Recommendations from GEC ESTRO Breast Cancer Working Group (II): Target definition and target delineation for accelerated or boost partial breast irradiation using multicatheter interstitial brachytherapy after breast conserving open cavity surgery

Prior information guided deep-learning model for tumor bed segmentation in breast cancer radiotherapy

BACKGROUND AND PURPOSE

Tumor bed (TB) is the residual cavity of resected tumor after surgery. Delineating TB from CT is crucial in generating clinical target volume for radiotherapy. Due to multiple surgical effects and low image contrast, segmenting TB from soft tissue is challenging. In clinical practice, titanium clips were used as marks to guide the searching of TB. However, this information is limited and may cause large error. To provide more prior location information, the tumor regions on both pre-operative and post-operative CTs are both used by the deep learning model in segmenting TB from surrounding tissues.

MATERIALS AND METHODS

For breast cancer patient after surgery and going to be treated by radiotherapy, it is important to delineate the target volume for treatment planning. In clinical practice, the target volume is usually generated from TB by adding a certain margin. Therefore, it is crucial to identify TB from soft tissue. To facilitate this process, a deep learning model is developed to segment TB from CT with the guidance of prior tumor location. Initially, the tumor contour on the pre-operative CT is delineated by physician for surgical planning purpose. Then this contour is transformed to the post-operative CT via the deformable image registration between paired pre-operative and post-operative CTs. The original and transformed tumor regions are both used as inputs for predicting the possible region of TB by the deep-learning model.

RESULTS

Compared to the one without prior tumor contour information, the dice similarity coefficient of the deep-learning model with the prior tumor contour information is improved significantly (0.812 vs. 0.520, P = 0.001). Compared to the traditional gray-level thresholding method, the dice similarity coefficient of the deep-learning model with the prior tumor contour information is improved significantly (0.812 vs.0.633, P = 0.0005).

CONCLUSIONS

The prior tumor contours on both pre-operative and post-operative CTs provide valuable information in searching for the precise location of TB on post-operative CT. The proposed method provided a feasible way to assist auto-segmentation of TB in treatment planning of radiotherapy after breast-conserving surgery.

Ultra-hypofractionated one-week locoregional radiotherapy for patients with early breast cancer: Acute toxicity results

Purpose

Moderate hypofractionated radiotherapy is the standard of care for all patients with breast cancer, irrespective of stage or prior treatments. While extreme hypofractionation is accepted for early-stage tumours, its application in irradiating locoregional lymph nodes remains controversial.

Materials and methods

A prospective registry analysis from July 2020 to September 2023 included 276 patients with early-stage breast cancer treated with one-week ultra-hypofractionation (UHF) at 26 Gy in 5 fractions on the whole breast (58.3 %) or thoracic wall (41.7 %) and ipsilateral regional lymph nodes and simultaneous integrated boost (58.3 %). Primary endpoint was assessment of acute adverse events (AEs). Secondarily, onset of early-delayed toxicity was assessed. A minimum 6-month follow-up was required for assessing potential treatment-related early-delayed complications. Acute or late complications attributable to treatment were assessed at inclusion using the Common Terminology Criteria for Adverse Events (CTCAE) v5.0 criteria.

Results

With a median follow-up of 19 months (range 1-49 months), 159 (57.6 %) patients reported AEs, predominantly grade (G) 1 (n = 139, 50.4 %) and G2 (n = 20, 7.8 %). Skin acute toxicity was common (G1/2: 134, G3: 14), while breast oedema occurred in 10 patients (G1: 9, G2: 1), and 15.9 % reported breast pain (G1: 42, G2: 2). Ipsilateral arm oedema was observed in 1.8 % patients. For patients with a follow-up beyond 6 months (n = 213), 23.4 % patients reported G1/G2 skin AEs, 8.8 % had G1/G2 breast/chest wall oedema, and 8.9 % experienced arm lymphedema. There were no cases of brachial plexopathy or G3 toxicity in this group of patients.

Conclusions

One-week UHF adjuvant locoregional radiation is well-tolerated, displaying low-toxicity profiles comparable to other studies using similar irradiation schedules.

Review of brachytherapy clinical trials: a cross-sectional analysis of ClinicalTrials.gov

INTRODUCTION

Characterizing the landscape of clinical trials including brachytherapy can provide an overview of the current status and research trends which may guide further areas of investigation.

METHOD

We queried 449,849 clinical trials from the ClinicalTrials.gov registry using brachytherapy-related keywords from 1980 to 2023, yielding 245 multi-arm and 201 single-arm, brachytherapy trials. Multi-arm and single-arm brachytherapy trials were compared using 12 trial protocol elements.

RESULTS

The number of trials including brachytherapy has increased over time, with over 60% of trials registered in 2010 onwards. The majority of clinical trials were Phase 2 or 3, evaluated both safety and efficacy, and were funded by academic sponsors. The most common tumor sites evaluated in brachytherapy clinical trials include prostate, cervix, liver, endometrium, and breast.

CONCLUSION

There remains continued interest in clinical trials including brachytherapy focused on evaluation of novel delivery systems, treatment planning, and new indications. More brachytherapy clinical trials are needed to define the optimal clinical utilization and advance prospective research in this field.

Prior information guided auto-segmentation of clinical target volume of tumor bed in postoperative breast cancer radiotherapy

BACKGROUND

Accurate delineation of clinical target volume of tumor bed (CTV-TB) is important but it is also challenging due to surgical effects and soft tissue contrast. Recently a few auto-segmentation methods were developed to improve the process. However, those methods had comparatively low segmentation accuracy. In this study the prior information was introduced to aid auto-segmentation of CTV-TB based on a deep-learning model.

METHODS

To aid the delineation of CTV-TB, the tumor contour on preoperative CT was transformed onto postoperative CT via deformable image registration. Both original and transformed tumor contours were used for prior information in training an auto-segmentation model. Then, the CTV-TB contour on postoperative CT was predicted by the model. 110 pairs of preoperative and postoperative CT images were used with a 5-fold cross-validation strategy. The predicted contour was compared with the clinically approved contour for accuracy evaluation using dice similarity coefficient (DSC) and Hausdorff distance.

RESULTS

The average DSC of the deep-learning model with prior information was improved than the one without prior information (0.808 vs. 0.734, P < 0.05). The average DSC of the deep-learning model with prior information was higher than that of the traditional method (0.808 vs. 0.622, P < 0.05).

CONCLUSIONS

The introduction of prior information in deep-learning model can improve segmentation accuracy of CTV-TB. The proposed method provided an effective way to automatically delineate CTV-TB in postoperative breast cancer radiotherapy.

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.

Modern Tools for Modern Brachytherapy

This review aims to showcase the brachytherapy tools and technologies that have emerged during the last 10 years. Soft-tissue contrast using magnetic resonance and ultrasound imaging has seen enormous growth in use to plan all forms of brachytherapy. The era of image-guided brachytherapy has encouraged the development of advanced applicators and given rise to the growth of individualised 3D printing to achieve reproducible and predictable implants. These advances increase the quality of implants to better direct radiation to target volumes while sparing normal tissue. Applicator reconstruction has moved beyond manual digitising, to drag and drop of three-dimensional applicator models with embedded pre-defined source pathways, ready for auto-recognition and automation. The simplified TG-43 dose calculation formalism directly linked to reference air kerma rate of high-energy sources in the medium water remains clinically robust. Model-based dose calculation algorithms accounting for tissue heterogeneity and applicator material will advance the field of brachytherapy dosimetry to become more clinically accurate. Improved dose-optimising toolkits contribute to the real-time and adaptive planning portfolio that harmonises and expedites the entire image-guided brachytherapy process. Traditional planning strategies remain relevant to validate emerging technologies and should continue to be incorporated in practice, particularly for cervical cancer. Overall, technological developments need commissioning and validation to make the best use of the advanced features by understanding their strengths and limitations. Brachytherapy has become high-tech and modern by respecting tradition and remaining accessible to all.

Low doses to the heart in daily practice for treating left-sided breast cancer using accelerated partial-breast irradiation by multicatheter brachytherapy and deep-inspiration breath-hold using a SIB

PURPOSE

The aim of this study was to analyze the heart dose for left-sided breast cancer that can be achieved during daily practice in patients treated with multicatheter brachytherapy (MCBT) accelerated partial-breast irradiation (APBI) and deep-inspiration breath-hold (DIBH) whole-breast irradiation (WBI) using a simultaneous integrated tumor bed boost (SIB)-two different concepts which nonetheless share some patient overlap.

MATERIALS AND METHODS

We analyzed the nominal average dose (Dmean) to the heart as well as the biologically effective dose (BED) and the equivalent dose in 2‑Gy fractions (EQD2) for an α/β of 3 in 30 MCBT-APBI patients and 22 patients treated with DIBH plus SIB. For further dosimetric comparison, we contoured the breast planning target volume (PTV) in each of the brachytherapy planning CTs according to the ESTRO guidelines and computed tangential field plans. Mean dose (Dmean), EQD2 Dmean, and BED Dmean for three dosing schemes were calculated: 50 Gy/25 fractions and two hypofractionated regimens, i.e., 40.05 Gy/15 fractions and 26 Gy/5 fractions. Furthermore, we calculated tangential field plans without a boost for the 22 cases treated with SIB with the standard dosing scheme of 40.05 Gy/15 fractions.

RESULTS

MCBT and DIBH radiation therapy both show low-dose exposure of the heart. As expected, hypofractionation leads to sparing of the heart dose. Although MCBT plans were not optimized regarding dose to the heart, Dmean differed significantly between MCBT and DIBH (1.28 Gy vs. 1.91 Gy, p < 0.001) in favor of MCBT, even if the Dmean in each group was very low. In MCBT radiation, the PTV-heart distance is significantly associated with the dose to the heart (p < 0.001), but it is not in DIBH radiotherapy using SIB.

CONCLUSION

In daily practice, both DIBH radiation therapy as well as MCBT show a very low heart exposure and may thus reduce long term cardiac morbidity as compared to currently available long-term clinical data of patients treated with conventional tangential field plans in free breathing. Our analysis confirms particularly good cardiac sparing with MCBT-APBI, so that this technique should be offered to patients with left-sided breast cancer if the tumor-associated eligibility criteria are fulfilled.

Sometimes it is better to just make it simple. De-escalation of oncoplastic and reconstructive procedures

Simple breast conservation surgery (sBCS) has technically advanced onto oncoplastic breast procedures (OBP) to avoid mastectomy and improve breast cancer patients' psychosocial well-being and cosmetic outcome. Although OBP are time-consuming and expensive, we are witnessing an increase in their use, even for cases that could be managed with sBCS. The choice between keeping it simple or opting for more complex oncoplastic procedures is difficult. This review proposes a pragmatic approach in assisting this decision. Medical literature suggests that OBP and sBCS might be similar regarding local recurrence and overall survival, and patients seem to have higher satisfaction levels with the aesthetic outcome of OBP when compared to sBCS. However, the lack of comprehensive high-quality research assessing their safety, efficacy, and patient-reported outcomes hinders these supposed conclusions. Postoperative complications after OBP may delay the initiation of adjuvant RT. In addition, precise displacement of the breast volume is not effectively recorded despite surgical clips placement, making accurate dose delivery tricky for radiation oncologists, and WBRT preferable to APBI in complex OBP cases. With a critical eye on financial toxicity, patient satisfaction, and oncological outcomes, OBP must be carefully integrated into clinical practice. The thoughtful provision of informed consent is essential for decision-making between sBCS and OBP. As we look into the future, machine learning and artificial intelligence can potentially help patients and doctors avoid postoperative regrets by setting realistic aesthetic expectations.

Feasibility study of defining planning target volume using surgical margins in permanent breast seed implant brachytherapy

PURPOSE

This study investigates the feasibility and potential impacts of utilizing a Groupe Européen de Curiethérapie-European Society for Therapeutic Radiation and Oncology (GEC ESTRO) recommended surgical margin-based planning margin in permanent breast seed implant (PBSI) brachytherapy.

METHODS AND MATERIALS

Seventy-nine patients were included in this retrospective study. Three margin selections were used for PTV construction: (1) 1.25 or 1.5 cm isotropic margin (PTV_PBSI), (2) 2 cm minus surgical margin in each direction as recommended by GEC ESTRO (PTV_aniso), and (3) 2 cm minus minimum surgical margin isotropically (PTV_iso). PTV volume and dose coverage using clinical PBSI plans were compared across three groups. New PBSI plans were constructed on PTV_aniso for 20 patients and planning parameters were compared to original plans constructed on PTV_PBSI.

RESULTS

Twenty patients had surgical margins in six directions reported, with a median value of 8 mm anteriorly, and 10 mm in all other directions. PTV_aniso (36.3 ± 15.0 cc) was overall smaller than PTV_PBSI (55.6 ± 14.3 cc), p value < 0.05. PBSI clinical plans showed satisfactory coverage on PTV_aniso, with a median (range) V100 of 97.9% (85.8%-100.0%). Comparing to original treatment plans, new plans constructed on PTV_aniso reduced the number of implant seeds and skin dose.

CONCLUSIONS

Clinical PBSI plans provide satisfactory coverage of GEC ESTRO recommended PTVs. In this patient cohort, GEC ESTRO planning margin resulted in smaller target volumes, and therefore, new plans constructed on PTV_aniso required fewer implanted seeds and lower skin doses were achieved. However, given PBSI delivery uncertainties, further investigations are required to determine if the GEC ESTRO planning margin will be sufficiently robust.

The application of multiple metrics in deformable image registration for target volume delineation of breast tumor bed

BACKGROUND AND PURPOSE

For postoperative breast cancer patients, deformable image registration (DIR) is challenged due to the large deformations and non-correspondence caused by tumor resection and clip insertion. To deal with it, three metrics (fiducial-, region-, and intensity-based) were jointly used in DIR algorithm for improved accuracy.

MATERIALS AND METHODS

Three types of metrics were combined to form a single-objective function in DIR algorithm. Fiducial-based metric was used to minimize the distance between the corresponding point sets of two images. Region-based metric was used to improve the overlap between the corresponding areas of two images. Intensity-based metric was used to maximize the correlation between the corresponding voxel intensities of two images. The two CT images, one before surgery and the other after surgery, were acquired from the same patient in the same radiotherapy treatment position. Twenty patients who underwent breast-conserving surgery and postoperative radiotherapy were enrolled in this study.

RESULTS

For target registration error, the difference between the proposed and the conventional registration methods was statistically significant for soft tissue (2.06 vs. 7.82, p = 0.00024 < 0.05) and body boundary (3.70 vs. 6.93, p = 0.021 < 0.05). For visual assessment, the proposed method achieved better matching result for soft tissue and body boundary.

CONCLUSIONS

Comparing to the conventional method, the registration accuracy of the proposed method was significantly improved. This method provided a feasible way for target volume delineation of tumor bed in postoperative radiotherapy of breast cancer patients.

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.

Radiotherapy of Breast Cancer-Professional Guideline 1st Central-Eastern European Professional Consensus Statement on Breast Cancer

The international radiotherapy (RT) expert panel has revised and updated the RT guidelines that were accepted in 2020 at the 4th Hungarian Breast Cancer Consensus Conference, based on new scientific evidence. Radiotherapy after breast-conserving surgery (BCS) is indicated in ductal carcinoma in situ (stage 0), as RT decreases the risk of local recurrence (LR) by 50-60%. In early stage (stage I-II) invasive breast cancer RT remains a standard treatment following BCS. However, in elderly (≥70 years) patients with stage I, hormone receptor-positive tumour, hormonal therapy without RT can be considered. Hypofractionated whole breast irradiation (WBI) and for selected cases accelerated partial breast irradiation are validated treatment alternatives to conventional WBI administered for 5 weeks. Following mastectomy, RT significantly decreases the risk of LR and improves overall survival of patients who have 1 to 3 or ≥4 positive axillary lymph nodes. In selected cases of patients with 1 to 2 positive sentinel lymph nodes axillary dissection can be substituted with axillary RT. After neoadjuvant systemic treatment (NST) followed by BCS, WBI is mandatory, while after NST followed by mastectomy, locoregional RT should be given in cases of initial stage III-IV and ypN1 axillary status.

The Role of Interstitial Brachytherapy for Breast Cancer Treatment: An Overview of Indications, Applications, and Technical Notes

Simple Summary

Breast cancer is the most common cancer in the female population. Adjuvant radiotherapy has become increasingly important as conservative treatment. Muticatheter interstitial brachytherapy is a type of radiation technique wherein the radioactive sources are directly implanted into or close to the target tissue and may be considered an extremely precise, versatile, and variable radiation technique. Literature data support muticatheter interstitial brachytherapy as the only method with strong scientific evidence to perform partial breast irradiation and reirradiation after previous conservative surgery and external beam radiotherapy. The aim of our work is to provide a comprehensive view of the use of interstitial brachytherapy, with particular focus on the implant description, limits, and advantages of the technique.

Abstract

Breast cancer represents the second leading cause of cancer-related death in the female population, despite continuing advances in treatment options that have significantly accelerated in recent years. Conservative treatments have radically changed the concept of healing, also focusing on the psychological aspect of oncological treatments. In this scenario, radiotherapy plays a key role. Brachytherapy is an extremely versatile radiation technique that can be used in various settings for breast cancer treatment. Although it is invasive, technically complex, and requires a long learning curve, the dosimetric advantages and sparing of organs at risk are unequivocal. Literature data support muticatheter interstitial brachytherapy as the only method with strong scientific evidence to perform partial breast irradiation and reirradiation after previous conservative surgery and external beam radiotherapy, with longer follow-up than new, emerging radiation techniques, whose effectiveness is proven by over 20 years of experience. The aim of our work is to provide a comprehensive view of the use of interstitial brachytherapy to perform breast lumpectomy boost, breast-conserving accelerated partial breast irradiation, and salvage reirradiation for ipsilateral breast recurrence, with particular focus on the implant description, limits, and advantages of the technique.

CyberKnife versus multicatheter interstitial brachytherapy for accelerated partial breast irradiation: a dosimetrical assessment with focus on organs at risk

Background

The purpose of the study was to dosimetrically compare multicatheter interstitial brachytherapy (MIBT) and stereotactic radiotherapy with CyberKnife (CK) for accelerated partial breast irradiation with special focus on dose to organs at risk (OARs).

Materials and methods

Treatment plans of thirty-one patients treated with MIBT were selected and additional CK plans were created on the same CT images. The OARs included ipsilateral non-target and contralateral breast, ipsilateral and contralateral lung, skin, ribs, and heart for left sided cases. The fractionation was identical (4 × 6.25 Gy). Dose-volume parameters were calculated for both techniques and compared.

Results

The D90 of the PTV for MIBT and CK were similar (102.4% vs. 103.6%, p = 0.0654), but in COIN the MIBT achieved lower value (0.75 vs. 0.91, p < 0.001). Regarding the V100 parameter of non-target breast CK performed slightly better than MIBT (V100: 1.1% vs. 1.6%), but for V90, V50 and V25 MIBT resulted in less dose. Every examined parameter of ipsilateral lung, skin, ribs and contralateral lung was significantly smaller for MIBT than for CK. Protection of the heart was slightly better with MIBT, but only the difference of D2cm³ was statistically significant (17.3% vs. 20.4%, p = 0.0311). There were no significant differences among the dose-volume parameters of the contralateral breast.

Conclusion

The target volume can be properly irradiated by both techniques with high conformity and similar dose to the OARs. MIBT provides more advantageous plans than CK, except for dose conformity and the dosimetry of the heart and contralateral breast. More studies are needed to analyze whether these dosimetrical findings have clinical significance.

Breast Radiotherapy after Oncoplastic Surgery-A Multidisciplinary Approach

Oncoplastic breast surgery encompasses a range of techniques used to provide equitable oncological outcomes compared with standard breast surgery while, simultaneously, prioritizing aesthetic outcomes. While the outcomes of oncoplastic breast surgery are promising, it can add an extra complexity to the treatment paradigm of breast cancer and impact on decision-making surrounding adjuvant therapies, like chemotherapy and radiotherapy. As such, early discussions at the multidisciplinary team meeting with surgeons, medical oncologists, and radiation oncologists present, should be encouraged to facilitate best patient care.

American brachytherapy society radiation oncology alternative payment model task force: Quality measures and metrics for brachytherapy

PURPOSE

Brachytherapy is an essential technique to deliver radiation therapy and is involved in the treatment of multiple disease sites as monotherapy or as an adjunct to external beam radiation therapy. With a growing focus on the cost and value of cancer treatments as well new payment models, it is essential that standardized quality measures and metrics exist to allow for straightforward assessment of brachytherapy quality and for the development of clinically significant and relevant clinical data elements. We present the American Brachytherapy Society consensus statement on quality measures and metrics for brachytherapy as well as suggested clinical data elements.

METHODS AND MATERIALS

Members of the American Brachytherapy Society with expertise in disease site specific brachytherapy created a consensus statement based on a literature review and clinical experience.

RESULTS

Key quality measures (ex. workup, clinical indications), dosimetric metrics, and clinical data elements for brachytherapy were evaluated for each modality including breast cancer, cervical cancer, endometrial cancer, prostate cancer, keratinocyte carcinoma, soft tissue sarcoma, and uveal melanoma.

CONCLUSIONS

This consensus statement provides standardized quality measures and dosimetric quality metrics as well as clinical data elements for each disease site to allow for standardized assessments of brachytherapy quality. Moving forward, a similar paradigm can be considered for external beam radiation therapy as well, providing comprehensive radiation therapy quality measures, metrics, and clinical data elements that can be incorporated into new payment models.

Comparison between Accelerated Partial Breast Irradiation with multicatheter interstitial brachytherapy and Whole Breast Irradiation, in clinical practice

Purpose

The aim of this study was to compare accelerated partial breast irradiation (APBI) with multicatheter interstitial brachytherapy (BT) and whole breast irradiation (WBI), in terms of toxicity, aesthetic result, quality of life and survival, in clinical practice.

Materials and methods

A comparative study of two prospectively recorded cohorts of 76 breast cancer patients who complied with the recommendations of GEC-ESTRO for APBI was conducted. The main objective was toxicity, quality of life measured through validated questionnaires and the aesthetic results. Secondary objectives were overall survival and disease-free survival.

Results

Seventy-six stage I/II breast cancer patients, with a mean age of 66 years entered the study. APBI group showed less acute G1-2 dermatitis (51.4 vs 94.9%, p < 0.001) and late hyperpigmentation (0 vs 17.9%, p = 0.04). There were no differences in aesthetic results, both assessed by the patient herself and by the doctor. Statistically significant differences in measures of quality of life were observed in favour of the APBI, both in EORTC QLQ-BR23 and body image scale questionnaires. With a median follow-up of 72 months (6 years), the estimated overall survival at 5 and 10 years was 96.8 and 77.7%, respectively, and disease-free survival at 5 and 10 years was 91.1 and 69.4%, respectively, without statistically significant differences between groups.

Discussion

APBI is an attractive alternative in candidate patients with initial breast cancer, with benefits in acute toxicity and quality of life and fewer visits to the hospital, without compromising tumor control or survival.

Interstitial multi-catheter breast brachytherapy: Technical aspects and experience feedback in a comprehensive cancer center

PURPOSE

To focus on technical aspects of the implementation of interstitial high dose rate brachytherapy, with a step-by-step approach.

MATERIALS AND METHODS

Patients were selected during multidisciplinary tumor boards, according to inclusion criteria adapted from GEC-ESTRO guidelines. A CT scan was performed a few days before implantation. On pre-implant CT, using surgical scar and clips, surgical and pathological reports, and preoperative images, we delineated the tumor bed to be included in the Clinical Target Volume (CTV), according to GEC ESTRO Recommendations. A 3D virtual implant simulation of the best catheter positions was performed in order to cover the target volume. Implantation was then carried out under local anaesthetic using 3D projections of the catheter inlets and outlets. Dosimetry was performed on post-implantation CT scan. A dose of 34Gy was delivered in 10 fractions. Acute and late side effects, and local control were evaluated 2 and 8 months after treatment.

RESULTS

Between July 2017 and January 2020, 20 patients were treated with accelerated partial breast irradiation. Dose constraints regarding target volume coverage, overdose, dose homogeneity, conformation index and organs at risk were met in 94.7%, 100%, 63.2%, 0% and 89.5% of the treatment plans, respectively. Grade 1-2 acute adverse events were observed in 21% of patients, with no grade 3-4 events.

CONCLUSION

The first dosimetric results and early clinical tolerance and efficacy achieved by the implementation of breast interstitial multicatheter brachytherapy in routine clinical practice are very encouraging, and confirm the interest of extending this practice.

Dosimetric comparison between interstitial brachytherapy and volumetric-modulated arc therapy for tumor bed boost in breast cancer

Purpose

To dosimetrically compare high-dose-rate interstitial brachytherapy (HDR-BT) with volumetric-modulated arc therapy (VMAT) for tumor bed boost, following breast conservative treatment.

Material and methods

50 patients with early-stage breast cancer who underwent breast conservation surgery, followed by either HDR-BT (n = 25) of 15 Gy in 6 fractions over a period of 3 days, or VMAT dose of 16 Gy in 8 fractions (n = 25) for tumor bed boost, were retrospectively reviewed. All patients received whole breast irradiation of 46 Gy in 23 fractions. Dosimetric parameters for organs at risk (OARs), including ipsilateral and contralateral lungs, heart, contralateral breast, skin, and ribs, were evaluated with the help of dose-volume histograms (DVH).

Results

Heart sparing was similar in both modalities (left-sided breast irradiation, HDR-BT D_2cc 20.5% vs. VMAT 30.2%, p-value = 0.243; right-sided breast irradiation, D_2cc 6.5% vs. 4.4%, p-value = 0.165). Left-sided cases received higher dose to heart compared to right-sided patients. Interstitial brachytherapy resulted in significantly less dose to contralateral breast (D_2cc 4.3% vs. 9.6%, p-value < 0.0001), ipsilateral lung (D_2cc 27.6% vs. 73.2%, p-value < 0.0001), contralateral lung (D_2cc 4.2% vs. 14.5%, p-value < 0.0001), ribs (D_2cc 24.1% vs. 41.2%, p-value < 0.0001), and skin (D_2cc 77.3% vs. 95%, p-value < 0.0001).

Conclusions

HDR-BT-based tumor bed boost irradiation results in significantly lower doses to most organs at risk with similar heart sparing compared to VMAT.

Interstitial multicatheter HDR-brachytherapy as accelerated partial breast irradiation after second breast-conserving surgery for locally recurrent breast cancer

Our aim was to evaluate the efficacy and toxicity of interstitial multicatheter high dose rate brachytherapy (imHDR-BRT) as accelerated partial breast irradiation (APBI) after second breast-conserving surgery (BCS) in patients with ipsilateral breast tumor recurrence (IBTR). Between January 2010 and December 2019, 20 patients with IBTR who refused salvage mastectomy (sMT) were treated with second BCS and post-operative imHDR-BRT as APBI. All patients had undergone primary BCS followed by adjuvant external beam radiotherapy. Median imHDR-BRT dose was 32 Gy delivered in twice-daily fractions of 4 Gy. Five-year IBTR-free survival, distant metastasis-free survival (DMFS), overall survival (OS) as well as toxicity and cosmesis were evaluated in the present retrospective analysis. Median age at recurrence and median time from the first diagnosis to IBTR was 65.1 years and 12.2 years, respectively. After a median follow-up of 69.9 months, two patients developed a second local recurrence resulting in 5-year IBTR free-survival of 86.8%. Five-year DMFS and 5-year OS were 84.6% and 92.3%, respectively. Grade 1-2 fibrosis was noted in 60% of the patients with no grade 3 or higher toxicity. Two (10%) cases of asymptomatic fat necrosis were documented. Cosmetic outcome was classified as excellent in 6 (37.5%), good in 6 (37.5%), fair in 3 (18.75%) and poor in 1 (6.25%) patient, respectively. We conclude that imHDR-BRT as APBI re-irradiation is effective and safe for IBTR and should be considered in appropriately selected patients.

Are we missing the post-operative cavity in whole breast radiotherapy?

BACKGROUND/PURPOSE

Whole breast radiotherapy (RT) following breast-conserving surgery is a standard treatment option in early-stage breast cancer patients. The whole breast RT technique targets the entire breast, traditionally identified based on breast palpation and the lumpectomy scar. The aim of this study is to evaluate dosimetry of the tumour bed (cavity) and location of recurrence in women treated with breast radiotherapy without explicit cavity delineation.

MATERIALS/METHODS

50 consecutive women previously treated with whole breast RT were retrospectively contoured to define the post-operative cavity with a 1.0 cm expansion for planning target volume (cPTV). The cavity and cPTV dosimetric coverage [volume receiving 92%(V92%) and 95%(V95%) prescription] were calculated. Cavity and cPTV location were classified as inside, at edge or outside of previous treatment fields and recurrence rates were collected.

RESULTS

Forty-five (90%) women had cavities located inside the previous treatment fields (CAVin) and 5 women (10%) had cavities located outside(4) or at edge(1) of previous fields (CAVout/edge). CAVout/edge were located in extreme aspects of the breast: lateral(3); medial(1); or superior(1). Mean cavity_V92% was 91.6% vs 98.5% for CAVout/edge vs CAVin (p = 0.042). Mean cPTV_V92% was 78.7% vs 97.2% for cPTVout/edge vs cPTVin (p<0.001). At 5-year follow-up, 20% (1/5) of the CAVout/edge had 1 in-breast recurrence near the cavity (at previous field edge). Within the CAVin cohort, 11 patients were lost to follow-up and 6% (2/34) patients had in-breast recurrence.

CONCLUSIONS

In patients treated with whole breast RT without cavity delineation, 10% did not have ideal dosimetric coverage of the cavity. Cavity delineation in treatment planning provides optimal tumour bed coverage for patients undergoing whole breast RT, and is of particular importance for the coverage of cavities located in the extreme margins of the breast.

Improving deformable image registration with point metric and masking technique for postoperative breast cancer radiotherapy

Background

Deformable image registration (DIR) is increasingly used for target volume definition in radiotherapy. However, this method is challenging for postoperative breast cancer patients due to the large deformations and non-correspondence caused by tumor resection and clip insertion. In this study, an improved B-splines based DIR method was developed to address this issue for higher registration accuracy.

Methods

The conventional B-splines based DIR method was improved with the introduction of point metric and masking technique. The point metric minimizes the distance between 2 point sets with known correspondence for regularization of intensity-based B-splines registration. The masking technique reduces the influence of non-corresponding regions in breast computed tomography (CT) images. Two sets of CT images before and after breast surgery were used for image registration. One set was the diagnostic CT image acquired before surgery, and another set was the planning CT image acquired after surgery for breast cancer radiotherapy. A total of 26 sets of CT images from 13 patients were collected retrospectively for the test. The improved DIR method's registration accuracy was evaluated by target registration error (TRE), the Jacobian determinant, and visual assessment.

Results

For soft tissue, the difference in the median TRE between the improved DIR method and the conventional DIR method was statistically significant (2.27 vs. 5.88, P<0.05). The Jacobian determinant of the deformation field was positive for all patients. For visual assessment, the improved DIR method with point metric achieved better matching for soft tissue.

Conclusions

The improved DIR method's registration accuracy was higher than the conventional DIR method based on the preliminary results. With point metric and masking technique, the influence of large deformations and non-correspondence on registration between pre- and post-operative CT images can be effectively reduced. Therefore, this method provides a feasible way for target volume definition in postoperative breast cancer radiotherapy treatment planning.

Five-year results of accelerated partial breast irradiation: A single-institution retrospective review of 289 cases

PURPOSE

The purpose of the study was to describe our institutional experience with accelerated partial breast irradiation (APBI) using multicatheter brachytherapy with high-dose-rate. We report 5-year survival outcomes, cosmesis, and treatment-related toxicity.

METHODS AND MATERIALS

This included a retrospective review of patients who underwent breast-conserving surgery followed by APBI at our institution from 2004 to 2017.

RESULTS

A total of 289 patients were evaluated. Median followup was 72 months. Median age was 70 years. APBI was the only primary treatment in 86.2% of cases with early-stage breast cancer and a second conservative treatment in 13.8%. The implant was performed postoperatively in 213 patients (73.7%) and intraoperatively in 76 (26.3%). The most common radiation schemes were 10 fractions of 3.4 Gy and eight fractions of 4 Gy. Elderly or frail patients (10%) received a single 16 Gy dose. Of the 289 patients, 215 met Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology criteria for APBI; in this group, late side effects included Grade 2 (G2) fibrosis (14.8%), skin discoloration at the catheter points (8.8%), and telangiectasia (0.5%). The cosmetic result was considered excellent or good in 88.3% of cases. Five-year local control, disease-free, cancer-specific, and overall survival rates were 98.9%, 96.7%, 99.1%, and 95.6%, respectively.

CONCLUSIONS

Local control and survival outcomes at 5 years of followup in this group of well-selected patients were excellent, with low rates of treatment-related toxicity. These findings confirm the safety and effectiveness of APBI, even in elderly and frail patients. These results provide further support for the clinical use of APBI in suitable patients.

Multicatheter interstitial brachytherapy versus stereotactic radiotherapy with CyberKnife for accelerated partial breast irradiation: a comparative treatment planning study with respect to dosimetry of organs at risk

Background

The aim of the study was to dosimetrically compare multicatheter interstitial brachytherapy (MIBT) and stereotactic radiotherapy with CyberKnife (CK) for accelerated partial breast irradiation (APBI) especially concerning the dose of organs at risk (OAR-s).

Patients and methods

Treatment plans of thirty-two MIBT and CK patients were compared. The OAR-s included ipsilateral non-target and contralateral breast, ipsilateral and contralateral lung, skin, ribs, and heart for left-sided cases. The fractionation was identical (4 x 6.25 Gy) in both treatment groups. The relative volumes (e.g. V100, V90) receiving a given relative dose (100%, 90%), and the relative doses (e.g. D0.1cm³, D1cm³) delivered to the most exposed small volumes (0.1 cm³, 1 cm³) were calculated from dose-volume histograms. All dose values were related to the prescribed dose (25 Gy).

Results

Regarding non-target breast CK performed slightly better than MIBT (V100: 0.7% vs. 1.6%, V50: 10.5% vs. 12.9%). The mean dose of the ipsilateral lung was the same for both techniques (4.9%), but doses irradiated to volume of 1 cm³ were lower with MIBT (36.1% vs. 45.4%). Protection of skin and rib was better with MIBT. There were no significant differences between the dose-volume parameters of the heart, but with MIBT, slightly larger volumes were irradiated by 5% dose (V5: 29.9% vs. 21.2%). Contralateral breast and lung received a somewhat higher dose with MIBT (D1cm³: 2.6% vs. 1.8% and 3.6% vs. 2.5%).

Conclusions

The target volume can be properly irradiated by both techniques with similar dose distributions and high dose conformity. Regarding the dose to the non-target breast, heart, and contralateral organs the CK was superior, but the nearby organs (skin, ribs, ipsilateral lung) received less dose with MIBT. The observed dosimetric differences were small but significant in a few parameters at the examined patient number. More studies are needed to explore whether these dosimetric findings have clinical significance.

Effective of Pre-operative 2-Deoxy-2-[fluorine-18] fluoro-d-glucose/Positron Emission Tomography/Computed Tomography in the Determination of Boost Volume in Adjuvant Radiotherapy after Breast-conserving Surgery

Objectives:

Determining boost volume (BV) during breast radiotherapy can be challenging at times. Therefore, surgical clips are now being widely used. At times, when surgical clips are inadequate in determining the BV, other additional imaging methods are required. In the present study, we aimed to demonstrate that pre-operative positron emission tomography/computed tomography (PET-CT) can be used to determine the BV after a breast-conversing surgery.

Methods:

We selected thirty patients who underwent breast-conserving surgery with surgical clips and had preoperative Fluorine-18-Fluorodeoxyglucose PET (18 FDG PET/CT). The BV in planning tomography (CT) and primary tumor volume (TV) in pre-operative F-18 FDG PET/CT was contoured by a radiation oncologist. These two volumes were superposed using rigid image fusion. In every patient, two BVs were measured. The mean shift between the two volumes by the calculation of the center of mass and percentage of the PET-CT TV (PET-CT TV) in planning the BV (planning target volume [PTV]-BV) was calculated.

Results:

The median age was 52 years (range 25–72 years). The pre-operative PET-CT TV median was 8.89 cm³ (range 1.00–64.30 cm³). The median PTV-BV was 62.92 cm³ (12.57–123.07 cm³). The median shifts between the center of volumes were 1.76 cm (range 0.90–3.50) in X(coronal), 1.73 cm (range 0.60–3.60) in the Y(axial), and 1.20 cm (0.40–2.80) in the Z(sagittal) directions, respectively. The shifts in these three planes were determined to be statistically significant (p<0.001). The percent volume of PET-CT TV included PTV TV, ranging from 35% to 100% (mean 54%, standard deviation 29.53) and 100% in two out of 31 patients.

Conclusion:

Our study has shown that pre-operative PET-CT cannot be used to determine the BV in patients who replaced surgical clips and had undergone breast-conserving surgery. To define a more accurate BV, surgical clips should be placed in four planes, and more PTV margins should be given in treatment planning.

Is stereotactic CyberKnife radiotherapy or multicatheter HDR brachytherapy the better option dosimetrically for accelerated partial breast irradiation?

OBJECTIVE

To compare dosimetrically the stereotactic CyberKnife (CK) therapy and multicatheter high-dose-rate (HDR) brachytherapy (BT) for accelerated partial breast irradiation (APBI).

METHODS

Treatment plans of 25 patients treated with CK were selected, and additional plans using multicatheter HDR BT were created on the same CT images. The prescribed dose was 6.25/25 Gy in both plans to the target volume (PTV). The dose-volume parameters were calculated for both techniques and compared.

RESULTS

The D90 total dose of the PTV was significantly lower with CK than with HDR BT, D90 was 25.7 Gy, and 27.0 Gy (p < 0.001). However, CK plans were more conformal than BT, COIN was 0.87, and 0.81 (p = 0.0030). The V50 of the non-target breast was higher with CK than with BT: 10.5% and 3.3% (p = 0.0010), while there was no difference in the dose of the contralateral breast and contralateral lung. Dose to skin, ipsilateral lung, and ribs were higher with CK than with BT: D₁ was 20.6 Gy vs. 11.5 Gy (p = 0.0018) to skin, 11.4 Gy vs. 9.6 Gy (p = 0.0272) to ipsilateral lung and 18.5 Gy vs. 12.3 Gy (p = 0.0013) to ribs, while D_0.1 to heart was lower, 3.0 Gy vs. 3.2 Gy (p = 0.0476), respectively.

CONCLUSIONS

Multicatheter HDR BT yields more advantageous plans than stereotactic CyberKnife treatment in accelerated partial breast irradiation, except in terms of dose conformality and the dose to the heart. There was no difference in the dose of the contralateral breast and lung.

Very accelerated partial breast irradiation Phase I-II multicenter trial (VAPBI): Feasibility and early results

PURPOSE

This is a multicenter Phase I-II trial endorsed by the GEC-ESTRO Breast Working Group, to analyze if very accelerated partial breast irradiation (VAPBI) with multicatheter interstitial brachytherapy is feasible and safe compared with the standard APBI treatment in 4-5 days for early stage breast carcinomas.

METHODS AND MATERIALS

We have included 81 patients with pT1-2 pN0 invasive carcinomas after breast-conserving surgery. Between August 2017 and July 2019, 33 women received high-dose-rate brachytherapy, four fractions of 6.25 Gy in 2-3 days, and 48 patients received three fractions of 7.45 Gy in 2 days. Thirty-six patients were implanted perioperatively and 45 postoperatively. Mean age was 68 (51-90). Free surgical margins were of 2 mm or greater.

RESULTS

Acute effects were 11% dermatitis, 18.5% hematoma, 3.7% infection, and 14.8% pain. At a median followup of 20 months (range 8-35), no relapse has occurred. Pigmentation changes in the entrance and exit of tubes were visible in 16%, but 1 year later, few cases remained. Patients developed G1-2 induration or fibrosis in 18.5% and 2.5%, respectively. No patient developed telangiectasia. The cosmetic outcome was good/excellent in 97.5% and fair in 2.5%.

CONCLUSIONS

VAPBI with multicatheter interstitial brachytherapy using four fractions of 6.25 Gy or three fractions of 7.45 Gy in two or 3 days is feasible. No excess has been observed in acute effects. At a mean followup of 20 months, late side effects seem to be similar to standard fractionation. VAPBI in two to 3 days is beneficial for the patients and reduces the workload of the brachytherapy units.

Accelerated partial breast irradiation with 3-dimensional conformal and image-guided intensity-modulated radiotherapy following breast conserving surgery - 7-Year results of a phase II trial

Purpose

To present the 7-year results of accelerated partial breast irradiation (APBI) using three-dimensional conformal (3D-CRT) and image-guided intensity-modulated radiotherapy (IG-IMRT) following breast-conserving surgery (BCS).

Patients and methods

Between 2006 and 2014, 104 patients were treated with APBI given by means of 3D-CRT using 3–5 non-coplanar, isocentric wedged fields, or IG-IMRT using kV-CBCT. The total dose of APBI was 36.9 Gy (9 × 4.1 Gy) using twice-a-day fractionation. Survival results, side effects and cosmetic results were assessed.

Results

At a median follow-up of 90 months three (2.9%) local recurrences, one (0.9%) regional recurrence and two (1.9%) distant metastases were observed. The 7-year local (LRFS), recurrence free survival was 98.9%. The 7-year disease-free (DFS), metastases free (MFS) and overall survival (OS) was 94.8%, 97.9% and 94.8%, respectively. Late side effects included G1 skin toxicity in 15 (14.4%), G1, G2, and G3 fibrosis in 26 (25%), 3 (2.9%) and 1 (0.9%) patients respectively. Asymptomatic (G1) fat necrosis occurred in 10 (9.6%) patients. No ≥ G2 or higher late side effects occurred with IMRT. The rate of excellent/good and fair/poor cosmetic results was 93.2% and 6.8%, respectively.

Conclusion

7-year results of APBI with 3D-CRT and IG-IMRT are encouraging. Toxicity profile and local tumor control are comparable to other series using multicatheter interstitial brachytherapy. Therefore, these external beam APBI techniques are valid alternatives to whole breast irradiation and brachytherapy based APBI.

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Phase II APBI trial using 3D-CRT or IG-IMRT.

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Twice-a-day fractionation, with a total dose of 36.9 Gy (9 × 4.1Gy).

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No Grade 2 or worst late side effects with IG-IMRT at median follow up of 90 months.

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These APBI techniques are valid alternatives to WBI or brachytherapy based APBI.

Accelerated partial breast irradiation in the elderly: 8-year oncological outcomes and prognostic factors

PURPOSE

The purpose of the study is to evaluate long-term clinical outcomes and prognostic factors after accelerated partial breast irradiation (APBI) in the elderly using high-dose-rate interstitial multicatheter brachytherapy (HIBT).

METHODS AND MATERIALS

Between 2005 and 2018, 109 patients underwent APBI using HIBT (34 Gy/10f/5d or 32 Gy/8f/4d). Based on a prospective database, outcomes were retrospectively analyzed (local relapse-free survival, metastatic-free survival, specific survival (SS), and overall survival (OS)). Prognostic factors were investigated. Late toxicity and cosmetic evaluation were reported.

RESULTS

With a median followup of 97 months [7-159], median age was 81.7 years [58-89]. In accordance with the GEC-ESTRO APBI classification, 72.5%, 11.9%, and 15.6% were classified as low, intermediate, and high risk, respectively. The histological type was mainly invasive ductal carcinoma (87.1%). The median tumor size was 10 mm [range 1-35]. Eight-year local relapse-free survival, SS, and OS were 96.7% [95% confidence interval (CI) [0.923; 1]), 96.7% [95% CI [0.924; 1], and 72% [95% CI [0.616; 0.837], respectively. In univariate analysis, APBI classification was not considered as prognostic factor, whereas molecular classification was prognostic factor for OS (p < 0.0001), SS (p = 0.007), and metastatic-free survival (p = 0.009) but not for local recurrence (p = 0.586). No Grade ≥3 late toxicity was observed, whereas 61 patients (88.4%) and 8 patients (11.6%) presented Grade 1 and 2 toxicities, respectively. The cosmetic outcome was excellent/good for 96.4%.

CONCLUSIONS

Long-term followup confirms that HIBT is safe and effective for elderly early breast cancer. Our results suggest that selected elderly women presenting with high-risk breast cancer could be also considered for APBI.

Matched-pair dosimetric comparison of cardiac radiation exposure between deep-inspiration breath-hold whole-breast radiation therapy with Active Breathing Coordinator and interstitial multicatheter high-dose-rate brachytherapy as accelerated partial breast irradiation in adjuvant treatment of left-sided breast cancer after breast-conserving surgery

BACKGROUND AND PURPOSE

To compare dosimetrically the radiation exposure to heart, left ventricle (LV), and left anterior descending artery (LAD) between whole-breast radiotherapy (WBRT) with Active Breathing Coordinator (ABC; ABC-WBRT) and interstitial multicatheter high-dose-rate (HDR) brachytherapy as accelerated partial breast irradiation (ABPI; imHDR-APBI) for left-sided breast cancer (BCA) after breast-conserving surgery (BCS).

MATERIALS AND METHODS

Between January 2016 and December 2019, 32 and 20 patients were treated with ABC-WBRT (63 Gy/2.25 Gy) and imHDR-APBI (32 Gy/4 Gy), respectively. Among them a matched-pair analysis was performed according to tumor location (clock position) before BCS as well as planning target volume of imHDR-APBI and boost volume of ABC-WBRT. This yielded 17 pairs of patients for whom dosimetric parameters for heart, LV, and LAD were evaluated. The Mann-Whitney test was used for comparison after adjusting for equivalent dose in 2‑Gy fractions (EQD2). In addition, a second analysis of ABC-WBRT to 40.05 Gy in 15 fractions was performed in order to account for the EQD2 difference between the 63-Gy ABC-WBRT and the imHDR-APBI protocol.

RESULTS

Tumor location for the 17 pairs of patients relative to breast quadrant was as follows: upper outer 8, lower outer 5, upper inner 3, and lower inner 1. There was no difference regarding mean heart dose (MHD) and V5, whereas D25%, D45%, V10, and V25 significantly favored imHDR-APBI. Likewise, mean dose- and V5-LV did not differ, while Dmax- and V23-LV were significantly higher for ABC-WBRT. For LAD, Dmax, D25%, and V30 significantly favored imHDR-APBI without differences for mean dose and V40. When comparing imHDR-APBI with the 40.05 Gy ABC-WBRT schedule, MHD and mean dose LV were significantly lower in favor of ABC-WBRT.

CONCLUSION

ABC-WBRT and imHDR-APBI yield similar low heart and LV exposure for left-sided BCA after BCS, whereas LAD can be better spared with imHDR-APBI.

What is the dosimetric impact of isotropic vs anisotropic safety margins for delineation of the clinical target volume in breast brachytherapy?

PURPOSE

The purpose of the study was to report dosimetric differences for breast brachytherapy plans optimized for clinical target volume (CTV) generated using conventional isotropic expansion of tumor bed volume (TBV) and Groupe Européen de Curiethérapie-European Society for Radiotherapy and Oncology (GEC-ESTRO) recommendations to expand the TBV anisotropically to achieve a total safety margin of 2 cm (resection margin size + added safety margin).

METHODS

Institutional records of 100 patients who underwent accelerated partial breast irradiation using multicatheter interstitial brachytherapy from May 2015 to March 2020 were reviewed retrospectively. Two sets of CT-based plans were made, one with 1-cm isotropic margins around the tumor bed (CTV_ISO) and the other with anisotropic margins (CTV_GEC). Plans were evaluated and compared using the American Brachytherapy Society and GEC-ESTRO guidelines.

RESULTS

The median TBV was 36.97 cc. The median margin widths were as follows: anterior 1.2, posterior 1.0, superior 1.0, inferior 0.9, medial 1.2, and lateral 1.2 cm. The mean tumor bed coverage index was 0.94; 0.93 [p.066], the CTV coverage index 0.86; 0.84 [p 0.001], the dose homogeneity index (DHI) 0.77; 0.75 [p < 0.001] and the conformity index 0.66; 0.64 [p < 0.001] in CTV_ISO and CTV_GEC plans, respectively. In smaller volume implants (TBV< 35 cc), the DHI was 0.76; 0.75 [p 0.008] and the conformity index was 0.66; 0.62 [p < 0.001], whereas in larger volumes >35 cc, the CTV coverage index was 0.86; 0.84 [p 0.003] and the DHI 0.78; 0.76 [p 0.001] in CTV_ISO and CTV_GEC plans, respectively.

CONCLUSIONS

In this cohort of patients who underwent accelerated partial breast irradiation, plans with anisotropic margins had lower conformity, the impact of which was predominantly seen in smaller implants. Rest of the dosimetric constraints were achieved in both the plans as per the American Brachytherapy Society and GEC-ESTRO guidelines.

DEGRO practical guideline for partial-breast irradiation

PURPOSE

This consensus statement from the Breast Cancer Working Group of the German Society for Radiation Oncology (DEGRO) aims to define practical guidelines for accelerated partial-breast irradiation (APBI).

METHODS

Recent recommendations for relevant aspects of APBI were summarized and a panel of experts reviewed all the relevant literature. Panel members of the DEGRO experts participated in a series of conferences, supplemented their clinical experience, performed a literature review, and formulated recommendations for implementing APBI in clinical routine, focusing on patient selection, target definition, and treatment technique.

RESULTS

Appropriate patient selection, target definition for different APBI techniques, and basic rules for appropriate APBI techniques for clinical routine outside of clinical trials are described. Detailed recommendations for APBI in daily practice, including dose constraints, are given.

CONCLUSION

Guidelines are mandatory to assure optimal results of APBI using different techniques.

The use of hyaluronic acid hydrogel as a tumour bed marker in breast-conserving therapy

PURPOSE

To evaluate usefulness of hyaluronic acid (HA) hydrogel as a tumour bed marker in breast conserving therapy (BCT). To analyze inter- (Inter-OV) and intraobserver (Intra-OV) variability of contouring boost target volume (CTV_boost) in external beam radiotherapy (EBRT).

MATERIALS AND METHODS

Thirty-two patients in the HA group and 30 patients in the control group with an early stage breast cancer were included in the study. During the surgery 1-3 ml of HA hydrogel was injected into breast to mark the tumour bed for every patient in the HA group. Moreover, surgical clips were placed underneath the lumpectomy cavity. Patients in the control group were marked only by metal markers. Three radiation oncologists delineated CTV_boost twice for every patient. Three parameters were calculated to quantify contouring variability: coefficient of variation for volumes (COV_V), center of mass displacement (CoMd) and conformity index (CI).

RESULTS

There were no significant differences between mean values of COV_V for HA and control group, neither for Intra-OV (0.14 vs 0.13) nor Inter-OV (0.19 vs 0.18) calculations. The mean CoMd were 6.1 mm and 9.1 mm for Inter-OV calculations and 3.9 mm and 6.4 mm for Intra-OV in the HA and the control group respectively. The mean CI for Intra-OV improved from 0.61 to 0.65 and from 0.47 to 0.56 for Inter-OV in the control and HA group respectively.

CONCLUSION

HA hydrogel used as a tumour bed marker improves tumour bed visibility and reduces inter- and intraobserver variability of EBRT boost target volume delineations.

Optimizing MR-Guided Radiotherapy for Breast Cancer Patients

Current research in radiotherapy (RT) for breast cancer is evaluating neoadjuvant as opposed to adjuvant partial breast irradiation (PBI) with the aim of reducing the volume of breast tissue irradiated and therefore the risk of late treatment-related toxicity. The development of magnetic resonance (MR)-guided RT, including dedicated MR-guided RT systems [hybrid machines combining an MR scanner with a linear accelerator (MR-linac) or 60Co sources], could potentially reduce the irradiated volume even further by improving tumour visibility before and during each RT treatment. In this position paper, we discuss MR guidance in relation to each step of the breast RT planning and treatment pathway, focusing on the application of MR-guided RT to neoadjuvant PBI.

Consensus statement on tumour bed localization for radiation after oncoplastic breast surgery

Background

Oncoplastic surgery (ops) is becoming the new standard of care for breast-conserving surgery, leading to some challenges with adjuvant radiation, particularly when accurate tumour bed (tbd) delineation is needed for focused radiation (that is, accelerated partial breast irradiation or boost radiation). Currently, no guidelines have been published concerning tbd localization for adjuvant targeted radiation after ops.

Methods

A modified Delphi method was used to establish consensus by a panel of 20 experts in surgical and radiation oncology at the Canadian Locally Advanced Breast Cancer National Consensus Group and in a subsequent online member survey.

Results

These are the main recommendations:■ Surgical clips are necessary and should, at a minimum, be placed along the 4 side walls of the cavity, plus 1-4 clips at the posterior margin if necessary.■ Operative reports should include pertinent information to help guide the radiation oncologists.■ Breast surgeons and radiation oncologists should have a basic understanding of ops techniques and work on "speaking a common language."■ Careful consideration is needed when determining the value of targeted radiation, such as boost, in higher-level ops procedures with extensive tissue rearrangement.

Conclusions

The panel developed a total of 6 recommendations on tbd delineation for more focused radiation therapy after ops, with more than 80% agreement on each statement. All are summarized, together with the corresponding evidence or expert opinion.

Implementation of Stereotactic Accelerated Partial Breast Irradiation Using Cyber-Knife - Technical Considerations and Early Experiences of a Phase II Clinical Study

To report the implementation, dosimetric results of and early experiences with stereotactic accelerated partial breast irradiation (SAPBI) following breast conserving surgery (BCS) for postmenopausal low-risk St I-II invasive breast cancer (IBC) patients. Between November 2018 and August 2019, 27 patients were registered in our phase II prospective study. SAPBI was performed with Cyber-Knife (CK) M6 machine, in 4 daily fractions of 6.25 Gy to a total dose of 25 Gy. Respiratory movements were followed with implanted gold markers and Synchrony system. Corrections for patient displacement and respiratory movement during treatment were performed with the robotic arm. Early side effects, cosmetic results, and dosimetric parameters were assessed. The average volume of the surgical cavity, clinical target volume (CTV), and planning target volume (PTV_EVAL) were 8.1 cm³ (range: 1.75–27.3 cm³), 55.3 cm³ (range: 26.2–103.5 cm³), and 75.7 cm³ (range: 40–135.4 cm³), respectively. The mean value of the PTV_eval/whole breast volume ratio was 0.09 (range: 0.04–0.19). No grade 2 or worst acute side-effect was detected. Grade 1 (G1) erythema occurred in 6 (22.2%) patients, while G1 oedema was reported by 3 (11.1%) cases. G1 pain was observed in 1 (3.4%) patient. Cosmetic result were excellent in 17 (62.9%) and good in 10 (37.1%) patients. SAPBI with CK is a suitable and practicable technique for the delivery of APBI after BCS for low-risk, St. I-II. IBC. Our early findings are encouraging, CK-SAPBI performed with four daily fractions is convenient and perfectly tolerated by the patients.

Adaptive radiation therapy of breast cancer by repeated imaging during irradiation

Breast cancer is the most frequent cancer among females and also a leading cause of cancer related mortality worldwide. A multimodality treatment approach may be utilized for optimal management of patients with combinations of surgery, radiation therapy (RT) and systemic treatment. RT composes an integral part of breast conserving treatment, and is typically used after breast conserving surgery to improve local control. Recent years have witnessed significant improvements in the discipline of radiation oncology which allow for more focused and precise treatment delivery. Adaptive radiation therapy (ART) is among the most important RT techniques which may be utilized for redesigning of treatment plans to account for dynamic changes in tumor size and anatomy during the course of irradiation. In the context of breast cancer, ART may serve as an excellent tool for patients receiving breast irradiation followed by a sequential boost to the tumor bed. Primary benefits of ART include more precise boost localization and potential for improved normal tissue sparing with adapted boost target volumes particularly in the setting of seroma reduction during the course of irradiation. Herein, we provide a concise review of ART for breast cancer in light of the literature.

Modern Approaches for Breast Brachytherapy

Breast brachytherapy represents a radiation technique that can be utilized as both monotherapy and as a tumor bed boost following breast conserving surgery. As monotherapy, the rationale for brachytherapy is that the majority of residual disease and therefore recurrences occur in close proximity to the lumpectomy cavity; for boost treatment, brachytherapy represents a technique that provided a more conformal approach prior to 3D treatment planning, and more recently can be used in conjunction with oncoplastic surgery. Multiple guidelines are available to assist clinicians with patient selection for accelerated partial breast irradiation (APBI), and recent guidelines support brachytherapy as an appropriate technique to deliver APBI. Modern breast brachytherapy can be performed with interstitial or applicator-based brachytherapy with multilumen and strut devices offering the ability to provide greater skin, chest wall, and normal breast sparing than previous devices. Novel strategies are being evaluated, including high dose rate perioperative/intraoperative radiotherapy, permanent breast seed implants, and noninvasive breast brachytherapy. Additionally, studies are evaluating shorter courses of brachytherapy. Multiple Level I studies are now available supporting interstitial brachytherapy to deliver APBI while prospective data and the National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Therapy Oncology Group 0413 trial are available with applicator brachytherapy and provide standardized prescriptions, target volume definitions, and dosimetric goals.

Accelerated partial breast irradiation with interstitial multicatheter brachytherapy after breast-conserving surgery for low-risk early breast cancer

Patients with low-risk invasive ductal carcinoma treated with breast-conserving surgery (BCS) were included in a multicatheter brachytherapy APBI protocol. The primary endpoint was ipsilateral breast recurrence. Between December 2008–December 2017, 186 low-risk breast cancer patients were treated with APBI using interstitial multicatheter brachytherapy and followed prospectively. At 5-years of follow-up, cumulative local recurrence (LR) and cause-specific survival was 1.1% (95% CI 0.3–1.9) and 98.3% (95% CI 97.3–99.3%) respectively. No grade 3 adverse effects were observed. Postoperative APBI using multicatheter brachytherapy after BCS in early breast cancer patients have excellent rates of local control and survival, without significant toxicity.

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Low risk early breast cancer patients have low rate of recurrences.

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APBI with interstitial multicatheter brachytherapy in low risk early breast cancer patients have excellent rates of local control and survival.

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Reducing time of treatment.

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Reducing adverse effects.

Does inverse planning improve plan quality in interstitial high-dose-rate breast brachytherapy?

Purpose

To investigate the effect of input parameters for an inverse optimization algorithm, and dosimetrically evaluate and compare clinical treatment plans made by inverse and forward planning in high-dose-rate interstitial breast implants.

Material and methods

By using a representative breast implant, input parameters responsible for target coverage and dose homogeneity were changed step-by-step, and their optimal values were determined. Then, effects of parameters on dosimetry of normal tissue and organs at risk were investigated. The role of dwell time modulation restriction was also studied. With optimal input parameters, treatment plans of forty-two patients were re-calculated using an inverse optimization algorithm (HIPO). Then, a pair-wise comparison between forward and inverse plans was performed using dose-volume parameters.

Results

To find a compromise between target coverage and dose homogeneity, we recommend using weight factors in the range of 70-90 for minimum dose, and in the range of 10-30 for maximum dose. Maximum dose value of 120% with a weight factor of 5 is recommended for normal tissue. Dose constraints for organs at risk did not play an important role, and the dwell time gradient restriction had only minor effect on target dosimetry. In clinical treatment plans, at identical target coverage, the inverse planning significantly increased the dose conformality (COIN, 0.75 vs. 0.69, p < 0.0001) and improved the homogeneity (DNR, 0.35 vs. 0.39, p = 0.0027), as compared to forward planning. All dosimetric parameters for non-target breast, ipsilateral lung, ribs, and heart were significantly better with inverse planning. The most exposed small volumes for skin were less in HIPO plans, but without statistical significance. Volume irradiated by 5% was 173.5 cm³ in forward and 167.7 cm³ in inverse plans (p = 0.0247).

Conclusions

By using appropriate input parameters, inverse planning can provide dosimetrically superior dose distributions over forward planning in interstitial breast implants.

Post-chemotherapy target volumes are safe as boost volume for intact breast radiotherapy in locally advanced breast cancer

PURPOSE

The purpose of our study is to evaluate the challenges in identification of postoperative complexes (POC), the utility of clips in delineation of clinical target volume for boost in LABC downstaged with neoadjuvant chemotherapy (NACT) and to correlate this with patterns of recurrence.

METHODS AND MATERIALS

LABC patients who underwent NACT followed by BCS and radiotherapy (2007-2014) were the subject of our analysis. The data on visibility and characteristics of postoperative cavity (POC), concordance of its volume with clip volume on radiation planning scan were retrieved. A 1 cm margin beyond POC was delineated as a clinical target volume (CTV). Postoperative whole breast and supraclavicular radiotherapy (50 Gy/25fractions/5wk or 42.4 Gy/16#/3 wk) followed by boost (10-16 Gy/5-8#/1-1.5wk) were delivered. Patterns of recurrence were evaluated.

RESULTS

Out of 60 patients, 28.3% patients had stage II disease and 71.7% had stage III disease. 25% patients achieved pathological CR (complete response). The median POC volume was 30 cc and the median clip volume was 40 cc. The concordance of POC volume with clip volume was seen in 80%. Clips served as a good surrogate for POC in 80% of patients. At a median follow-up of 65 months (IQ range 32-84 months), and a lost to follow-up rate of 11.6 %, 3.3% (n = 2) patients had local recurrence (LR) and 8.3% (n = 5) had regional recurrence (LRR) in the supraclavicular region.

CONCLUSIONS

Delineation of post NACT excision cavity as POC for boost radiotherapy is safe. Clips serve as a good surrogate for CTV delineation in 75% patients.

Can brachytherapy be properly considered in the clinical practice? Trilogy project: The vision of the AIRO (Italian Association of Radiotherapy and Clinical Oncology) Interventional Radiotherapy study group

Purpose

Brachytherapy (BT, interventional radiotherapy - IRT) is a kind of radiation therapy, in which the radioactive source is placed nearby or even inside the cancer itself. Even though this kind of radiation therapy appears effective and valuable, BT has been facing a slow but progressive decline over the past decades in Europe, particularly in Italy. Aims of this study were to identify the practical and theoretical reasons why BT is facing a slow decline in Italy, and to define a vision of the Italian Association of Radiotherapy and Clinical Oncology (AIRO) and a strategy about this emerged issues.

Material and methods

A programmatic path divided into three steps like a trilogy was launched by AIRO Interventional Radiotherapy study group. The study group performed an initial data collection to highlight both the clinical and the educational topics and problems through specific surveys. After having analyzed the results of the surveys and shared a vision about the emerged issues, a specific strategy was adopted.

Results

Four relevant domains were identified and for each ones, a strategy has been discussed and defined. This manuscript shows in detail the individual actions defined (accomplished or in progress).

Conclusions

The AIRO vision implies that specific strategic interventions must be carried out in the field of national guidelines, education, research, and communication with patients and colleagues of other specialties in an interdisciplinary setting.

Is adaptive treatment planning in multi-catheter interstitial breast brachytherapy necessary?

PURPOSE

For 55 patients treated with interstitial multi-catheter breast brachytherapy the need for adaptive treatment planning was assessed.

METHODS AND MATERIALS

For all patients a treatment planning computed tomography (CT) and a follow-up CT were acquired and used for the retrospective evaluation. Keeping dwell time and dwell positions constant, the treatment plan assessed directly after catheter implantation was compared to the situation 48 h after implantation. Both manual catheter reconstructions, based on the planning and follow-up CT, were rigid registered to each other and the resulting deviations analyzed, like the difference between corresponding dwell positions (ΔDP) or the discrete Fréchet distance. Further, the dosimetric changes, e.g., coverage index (ΔCI), conformal index (ΔCOIN) and dose non-uniformity ratio (ΔDNR) were considered for a deformed planning target volume (PTV) and the rigid warped PTV structure. The PTV was deformed according to the vector field estimated between the two acquired CTs.

RESULTS

Over all patients with rigid aligned CTs a mean ΔDP, ΔCI, ΔCOIN and ΔDNR were determined to 2.41 ± 1.73 mm, 3.10 ± 3.17%, 0.009 ± 0.007 and 0.036 ± 0.040, respectively. Considering the deformed PTV ΔCI was estimated to 5.05 ± 4.14%.

CONCLUSION

In conclusion, in 4% of the cases re-planning would have been beneficial to ensure the planned dose delivery. Large PTV changes or large DP deviations were found to be the main reasons for dosimetric variations.

Experience in multicatheter interstitial high-dose-rate breast brachytherapy: dose-volume histogram analysis of the first results

Purpose

To report characteristics of our treatment scheme of high-dose-rate (HDR) brachytherapy of breast cancer and to show the first outcomes of dosimetric planning analysis based on dose-volume histogram (DVH).

Material and methods

Since August 2017, 25 patients diagnosed with T1N0M0 breast cancer have received a treatment in our center. There was lumpectomy and following breast HDR brachytherapy (10 fractions of 3.4 Gy) administered to each patient. A planning target volume (PTV) and organs at risk (OARs) were recorded with DVH analysis.

Results

The study describes the full procedure of breast HDR brachytherapy with the lumpectomy. Twenty-five patients were treated, including 9 with cancer of the left breast and 16 of the right breast. The median age was 65 years. The first analysis of DVH data shows that the main OARs were ribs and skin. Mean value of D_max (ribs) for all patients was 19.90 Gy (55.88% of prescribed dose) and for the skin 30.88 Gy (90.74% of prescribed dose). During the treatment, there was only one case of toxic effects, which was pigmentation on the skin due to excess of dose limit of 1.4 Gy. Therefore, the limit exceeding of 1 Gy does not give any significant toxic effects.

Conclusions

This study is the first stage of the dosimetric evaluation of a new method. The analysis allows treating complex localizations of the breast cancer, for example, in a close position to the skin or ribs. In order to minimize the toxic effects, it is necessary to consider patient selection, catheter administration, and dose optimization.

Estimation of inter-fractional variations in interstitial multi-catheter breast brachytherapy using a hybrid treatment delivery system

PURPOSE

Irradiation of the tumor bed using interstitial multi-catheter brachytherapy is one of the treatment options for breast cancer patients. In order to ensure the planned dose delivery an advanced quality intervention method using an electromagnetic tracking (EMT) system is presented. The system is used to assess inter-fractional variations within the framework of a patient study.

METHODS AND MATERIALS

Until now 41 patients were included in the study for the evaluation and overall 355 EMT measurements were performed. The catheter traces are measured automatically and sequentially using an afterloader prototype (Flexitron, Elekta, Veenendaal, The Netherlands) equipped with an EMT sensor. The implant geometry is tracked directly after implantation, after CT imaging and after each irradiation fraction. The acquired data is rigidly registered to the catheter traces defined in the treatment plan and the dwell positions (DP) are reconstructed. DPs defined in treatment planning serve as reference. Breathing motion was corrected and recorded using three reference 6DoF sensors placed on the patients' skin. The Euclidean distance between the planned and reconstructed DPs provides information about possible inter-fractional deviations. Further, the influence of various factors on the occurrence of large deviations was investigated, like the patients' age, the length of the catheter, the breast volume, etc. RESULTS: Over all patient measurements a median Euclidean distance of 2.19 mm was determined between the reconstructed DPs and the reference DPs. The median deviation combining all datasets was minimal (1.67 mm) at the measurement directly after CT imaging. The deviations between the different fractions have a median distance of 2.31 mm which could be improved to 2.05 mm by adapting the treatment plan according to the follow-up CT. No correlation between the distance to the skin, ribs, mammilla or the breast volume and the occurrences of large deviations was found. The largest deviations were determined in the upper inner quadrant of the breast.

CONCLUSION

The afterloader prototype could be well integrated into the clinical routine and is beneficial for ensuring the quality of the brachytherapy. Overall, a small median DP deviation, lower than the used step size of 2.5 mm, was detected.