Hybrid volumetric-modulated arc therapy for postoperative breast cancer including regional lymph nodes: the advantage of dosimetric data and safety of toxicities

Executive Summary of the American Radium Society Appropriate Use Criteria: Regional Nodal Irradiation for Breast Cancer

OBJECTIVES

Recent literature has provided additional data to further individualize treatment recommendations on regional nodal irradiation (RNI) patient selection and delivery techniques, but controversies surrounding optimal RNI utilization remain, including radiation technique, modality selection, and internal mammary lymph node (IMN) inclusion. The American Radium Society (ARS) Breast Appropriate Use Criteria (AUC) Committee performed a systematic review and developed a consensus guideline to summarize recent data and provide evidence-based recommendations.

METHODS

A multidisciplinary panel comprised of 15 members representing radiation oncologists, medical oncologists, and surgical oncologists specializing in the treatment of breast cancer conducted an analysis of the medical literature from January 1, 2011 to April 1, 2024. Modified Delphi methodology was used to rate the appropriateness of treatments for variants across 3 key questions.

RESULTS

Patients with intermediate-risk breast cancer, such as limited nodal involvement or large primary tumor size, are reasonable candidates for RNI, although a subset of patients with overall favorable clinicopathologic features may be considered for treatment de-escalation. Data on the use of advanced radiation techniques for RNI were limited in scope and strength, and the panel agreed that careful patient selection is needed when using these tools. Evidence suggests that the IMN should be included when delivering RNI given the absolute benefit demonstrated in multiple randomized trials.

CONCLUSION

A systematic review and evidence-based summary of recommendations are provided in these consensus guidelines from the ARS Breast AUC Committee to provide current comprehensive guidance on the optimal management of non-metastatic breast cancer patients being considered for RNI.

Dose comparison between hybrid volumetric modulated arc therapy, volumetric modulated arc therapy, and three-dimensional conformal radiotherapy for breast/chest wall irradiation, including regional lymph node irradiation using deep inspiration breath-hold technique

PURPOSE

Breast radiation treatment has been linked to complications such as pneumonitis and cardiac toxicity, necessitating dose optimization. This study aims to determine the optimal integration plan of volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3DCRT) in a deep inspiration breath-hold regimen.

MATERIALS AND METHODS

CT imaging data from twenty patients with breast or chest wall cancer, either right or left-sided, and with supraclavicular and internal mammary chain lymph nodes were retrieved. The CT data planned with a hybrid VMAT of three different weighting proportions: 30 % using 3DCRT and 70 % using VMAT, 50 % using 3DCRT and 50 % using VMAT, and 70% using 3DCRT and 30 % using VMAT and compared with full 3DCRT and full VMAT plan (classic and five arc design).

RESULTS

The homogeneity and conformity indices were better in the hybrid VMAT plans than in plans using VMAT or 3DCRT alone (P<0.005). Results of all hybrid VMAT plans showed a considerable drop of volumes receiving more than 4Gy, 8Gy or 16Gy in the ipsilateral lung compared to the full VMAT plan (P<0.001). There was a noticeable decrease in the mean dose to the heart and the dose in 5% of the contralateral breast in the plan using 70 % 3DCRT and 30 % VMAT compared to full VMAT (P<0.001). The plan using 70 % 3DCRT and 30% VMAT achieved a balance between the target and surrounding areas, compared to using only 3DCRT or VMAT.

CONCLUSION

A hybrid plan using 70 % 3DCRT contribution achieved a balanced outcome for breast or chest wall irradiation, considering both planning target volume and organs at risk. Utilizing our VMAT arc design, incorporating one shortened arc can significantly reduce doses to organs at risk further. It is important to consider the patient's anatomy when making this decision.

Patient and treatment-related factors that influence dose to heart and heart substructures in left-sided breast cancer radiotherapy

BACKGROUND

Cardiac substructures are critical organs at risk in left-sided breast cancer radiotherapy being often overlooked during treatment planning. The treatment technique plays an important role in diminishing dose to critical structures. This review aims to analyze the impact of treatment- and patient-related factors on heart substructure dosimetry and to identify the gaps in literature regarding dosimetric reporting of cardiac substructures.

METHODS

A systematic search of the literature was conducted in Medline/Pubmed database incorporating data published over the past 10 years, leading to 81 eligible studies. Treatment-related factors analyzed for their impact on patient outcome included the number of treatment fields, field geometry, treatment time and monitor units. Additionally, patient-related parameters such as breast size and tumor shape were considered for cardiac dosimetry evaluation.

RESULTS

Limited number of fields appeared to be an advantage for mean heart dose reduction when tangential IMRT versus multiple fields IMRT was evaluated. Larger breast size (910.20 ± 439.80 cm3) is linked to larger treatment fields and higher heart doses. Internal mammary node irradiation further escalates cardiac substructures dosimetry treated with 3DCRT and IMRT/VMAT. Proton therapy delivers lower mean heart dose regardless of breathing condition (free or respiratory-gated).

CONCLUSION

The management of treatment- and patient-related factors must be taken into account regardless of the treatment technique when evaluating cardiac dose. Furthermore, the gap found in the literature regarding heart toxicity assessment in left-sided breast cancer patients emphasizes the need for cardiac substructure contouring to better manage and control radiation-induced cardiac toxicities in this patient group.

Hybrid Treatment Planning for Chest Wall Irradiation Utilizing Three-Dimensional Conformal Radiotherapy (3DCRT), Intensity-Modulated Radiation Therapy (IMRT), and Volumetric Modulated Arc Therapy (VMAT): A Systematic Review

Novel hybrid approaches for chest wall irradiation show promising outcomes regarding target coverage and sparing organs at risk (OARs). In this systematic review, we compared hybrid volumetric modulated arc therapy (H-VMAT) or hybrid intensity-modulated radiotherapy (H-IMRT) techniques with non-hybrid techniques, such as three-dimensional conformal radiation therapy (3DCRT), field-in-field (FIF), intensity-modulated arc therapy (IMRT), and volumetric modulated arc therapy (VMAT), for breast cancer patients with mastectomy. Our focus was the plan quality and dose distribution to the OARs. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, we performed a systematic review and quality appraisal of primary studies evaluating hybrid therapy to the chest wall and the OARs. An extensive online search of PubMed and Scopus databases was conducted using appropriate keywords. The dose to the OARs (lung, heart, and contralateral breast), planning target volume (PTV), homogeneity index (HI), and conformity index (CI) were extracted. The data were then tabulated and compared for the outcomes between modalities among the studies. Nine studies that met the search criteria were selected to evaluate the PTV coverage and dosimetric results of hybrid and non-hybrid techniques. In terms of 95% PTV coverage, among nine reviewed studies, the largest difference between the two techniques was between VMAT (47.6 Gy) and H-VMAT (48.4 Gy); for the conformity index, the largest difference was noted between 3DCRT (0.58) and H-VMAT (0.79). In both cases, differences were statistically significant (P < 0.005). Two studies showed dose homogeneity improvement within the treatment target in H-VMAT (0.15 and 0.07) compared with 3DCRT (0.41 and 0.12), with a P value of <0.001. Two studies did not report on the homogeneity index, and three others observed no statistical difference. Regarding OARs, in the comparison of H-VMAT and VMAT, the largest significant change was in the volume receiving 5 Gy (V5Gy) of the ipsilateral lung and the V10Gy of the contralateral lung. For the ipsilateral lung, V5Gy was 90.7% with VMAT versus 51.45% with H-VMAT. For the contralateral lung, V10Gy was 54.9% with VMAT versus 50.5% with H-VMAT. In six studies, the mean dose of the contralateral breast was lower in hybrid techniques than in single modalities: VMAT (4.2%, 6.0%, 1.9%, 7.1%, 4.57%) versus H-VMAT (1.4%, 3.4%, 1.8%, 3.5%, 2.34%) and IMRT (9.1%) versus H-IMRT (4.69%). Although most studies did not report on monitor units and treatment time, those that included them showed that hybrids had lower monitor units and shorter treatment times. Hybrid techniques in radiotherapy, such as combining two modalities, can indeed facilitate lower doses to OARs for patients with a high risk of toxicities. Prospective clinical studies are needed to determine the outcomes of breast cancer treated with hybrid techniques.

Hybrid VMAT-3DCRT as breast cancer treatment improvement tool

Radiation therapy is an important tool in the treatment of breast cancer and can play a crucial role in improving patient outcomes. For breast cancer, if the technique has been for a long time the use of 3DCRT, clinicians have seen the management evolve greatly in recent years. Field-in-field and IMRT approaches and more recently dynamic arctherapy are increasingly available. All of these approaches are constantly trying to improve tumour coverage and to preserve organs at risk by minimising the doses delivered to them. If arctherapy allows a considerable reduction of high doses received by healthy tissues, no one can deny that it also leads to an increase of low doses in tissues that would not have received any with other techniques. We propose a hybrid approach combining the robustness of the 3DCRT approach and the high technicality and efficiency of arctherapy. Statistical tests (ANOVA, Wilcoxon, determination coefficient, ROC, etc.) allow us to draw conclusions about the possibility of using the hybrid approach in certain cases (right breast, BMI [Formula: see text], age [Formula: see text], target volume [Formula: see text] cc, etc.). Depending on the breast laterality and patients morphological characteristics, hybridization may prove to be a therapeutic tool of choice in the management of breast cancer in radiotherapy.

Dose-Volume Predictors for Radiation Esophagitis in Patients With Breast Cancer Undergoing Hypofractionated Regional Nodal Radiation Therapy

PURPOSE

Our objective was to assess the incidence and dose-volume predictors of radiation esophagitis (RE) in patients with breast cancer undergoing hypofractionated regional nodal irradiation.

METHODS AND MATERIALS

Eligible patients who received intensity modulated radiation therapy (RT) at the chest wall, the supraclavicular/infraclavicular fossa, level II axilla, and/or the internal mammary chain after mastectomy were included. The prescribed dose was 43.5 Gy in 15 fractions. RE was evaluated weekly during RT and at 1 and 2 weeks, followed by 3 and 6 months after RT, and was graded according to National Cancer Institute Common Toxicity Criteria for Adverse Events, version 3.0. The esophagus was contoured from the lower border level of the cricoid cartilage to the lower margin of the aortic arch. Esophageal total volume, mean dose, maximum dose, and the relative volumes (RV) and absolute volumes (AV) receiving at least 5 to 45 Gy by 5-Gy increments (RV5-RV45 and AV5-AV45) were evaluated. Univariable and multivariable logistic regression analyses were performed to determine risk factors for RE, and receiver operating characteristic curves were obtained to identify the thresholds of esophageal dosimetric parameters.

RESULTS

In total, 298 patients were included between May 8, 2020, and January 5, 2022 (minimum post-RT follow-up: 6 months). Grade 2 and 3 RE incidence was 40.9% (122/298) and 0.3% (1/298), respectively. No grade 4 or 5 RE was observed. Esophageal RV20-RV40 and AV35-AV40 were significantly associated with the risk of grade ≥2 RE after adjusting for tumor laterality and internal mammary nodal irradiation. RV25 and AV35 were optimum dose-volume predictors for grade ≥2 RE at thresholds 20% for RV25 (35.9% vs 60.9%; P = .04) and 0.27 mL for AV35 (31.0% vs 54.6%; P = .04).

CONCLUSIONS

RE is common in patients with breast cancer undergoing hypofractionated regional nodal irradiation. Maintaining the upper esophageal V25 at <20% and V35 at <0.27 mL may decrease the risk of RE.

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.

Improved treatment robustness of postoperative breast cancer radiotherapy including supraclavicular nodes

A combination of a three-dimensional conformal radiation therapy (3D-CRT) plan with a dose gradient of the chest wall area and a volumetric modulated arc therapy (VMAT) plan of the supraclavicular area might improve the dose distribution robustness in the junction. To investigate the impact of patient motion on the dose distribution, hybrid 3D-CRT and VMAT plans were recalculated by shifting the isocenter of the VMAT plan. Compared to the nominal plan, the target D_98% for high- vs low-dose gradients decreased by 24% vs 12%. Hybrid VMAT with a low-dose gradient 3D-CRT plan was found to be robust towards patient motion.

Retrospective evaluation of a robust hybrid planning technique established for irradiation of breast cancer patients with included mammary internal lymph nodes

Background

The irradiation of breast cancer patients with included internal mammary lymph nodes challenges radiation planning with regard to robustness and protection of OARs. In this publication, a feasible hybrid radiation technique is presented with a retrospective dosimetric and radiobiological analysis of patient data of our institute from 2016 to 2020 and robustness analysis.

Methods

The proposed hybrid irradiation technique consists of two IMRT tangents and two partial VMAT fields. The retrospective dosimetric and radiobiological evaluation are made for 217 patient treatments (right- and left-sided). The robustness is evaluated regarding an artificial swelling from 0.4 to 1.5 cm for a random example patient and compared to a pure VMAT planning technique with use of a virtual bolus. The out of field stray dose is calculated for a selected patient plan and compared to alternative radiation techniques.

Results

The coverage D95% of the PTVEval (with breast swelling of 1.5 cm) changes for the hybrid plan from 96.1 to 92.1% of prescribed dose and for the pure VMAT plan from 94.3 to 87%. The retrospective dosimetric evaluation of patient irradiations reveals a Dmean for total lung 6.5 ± 0.9 Gy (NTCP[Semenenko 2008] 2.8 ± 0.5%), ipsilateral lung 10.9 ± 1.5 Gy, contralateral lung 2.2 ± 0.6 Gy, heart 2.1 ± 1.1 Gy (ERR[Schneider 2017] 0.02 ± 0.17%) and contralateral breast 1.7 ± 0.6 Gy. The scatter dose of the hybrid irradiation technique is higher than for pure VMAT and lower than for pure IMRT irradiation.

Conclusions

The feasibility of the proposed planning technique is shown by treating many patients with this technique at our radiotherapy department. The hybrid radiation technique shows a good sparing of the OARs in the retrospective analysis and is robust with regards to a breast swelling of up to 1.5 cm. The slightly higher stray dose of the hybrid technique compared to a pure VMAT technique originates from higher number of MUs and lower conformity.

Impact of CBCT frequency on target coverage and dose to the organs at risk in adjuvant breast cancer radiotherapy

The current study aims to assess the effect of cone beam computed tomography (CBCT) frequency during adjuvant breast cancer radiotherapy with simultaneous integrated boost (SIB) on target volume coverage and dose to the organs at risk (OAR). 50 breast cancer patients receiving either non-hypofractionated or hypofractionated radiotherapy after lumpectomy including a SIB to the tumor bed were selected for this study. All patients were treated in volumetric modulated arc therapy (VMAT) technique and underwent daily CBCT imaging. In order to estimate the delivered dose during the treatment, the applied fraction doses were recalculated on daily CBCT scans and accumulated using deformable image registration. Based on a total of 2440 dose recalculations, dose coverage in the clinical target volumes (CTV) and OAR was compared depending on the CBCT frequency. The estimated delivered dose (V95%) for breast-CTV and SIB-CTV was significantly lower than the planned dose distribution, irrespective of the CBCT-frequency. Between daily CBCT and CBCT on alternate days, no significant dose differences were found regarding V95% for both, breast-CTV and SIB-CTV. Dose distribution in the OAR was similar for both imaging protocols. Weekly CBCT though led to a significant decrease in dose coverage compared to daily CBCT and a small but significant dose increase in most OAR. Daily CBCT imaging might not be necessary to ensure adequate dose coverage in the target volumes while efficiently sparing the OAR during adjuvant breast cancer radiotherapy with SIB.