repopulation of residual tumour cells in the tumour bed implies that some patients are likely to have very few residual tumour cells which may be cured even by low doses to the tumour bed. The highly localised dose distribution of IORT has the potential to inactivate tumour cells while sparing normal tissue by minimising the volume exposed to high doses. Whether special effects of high single doses also contribute to the efficacy will require further experimental and clinical studies.

Intraoperative radiotherapy (IORT) as boost in breast cancer

The term IORT (intraoperative radiotherapy) is currently used for various techniques that show huge differences in dose delivery and coverage of the tissue at risk. The largest evidence for boost IORT preceding whole breast irradiation (WBI) originates from intraoperative electron treatments (IOERT) with single doses around 10 Gy. At median follow-up periods at 6 years, outstandingly low local recurrence rates of less than 1% are observed. Higher local relapse rates were described for G3 tumors and triple negative breast cancers as well as for IORT following primary systemic treatment for locally advanced tumors. Even there, long term (>5y) local tumor control rates mostly beyond 95% were maintained. Compared to other boost methods, an intraoperative treatment has evident advantages in terms of precision (by avoiding a “spatial and/or temporal miss”), cosmetic outcome and patient comfort. Direct visualisation of a tumor bed during surgery guarantees for an accurate dose delivery, which has additionally gained importance in times of primary reconstruction techniques after lumpectomy, since IORT is performed before breast tissue including parts of the tumor bed is mobilized for plastic purposes. 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. Boost IORT marginally prolongs the surgical procedure, while significantly shortening postoperative radiotherapy. Its combination with external beam radiotherapy to the whole breast (WBI) is currently tested in two multicentric prospective trials: as kV-IORT in the multicentric TARGIT-B (oost) study, and as IOERT in the HIOB trial (3 weeks hypofractionated WBI preceded by IORT electron boost).