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

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.

Intraoperative Radiotherapy as a Tumour-Bed Boost Combined with Whole Breast Irradiation Versus Conventional Radiotherapy in Patients with Early-Stage Breast Cancer: A Systematic Review and Meta-analysis

BACKGROUND

There is no definitive answer regarding the efficacy of intraoperative radiotherapy (IORT) as a tumour bed boost for patients with early-stage breast cancer. The purpose of this meta-analysis was to summarise the available evidence and explore the efficacy and safety of IORT combined with whole breast irradiation (WBI) versus conventional radiotherapy in women with early-stage breast cancer who underwent breast-conserving surgery.

METHODS

The PUBMED, MEDLINE, EMBASE, Web of Science, and Cochrane Library databases were searched from inception to December 31, 2022. We collected studies on the efficacy, cosmetic outcome, and safety of IORT boost combined with WBI compared with those of conventional radiotherapy in patients with early-stage breast cancer after breast-conserving surgery. Two authors independently performed the literature selection and data extraction. The quality of the randomised, controlled trials (RCTs) was assessed according to the PEDro scale. The quality of non-RCTs was assessed according to the Methodological Index for Non-Randomised Studies. Risk ratios (RRs) for the local recurrence rate (LRR), distant metastasis rate (DMR), disease-free survival (DFS), cosmetic outcome, and toxicity were pooled using fixed or random effects models. Meta-analysis of the included studies was performed by using RevMan 5.3 software.

RESULTS

Nine studies, including one RCT and eight non-RCTs, with a total of 3219 patients were included. In terms of LRR, there was no significant benefit of IORT boost+WBI over conventional radiotherapy (with or without the tumour bed boost) (RR = 0.77, 95% confidence interval (CI): 0.54-1.09, P = 0.14), but a trend towards benefit could be identified. There was a significant reduction in DMR in the IORT boost+WBI group (RR = 0.63, 95% CI: 0.46-0.85, P = 0.003) and a significant improvement in DFS (RR = 0.40, 95% CI: 0.25-0.65, P = 0.0002). Exploratory subgroup analysis showed that the DMR and DFS of the electron boost group were significantly better than those of conventional radiotherapy group, and there was a tendency for LRR to improve in the electron boost group. However, the LRR, DMR, and DFS did not effectively improve in the x-ray boost group. In terms of appearance and toxicity, there were no significant differences in cosmetic outcome, fibrosis, and hyperpigmentation between the two groups (RR = 0.99, 95% CI: 0.91-1.07, P = 0.78; RR = 1.02, 95% CI: 0.41-2.56, P = 0.96; RR = 0.42, 95% CI: 0.10-1.72, P = 0.23), but the incidence of oedema was significantly reduced in the IORT boost+WBI group (RR = 0.27, 95% CI: 0.13-0.59, P = 0.0009).

CONCLUSIONS

IORT boost+WBI is more effective than conventional radiotherapy after breast-conserving surgery in patients with early-stage breast cancer, and electron boost exhibits better efficacy than x-ray boost. In addition, the cosmetic and safety profiles of IORT boost+WBI are not inferior to those of conventional radiotherapy.

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.