Redefining radiotherapy for early-stage breast cancer with single dose ablative treatment: a study protocol

Very accelerated partial breast irradiation in 1 or 2 days: Late toxicity and early oncological outcome of the GEC-ESTRO VAPBI cohort

PURPOSE

To analyze late toxicity after very accelerated partial breast irradiation (VAPBI) for low-risk breast cancer.

MATERIALS

Methods: In this retrospective, observational, international multicenter study (HDH F20220713143949), patients with low-risk breast cancer underwent lumpectomy + vAPBI (high-dose rate multicatheter interstitial brachytherapy-MIBT). VAPBI was performed with 4(4x6.2 Gy/2d), 3(3x7.45 Gy/2d) or 1 fraction (1x16Gy or 1x18Gy/1d). Primary endpoint was late toxicity. Secondary endpoints were cumulative incidence of breast cancer local relapse (LR) and distant metastatic relapse (DMR) and specific (SS) and overall (OS) survivals. Prognostic factors for late toxicity were analyzed.

RESULTS

From 01/2012 to 06/2022, 516 pts with early breast cancer were enrolled. Median follow-up was 44 months [95 %CI 39-46]. Median age was 71 years [40-100]. Median tumor size was 12 mm [1-35]. VAPBI delivered 1, 3 and 4 fractions for 205pts (39.7 %), 167pts (32.4 %) and 144pts (28 %) respectively. 221 late toxicity events were observed in 168pts (32.6 %) (Fibrosis, dyschromia, pain and telangiectasia). Grade 2 and 3 late toxicities were observed in 7.2 and 0.6 % respectively (no G4) with no difference between 1 and ≥ 2 treatment days. CTV > 50 cc (p = 0.007) and V150 > 40 % (p = 0.027) were prognostic factors for G ≥ 2 late toxicity. Four-year cumulative incidence rates of LR and DMR were 2 % [95 %CI 0-3] and 1 % [95 %CI 0-2] respectively.

CONCLUSIONS

VAPBI based on 1 or ≥ 2 days of MIBT represents an attractive de-escalation of irradiation approach for low-risk breast cancer. Late toxicity profile appears acceptable while early oncological outcome shows encouraging local control. Longer follow-up is warranted in order to confirm these preliminary results.

Hyperbaric Oxygen Therapy and Late Local Toxic Effects in Patients With Irradiated Breast Cancer: A Randomized Clinical Trial

Importance

Hyperbaric oxygen therapy (HBOT) is proposed as treatment for late local toxic effects after breast irradiation. Strong evidence of effectiveness is lacking.

Objective

To assess effectiveness of HBOT for late local toxic effects in women who received adjuvant radiotherapy for breast cancer.

Design, Setting, and Participants

This was a hospital-based, pragmatic, 2-arm, randomized clinical trial nested within the prospective UMBRELLA cohort following the trials within cohorts design in the Netherlands. Participants included 189 women with patient-reported moderate or severe breast, chest wall, and/or shoulder pain in combination with mild, moderate, or severe edema, fibrosis, or movement restriction 12 months or longer after breast irradiation. Data analysis was performed from May to September 2023.

Intervention

Receipt of 30 to 40 HBOT sessions over a period of 6 to 8 consecutive weeks.

Main Outcomes and Measures

Breast, chest wall, and/or shoulder pain 6 months postrandomization measured by the European Organization for Research and Treatment of Cancer QLQ-BR23 questionnaire. Secondary end points were patient-reported fibrosis, edema, movement restriction, and overall quality of life. Data were analyzed according to intention-to-treat (ITT) and complier average causal effect (CACE) principles.

Results

Between November 2019 and August 2022, 125 women (median [range] age at randomization, 56 [37-85] years) with late local toxic effects were offered to undergo HBOT (intervention arm), and 61 women (median [range] age at randomization, 60 [36-80] years) were randomized to the control arm. Of those offered HBOT, 31 (25%) accepted and completed treatment. The most common reason for not accepting HBOT was high treatment intensity. In ITT, moderate or severe pain at follow-up was reported by 58 of 115 women (50%) in the intervention arm and 32 of 52 women (62%) in the control arm (odds ratio [OR], 0.63; 95% CI, 0.32-1.23; P = .18). In CACE, the proportion of women reporting moderate or severe pain at follow-up was 32% (10 of 31) among those completing HBOT and 75% (9.7 of 12.9) among control participants expected to complete HBOT if offered (adjusted OR, 0.34; 95% CI, 0.15-0.80; P = .01). In ITT, moderate or severe fibrosis was reported by 35 of 107 (33%) in the intervention arm and 25 of 49 (51%) in the control arm (OR, 0.36; 95% CI, 0.15-0.81; P = .02). There were no significant differences in breast edema, movement restriction, and quality of life between groups in ITT and CACE.

Conclusions and Relevance

In this randomized clinical trial, offering HBOT to women with late local toxic effects was not effective for reducing pain, but was effective for reducing fibrosis. In the subgroup of women who completed HBOT, a significant reduction in pain and fibrosis was observed. A smaller than anticipated proportion of women with late local toxic effects was prepared to undergo HBOT.

Trial Registration

ClinicalTrials.gov Identifier: NCT04193722.

Treatment Options for Early Stage Inoperable Breast Cancer: Cryoablation or Radiotherapy?

Background

Surgical removal of the tumour is the gold standard treatment for early stage invasive breast cancer. However, with a global ageing population, a larger number of diagnoses are occurring in women with comorbidities that render them unsuitable for surgery. Hence, it is of interest to explore alternative treatment strategies for this group of women.

Summary

Our narrative review aims to explore two such techniques, cryoablation and external beam radiotherapy, providing a brief summary of the evidence behind each technique. Following this, we discuss which groups of patients would gain the most benefit from each technique. Factors favouring the use of radiotherapy include patients with larger tumours, more superficial tumours, and those with less well-demarcated tumours where there is uncertainty regarding tumour extent. Meanwhile, patients who may benefit more from cryoablation include those who desire a smaller number of treatment sessions, have concerns regarding cosmesis and skin pigmentation, or who have relative contraindications to radiotherapy such as scleroderma, systemic lupus erythematosus, reduced lung function, or cardiac comorbidities.

Key Messages

Continued advancements in both cryoablation and radiotherapy technologies are taking place, in tandem with imaging technologies enabling greater certainty in tumour detection and delineation. These factors will help increase local control rates in this group of non-operable early stage breast cancer patients. Through this review, we hope to aid in the clinical decision-making process regarding the selection and referral of patients for each treatment.

A narrative review for radiation oncologists to implement preoperative partial breast irradiation

The strategy to anticipate radiotherapy (RT) before surgery, for breast cancer (BC) treatment, has recently generated a renewed interest. Historically, preoperative RT has remained confined either to highly selected patients, in the context of personalized therapy, or to clinical research protocols. Nevertheless, in the recent years, thanks to technological advances and increased tumor biology understanding, RT has undergone great changes that have also impacted the preoperative settings, embracing the modern approach to breast cancer. In particular, the reappraisal of preoperative RT can be viewed within the broader view of personalized and tailored medicine. In fact, preoperative accelerated partial breast irradiation (APBI) allows a more precise target delineation, with less variability in contouring among radiation oncologists, and a smaller treatment volume, possibly leading to lower toxicity and to dose escalation programs. The aim of the present review, which represents a benchmark study for the AIRC IG-23118, is to report available data on different technical aspects of preoperative RT including dosimetric studies, patient's selection and set-up, constraints, target delineation and clinical results. These data, along with the ones that will become available from ongoing studies, may inform the design of the future trials and representing a step toward a tailored APBI approach with the potential to challenge the current treatment paradigm in early-stage BC.Trial registration: The study is registered at clinicaltrials.gov (NCT04679454).

Definitive ablative stereotactic partial breast irradiation in early stage inoperable breast cancer

PURPOSE

This case series and literature review aims to investigate the efficacy and safety of definitive ablative radiation therapy as a treatment modality for non-operable patients with early stage breast cancer. We present two cases demonstrating the potential of this approach to achieve durable responses.

METHODS

We assessed the long-term response of two non-operable patients diagnosed with Stage II (cT2N0M) and Stage IA (T1bN0M0) invasive ductal carcinoma (IDC), who were deemed unfit for surgery due to significant co-morbid conditions. Definitive ablative radiation therapy was administered using stereotactic partial breast irradiation with ablative doses delivered in either a single fraction or two fractions. Serial imaging was conducted to assess treatment response and monitor adverse events.

RESULTS

Both patients exhibited notable treatment responses following definitive ablative radiation therapy. The first patient, an 84-year-old woman, experienced a 69% reduction in tumor size over a follow-up period exceeding 2 years. The second patient, an 87-year-old woman, achieved complete resolution of disease on imaging, with no signs of progression even 26 month post-treatment. Both patients tolerated the treatment well, without significant treatment-related adverse events.

CONCLUSIONS

Our case series suggests that definitive ablative radiation therapy may serve as a safe and effective treatment option for non-operable patients with early stage breast cancer. The observed durable treatment responses and minimal toxicity support the potential of this approach. Furthermore, a longer interval between ablative radiation therapy and surgery may enhance treatment response, potentially leading to increased complete pathologic response rates.

Preoperative single fraction breast radiotherapy: Intra-fraction geometric uncertainties and dosimetric implications

PURPOSE

A preoperative breast robotic radiosurgery trial was concluded in our centre. Purposes of the present study were to evaluate retrospectively over the enrolled patients: i) respiratory patterns ii) tracking uncertainties iii) necessity of respiratory compensation iv) tracking errors dosimetric effects.

METHODS

22 patients were treated in 21 Gy single fraction using CyberKnife (CK) respiratory modelling and tracking (SynchronyResp) and data extracted from log-files. Respiratory motion and baseline drifts (BD) were analyzed. SynchronyResp uncertainties were computed and compared with errors simulated for CK fiducial tracking without respiratory compensation. Plans were perturbed by tracking errors and perturbed doses calculated on the planning CT scan in order to simulate the dosimetric consequences of intra-fraction errors.

RESULTS

After BD correction, respiratory amplitudes were below 5.5 mm except one value of 8 mm. 50% of patients showed BD above 3 mm. Standard deviations of SynchronyResp errors remained within 2.1 mm. Standard deviations of tracking errors without respiratory compensation were comparable and below 2.5 mm. Using a 3 mm PTV margin, perturbed CTV coverage was below 95% (93.7%) just for one patient. The latter case presented a large CTV-Skin interface. Perturbed OAR doses were always judged clinically acceptable.

CONCLUSION

Intra-fraction geometric uncertainties and their effects were quantified for breast neoadjuvant CK treatments. Data indicated that in the majority of cases respiratory compensation may be disabled without increasing uncertainties and reducing treatment time, provided that fiducial intra-fraction tracking is performed to account for BD. Dosimetric effects are mostly not clinically relevant.

Adaptive radiotherapy for breast cancer

Research in the field of local and locoregional breast cancer radiotherapy aims to maintain excellent oncological outcomes while reducing treatment-related toxicity. Adaptive radiotherapy (ART) considers variations in target and organs at risk (OARs) anatomy occurring during the treatment course and integrates these in re-optimized treatment plans. Exploiting ART routinely in clinic may result in smaller target volumes and better OAR sparing, which may lead to reduction of acute as well as late toxicities. In this review MR-guided and CT-guided ART for breast cancer patients according to different clinical scenarios (neoadjuvant and adjuvant partial breast irradiation, whole breast, chest wall and regional nodal irradiation) are reviewed and their advantages as well as challenging aspects discussed.

Single fraction ablative preoperative radiation treatment for early-stage breast cancer: the CRYSTAL study – a phase I/II clinical trial protocol

Background

Breast-conserving surgery (BCS) and whole breast radiation therapy (WBRT) are the standard of care for early-stage breast cancer (BC). Based on the observation that most local recurrences occurred near the tumor bed, accelerated partial breast irradiation (APBI), consisting of a higher dose per fraction to the tumor bed over a reduced treatment time, has been gaining ground as an attractive alternative in selected patients with low-risk BC. Although more widely delivered in postoperative setting, preoperative APBI has also been investigated in a limited, though increasing, and number of studies. The aim of this study is to test the feasibility, safety and efficacy of preoperative radiotherapy (RT) in a single fraction for selected BC patients.

Methods

This is a phase I/II, single-arm and open-label single-center clinical trial using CyberKnife. The clinical investigation is supported by a preplanning section which addresses technical and dosimetric issues. The primary endpoint for the phase I study, covering the 1st and 2nd year of the research project, is the identification of the maximum tolerated dose (MTD) which meets a specific target toxicity level (no grade 3–4 toxicity). The primary endpoint for the phase II study (3rd to 5th year) is the evaluation of treatment efficacy measured in terms of pathological complete response rate.

Discussion

The study will investigate the response of BC to the preoperative APBI from different perspectives. While preoperative APBI represents a form of anticipated boost, followed by WBRT, different are the implications for the scientific community. The study may help to identify good responders for whom surgery could be omitted. It is especially appealing for patients unfit for surgery due to advanced age or severe co-morbidities, in addition to or instead of systemic therapies, to ensure long-term local control. Moreover, patients with oligometastatic disease synchronous with primary BC may benefit from APBI on the intact tumor in terms of tumor progression free survival. The study of response to RT can provide useful information about BC radiobiology, immunologic reactions, genomic expression, and radiomics features, to be tested on a larger scale.

Trial registration

The study was prospectively registered at clinicaltrials.gov (NCT04679454).

Dynamic Contrast-enhanced and Diffusion-weighted Magnetic Resonance Imaging for Response Evaluation After Single-Dose Ablative Neoadjuvant Partial Breast Irradiation

Purpose

We aimed to evaluate changes in dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) magnetic resonance imaging (MRI) scans acquired before and after single-dose ablative neoadjuvant partial breast irradiation (NA-PBI), and explore the relation between semiquantitative MRI parameters and radiologic and pathologic responses.

Methods and Materials

We analyzed 3.0T DCE and DW-MRI of 36 patients with low-risk breast cancer who were treated with single-dose NA-PBI, followed by breast-conserving surgery 6 or 8 months later. MRI was acquired before NA-PBI and 1 week, 2, 4, and 6 months after NA-PBI. Breast radiologists assessed the radiologic response and breast pathologists scored the pathologic response after surgery. Patients were grouped as either pathologic responders or nonresponders (<10% vs ≥10% residual tumor cells). The semiquantitative MRI parameters evaluated were time to enhancement (TTE), 1-minute relative enhancement (RE_1min), percentage of enhancing voxels (%EV), distribution of washout curve types, and apparent diffusion coefficient (ADC).

Results

In general, the enhancement increased 1 week after NA-PBI (baseline vs 1 week median – TTE: 15s vs 10s; RE_1min: 161% vs 197%; %EV: 47% vs 67%) and decreased from 2 months onward (6 months median – TTE: 25s; RE_1min: 86%; %EV: 12%). Median ADC increased from 0.83 × 10⁻³ mm²/s at baseline to 1.28 × 10⁻³ mm²/s at 6 months. TTE, RE_1min, and %EV showed the most potential to differentiate between radiologic responses, and TTE, RE_1min, and ADC between pathologic responses.

Conclusions

Semiquantitative analyses of DCE and DW-MRI showed changes in relative enhancement and ADC 1 week after NA-PBI, indicating acute inflammation, followed by changes indicating tumor regression from 2 to 6 months after radiation therapy. A relation between the MRI parameters and radiologic and pathologic responses could not be proven in this exploratory study.

Multi-parametric MRI (mpMRI) for treatment response assessment of radiation therapy

Magnetic resonance imaging (MRI) plays an important role in the modern radiation therapy (RT) workflow. In comparison with computed tomography (CT) imaging, which is the dominant imaging modality in RT, MRI possesses excellent soft-tissue contrast for radiographic evaluation. Based on quantitative models, MRI can be used to assess tissue functional and physiological information. With the developments of scanner design, acquisition strategy, advanced data analysis, and modeling, multiparametric MRI (mpMRI), a combination of morphologic and functional imaging modalities, has been increasingly adopted for disease detection, localization, and characterization. Integration of mpMRI techniques into RT enriches the opportunities to individualize RT. In particular, RT response assessment using mpMRI allows for accurate characterization of both tissue anatomical and biochemical changes to support decision-making in monotherapy of radiation treatment and/or systematic cancer management. In recent years, accumulating evidence have, indeed, demonstrated the potentials of mpMRI in RT response assessment regarding patient stratification, trial benchmarking, early treatment intervention, and outcome modeling. Clinical application of mpMRI for treatment response assessment in routine radiation oncology workflow, however, is more complex than implementing an additional imaging protocol; mpMRI requires additional focus on optimal study design, practice standardization, and unified statistical reporting strategy to realize its full potential in the context of RT. In this article, the mpMRI theories, including image mechanism, protocol design, and data analysis, will be reviewed with a focus on the radiation oncology field. Representative works will be discussed to demonstrate how mpMRI can be used for RT response assessment. Additionally, issues and limits of current works, as well as challenges and potential future research directions, will also be discussed.

The many facets of Notch signaling in breast cancer: toward overcoming therapeutic resistance

In this review, Nandi et al. revisit the mechanisms by which Notch receptors and ligands contribute to normal mammary gland development and breast tumor progression. The authors also discuss combinatorial approaches aimed at disrupting Notch- and TME-mediated resistance that may improve prognosis in breast cancer patients.

Breast cancer is the second leading cause of cancer-related death in women and is a complex disease with high intratumoral and intertumoral heterogeneity. Such heterogeneity is a major driving force behind failure of current therapies and development of resistance. Due to the limitations of conventional therapies and inevitable emergence of acquired drug resistance (chemo and endocrine) as well as radio resistance, it is essential to design novel therapeutic strategies to improve the prognosis for breast cancer patients. Deregulated Notch signaling within the breast tumor and its tumor microenvironment (TME) is linked to poor clinical outcomes in treatment of resistant breast cancer. Notch receptors and ligands are also important for normal mammary development, suggesting the potential for conserved signaling pathways between normal mammary gland development and breast cancer. In this review, we focus on mechanisms by which Notch receptors and ligands contribute to normal mammary gland development and breast tumor progression. We also discuss how complex interactions between cancer cells and the TME may reduce treatment efficacy and ultimately lead to acquired drug or radio resistance. Potential combinatorial approaches aimed at disrupting Notch- and TME-mediated resistance that may aid in achieving in an improved patient prognosis are also highlighted.

Synthetic CT for single-fraction neoadjuvant partial breast irradiation on an MRI-linac

A synthetic computed tomography (sCT) is required for daily plan optimization on an MRI-linac. Yet, only limited information is available on the accuracy of dose calculations on sCT for breast radiotherapy. This work aimed to (1) evaluate dosimetric accuracy of treatment plans for single-fraction neoadjuvant partial breast irradiation (PBI) on a 1.5 T MRI-linac calculated on a) bulk-density sCT mimicking the current MRI-linac workflow and b) deep learning-generated sCT, and (2) investigate the number of bulk-density levels required. For ten breast cancer patients we created three bulk-density sCTs of increasing complexity from the planning-CT, using bulk-density for: (1) body, lungs, and GTV (sCT_BD1); (2) volumes for sCT_BD1plus chest wall and ipsilateral breast (sCT_BD2); (3) volumes for sCT_BD2plus ribs (sCT_BD3); and a deep learning-generated sCT (sCT_DL) from a 1.5 T MRI in supine position. Single-fraction neoadjuvant PBI treatment plans for a 1.5 T MRI-linac were optimized on each sCT and recalculated on the planning-CT. Image evaluation was performed by assessing mean absolute error (MAE) and mean error (ME) in Hounsfield Units (HU) between the sCTs and the planning-CT. Dosimetric evaluation was performed by assessing dose differences, gamma pass rates, and dose-volume histogram (DVH) differences. The following results were obtained (median across patients for sCT_BD1/sCT_BD2/sCT_BD3/sCT_DLrespectively): MAE inside the body contour was 106/104/104/75 HU and ME was 8/9/6/28 HU, mean dose difference in the PTV_GTVwas 0.15/0.00/0.00/-0.07 Gy, median gamma pass rate (2%/2 mm, 10% dose threshold) was 98.9/98.9/98.7/99.4%, and differences in DVH parameters were well below 2% for all structures except for the skin in the sCT_DL. Accurate dose calculations for single-fraction neoadjuvant PBI on an MRI-linac could be performed on both bulk-density and deep learning sCT, facilitating further implementation of MRI-guided radiotherapy for breast cancer. Balancing simplicity and accuracy, sCT_BD2showed the optimal number of bulk-density levels for a bulk-density approach.

APBI Versus Ultra-APBI in the Elderly With Low-Risk Breast Cancer: A Comparative Analysis of Oncological Outcome and Late Toxicity

PURPOSE

Accelerated partial breast irradiation (APBI) represents a validated technique for low-risk breast cancer. Recently, ultra-APBI (uAPBI) using fewer than 5 fractions was described in the literature. We compared clinical outcomes and late toxicity after APBI or uAPBI in older patients.

METHODS AND MATERIALS

Two cohorts of older patients (aged ≥70 years) with low-risk breast cancer treated with APBI (interstitial brachytherapy) were analyzed retrospectively. A total dose of 34 Gy in10 fractions (APBI) or 16 Gy in 1 fraction (uAPBI) was delivered from 2004 to 2012 and from 2013 to 2018, respectively. Oncologic outcome analyzed the cumulative incidence of local relapse, regional relapse, and distant metastases with disease-free survival, cause-specific survival, and overall survival. Late toxicity and cosmetic results were investigated.

RESULTS

One hundred fifty-seven patients (APBI, n = 109 patients; uAPBI, n = 48 patients) underwent APBI according to the same selection criteria. Apart from the median follow-up (97 vs 72 months for APBI and uAPBI; P < .002), no significant difference was noted between the 2 groups. Regarding 6-year oncologic outcome, no significant difference was observed between APBI and uAPBI for local recurrence (1.3% vs 0%; P = .4), regional recurrence (2.5% vs 2.3%; P = .9), distant metastases (4.3% vs. 2.4%; P = .6), disease-free survival (85.2% vs. 82.2%; P = .8), cause-specific survival (96.7% vs. 96.2%; P = .9), and overall survival (86.7% vs. 82.2%; P = .7). Regarding late toxicity, no significant difference was observed between APBI and uAPBI (total complication number, 45 vs 33%; P = .173) with only grade 1 (88.4% vs. 95%) and grade 2 (11.6% vs. 5%) late toxicities (P = .677). Similarly, no significant difference was observed for excellent/good cosmetic results between the 2 cohorts (P = .98).

CONCLUSIONS

We report the first study comparing APBI versus uAPBI in a cohort of older patients with low-risk breast cancer. No significant difference was found between the 2 treatment groups regarding oncologic outcome, late toxicity, and cosmetic result. uAPBI based on a single fraction of brachytherapy represents an attractive option for therapeutic de-escalation in older patients with breast cancer.

Stereotactic body radiotherapy in Cyberknife® for partial breast irradiation: a review

Introduction:

Partial breast irradiation (PBI) can reduce the volume of treatment and number of treatment sessions in low-risk breast cancer patients. Stereotactic body radiotherapy (SBRT) allows the administration of high doses per fraction thereby reducing the number of fractions and reducing the dose to the surrounding tissues. The objective of this study is to review the literature on the use of SBRT in PBI using the Cyberknife® (CK) unit.

Material and methods:

In this review, we analysed the literature in PubMed and MEDLINE with articles published in the last 10 years. All citations were evaluated for relevant content and validity.

Results:

We include articles in the English language with information about PBI, SBRT in PBI, the use of the CK unit in PBI and other applications of SBRT in breast carcinoma. A total of 68 articles were found and 28 articles were selected for inclusion in this review.

Conclusions:

The treatment of PBI using the CK unit has clear advantages in reducing the treatment volume, and therefore theoretically reducing side effects and good cosmetic results with adequate tumour control. However, the placement of fiducial markers is necessary, requiring an adequate learning curve for the placement of the markers and longer treatment times.

Ultra-Short Fraction Schedules as Part of De-intensification Strategies for Early-Stage Breast Cancer

Adjuvant radiation therapy (RT) following breast-conserving surgery (BCS) represents a standard approach for most patients treated with breast-conserving therapy (BCT) for early-stage breast cancer. The first-generation of adjuvant RT schedules delivered daily treatment to the whole breast over 5-7 weeks. Although efficacious, this presented patients with a protracted course of treatment, reducing compliance and quality of life. While hypofractionated whole-breast irradiation (WBI) has become the standard, and part of the second-generation of RT regimens, it still requires 3-4 weeks. Concurrently, partial-breast irradiation (PBI) has also been explored as a technique to complete RT in a much shorter time period (1-3 weeks). There are now seven trials confirming the efficacy of this shorter treatment approach compared with standard WBI. In an effort to further reduce treatment duration, ultra-short WBI and PBI regimens have recently emerged as the third-generation of breast radiation schedules, allowing for the completion of treatment in 5 days or less. With respect to WBI, recent data from the FAST-Forward trial (which evaluated five fractions of WBI delivered in 1 week) demonstrated no difference in clinical outcomes at 5 years, with limited difference in toxicity, compared with hypofractionated 3-week WBI. Regarding PBI, published data on five-fraction regimens delivered in 2 weeks have also demonstrated comparable outcomes at 10 years, with reduced toxicities with long-term follow-up. This report will review additional ongoing studies evaluating even shorter courses of adjuvant RT treatment (one to five fractions), including single-fraction PBI or WBI.

Consensus on Contouring Primary Breast Tumors on MRI in the Setting of Neoadjuvant Partial Breast Irradiation in Trials

PURPOSE

Our purpose was to present and evaluate expert consensus on contouring primary breast tumors on magnetic resonance imaging (MRI) in the setting of neoadjuvant partial breast irradiation in trials.

METHODS AND MATERIALS

Expert consensus on contouring guidelines for target definition of primary breast tumors on contrast-enhanced MRI in trials was developed by an international team of experienced breast radiation oncologists and a dedicated breast radiologist during 3 meetings. At the first meeting, draft guidelines were developed through discussing and contouring 2 cases. At the second meeting 6 breast radiation oncologists delineated gross tumor volume (GTV) in 10 patients with early-stage breast cancer (cT1N0) according to draft guidelines. GTV was expanded isotropically (20 mm) to generate clinical target volume (CTV), excluding skin and chest wall. Delineations were reviewed for disagreement and guidelines were clarified accordingly. At the third meeting 5 radiation oncologists redelineated 6 cases using consensus-based guidelines. Interobserver variation of GTV and CTV was assessed using generalized conformity index (CI). CI was calculated as the sum of volumes each pair of observers agreed upon, divided by the sum of encompassing volumes for each pair of observers.

RESULTS

For the 2 delineation sessions combined, mean GTV ranged between 0.19 and 2.44 cm3, CI for GTV ranged between 0.28 and 0.77, and CI for CTV between 0.77 and 0.94. The largest interobserver variation in GTV delineations was observed in cases with extended tumor spiculae, blood vessels near or markers within the tumor, or with increased enhancement of glandular breast tissue. Consensus-based guidelines stated to delineate all visible tumors on contrast enhanced-MRI scan 1 to 2 minutes after contrast injection and if a marker was inserted in the tumor to include this.

CONCLUSIONS

Expert-based consensus on contouring primary breast tumors on MRI in trials has been reached. This resulted in low interobserver variation for CTV in the context of a uniform 20 mm GTV to CTV expansion margin.

RF-PCA: A New Solution for Rapid Identification of Breast Cancer Categorical Data Based on Attribute Selection and Feature Extraction

Breast cancer is one of the most common cancer diseases in women. The rapid and accurate diagnosis of breast cancer is of great significance for the treatment of cancer. Artificial intelligence and machine learning algorithms are used to identify breast malignant tumors, which can effectively solve the problems of insufficient recognition accuracy and long time-consuming in traditional breast cancer diagnosis methods. To solve these problems, we proposed a method of attribute selection and feature extraction based on random forest (RF) combined with principal component analysis (PCA) for rapid and accurate diagnosis of breast cancer. Firstly, RF was used to reduce 30 attributes of breast cancer categorical data. According to the average importance of attributes and out of bag error, 21 relatively important attribute data were selected for feature extraction based on PCA. The seven features extracted from PCA were used to establish an extreme learning machine (ELM) classification model with different activation functions. By comparing the classification accuracy and training time of these different models, the activation function of the hidden layer was determined as the sigmoid function. When the number of neurons in the hidden layer was 27, the accuracy of the test set was 98.75%, the accuracy of the training set was 99.06%, and the training time was only 0.0022 s. Finally, in order to verify the superiority of this method in breast cancer diagnosis, we compared with the ELM model based on the original breast cancer data and other intelligent classification algorithm models. The algorithm used in this article has a faster recognition time and a higher recognition accuracy than other algorithms. We also used the breast cancer data of breast tissue reactance features to verify the reliability of this method, and ideal results were obtained. The experimental results show that RF-PCA combined with ELM can significantly reduce the time required for the diagnosis of breast cancer, which has the ability of rapid and accurate identification of breast cancer and provides a theoretical basis for the intelligent diagnosis of breast cancer.

Definitive single fraction stereotactic ablative radiotherapy for inoperable early-stage breast cancer: A case report

We review a case of inoperable early stage breast cancer treated definitively with the use of stereotactic ablative radiotherapy (SABR). A 57-year-old female with a history of decompensated cirrhosis with early stage breast cancer was treated with 25 Gy in one fraction. At her 7-month follow up visit, there was a complete resolution of disease on imaging. This case represents a novel approach for the treatment of breast cancer with SABR when surgery is contraindicated.

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.

Tumour response 3 months after neoadjuvant single-fraction radiotherapy for low-risk breast cancer

Introduction

Standard treatment for early-stage invasive breast cancer (bca) consists of breast-conserving surgery and several weeks of adjuvant radiotherapy (rt). Neoadjuvant single-fraction rt is a novel approach for early-stage bca. We sought to investigate the effect of delaying surgery after neoadjuvant rt with respect to the rate of pathologic response (pr).

Methods

Women 65 years of age or older with a new diagnosis of stage i luminal A bca were eligible for inclusion. A single 20 Gy dose to the primary breast tumour was given, followed by breast-conserving surgery 3 months later. The primary endpoint was the pr rate assessed by microscopic evaluation using the Miller-Payne system.

Results

To date, 10 patients have been successfully treated. Median age of the patients was 72 years (range: 65-84 years). In 8 patients, neoadjuvant rt resulted in a tumour pr with median residual cellularity of 3%. No immediate rt complications other than mild dermatitis were noted.

Conclusions

This study demonstrates a method for delivering single-fraction rt that can lead to a high level of pr in most patients. Continued accrual to this study and subsequent trials are needed to determine the feasibility, safety, and role of this novel technique in the management of early-stage bca.

Five-Year Results of the Preoperative Accelerated Partial Breast Irradiation (PAPBI) Trial

PURPOSE

In this multicenter phase 2 feasibility study, we investigated the impact of preoperative accelerated partial breast irradiation (PAPBI) on local control, breast fibrosis, and cosmetic outcome.

METHODS AND MATERIALS

Women aged >60 years with an invasive, unifocal (mammography and magnetic resonance imaging), nonlobular adenocarcinoma of the breast were treated with PAPBI. Six weeks after radiation therapy, a wide local excision was performed. Radiation therapy consisted of 10 × 4 Gy (2010-2013) or 5 × 6 Gy (after 2013) to the tumor (gross target volume) with a 25 mm margin (20 mm from gross target volume to clinical target volume, 5 mm planning target volume).

RESULTS

One hundred thirty-three patients treated between 2010 and 2016 were analyzed with a median follow-up of 5.0 years (0.9-8.8 years). Seventy-eight (59%) patients were treated with 10 × 4 Gy in 2 weeks and 55 (41%) patients with 5 × 6 Gy in 1 week. Eighteen postoperative complications (14%) occurred in 15 patients (11%). The proportion of patients with no to mild fibrosis in the treated part of the breast at 2 years and later time points was around 90%. Cosmesis improved over time in several patients: excellent to good cosmetic score as rated by the physician was 68% at 6 months and 92% at 5 years. Seventy-seven percent (6 months) to 82% (5 years) of patients were "satisfied" or "very satisfied" with their cosmetic outcome. Three recurrences were detected in the biopsy track and 1 recurrence in the ipsilateral breast.

CONCLUSIONS

PAPBI is a feasible method with a low postoperative complication rate, limited fibrosis, and good to excellent cosmetic outcome. The local recurrence rate was 3% at 5 years; however, no local recurrences were observed since removal of the needle biopsy track.

Accuracy and efficiency of image-guided radiation therapy (IGRT) for preoperative partial breast radiosurgery

OBJECTIVE

To analyze and evaluate accuracy and efficiency of IGRT process for preoperative partial breast radiosurgery.

METHODS

Patients were initially setup with skin marks and 5 steps were performed: (1) Initial orthogonal 2D kV images, (2) pre-treatment 3D CBCT images, (3) verification orthogonal 2D kV images, (4) treatment including mid-treatment 2D kV images (for the final 15 patients only), and (5) post-treatment orthogonal 2D kV or 3D CBCT images. Patient position was corrected at each step to align the biopsy clip and to verify surrounding soft tissue positioning.

RESULTS

The mean combined vector magnitude shifts and standard deviations at the 5 imaging steps were (1) 0.96 ± 0.69, (2) 0.33 ± 0.40, (3) 0.05 ± 0.12, (4) 0.15 ± 0.17, and (5) 0.27 ± 0.24 in cm. The mean total IGRT time was 40.2 ± 13.2 minutes. Each step was shortened by 2 to 5 minutes with improvements implemented. Overall, improvements in the IGRT process reduced the mean total IGRT time by approximately 20 minutes. Clip visibility was improved by implementing oblique orthogonal images.

CONCLUSION

Multiple imaging steps confirmed accurate patient positioning. Appropriate planning and imaging strategies improved the effectiveness and efficiency of the IGRT process for preoperative partial breast radiosurgery.

Single dose partial breast irradiation using an MRI linear accelerator in the supine and prone treatment position

Background

In selected patients with early-stage and low-risk breast cancer, an MRI-linac based treatment might enable a radiosurgical, non-invasive alternative for current standard breast conserving therapy.

Aim

To investigate whether single dose accelerated partial breast (APBI) to the intact tumor in both the prone and supine radiotherapy positions on the MRI-linac is dosimetrically feasible with respect to predefined coverage and organs at risk (OAR) constraints.

Material & methods

For 20 patients with cTis or low-risk cT1N0M0 non-lobular breast carcinoma, previously treated with single dose preoperative APBI in the supine (n = 10) or prone (n = 10) position, additional intensity modulated radiotherapy plans with 7 coplanar beams in the presence of a 1.5T magnetic field were generated. A 20 Gy and 15 Gy dose was prescribed to the gross tumor and clinical target volume, respectively. The percentage of plans achieving predefined organ at risk (OAR) constraints, currently used in clinical practice, was assessed. Dosimetry differences between the prone versus supine approach and the MRI-linac versus clinically delivered plans were evaluated.

Results

All MRI-linac plans met the coverage and predefined OAR constraints. The prone approach appeared to be more favorable with respect to the chest wall, and ipsilateral lung dose compared to the supine position. No dosimetric differences were observed for the ipsilateral breast. No treatment position was clearly more beneficial for the skin or heart, since dosimetry varied among parameters. Overall, the MRI-linac and clinical plans were comparable, with minor absolute dosimetric differences.

Conclusion

MRI-linac based single dose APBI to the intact tumor is a promising and a dosimetrically feasible strategy in patients with low-risk breast cancer. Preliminary OAR dosimetry favored the prone radiotherapy position.

Establishing the Role of Stereotactic Ablative Body Radiotherapy in Early-Stage Breast Cancer

Stereotactic ablative body radiotherapy (SABR) has a role as definitive therapy in many tumor sites; however, its role in the treatment of breast cancer is less well explored. Currently, SABR has been investigated in the neoadjuvant and adjuvant setting with a number of ongoing feasibility studies. However, its use comes with a number of radiobiological and technical challenges that require further evaluation. We have learned much from other extracranial disease sites such as lung, brain, and spine, where definitive treatment with SABR has shown encouraging outcomes. In women with breast cancer, SABR may eliminate the need for invasive surgery, reducing healthcare costs and hospital stays and providing an additional curative option for early-stage disease. This poses the following question: is there a role for SABR as a definitive therapy in breast cancer?