Long term results of a phase II trial of hypofractionated adjuvant radiotherapy for early-stage breast cancer with volumetric modulated arc therapy and simultaneous integrated boost

Dose constraints in breast cancer radiotherapy. A critical review

Radiotherapy plays an essential role in the treatment of breast cancer (BC). Recent advances in treatment technology and radiobiological knowledge have a major impact in BC patients with locoregional disease as the majority are now long-term survivors. Over the last three decades, intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and deep inspiration breath-hold (DIBH) techniques, together with the increasing adoption of moderately hypofractionated and ultra-hypofractionated treatment schedules as well as the possibility to offer partial breast radiotherapy to a well-defined patient subset have significantly changed radiotherapy for BC patients. As dose-volume constraints (DVCs) have to be adapted to these new treatment paradigms we have reviewed available evidence-based data concerning dose-constraints for the main organs at risk (OARs) that apply to the treatment of whole breast/chest wall radiotherapy, whole breast/chest wall radiotherapy including regional nodal irradiation (RNI) and partial breast irradiation (PBI), for the most relevant fractionation schedules that have been introduced recently. This narrative review provides a comprehensive summary that may help to harmonize treatment planning strategies.

Defining a parameter to select the best radiotherapy technique in patients with right breast cancer after conservative surgery: Evaluation of high doses and risk of radio-induced second tumors to the ipsilateral lung

PURPOSE

In the adjuvant right breast radiation therapy, after breast-conserving surgery, we wanted to look for a parameter that would help in the choice between the 3D-CRT or VMAT techniques, considering the risk of pneumonia to the ipsilateral lung (IL) linked to high doses. We also investigated the risk of second tumors in the IL related to the VMAT low doses.

METHODS

We examined twenty-five 3D-CRT and thirty-five VMAT technique plans, between September 2022 and September 2023. We collected the MAximum Thickness of Ipsilateal Lung (MATIL) included between lateral and medial target borders for evaluating the risk of pneumonia due to the high dose (V20Gy), finally we calculated the Excess of Absolute Risk related to the second tumor risk due to the low dose.

RESULTS

VMAT technique showed a better dose conformity than 3D-CRT. We detected a linear relationship between the V20Gy and MATIL of the IL only for the 3D-CRT technique; over a threshold value of MATIL the 3D-CRT is disadvantaged compared to the VMAT in terms of the risk of toxicity to the IL. We calculated that for every Gy more in average dose, a 12 % increase in the risk of induced cancer is expected.

CONCLUSIONS

In the adjuvant right breast RT, the MATIL is a good surrogate parameter to predict the need to use a VMAT technique to limit high doses to IL. VMAT technique, according to the IL second tumor estimated risk, seems justified.

High-dose hyperfractionated simultaneous integrated boost radiotherapy versus standard-dose radiotherapy for limited-stage small-cell lung cancer in China: a multicentre, open-label, randomised, phase 3 trial

BACKGROUND

For the past 20 years, twice-daily thoracic radiotherapy with concurrent chemotherapy has been the treatment of choice for limited-stage small-cell lung cancer (LS-SCLC), which has a poor prognosis. We aimed to assess the efficacy and safety of high-dose, accelerated, hyperfractionated, twice-daily thoracic radiotherapy (54 Gy in 30 fractions) versus standard-dose radiotherapy (45 Gy in 30 fractions) as a first-line treatment for LS-SCLC.

METHODS

This open-label, randomised, phase 3 trial was performed at 16 public hospitals in China. The key inclusion criteria were patients aged 18-70 years, with histologically or cytologically confirmed LS-SCLC, who had an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1, and who were previously untreated or had received one course of cisplatin or carboplatin and etoposide. Eligible patients were randomly assigned (1:1) to receive volumetric-modulated arc radiotherapy (VMAT) of 45 Gy in 30 fractions to the gross tumour volume or VMAT with a simultaneous integrated boost of 54 Gy in 30 fractions to the gross tumour volume starting 0-42 days after the first chemotherapy course. Both groups received 10 fractions of twice-daily thoracic radiotherapy per week. The planning target volume was 45 Gy in 30 fractions in both groups. Patients with responsive disease received prophylactic cranial radiotherapy (25 Gy in 10 fractions). Randomisation was performed using a centralised interactive web response system, stratified by ECOG performance status, disease stage, previous chemotherapy course, and chemotherapy choice. The primary outcome was overall survival in the intention-to-treat population. Safety was analysed in the as-treated population. This study was registered at ClinicalTrials.gov, NCT03214003.

FINDINGS

From June 30, 2017, to April 6, 2021, 224 patients (102 [46%] females and 122 [54%] males; median age 64 years [IQR 58-68]) were enrolled and randomly assigned to the 54 Gy group (n=108) or 45 Gy (n=116) group. The median follow-up was 46 months (IQR 33-56). The median overall survival was significantly longer in the 54 Gy group (60·7 months [95% CI 49·2-62·0]) than in the 45 Gy group (39·5 months [27·5-51·4]; hazard ratio 0·55 [95% CI 0·37-0·72]; p=0·003). Treatment was tolerable, and the chemotherapy-related and radiotherapy-related toxicities were similar between the groups. The grade 3-4 radiotherapy toxicities were oesophagitis (14 [13%] of 108 patients in the 54 Gy group vs 14 [12%] of 116 patients in the 45 Gy group; p=0·84) and pneumonitis (five [5%] of 108 patients vs seven [6%] of 116 patients; p=0·663). Only one treatment-related death occurred in the 54 Gy group (myocardial infarction). The study was prematurely terminated by an independent data safety monitoring board on April 30, 2021, based on evidence of sufficient clinical benefit.

INTERPRETATION

Compared with standard-dose thoracic radiotherapy (45 Gy), high-dose radiotherapy (54 Gy) improved overall survival without increasing toxicity in a cohort of patients aged 18-70 years with LS-SCLC. Our results support the use of twice-daily accelerated thoracic radiotherapy (54 Gy) with concurrent chemotherapy as an alternative first-line LS-SCLC treatment option.

FUNDING

Chinese Society of Clinical Oncology-Linghang Cancer Research, the Wu Jieping Medical Foundation, and Clinical Research Fund For Distinguished Young Scholars of Peking University Cancer Hospital and Beijing Municipal Administration of Hospitals Incubating Program.

A novel x-Ray and γ-Ray combination strategy for radiotherapy after breast-conserving surgery in patients with right breast cancer

Background and purpose

Radiotherapy is a primary therapeutic approach for breast cancer following breast-conserving surgery. The TaiChiB dual-modality radiotherapy system combining X-ray and focused γ-ray, offers a new approach to reduce the radiation dose of organs at risk (OARs) and has the potential to mitigate the adverse effects of radiotherapy. Currently, there are few studies on the dosimetric characteristics of the TaiChiB dual-modality system for actual treatment plans for specific diseases. The purpose of this work is to study the dosimetric advantages of dual-modal systems for right breast patients after breast-conserving surgery.

Material and methods

Treatment plans for 20 patients with right breast cancer were generated for a linear accelerator (LINAC) based system and the TaiChiB dual-modality system, respectively. Volumetric modulated arc therapy plans with simultaneous integrated boost (VMAT-SIB) were made for the LINAC. Focused γ-ray was used to deliver the boost dose with the dual-modality system. The dosimetric parameters of the target and OARs were evaluated and compared between the treatment plans generated for the two systems.

Results

The TaiChiB dual-modality plans exhibit a higher conformal index (CI) and lower gradient index (GI) for the PGTV and PTV compared with the LINAC-based VMAT-SIB plans. Compared to VMAT-SIB plans, the PTV Dmax, PTV Dmean, PTV V110, PGTV Dmax, and PGTV Dmean of the TaiChiB dual-modality plans are significantly lower. Meanwhile, the dose to OARs, such as the Dmean of the heart, the V5 of liver, the Dmean of ipsilateral lung, the V30 of ipsilateral lung, the V20 of ipsilateral lung, the V5 of ipsilateral lung, the Dmean of contralateral lung, Dmax of contralateral breast and the Dmean of contralateral breast are significantly reduced.

Conclusions

Our study demonstrates the dosimetric advantages of the novel TaiChiB dual-modality radiotherapy system for the treatment of right-sided breast cancer. Overall, for the TaiChiB dual-modality radiotherapy system, the radiation dose outside the target region decreases rapidly, thereby minimizing radiation exposure to neighboring organs and ensuring the conformity of the target area. Our research confirms the potential of the TaiChiB dual-modality system for future radiotherapy.

Intensity Modulated Therapy for Patients With Breast Cancer. Practical Guidelines and Tips for an Effective Treatment Planning Strategy

Purpose

Practical guidelines and tips for effective and robust radiation therapy treatment planning for patients with breast cancer are addressed for fixed-field intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) techniques. The concepts described here are general and valid on all treatment planning systems. However, some details shown here have been applied to the Varian platforms used at the authors' institutions.

Methods and Materials

The specific aspects of using C-arm- or O-ring-mounted linear accelerators are covered in the document, as well as tips for dealing with certain resource constraints, target cropping, and skin flash aiming to reduce risks of skin toxicity and to manage (residual after breath control) respiration motion or edema.

Results

A decision tree is presented, and practical solutions for cases where a target volume is contoured or not and where volumetric modulated arc therapy or fixed-beam intensity modulation should be applied and details about the technical implementation (tangential IMRT, butterfly IMRT or VMAT, and large partial VMAT arcs) are discussed. Target cropping and skin flash implications are discussed in detail, and links to plan robustness are outlined.

Conclusions

Practical guidelines for breast planning are presented and summarized with a decision tree and technical summaries.

Simultaneous integrated boost intensity-modulated radiotherapy post breast-conserving surgery: clinical efficacy, adverse effects, and cosmetic outcomes in breast cancer patients

BACKGROUND

Simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) is an innovative technique delivering a higher dose to the tumor bed while irradiating the entire breast. This study aims to assess the clinical outcomes, adverse effects, and cosmetic results of SIB-IMRT following breast-conserving surgery in breast cancer patients.

METHODS

We conducted a retrospective analysis of 308 patients with stage 0-III breast cancer who underwent breast-conserving surgery and SIB-IMRT from January 2016 to December 2020. The prescribed doses included 1.85 Gy/27 fractions to the whole breast and 2.22 Gy/27 fractions or 2.20 Gy/27 fractions to the tumor bed. Primary endpoints included overall survival (OS), local-regional control (LRC), distant metastasis-free survival (DMFS), acute and late toxicities, and cosmetic outcomes.

RESULTS

The median follow-up time was 36 months. The 3-year OS, LRC, and DMFS rates were 100%, 99.6%, and 99.2%, respectively. Five patients (1.8%) experienced local recurrence or distant metastasis, and one patient succumbed to distant metastasis. The most common acute toxicity was grade 1-2 skin reactions (91.6%). The most common late toxicity was grade 0-1 skin and subcutaneous tissue reactions (96.7%). Five patients (1.8%) developed grade 1-2 upper limb lymphedema, and three patients (1.1%) had grade 1 radiation pneumonitis. Among the 262 patients evaluated for cosmetic outcomes at least 2 years post-radiotherapy, 96.9% achieved excellent or good results, while 3.1% had fair or poor outcomes.

CONCLUSIONS

SIB-IMRT after breast-conserving surgery in breast cancer patients demonstrated excellent clinical efficacy, mild acute and late toxicities, and satisfactory cosmetic outcomes in our study. SIB-IMRT appears to be a feasible and effective option for breast cancer patients suitable for breast-conserving surgery.

Methodological guide for assessing the carbon footprint of external beam radiotherapy: A single-center study with quantified mitigation strategies

Background and purposes

Data on the carbon footprint of external beam radiotherapy (EBRT) are scarce. Reliable and exhaustive data, including a detailed carbon inventory, are needed to determine effective mitigation strategies.

Materials and methods

This study proposes a methodology for calculating the carbon footprint of EBRT and applies it to a single center. Mitigation strategies are derived from the carbon inventory, and their potential reductions are quantified whenever possible.

Results

The average emission per treatment and fraction delivered was 489 kg CO₂eq and 27 kg CO₂eq, respectively. Patient transportation (43 %) and the construction and maintenance of linear accelerators (LINACs) and scanners (17 %) represented the most significant components. Electricity, the only energy source used, accounted for only 2 % of emissions.Derived mitigation strategies include a data deletion policy (reducing emissions in 30 years by 12.5 %), geographical appropriateness (-12.2 %), transportation mode appropriateness (-9.3 %), hypofractionation (-5.9 %), decrease in manufacturers' carbon footprint (-5.2 %), and an increase in machine durability (-3.5 %).

Conclusion

Our findings indicate that a significant reduction in the carbon footprint of a radiotherapy unit can be achieved without compromising the quality of care.This study provides a methodology and a starting point for comparison and proposes and quantifies mitigation strategies, paving the way for others to follow.

Adjuvant Hypofractionated Whole Breast Irradiation (WBI) vs. Accelerated Partial Breast Irradiation (APBI) in Postmenopausal Women with Early Stage Breast Cancer: 5Years Update of the HYPAB Trial

Therapeutical strategies in breast cancer are continuously updating. Recent researches assessed the possibility of irradiating only the surgical bed in selected patients (Partial Breast Irradiation, PBI). In 2014 we designed a study to evaluate toxicity and cosmesis of APBI using Volumetric Modulated Arc Therapy-Rapid Arc compared with hypofractionated whole breast irradiation (WBI). We present here the 5-years updated data. HYPAB was a single-institution randomized trial that recruited 172 patients from 2015 to 2018. Patients underwent conserving surgery and were randomized to either adjuvant WBI (40.5Gy/15 fractions with simultaneous boost to 48 Gy to tumoral bed) or APBI (30Gy/5 fractions), both delivered with VMAT-RA technique. Clinical evaluation was performed during the first visit, once a week during radiotherapy and during follow up. Cosmesis was assessed using the Harvard Scale for Breast Cosmesis. At the time of the analysis 161 patients were eligible, 53% in the WBI and 47% in the APBI group, with a median follow-up of 67 months. Most common late skin toxicities were G1 fibrosis (32%) and oedema (28%) and were higher in the WBI group; no G3 toxicities were observed. Cosmesis was rated poor in only 6 cases. 147 patients had no evidence of disease at the last follow-up, and no patients died of the disease. Mature results confirm the safety and efficacy of APBI in selected early stage breast cancer patients. Late toxicity is improved in the APBI arm at the cost of a slight increase in local relapse. Further studies are ongoing to better elucidate the use of APBI as a de-escalation approach.

Noninferiority of Local Control and Comparable Toxicity of Intensity Modulated Radiation Therapy With Simultaneous Integrated Boost in Breast Cancer: 5-Year Results of the IMRT-MC2 Phase III Trial

PURPOSE

The IMRT-MC2 trial was conducted to demonstrate the noninferiority of conventionally fractionated intensity modulated radiation therapy with a simultaneous integrated boost to 3-dimensional conformal radiation therapy with a sequential boost for adjuvant breast radiation therapy.

METHODS AND MATERIALS

A total of 502 patients were randomized between 2011 and 2015 for the prospective, multicenter, phase III trial (NCT01322854). Five-year results of late toxicity (late effects normal tissue task force-subjective, objective, management, and analytical), overall survival, disease-free survival, distant disease-free survival, cosmesis (Harvard scale), and local control (noninferiority margin at hazard ratio [HR] of 3.5) were analyzed after a median follow-up of 62 months.

RESULTS

The 5-year local control rate for the intensity modulated radiation therapy with simultaneous integrated boost arm was non-inferior to the control arm (98.7% vs 98.3%, respectively; HR, 0.582; 95% CI, 0.119-2.375; P = .4595). Furthermore, there was no significant difference in overall survival (97.1% vs 98.3%, respectively; HR, 1.235; 95% CI, 0.472-3.413; P = .6697), disease-free survival (95.8% vs 96.1%, respectively; HR, 1.130; 95% CI, 0.487-2.679; P = .7758), and distant disease-free survival (97.0% vs 97.8%, respectively; HR, 1.667; 95% CI, 0.575-5.434; P = .3601). After 5 years, late toxicity evaluation and cosmetic assessment further showed no significant differences between treatment arms.

CONCLUSIONS

The 5-year results of the IMRT-MC2 trial provide strong evidence that the application of conventionally fractionated simultaneous integrated boost irradiation for patients with breast cancer is both safe and effective, with noninferior local control compared with 3-dimensional conformal radiation therapy with sequential boost.

Single-Institution Prospective Evaluation of Moderately Hypofractionated Whole-Breast Radiation Therapy With Simultaneous Integrated Boost With or Without Lymphatic Drainage Irradiation After Breast-Conserving Surgery

Purpose

We report treatment outcomes for patients who received adjuvant moderate hypofractionated whole-breast radiation therapy with simultaneous integrated boost (SIB-mhWBRT) after breast-conserving surgery.

Methods and Materials

SIB-mhWBRT for patients with breast cancer was introduced in our department in July 2017. This prospective evaluation includes 424 consecutive patients treated with SIB-mhWBRT for stage I-III invasive breast cancer (n = 391) and/or ductal carcinoma in situ (n = 33) until December 2021. SIB-mhWBRT was applied with 40 Gy in 15 daily fractions over 3 weeks according to the START B trial, with an SIB dose to the tumor bed of 48 Gy according to Radiation Therapy Oncology Group 1005/UK-IMPORT-HIGH, delivered as 3-dinemsional conformal radiation therapy (RT; n = 402), intensity modulated RT (n = 4), or volumetric modulated arc therapy (n = 18). The mean patient age was 60 years (range, 27-88). Since May 2018, patients with indications for lymphatic pathway RT were included (n = 62). Baseline parameters and follow-up data were recorded and reported, including objective assessment of treatment-related outcomes and subjective patient-reported outcome measures (PROMs).

Results

Mean/median follow-up was 29/33 months (range, 2-60). Acute toxicity grade 0, 1, 2, and 3 was observed in 25.0%, 61.4%, 13.3%, and 0%, respectively, at the completion of RT. Data of 281, 266, 243, 172, and 58 patients were available for 6-month and 1-, 2-, 3-, and 4-year follow-up, respectively. Grade 2 late effects were identified in 8.5%, 6.0%, 4.9%, 2.2%, and 10.2% and grade 3 in 2.8%, 1.1%, 1.2%, 0%, and 0% of patients at 6-month and 1-, 2-, 3-, and 4-year follow-up, respectively. Medical treatment of breast edema was the only grade 3 late effect observed. PROM cosmesis results were evaluated as excellent-good, fair, and poor in 97.2%, 2.5%, and 0.4%; 96.5%, 3.1%, and 0.4%; 97.4%, 2.2%, and 0.4%; 97.5%, 2.5%, and 0%; and 96.5%, 3.5%, and 0.0% at 6 months and 1, 2, 3, and 4 years post-RT, respectively. For all patients, the 3-year overall, cancer-specific, and disease-free survival rates were 98.2%, 99.1%, and 95.9%, respectively. Three-year risk of any locoregional recurrence was 0.6%. No mortality or relapse was observed in patients with ductal carcinoma in situ.

Conclusions

SIB-mhWBRT demonstrated very favorable side effect profiles and cosmesis/PROMs. Three-year results demonstrate excellent locoregional control. This short-term regimen offers substantial patient comfort and improves institutional efficacy.

Comparing brass mesh to tissue equivalent bolus materials for volumetric modulated arc therapy chest wall irradiation

PURPOSE

To compare the superficial dose when using brass mesh bolus (BMB), no bolus, or 3 mm tissue-equivalent bolus with a pseudo-flash volumetric modulated arc therapy (VMAT) breast treatment planning technique.

METHODS

Two different beam arrangements for right-sided irradiation and one beam arrangement for bilateral irradiation were planned on an inhomogeneous thorax phantom in accordance with our clinical practice for VMAT postmastectomy radiotherapy (PMRT). Plans were optimized using pseudo-flash and representative critical organ optimization structures were used to shape the dose. Plans were delivered without bolus, with 3 mm tissue-equivalent bolus (TEB), or with one-layer BMB. Optically stimulated luminescence dosimeter (OSLD) and radiochromic film measurements were taken and analyzed to determine the superficial dose in each case and the relative enhancement from the no bolus delivery.

RESULTS

Superficial dose measured with OSLDs was found to be 76.4 ± 4.5%, 103.0 ± 6.1%, and 98.1 ± 5.8% of prescription for no physical bolus (NB), TEB, and BMB, respectively. Superficial dose was observed to increase from lateral to medial points when measured with film. However, the relative increase in superficial dose from NB was consistent across the profile with an increase of 43 ± 2.1% and 34 ± 3.3% of prescription for TEB and BMB, respectively. The results are in good agreement with expectations from the literature and the experience with tangential radiotherapy.

CONCLUSION

Three millimeter TEB and one-layer BMB were shown to provide similar enhancement to the superficial dose compared to delivery without bolus. BMB, which does not significantly affect dose at depth and is more conformal to the patient surface, is an acceptable alternative to 3 mm TEB for chest wall PMRT patients treated with pseudo-flash PMRT.

Safety of hypofractionated volumetric modulated arc therapy for early breast cancer: A preliminary report

The present study attempts to evaluate the acute and subacute toxicities of hypofractionated volumetric modulated arc therapy (HFX-VMAT) in patients with early breast cancer (EBC). It is a retrospective analysis of 23 patients treated with HFX-VMAT after breast-conserving surgery between September 2021 and February 2022. A total dose of 50.05 to 52.55 Gy was delivered, consisting of 40.05 Gy to the ipsilateral whole breast in 15 fractions of 2.67 Gy and a tumor bed boost dose of 10-12.5 Gy in 4-5 fractions. The primary endpoint was acute/subacute radiation pneumonitis (RP). The secondary endpoint was poor cosmesis, indicating acute/subacute radiation dermatitis. Chest computed tomography (CT) and the Common Terminology Criteria for Adverse Events v.5.0 were used to assess acute and subacute RP and dermatitis, respectively, during radiotherapy (RT) and at 3- and 6-months post-RT. The median follow-up duration was 3.8 months (range, 2.3-4.2). A total of seven patients developed RP. None of these patients presented RP-related symptoms; the diagnosis was based on radiologic findings observed on follow-up chest CT. Among the seven patients with RP, five had right-sided, and two had left-sided breast tumors (71.4 vs. 28.6%; P=0.026). Grade 1 erythema was observed in 19 patients (82.6%) and grade 2 erythema in four (17.4%). The mean target dose, D_105% (the dose received by 105% of the target volume), homogeneity index, mean lung dose, ipsilateral lung V₂₀ (the percentage volume receiving 20 Gy), and V₃₀ (the percentage volume receiving 30 Gy) for ipsilateral whole breast RT were significantly associated with RP (P=0.039, 0.047, 0.018, 0.015, 0.018 and 0.003, respectively.). HFX-VMAT showed tolerable acute/subacute toxicities. Therefore, HFX-VMAT is an effective and safe treatment option for EBC.

Comparison of intraoperative radiotherapy as a boost vs. simultaneously integrated boosts after breast-conserving therapy for breast cancer

Background

Currently, there are no data from randomized trials on the use of intraoperative radiotherapy (IORT) as a tumor bed boost in women at high risk of local recurrence. The aim of this retrospective analysis was to compare the toxicity and oncological outcome of IORT or simultaneous integrated boost (SIB) with conventional external beam radiotherapy (WBI) after breast conserving surgery (BCS).

Methods

Between 2009 and 2019, patients were treated with a single dose of 20 Gy IORT with 50 kV photons, followed by WBI 50 Gy in 25 or 40.05 in 15 fractions or WBI 50 Gy with SIB up to 58.80-61.60 Gy in 25-28 fractions. Toxicity was compared after propensity score matching. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method.

Results

A 1:1 propensity-score matching resulted in an IORT + WBI and SIB + WBI cohort of 60 patients, respectively. The median follow-up for IORT + WBI was 43.5 vs. 32 months in the SIB + WBI cohort. Most women had a pT1c tumor: IORT group 33 (55%) vs. 31 (51.7%) SIB group (p = 0.972). The luminal-B immunophenotype was most frequently diagnosed in the IORT group 43 (71.6%) vs. 35 (58.3%) in the SIB group (p = 0.283). The most reported acute adverse event in both groups was radiodermatitis. In the IORT cohort, radiodermatitis was grade 1: 23 (38.3%), grade 2: 26 (43.3%), and grade 3: 6 (10%) vs. SIB cohort grade 1: 3 (5.1%), grade 2: 21 (35%), and grade 3: 7 (11.6%) without a meaningful difference (p = 0.309). Fatigue occurred more frequently in the IORT group (grade 1: 21.7% vs. 6.7%; p = 0.041). In addition, intramammary lymphedema grade 1 occurred significantly more often in the IORT group (11.7% vs. 1.7%; p = 0.026). Both groups showed comparable late toxicity. The 3- and 5-year local control (LC) rates were each 98% in the SIB group vs. 98% and 93% in the IORT group (LS: log rank p = 0.717).

Conclusion

Tumor bed boost using IORT and SIB techniques after BCS shows excellent local control and comparable late toxicity, while IORT application exhibits a moderate increase in acute toxicity. These data should be validated by the expected publication of the prospective randomized TARGIT-B study.

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.

Journey to hypofractionation in radiotherapy for breast cancer: critical reviews for recent updates

Historical conventional fractionated radiation therapy (RT) for breast cancer consisted of 1.8-2.0 Gy per fraction with a total dose of 45-60 Gy over 5-7 weeks. Based on radiobiological characteristics, a low α/β is suspected of breast cancer resulting in sensitivity to higher dose per fraction (2.5-3.0 Gy). Over the past 10 years, multiple clinical trials support the application of shorter treatment regimen with hypofractionated RT (HypoRT). Recently, ultra-HypoRT with 5 fractions showed favorable outcomes. Although the safety and efficacy of HypoRT has been supported by high-quality randomized trials, there are still some worries and doubts around HypoRT from radiation oncologists. However, the radiation oncology community have now reached an important timepoint for adopting HypoRT during the COVID-19 pandemic. The aim of this review is to provide an overview of HypoRT in breast cancer based on prospective randomized trials and discuss the special consideration regarding HypoRT.

Hypofractionation with simultaneous integrated boost after breast-conserving surgery: Long term results of two phase-II trials

Purpose

Methods

Results

Conclusion

•

Hypofractionated breast radiotherapy with SIB was safe and feasible.

•

The local control rate at 5 years was 99.6%.

•

The rate of late grade 3 toxicity was 0.7%.

Real-World Practice of Hypofractionated Radiotherapy in Patients With Invasive Breast Cancer

Purpose

Application of hypofractionated radiotherapy (HFRT) is growing in patients with breast cancer (BC). This study aimed to explore a real-world practice of HFRT in early and locally advanced BC.

Methods

Patients with invasive BC between 2015 and 2019 were retrospectively reviewed. Radiotherapy (RT) was delivered by HFRT and conventionally fractionated radiotherapy (CFRT). Locoregional recurrence-free survival (LRRFS) and disease-free survival (DFS) were calculated by Kaplan–Meier curve and compared by Log-rank test. The effect of treatment modality on DFS was estimated by univariate and multivariable analyses.

Results

A total of 1,010 patients were included in this study, and 903 (89.4%) were treated with HFRT. At a median follow-up of 49.5 months, there was no significant difference in a 4-year cumulative incidence of LRRFS in HFRT group (1.5%) and in CFRT group (3.8%) (p = 0.23), neither in different nodal stages nor in N2–3 patients with different molecular subtypes. The 4-year DFS was 93.5% in HFRT group compared with 89.9% in CFRT group with no significant difference either (p = 0.17). Univariate and multivariable analyses also showed no significant difference in DFS between HFRT and CFRT group. However, DFS of HFRT group tended to be lower in N2–3 patients with triple negative BC compared with that of CFRT group (76.2% versus 100%).

Conclusion

HFRT can achieve similar cumulative incidence of LRRFS and DFS in patients with BC after lumpectomy or mastectomy, and also in different nodal stage, and in locally advanced stage with different molecular subtypes.