The use of bolus in postmastectomy radiation therapy for breast cancer: A systematic review

Protons Versus Photons Postmastectomy Radiation Therapy Effects on Breast Reconstruction Outcomes and Dosimetry Analysis

PURPOSE

To compare the impact of proton versus photon postmastectomy radiation therapy (PMRT) on implant-related complications.

METHODS AND MATERIALS

The records of patients with breast cancer treated with mastectomy and expander and/or implant reconstruction followed by PMRT at our institution between 2011 and 2022 were reviewed. Patients were divided into 2 groups by treatment modality: proton and photon groups. All identified patients in the proton group were treated using conventional fractionation, and radiobiological effectiveness (RBE) was scaled to 1.1. Recorded complications included infection/skin necrosis requiring operative debridement, capsular contracture necessitating capsulotomy, absolute reconstruction failure implying complete loss of reconstruction, and overall reconstruction failure defined as multiple revisions leading to replacement of the implant or salvage autologous reconstruction. Subgroup analysis for patients in the proton group explored the correlation between dosimetric parameters and complications. Logistic regression and Cox proportional hazards regression models were used.

RESULTS

A total of 203 patients with an overall median follow-up of 4.7 years were identified. Among those 203 patients, 50 patients (25%) received proton PMRT, while 153 patients (75%) received photon PMRT. The complication rates for proton versus photon therapies were infection/necrosis (20% vs 13%; OR, 1.6; P = .2), capsular contracture (30% vs 10%; OR, 3.9; P < .001), absolute reconstruction failure (16% vs 12%; OR, 1.4; P = .4), and overall reconstruction failure (56% vs 36%; OR, 2.2; P = .01). Sensitivity analyses and time-to-event models yielded similar results. The median (Dmean) for clinical target volume, implant, and skin was 50.6, 50.8, and 6.7 Gy (RBE), respectively. The median hot spot (D1cc) for clinical target volume, implant, and skin was 52.8, 52.7, and 49.8 Gy (RBE), respectively. None of these parameters were significantly correlated with complications. The 5-year local failure cumulative incidence was 0% versus 4% (P = .13) for proton and photon cohorts, respectively.

CONCLUSIONS

Proton PMRT was associated with higher rates of implant capsular contracture and reconstruction failures than photon PMRT with comparable local control. No dosimetric parameter correlated with reconstruction complications.

Feature-Based vs. Deep-Learning Fusion Methods for the In Vivo Detection of Radiation Dermatitis Using Optical Coherence Tomography, a Feasibility Study

Acute radiation dermatitis (ARD) is a common and distressing issue for cancer patients undergoing radiation therapy, leading to significant morbidity. Despite available treatments, ARD remains a distressing issue, necessitating further research to improve prevention and management strategies. Moreover, the lack of biomarkers for early quantitative assessment of ARD impedes progress in this area. This study aims to investigate the detection of ARD using intensity-based and novel features of Optical Coherence Tomography (OCT) images, combined with machine learning. Imaging sessions were conducted twice weekly on twenty-two patients at six neck locations throughout their radiation treatment, with ARD severity graded by an expert oncologist. We compared a traditional feature-based machine learning technique with a deep learning late-fusion approach to classify normal skin vs. ARD using a dataset of 1487 images. The dataset analysis demonstrates that the deep learning approach outperformed traditional machine learning, achieving an accuracy of 88%. These findings offer a promising foundation for future research aimed at developing a quantitative assessment tool to enhance the management of ARD.

Innovative applications of visualized thermosensitive color-changing personalized boluses in post-mastectomy radiotherapy: a dosimetric analysis

BACKGROUND AND PURPOSE

To explore the feasibility and advantages of the visualized thermosensitive color-changing personalized bolus in post-mastectomy radiotherapy (PMRT).

MATERIALS AND METHODS

Forty PMRT patients (June 2023-June 2024) were randomized into two groups. Group A (experimental group, 20 patients) underwent two CT scans: A1 (without compensator) and A2 (with the visualized thermosensitive color-changing personalized bolus), followed by treatment with the thermosensitive color-changing personalized bolus. Group B (control group, 20 patients) also underwent two CT scans: B1 (without bolus) and B2 (with a conventional commercial bolus), followed by treatment with the commercial bolus. Treatment plans were generated for virtual bolus (A1-Plan, B1-Plan) and real bolus (A2-Plan, B2-Plan). A3-Plan (A1-Plan applied to thermosensitive bolus treatment) and B2-Plan (B1-Plan applied to commercial bolus treatment) were compared to evaluate dosimetric differences in target volumes, organs at risk (OARs), and skin toxicity.

RESULTS

In Group A, A1-Plan and A2-Plan showed no significant differences in OAR doses (e.g., ipsilateral lung, heart, contralateral breast, skin Dmax/Dmean) or target metrics (V50Gy, Dmax, homogeneity index (HI), conformity index (CI), monitor units (MU)). A3-Plan compared to A1-Plan had minor differences in target coverage (94.05% vs. 95.14%), HI (0.148 vs. 0.147), and CI (0.83 vs. 0.84). In Group B, B2-Plan had significantly reduced target coverage (89.9% vs. 95%), homogeneity (0.153 vs. 0.136), and conformity (0.817 vs. 0.810) compared to B1-Plan, attributed to air gaps from the commercial bolus. The thermosensitive color-changing personalized bolus had better skin adherence, significantly reduced air cavity volumes (3833 mm³ vs. 21498 mm³), and maintained equivalent dosimetric performance to virtual boluses. Skin toxicity was Grade I in all patients without differences between groups.

CONCLUSIONS

The visualized thermosensitive color-changing personalized bolus demonstrated superior skin adherence, smaller air gaps, and better positional reproducibility compared to commercial boluses. Its dosimetric performance was consistent with virtual bolus plans, ensuring target coverage and OAR protection without increased skin toxicity. These findings support its clinical application in PMRT.

Can the daily position of bolus material influence radiotherapy treatment?

Background

Daily bolus positioning implies a high degree of variability, which can affect the dose distribution within the planning target volume (PTV) and the organs at risk (OAR). We carried out a retrospective study to evaluate bolus positioning in patients with breast cancer.

Materials and methods

We evaluated 7 cases with left and 5 cases with right chest-wall with comprehensive nodal region irradiation in which bolus material was used to obtain better skin surface coverage. The bolus positioning on the daily cone-beam computed tomography (CBCT) images was compared to the reference image from the treatment planning system. Deviations from the reference position of the bolus were categorized as positive shifts (PosS) or negative shifts (NegS), depending on the material's overlapping with its planned position. Subsequently, a second plan was calculated using the information from the CBCT images for comparison with the original treatment plan. We performed a statistical and dosimetric analysis on the results.

Results

For both the 95% dose coverage for the PTV for the chest wall and for the lymph node regions, about 2% variation between initial and recalculated plans was seen, with a shift of the hotspots' position in some cases. The average mean heart dose was 4.1 ± 0.3 Gy, whereas the values for PosS and NegS mean heart doses were 3.8 ± 0.4 Gy and 4.0 ± 0.6 Gy, respectively. In contrast to the original values for the ipsilateral lung V5 (57.1 ± 12.9%), V20 (30.2 ± 2.7%), and Dmean (15.0 ± 1.7 Gy), the values for PosS were 56.1 ± 4.2% for V5:, 30.1 ± 3.3% for V20, and 14.9 ± 1.2 Gy for Dmean while for NegS we obtained 56.9 ± 8.9% for V5, 30.0 ± 2.3% for V20, and 15.2 ± 1.8 Gy for Dmean.

Conclusion

We observed dosimetric differences between the initial and given treatment plans depending on the position of the bolus for all cases, indifferent of the shift direction. Although the differences were not statistically significant, we identified a few specific instances where the variations might cause uncertainties regarding doses to the organs at risk (OAR). We suggest therefore that strategies for correct daily reproducibility of the bolus need to be implemented on a departmental level.

A critical review of randomized controlled trials on topical corticosteroids for the prevention of radiation dermatitis in breast cancer

INTRODUCTION

Topical steroids have shown effectiveness in preventing radiation dermatitis (RD) in breast cancer patients in randomized controlled trials (RCTs). This review provides an in-depth analysis of the study methodology of these RCTs to review whether topical steroids should be employed in routine clinical practice.

METHODS

A systematic literature search of MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials was conducted from database inception until May 31, 2024. RCTs comparing topical steroids with moisturizers or placebo for the prophylaxis of RD in breast cancer patients were included. The methodology of the RCTs, including how topical steroids were applied, whether crossover in the control arm was allowed, if stratification factors were employed, and the reporting of side effects was evaluated.

RESULTS

Twelve RCTs met inclusion criteria. Four different topical steroids were used, including betamethasone 0.1%, mometasone 0.1%, hydrocortisone 1%, and beclomethasone. Eleven studies (92%) showed that topical steroids were effective in reducing incidence or delaying occurrence of grade 2 or above RD with a relative risk of 0.69 (range, 0.19 to 0.98). In all RCTs, topical steroids were consistently used from the start of radiotherapy (RT) until completion to 3 weeks post-RT. Five RCTs (42%) provided patient education on topical steroid application. Six (50%) reported on subsequent management if moist desquamation occurred. Four studies (33%) stratified potential risk factors of RD during randomization. No studies reported any long-term side effects of topical steroids.

CONCLUSION

Topical steroids are effective in reducing the incidence of RD. However, heterogeneity was observed among the RCTs with regard to how and when the topical steroids were applied. The long-term safety profile of topical steroids is not well studied. In the context of modern radiotherapy planning techniques and increased use of hypofractionation radiation schedules, a repeat RCT addressing these methodological concerns may provide more guidance to clinicians.

Outcome and toxicities of postmastectomy radiotherapy with integral cervicothoracic thermoplastic mask

BACKGROUND

Appropriate immobilization setup for postmastectomy radiotherapy may help to improve tumor control and to reduce radiation-related toxicities. This study aims at retrospectively evaluate the outcome and toxicities of postmastectomy radiotherapy (PMRT) with a novel integral cervicothoracic thermoplastic mask strategy.

METHODS

Breast cancer patients were treated with modified radical mastectomy and PMRT. Patient immobilization setup was performed with the placement of a 1-cm thickened wax film on the ipsilateral chest wall and an integral cervicothoracic thermoplastic mask. PMRT was delivered according to the institutional protocol. Dose distribution, disease control, patient survival and radiation-induced toxicities were evaluated.

RESULTS

Four-hundred nineteen eligible patients with complete follow-up information were included in the final analysis. The median follow-up was 40.2 (95%CI: 38.9-41.6) months. Two (0.5%) patients had local recurrence and 48 (11.4%) patients had distant metastasis. There were 22 (5.3%) deaths from all causes, of which 19 were caused by breast cancer. The 3-year overall survival (OS) rate was 94.8%. ER status, PR status, triple negative status, and T stages were significantly related to patient survival (p < 0.05). HER2 expression, N stage were not significantly related to patient survival. Most common radiation-induced toxicities included grade I (87.6%) and grade II (10.2%) dermatitis, and grade I pneumonitis (28.9%) found by chest X-ray or CT scans. No clinical detectable cardiovascular event related to radiotherapy was identified.

CONCLUSION

Postmastectomy radiotherapy with integral cervicothoracic thermoplastic mask leads to favorable outcome and moderate toxicities compared with results reported in literature and might be of clinical significance in breast cancer patient. However, this approach has not been compared directly with postmastectomy radiotherapy without immobilization, and its applicability in other regions with different treatment protocols requires further investigation.

Post-mastectomy radiotherapy: Impact of bolus thickness and irradiation technique on skin dose

PURPOSE

To determine 10 MV IMRT and VMAT based protocols with a daily bolus targeting a skin dose of 45 Gy in order to replace the 6 MV tangential fields with a 5 mm thick bolus on alternate days method for post-mastectomy radiotherapy.

METHOD

We measured the mean surface dose along the chest wall PTV as a function of different bolus thicknesses for sliding window IMRT and VMAT plans. We analyzed surface dose profiles and dose homogeneities and compared them to our standard 6 MV strategy. All measurements were performed on a thorax phantom with Gafchromic films while dosimetric plans were computed using the Acuros XB algorithm (Varian).

RESULTS

We obtained the best compromise between measured surface dose (mean dose and homogeneity) and skin toxicity threshold obtained from the literature using a daily 3 mm thick bolus. Mean surface doses were 91.4 ± 2.8% [85.7% - 95.4%] and 92.2 ± 2.3% [85.6% - 95.2%] of the prescribed dose with IMRT and VMAT techniques, respectively. Our standard 6 MV alternate days 5 mm thick bolus leads to 89.0 ± 3.7% [83.6% - 95.5%]. Mean dose differences between measured and TPS results were < 3.2% for depths as low as 2 mm depth.

CONCLUSION

10 MV IMRT-based protocols with a daily 3 mm thick bolus produce a surface dose comparable to the standard 6 MV 5 mm thick bolus on alternate days method but with an improved surface dose homogeneity. This allows for a better control of skin toxicity and target volume coverage.

Impact of Radiation Therapy Modalities on Loco-regional Control in Inflammatory Breast Cancer

PURPOSE

In inflammatory breast cancer, radiation therapy intensification is considered a standard of care by some teams, although the level of evidence remains low. We sought to analyze the impact of radiation therapy modalities on the risk of loco-regional and distant relapse.

METHODS AND MATERIALS

This retrospective multicenter study included patients with localized inflammatory breast cancer treated between 2010 and 2017. Standard postmastectomy radiation therapy consisted of daily fractions to a total dose of 50 Gy equivalent without a boost or bolus, while intensified radiation therapy referred to the use of a boost or bolus. The cumulative incidence curves of locoregional and distant recurrence were displayed using the competing risk method.

RESULTS

Of the 241 included patients, 165 were treated with standard and 76 with intensified radiation therapy. There was significantly more nodal involvement in the intensified group. With a median follow-up of 40 months postradiation therapy, there was no difference between standard versus intensified radiation therapy regarding the cumulative incidence of locoregional (P = .68) or distant recurrence (P = .29). At 5 years, the risks of locoregional and distant recurrence were 12.1% (95% CI, 7.5; 17.7) and 29.4% (95% CI, 21.8; 37.3) for patients treated with standard radiation therapy and 10.4% (95% CI, 4.4; 19.3) and 21.4% (95% CI, 12.6; 31.9) for those treated with intensified radiation therapy. In multivariate analyses, triple-negative subtype and absence of complete pathologic response were associated with a higher risk of loco-regional recurrence. Radiation therapy intensification had no significant impact on locoregional and distant recurrence. For patients with a non-complete pathologic response (n = 172, 71.7%), no significant differences were observed between the 2 groups for loco-regional (P = .80) and distant (P = .39) recurrence. Severe toxicity rates were similar in both groups.

CONCLUSIONS

Contrary to other important series, this large retrospective multicentric study did not show a locoregional or distant control benefit of intensified radiation therapy. Pooled prospective studies and meta-analyses of intensified radiation therapy are warranted to endorse this approach.

A Customized 3D-Printed Bolus for High-Risk Breast Cancer with Skin Infiltration: A Pilot Study

BACKGROUND

In high-risk breast cancer patients with skin infiltration, the administration of a uniform dose to superficial tissues is fundamental in order to reduce local skin relapse. A personalized bolus may prevent the potential inadequate dose distribution of a standard bolus due to air gaps between the bolus and the skin. In this pilot study, we introduced into clinical practice the use of a personalized 3D-printed bolus filled with ultrasound transmission gel.

METHODS

Seven patients undergoing radiotherapy after mastectomy were selected. A 3D-printed bolus dosimetric assessment was performed with MOSFET dosimeters on an anthropomorphic phantom and, subsequently, on three selected cases with increasing bolus shape irregularity. Acute/late toxicity and local control were assessed.

RESULTS

Overall, for the clinical cases, the percentage median difference between the measured and calculated doses was -2.7% (-7.0-4.9%). The median follow-up was 21 months. After two years, one patient showed G2 pain, one patient manifested G1 telangiectasia, one patient showed G1 hyperpigmentation, and two patients had no relevant toxicity.

CONCLUSIONS

A personalized 3D-printed bolus filled with ultrasound gel may easily reproduce the standard bolus' consistency and provide accurate coverage of the target area with tolerable acute/late toxicity grades. This is a pilot study, and further investigations are needed.

A nationwide study of breast reconstruction after mastectomy in patients with breast cancer receiving postmastectomy radiotherapy: comparison of complications according to radiotherapy fractionation and reconstruction procedures

BACKGROUND

We examined the patterns of breast reconstruction postmastectomy in breast cancer patients undergoing postmastectomy radiotherapy (PMRT) and compared complications based on radiotherapy fractionation and reconstruction procedures.

METHODS

Using National Health Insurance Service (NHIS) data (2015-2020), we analysed 4669 breast cancer patients with PMRT and reconstruction. Using propensity matching, cohorts for hypofractionated fractionation (HF) and conventional fractionation (CF) were created, adjusting for relevant factors and identifying grade ≥3 complications.

RESULT

Of 4,669 patients, 30.6% underwent HF and 69.4% CF. The use of HF has increased from 19.4% in 2015 to 41.0% in 2020. Immediate autologous (32.9%) and delayed two-stage implant reconstruction (33.9%) were common. Complication rates for immediate (N = 1286) and delayed two-stage (N = 784) reconstruction were similar between HF and CF groups (5.1% vs. 5.4%, P = 0.803, and 10.5% vs. 10.7%, P = 0.856, respectively) with median follow-ups of 2.5 and 2.6 years. HF showed no increased risk of complications across reconstruction methods.

CONCLUSION

A nationwide cohort study revealed no significant difference in complication rates between the HF and CF groups, indicating HF for reconstructed breasts is comparable to CF. However, consultation regarding the fractionation for reconstructed breast cancer patients may still be necessary.

3D-printed boluses for radiotherapy: influence of geometrical and printing parameters on dosimetric characterization and air gap evaluation

The work investigates the implementation of personalized radiotherapy boluses by means of additive manufacturing technologies. Boluses materials that are currently used need an excessive amount of human intervention which leads to reduced repeatability in terms of dosimetry. Additive manufacturing can solve this problem by eliminating the human factor in the process of fabrication. Planar boluses with fixed geometry and personalized boluses printed starting from a computed tomography scan of a radiotherapy phantom were produced. First, a dosimetric characterization study on planar bolus designs to quantify the effects of print parameters such as infill density and geometry on the radiation beam was made. Secondly, a volumetric quantification of air gap between the bolus and the skin of the patient as well as dosimetric analyses were performed. The optimization process according to the obtained dosimetric and airgap results allowed us to find a combination of parameters to have the 3D-printed bolus performing similarly to that in conventional use. These preliminary results confirm those in the relevant literature, with 3D-printed boluses showing a dosimetric performance similar to conventional boluses with the additional advantage of being perfectly conformed to the patient geometry.

Essential requirements for reporting radiation therapy in breast cancer clinical trials: An international multi-disciplinary consensus endorsed by the European Society for Radiotherapy and Oncology (ESTRO)

The European Society for Radiotherapy and Oncology (ESTRO) has advocated the establishment of guidelines to optimise precision radiotherapy (RT) in conjunction with contemporary therapeutics for cancer care. Quality assurance in RT (QART) plays a pivotal role in influencing treatment outcomes. Clinical trials incorporating QART protocols have demonstrated improved survival rates with minimal associated toxicity. Nonetheless, in routine clinical practice, there can be variability in the indications for RT, dosage, fractionation, and treatment planning, leading to uncertainty. In pivotal trials reporting outcomes of systemic therapy for breast cancer, there is limited information available regarding RT, and the potential interaction between modern systemic therapy and RT remains largely uncharted. This article is grounded in a consensus recommendation endorsed by ESTRO, formulated by international breast cancer experts. The consensus was reached through a modified Delphi process and was presented at an international meeting convened in Florence, Italy, in June 2023. These recommendations are regarded as both optimal and essential standards, with the latter aiming to define the minimum requirements. A template for a case report form (CRF) has been devised, which can be utilised by all clinical breast cancer trials involving RT. Optimal requirements include adherence to predefined RT planning protocols and centralised QART. Essential requirements aim to reduce variations and deviations from the guidelines in RT, even when RT is not the primary focus of the trial. These recommendations underscore the significance of implementing these practices in both clinical trials and daily clinical routines to generate high-quality data.

The impact of bolus on clinical outcomes for post-mastectomy breast cancer patients treated with IMRT: data from China

PURPOSE

This study aims to investigate the effects of chest wall bolus in intensity-modulated radiotherapy (IMRT) technology on clinical outcomes for post-mastectomy breast cancer patients.

MATERIALS AND METHODS

This retrospective study included patients with invasive carcinoma ((y)pT0-4, (y)pN0-3) who received photon IMRT after mastectomy at the Affiliated Hospital of Qingdao University from 2014 to 2019. The patients were divided into two groups based on whether they received daily bolus application or not, and the baseline characteristics were matched using propensity score matching (PSM). Cumulative incidence (CI) of local recurrence (LR), locoregional recurrence (LRR), overall survival (OS) and disease-free survival (DFS) were evaluated with a log-rank test. Acute skin toxicity and late radiation pneumonia was analyzed using chi-square test.

RESULTS

A total of 529 patients were included in this study, among whom 254 (48%) patients received bolus application. The median follow-up time was 60 months. After matching, 175 well-paired patients were selected. The adjusted 5-year outcomes (95% confidence interval) in patients treated with and without bolus were, respectively: CI of LR 2.42% (0.04-4.74) versus 2.38% (0.05-4.65), CI of LRR 2.42% (0.04-4.74) versus 3.59% (0.73-6.37), DFS 88.12% (83.35-93.18) versus 84.69% (79.42-90.30), OS 94.21% (90.79-97.76) versus 95.86% (92.91-98.91). No correlation between bolus application and skin toxicity (P = 0.555) and late pneumonia (P = 0.333) was observed.

CONCLUSIONS

The study revealed a low recurrence rate using IMRT technology. The daily used 5 mm chest wall bolus was not associated with improved clinical outcomes.

Dosimetric evaluation of different planning strategies for hypofractionated whole-breast irradiation technique

Purpose.The dose hotspot areas in hypofractionated whole-breast irradiation (WBI) greatly increase the risk of acute skin toxicity because of the anatomical peculiarities of the breast. In this study, we presented several novel planning strategies that integrate multiple sub-planning target volumes (sub-PTVs), field secondary placement, and RapidPlan models for right-sided hypofractionated WBI.Methods.A total of 35 cases of WBI with a dose of 42.5 Gy for PTVs using tangential intensity-modulated radiotherapy (IMRT) were selected. Both PTVs were planned for simultaneous treatment using the original manual multiple sub-PTV plan (OMMP) and the original manual single-PTV plan (OMSP). The manual field secondary placement multiple sub-PTV plan (m-FSMP) with multiple objects on the original PTV and the manual field secondary placement single-objective plan (m-FSSP) were initially planned, which were distribution-based of V105 (volume receiving 105% of the prescription dose). In addition, two RapidPlan-based plans were developed, including the RapidPlan-based multiple sub-PTVs plan (r-FSMP) and the RapidPlan-based single-PTV plan (r-FSSP). Dosimetric parameters of the plans were compared, and V105 was evaluated using multivariate analysis to determine how it was related to the volume of PTV and the interval of lateral beam angles (ILBA).Results.The lowest mean V105 (5.64 ± 6.5%) of PTV was observed in m-FSMP compared to other manual plans. Upon validation, r-FSSP demonstrated superior dosimetric quality for OAR compared to the two other manual planning methods, except for V5(the volume of ipsilateral lung receiving 5 Gy) of the ipsilateral lung. While r-FSMP showed no significant difference (p = 0.06) compared to r-FSSP, it achieved the lowest V105 value (4.3 ± 4.5%), albeit with a slight increase in the dose to some OARs. Multivariate GEE linear regression showed that V105 is significantly correlated with target volume and ILBA.Conclusions.m-FSMP and r-FSMP can substantially enhance the homogeneity index (HI) and reduce V105, thereby minimizing the risk of acute skin toxicities, even though there may be a slight dose compromise for certain OARs.

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.

Quantify the Effect of Air Gap Errors on Skin Dose for Breast Cancer Radiotherapy

Purpose: Determining the impact of air gap errors on the skin dose in postoperative breast cancer radiotherapy under dynamic intensity-modulated radiation therapy (IMRT) techniques. Methods: This was a retrospective study that involved 55 patients who underwent postoperative radiotherapy following modified radical mastectomy. All plans employed tangential IMRT, with a prescription dose of 50 Gy, and bolus added solely to the chest wall. Simulated air gap depth errors of 2 mm, 3 mm, and 5 mm were introduced at depression or inframammary fold areas on the skin, resulting in the creation of air gaps named Air2, Air3, and Air5. Utilizing a multivariable GEE, the average dose (Dmean) of the local skin was determined to evaluate its relationship with air gap volume and the lateral beam's average angle (AALB). Additionally, an analysis was conducted on the impact of gaps on local skin. Results: When simulating an air gap depth error of 2 mm, the average Dmean in plan2 increased by 0.46 Gy compared to the initial plan (planO) (p < .001). For the 3-mm air gap, the average Dmean of plan3 was 0.51 Gy higher than that of planO (p < .001). When simulating the air gap as 5 mm, the average Dmean of plan5 significantly increased by 0.59 Gy compared to planO (p < .001). The TCP results showed a similar trend to those of Dmean. As the depth of air gap error increases, NTCP values also gradually rise. The linear regression of the multivariable GEE equation indicates that the volume of air gaps and the AALB are strong predictors of Dmean. Conclusion: With small irregular air gap errors simulated in 55 patients, the values of skin's Dmean, TCP, and NTCP increased. A multivariable linear GEE regression model may effectively explain the impact of air gap volume and AALB on the local skin.

Individualized 3D-printed bolus promotes precise postmastectomy radiotherapy in patients receiving breast reconstruction

Purpose

To evaluate the efficacy and safety of 3D-printed tissue compensations in breast cancer patients receiving breast reconstruction and postmastectomy radiotherapy (PMRT).

Methods and materials

We enrolled patients with breast cancer receiving breast reconstruction and PMRT. The dose distribution of target and skin, conformability, and dose limit of organs at risk (OARs) were collected to evaluate the efficacy of the 3D-printed bolus. Radiation Therapy Oncology Group (RTOG) radiation injury classification was used to evaluated the skin toxicities.

Results

A total of 30 patients diagnosed between October 2019 to July 2021 were included for analysis. Among all the patients, the 3D-printed bolus could ensure the dose coverage of planning target volume (PTV) [homogeneity index (HI) 0.12 (range: 0.08-0.18)], and the mean doses of D99%, D98%, D95%, D50%, D2% and Dmean were 4606.29cGy, 4797.04cGy, 4943.32cGy, 5216.07cGy, 5236.10cGy, 5440.28cGy and 5462.10cGy, respectively. The bolus demonstrated an excellent conformability, and the mean air gaps between the bolus and the chest wall in five quadrants were 0.04cm, 0.18cm, 0.04cm, 0.04cm and 0.07cm, respectively. In addition, the bolus had acceptable dosage limit of OARs [ipsilateral lung: Dmean 1198.68 cGy, V5 46.10%, V20 21.66%, V30 16.31%); heart: Dmean 395.40 cGy, V30 1.02%, V40 0.22%; spinal cord planning risk volume (PRV): Dmax 1634 cGy] and skin toxicity (grade 1, 76.0%; grade 2, 21.0%; grade 3, 3.3%).

Conclusion

The 3D-printed bolus offers advantages in terms of dose uniformity and controllable skin toxicities in patients receiving breast reconstruction and PMRT. Further research is needed to comprehensively evaluate the effectiveness of the 3Dprinted bolus in this patient subset.

Adjuvant Radiation Treatment of Breast Cancer After Mastectomy: Advanced Algorithms and Partial Bolus Improve the Dose Calculation Accuracy in the Case of Thin-Chest-Wall Irradiation

Purpose

The aim of this study was to examine measured and calculated dose distributions in a thin-chest-wall phantom and estimate the variations in the dose-volume histogram (DVH) parameters used in plan evaluation for patient geometries with chest-wall thicknesses <15 mm with and without bolus implementation.

Methods and Materials

Measurements were made using thermoluminescent dosimeters in a chest-wall phantom. The Monte Carlo method, anisotropic analytical algorithm, and Acuros XB Eclipse algorithms were used to calculate dose distributions for clinical plans. DVH parameters for clinical target volume tumor (CTVT) and planning target volume (PTV) and mean doses were evaluated for 15 patients with a chest-wall thickness of 8 to 15 mm with and without partial bolus and for 10 patients with a chest-wall thickness of 20 to 25 mm without bolus.

Results

Measurements showed that the dose at a depth of 2 to 12 mm at the beam entrance and laterally was within 90% of the dose at 8 mm depth. Monte Carlo and Acuros XB calculations were well aligned with the experimental data, whereas the anisotropic analytical algorithm underestimated the beam entrance and lateral doses. The DVH parameters for the patients with a thin chest wall were sensitive to calculation algorithm, resolution, body structure definition, and patient geometry. The parameters CTVT_V95%, CTVT_D98%, and PTV_D98% were much lower than the tolerance criteria. Partial bolus improved the values for all algorithms and decreased the variations due to patient geometry. Dose calculations for patients with a chest-wall thickness of 20 to 25 mm resulted in sufficient target coverage and low dependence on patient geometry and calculation algorithm without the use of bolus.

Conclusions

Dose calculations using advanced algorithms and resolution <2 mm are recommended for patients with a thin chest wall. Specific DVH criteria or the implementation of partial bolus was needed to facilitate plan development and evaluation for this patient group.

Effect of internal port on dose distribution in post-mastectomy radiotherapy for breast cancer patients after expander breast reconstruction

BACKGROUND

In patients with expander-based reconstruction a few dosimetric analyses detected radiation therapy dose perturbation due to the internal port of an expander, potentially leading to toxicity or loss of local control. This study aimed at adding data on this field.

MATERIALS AND METHODS

A dosimetric analysis was conducted in 30 chest wall treatment planning without and with correction for port artifact. In plans with artifact correction density was overwritten as 1 g/cm3. Medium, minimum and maximum chest wall doses were compared in the two plans. Both plans, with and without correction, were compared on an anthropomorphic phantom with a tissue expander on the chest covered by a bolus simulating the skin. Ex vivo dosimetry was carried out on the phantom and in vivo dosimetry in three patients by using film strips during one treatment fraction. Estimated doses and measured film doses were compared.

RESULTS

No significant differences emerged in the minimum, medium and maximum doses in the two plans, without and with correction for port artifacts. Ex vivo and in vivo analyses showed a good correspondence between detected and calculated doses without and with correction.

CONCLUSIONS

The port did not significantly affect dose distribution in patients who will receive post-mastectomy radiation therapy.

The transition in practice to reduce bolus use in post-mastectomy radiotherapy: A dosimetric study of skin and subcutaneous tissue

To inform clinical practice for women receiving post-mastectomy radiotherapy (PMRT), this study demonstrates the dosimetric impact of removing daily bolus on skin and subcutaneous tissue. Two planning strategies were used: clinical field-based (n = 30) and volume-based planning (n = 10). The clinical field-based plans were created with bolus and recalculated without bolus for comparison. The volume-based plans were created with bolus to ensure a minimum target coverage of the chest wall PTV and recalculated without bolus. In each scenario, the dose to superficial structures, including skin (3 mm and 5 mm) and subcutaneous tissue (a 2 mm layer, 3 mm deep from surface) were reported. Additionally, the difference in the clinically evaluated dosimetry to skin and subcutaneous tissue in volume-based plans were recalculated using Acuros (AXB) and compared to the Anisotropic Analytical Algorithm (AAA) algorithm. For all treatment planning strategies, chest wall coverage (V90%) was maintained. As expected, superficial structures demonstrate significant loss in coverage. The largest difference observed in the most superficial 3 mm where V90% coverage is reduced from a mean (± standard deviation) of 95.1% (± 2.8) to 18.9% (± 5.6) for clinical field-based treatments with and without bolus, respectively. For volume-based planning, the subcutaneous tissue maintains a V90% of 90.5% (± 7.0) compared to the clinical field-based planning coverage of 84.4% (± 8.0). In all skin and subcutaneous tissue, the AAA algorithm underestimates the volume of the 90% isodose. Removing bolus results in minimal dosimetric differences in the chest wall and significantly lower skin dose while dose to the subcutaneous tissue is maintained. Unless the skin has disease involvement, the most superficial 3 mm is not considered part of the target volume. The continued use of the AAA algorithm is supported for the PMRT setting.

The effect of antiperspirant and deodorant use on acute radiation dermatitis in breast cancer patients during radiotherapy: a systematic review and meta-analysis

PURPOSE

While some authors have investigated the impact of antiperspirant /deodorant on the development of acute radiation dermatitis (RD) among patients undergoing radiotherapy (RT) for breast cancer, recommendations supporting the use of antiperspirant/deodorant during breast RT remain highly variable. This systematic review and meta-analysis aims to evaluate the evidence investigating the effect of antiperspirant/deodorant on the development of acute RD during post-operative breast RT.

METHODS

A literature search has been performed using OVID MedLine, Embase, and Cochrane databases (1946 to September 2020) to identify randomized controlled trials (RCTs) that have investigated deodorant/antiperspirant use during RT. The meta-analysis was conducted using RevMan 5.4 to calculate pooled effect sizes and 95% confidence intervals (CI).

RESULTS

Five RCTs met the inclusion criteria. The use of antiperspirant/deodorant did not significantly affect the incidence of grade (G) 1 + RD (OR 0.81, 95% CI 0.54-1.21, p = 0.31). Prohibition of deodorant use did not significantly prevent the occurrence of G2 + acute RD (OR 0.90, 95%, CI 0.65-1.25, p = 0.53). No significant effect was reported in preventing G3 RD between the antiperspirant/deodorant and control groups (OR 0.54, 95%, CI 0.26-1.12, p = 0.10). There was no significant difference in pruritus and pain between patients undergoing skin care protocols with or without antiperspirant/deodorant (OR 0.73, 95% CI 0.29, 1.81, p = 0.50, and OR 1.05, 95% CI 0.43-2.52, p = 0.92, respectively).

CONCLUSIONS

The use of antiperspirant/deodorant during breast RT does not significantly affect the incidence of acute RD, pruritus, and pain. As such, the current evidence does not support recommendation against antiperspirant/deodorant use during RT.

Risk-Adapted Target Delineation for Breast Cancer: Controversies and Considerations

The advent of computed tomography-based planning coupled with modern tools for target delineation and hypofractionated treatment schedules has increased efficiency and throughput for patients with breast cancer. While the benefit of adjuvant radiation therapy (RT) in reducing locoregional recurrences is established, disentangling local versus regional recurrence risks with modern treatment protocols has become an area of active research to de-escalate treatment. Delineation guidelines for nodal regions either attempt to replicate results of conventional RT techniques by translating bony landmarks to clinical target volumes or use landmarks based on the fact that lymphatic channels run along the vasculature. Because direct comparisons of both approaches are implausible, mapping studies of nodal recurrences have reported on the proportion of nodes included in these delineation guidelines, and larger, bony, landmark-based guidelines appear intuitively appealing for patients with unfavorable risk factors. A pooled analysis of these studies is reported here, along with literature supporting the exclusion of the true chest wall from postmastectomy/breast-conserving surgery clinical target volumes and the selective (versus routine) use of bolus during postmastectomy RT. The risk-adapted approach suggested here accounts for the risk of recurrence as well as toxicity and endorses nuanced target volume delineation rather than a one-size-fits-all approach.

Optimising post-operative radiation therapy after oncoplastic and reconstructive procedures

Surgical techniques for breast cancer have been refined over the past decades to deliver an aesthetic outcome as close as possible to the contralateral intact breast. Current surgery further allows excellent aesthetic outcome even in case of mastectomy, by performing skin sparing or nipple sparing mastectomy in combination with breast reconstruction. In this review we discuss how to optimise post-operative radiation therapy after oncoplastic and breast reconstructive procedures, including dose, fractionation, volumes, surgical margins, and boost application.

Hypofractionated radiotherapy in postmastectomy locally advanced breast cancer: an interim report on acute toxicities and dosimetry

Background

There is a growing interest in the use of hypofractionation in the setting of post-mastectomy radiation therapy (PMRT). Here, we present an interim report on the acute toxicities and the dosimetry of a 15-day hypofractionated regimen.

Materials and methods

Patients aged 18-75 years who underwent mastectomy and had pathological stage IIB-IIIC or any clinical stage who had received neoadjuvant chemotherapy were treated with PMRT at a dose of 43.5 Gy in 15 fractions. Acute toxicities were scored using Common Terminology Criteria for Adverse Events (CTCAE) version 4.0.

Results

Between September 2020 and September 2021, 92 patients were enrolled in the study. Majority experienced grade 1 dermatitis during the course of treatment. Skin toxicities peaked two weeks after PMRT in which 57 patients (62%) had grade 2 dermatitis and 6 patients (7%) had grade 3 dermatitis. Most resolved one month after treatment, with all resolving at three months. Grade 2 fatigue occurred in 4 patients (4%). There were no grade 3 fatigue or pneumonitis of any grade. The average V95% for the chest wall, axilla, and supraclavicular fossa were 91.5%, 99.3%, and 97.5%, respectively. Average ipsilateral lung V17 was 43.6%, while the mean heart dose averaged at 3.46 Gy.

Conclusion

This interim report showed that hypofractionated PMRT is associated with a low incidence of clinically significant acute toxicities. With the use of the 3-dimensional conformal radiotherapy technique and volume-based planning, adequate target volume coverage and acceptable heart doses were achieved, although with a slightly higher ipsilateral lung dose.

Randomized clinical trial of tissue equivalent bolus prescription in postmastectomy radiotherapy stratified by skin involvement status

Purpose

To assess the impact and optimize the prescription of tissue-equivalent bolus in postmastectomy radiotherapy (PMRT), we compared the use of different bolus regimens tailored by skin involvement status.

Methods

Patients with breast cancer who required PMRT were recruited (NCT01925651) and classified into two groups: standard-risk (SR, without skin involvement) and high-risk (HR, with skin involvement). SR was randomized between no bolus or 5 mm-bolus on alternate days and HR between 5 mm-bolus on alternate days or daily. Conventional fractionation (50.4 Gy; 1.8 Gy/daily) was used. Acute skin toxicity was evaluated blindly and the radiodermatitis-specific toxicity index [rads-TI] calculated. Subsequently, patients were followed up to assess oncologic outcomes, focusing on chest wall (CW) local control.

Results

Fifty-eight patients were enrolled (34 SR and 24 HR). Baseline characteristics were similar between arms within the same risk group. Overall, maximal radiodermatitis rates were 29.4 % (G2) and 15.7 % (G3). In the SR group, no difference existed in G2 radiodermatitis incidence between the subgroups (p = 0.70) and no G3 events occurred. In the HR group, incidences of G2 (100 % vs 44.5 %, p = 0.01) and G3 radiodermatitis (70 % vs 11.1 %, p = 0.02) were higher with daily bolus. After adjusting for confounders, the daily bolus had a higher incidence of G2 (p = 0.03), G3 radiodermatitis (p = 0.04), and worse rads-TI (p < 0.01). After a median follow-up of 6.2 years, the 5-year local control was 95.8 % (95 %CI: 88.2 %-100 %) in the SR and 91.7 % (95 %CI: 77.3 %-100 %) in the HR groups. Per risk group, there was no difference in local control between the SR (p = 0.90) or the HR bolus regimens (p = 0.70).

Conclusion

Daily 5 mm bolus prescription significantly increased the overall toxicity burden. In this preliminary study, within the same risk group, no detriment in CW local control was detected with less intense bolus regimens (SR: no bolus; HR: alternate-days bolus). Additionally, the rads-TI was able to distinguish overall radiodermatitis burden.

Application of thermoplastic elastomer (TPE) bolus in postmastectomy radiotherapy

PURPOSE

To assess the planned dose, in vivo dosimetry, acute skin toxicity, pain, and distress using Thermoplastic Elastomer (TPE) bolus for postmastectomy radiotherapy (PMRT).

MATERIAL AND METHODS

Thirty-two PMRT patients with TPE bolus (17 patients for 25 fractions, 15 patients for the first 20 fractions) were selected for the study. The acute skin toxicity, pain, and psychological distress were assessed from the first treatment week to the fourth week after the end of treatment. At the first treatment, the MOSFET was used in vivo dosimetry measurement.

RESULTS

In vivo dosimetry with the bolus, the dose deviation ranged from -6.22% to -1.56% for 5 points. The presence of grade 1 and 2 skin toxicity reached its peak (70.0% and 13.3%) in the sixth week. Two patients (6.6%) with 25 fractions bolus experienced moist desquamation in the fifth and seventh week, with pain score 2 and 3, and interruptions of 3 and 5 days, respectively. The incidence of pain score 1, 2, and 3 peaked in the fifth (33.3%), fourth (33.3%), and seventh (10.0%) week. No patients experienced grade 3 skin toxicity and severe pain. One patient had significant anxiety, and two patients had significant depression.

CONCLUSION

The TPE bolus can accurately fit skin and improve the surface dose to more than 90%. Twenty fractions with TPE bolus had similar skin toxicity and pain to those without bolus and did not increase patients' distress and clinical workload, compared with the literature's data, which is an alternative to the 3D printing bolus for PMRT.

3D-printed bolus ensures the precise postmastectomy chest wall radiation therapy for breast cancer

Purpose

To investigate the values of a 3D-printed bolus ensuring the precise postmastectomy chest wall radiation therapy for breast cancer.

Methods and materials

In the preclinical study on the anthropomorphic phantom, the 3D-printed bolus was used for dosimetry and fitness evaluation. The dosimetric parameters of planning target volume (PTV) were assessed, including D_min, D_max, D_mean, D_95%, homogeneity index (HI), conformity index (CI), and organs at risk (OARs). The absolute percentage differences (|%diff|) between the theory and fact skin dose were also estimated, and the follow-up was conducted for potential skin side effects.

Results

In preclinical studies, a 3D-printed bolus can better ensure the radiation coverage of PTV (HI 0.05, CI 99.91%), the dose accuracy (|%diff| 0.99%), and skin fitness (mean air gap 1.01 mm). Of the 27 eligible patients, we evaluated the radiation dose parameter (median(min–max): D_min 4967(4789–5099) cGy, D_max 5447(5369–5589) cGy, D_mean 5236(5171–5323) cGy, D_95% 5053(4936–5156) cGy, HI 0.07 (0.06–0.17), and CI 99.94% (97.41%–100%)) and assessed the dose of OARs (ipsilateral lung: D_mean 1341(1208–1385) cGy, V₅ 48.06%(39.75%–48.97%), V₂₀ 24.55%(21.58%–26.93%), V₃₀ 18.40%(15.96%–19.16%); heart: D_mean 339(138–640) cGy, V₃₀ 1.10%(0%–6.14%), V₄₀ 0.38%(0%–4.39%); spinal cord PRV: D_max 639(389–898) cGy). The skin doses in vivo were D_theory 208.85(203.16–212.53) cGy, D_fact 209.53(204.14–214.42) cGy, and |%diff| 1.77% (0.89–2.94%). Of the 360 patients enrolled in the skin side effect follow-up study (including the above 27 patients), grade 1 was the most common toxicity (321, 89.2%), some of which progressing to grade 2 or grade 3 (32, 8.9% or 7, 1.9%); the radiotherapy interruption rate was 1.1%.

Conclusion

A 3D-printed bolus can guarantee the precise radiation dose on skin surface, good fitness to skin, and controllable acute skin toxicity, which possesses a great clinical application value in postmastectomy chest call radiation therapy for breast cancer.

Oncoplastic breast consortium recommendations for mastectomy and whole breast reconstruction in the setting of post-mastectomy radiation therapy

Aim

Demand for nipple- and skin- sparing mastectomy (NSM/SSM) with immediate breast reconstruction (BR) has increased at the same time as indications for post-mastectomy radiation therapy (PMRT) have broadened. The aim of the Oncoplastic Breast Consortium initiative was to address relevant questions arising with this clinically challenging scenario.

Methods

A large global panel of oncologic, oncoplastic and reconstructive breast surgeons, patient advocates and radiation oncologists developed recommendations for clinical practice in an iterative process based on the principles of Delphi methodology.

Results

The panel agreed that surgical technique for NSM/SSM should not be formally modified when PMRT is planned with preference for autologous over implant-based BR due to lower risk of long-term complications and support for immediate and delayed-immediate reconstructive approaches. Nevertheless, it was strongly believed that PMRT is not an absolute contraindication for implant-based or other types of BR, but no specific recommendations regarding implant positioning, use of mesh or timing were made due to absence of high-quality evidence. The panel endorsed use of patient-reported outcomes in clinical practice. It was acknowledged that the shape and size of reconstructed breasts can hinder radiotherapy planning and attention to details of PMRT techniques is important in determining aesthetic outcomes after immediate BR.

Conclusions

The panel endorsed the need for prospective, ideally randomised phase III studies and for surgical and radiation oncology teams to work together for determination of optimal sequencing and techniques for PMRT for each patient in the context of BR

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Autologous breast reconstruction is increasingly preferred over implants in the setting of radiation therapy.

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Use of patient-reported outcomes is endorsed.

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Shape and size of reconstructed breasts can hinder radiotherapy planning.

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There is a need for randomised phase III trials.

A Delphi study and International Consensus Recommendations: The use of bolus in the setting of postmastectomy radiation therapy for early breast cancer

Bolus serves as a tissue equivalent material that shifts the 95-100% isodose line towards the skin and subcutaneous tissue. The need for bolus for all breast cancer patients planned for postmastectomy radiation therapy (PMRT) has been questioned. The work was initiated by the faculty of the European SocieTy for Radiotherapy & Oncology (ESTRO) breast cancer courses and represents a multidisciplinary international breast cancer expert collaboration to optimize PMRT. Due to the lack of randomised trials evaluating the benefits of bolus, we designed a stepwise project to evaluate the existing evidence about the use of bolus in the setting of PMRT to achieve an international consensus for the indications of bolus in PMRT, based on the Delphi method.