Techniques of tumour bed boost irradiation in breast conserving therapy: current evidence and suggested guidelines

Master Breast Radiation Planning: Simple Guide for Radiation Oncology Residents

This article focuses on various aspects of breast radiation treatment planning, from simulation to field design. It covers the most common techniques including tangents, mono isocentric, dual isocentric, electron-photon match, and VMAT. This can serve as a guide for radiation oncology residents and medical students to advance their understanding of key aspects of breast radiation treatment and planning processes.

The King is in the altogether: Radiation therapy after oncoplastic breast surgery

Breast cancer is the most common malignancy, and the majority of the patients are diagnosed at an early disease stage. Breast conservation is the preferred locoregional approach, and oncoplastic breast conservation surgery is becoming more popular. This narrative review aims to discuss the challenges and uncertainties in target volume definition for postoperative radiation after these procedures, to improve radiation therapy decisions and encourage multidisciplinary.

Dosimetric benefits of 3D-printed modulated electron bolus following lumpectomy and whole-breast radiotherapy for left breast cancer

Radiotherapy with electrons is commonly applied to the tumor bed after whole-breast radiotherapy following breast conservation surgery for breast cancer patients. However, the radiation dose to adjacent organs-at-risk (OARs) and conformity of planning target volume (PTV) cannot be optimized. In this study, we examine the feasibility of using modulated electron bolus (MEB) to improve PTV conformity and reduce the dose to these OARs. Twenty-seven patients with left breast cancer were retrospectively selected in this study. For each patient, a tangential photon plan in RayStation treatment planning system with prescription of 26 Gy in 5 fractions was created as base plan. Two electron plans, one without bolus and one with MEB using Adaptiiv software based on the PTV were created. Various dosimetric parameters of OARs including left lung, heart, left anterior descending artery (LAD) and ribs and the conformity indices of PTV of these 2 electron plans together with the base plans were compared. Statistically significant decreases in the dosimetric parameters (V_5Gy, V_10Gy, V_20Gy, and mean dose) of the ipsilateral left lung and the heart were observed with MEB. The median maximum dose to the LAD and the ribs decreased by 6.2% and 4.5% respectively. The median conformity index was improved by 14.3% with median increases of monitor units by 1.7%. Our results show that MEB is feasible resulting in reduction of doses to the predefined OARs and an improved conformity of PTV. By using 3D printing, MEB might be considered as an alternative to conventional electron boost.

Comparison of different registration methods in cone-beam computed tomography for breast boost radiation therapy

Introduction:

The aim of this study is to compare patient geometrical uncertainties in the treatment of breast boost three-dimensional conformal radiation therapy (3D-CRT) considering both manual alignment and automatic different registration methods in cone-beam computed tomography (CBCT).

Methods:

A total of 85 patients were chosen for this study. A total of 254 registrations of CBCT vs planning computed tomography (CT) were retrospectively performed using automatic registration algorithms from Elekta XVI system (Clipbox and Mask) to detect patient setup uncertainties. All CBCTs were also matched manually by three health professionals. Mean shift values obtained with manual registration performed by health professionals were used as reference. Absolute value of difference between automatic algorithm shifts and reference values shifts was collected for each enrolled patient considering the three different spatial directions (x, y ,z), and the magnitude was calculated (δm for Mask and δc for Clipbox).

Results:

Data analysis showed a significant difference in δm and δc. t-Test statistics showed a high difference between Mask and Clipbox, in particular mean δm = (1.3 ± 0.1) mm and δc = (3.3 ± 1.2) mm (p-value <0.0001). Mask algorithm was performed in a very similar way with respect to the reference alignment, and the differences between these two procedures were of the order of 1 mm. Clipbox algorithm showed larger differences with manual registration.

Conclusions:

These results suggest that the Mask algorithm may be the optimal choice for patient setup verification in clinical practice for breast boost treatment in 3D-CRT.

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

Purpose

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

Material and methods

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

Results

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

Conclusions

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

Post-lumpectomy radiation therapy boost in breast cancer patients: evidence revisited

Purpose

Radiation therapy is an integral part in the management of breast cancer after breast conservative surgery. In selected patients at high risk for local recurrence (LR), a boost radiation dose is commonly applied to the tumour bed.

Methods

We performed a review of the English literature using PubMed, Medline and Google Scholar for published manuscripts addressing the effect of boost radiation in breast cancer patients, focusing mainly on LR and overall survival (OS).

Results

A total of seven studies were included in our review. Most studies (6/7, 85.7%) showed a significant improvement in local control independent of age (hazard ratios ranging between 0.34 and 0.73), with the largest absolute benefit in younger patients. None of the studies, however, was able to demonstrate an improvement in OS.

Conclusions

With lack of sufficient studies addressing the role of boost radiation, individualised treatment decisions are recommended, taking into account the risk factors for LR, including tumour biology. Real-life data are sorely needed to better assess the role of tumour bed boost in the contemporary era.

Study of Chemotherapy-Induced Cognitive Impairment in Women with Breast Cancer

Background: Oncology patients experience a large number of symptoms and, those referring to cognitive performance has an ever-increasing importance in clinical practice, due to the increase in survival rates and interest in the patient’s quality of life. The studies reviewed showed that chemotherapy-related cognitive impairment might occur in 15 and 50% of oncology patients. The main objective of this research was to study the impact of chemotherapy on the cognitive function of patients with locoregional breast cancer. Method: Analytical, prospective, longitudinal study using three measures, unifactorial intrasubject design, non-probability, and random selection sampling. The sample comprised women newly diagnosed with locoregional breast cancer in stages I, II, IIIA who received chemotherapy at the University Hospital of Salamanca (Complejo Asistencial Universitario de Salamanca), randomly selected for three years. Semi-structured interviews were conducted, and anxiety and depression (Hospital Anxiety and Depression scale, HAD); quality of life (QLQ-BR23 scale) and the following cognitive variables were assessed—processing speed, attention, memory, and executive functions (subtests of the Wechsler Intelligence Scale and the Trail Making Test). Results: The final sample size included 151 participants; 23 were excluded. A decline in cognitive performance was observed in patients, which did not completely recover two months after chemotherapy was completed. Additionally, worse cognitive performance was observed in patients with anxious or depressive symptoms. There was a negative impact on the quality of life. Conclusion: Chemotherapy had an impact on the cognitive performance of oncology patients in most cognitive domains studied.

Local Disease-Free Survival Rate (LSR) Application to Personalize Radiation Therapy Treatments in Breast Cancer Models

Cancer heterogeneity represents the main issue for defining an effective treatment in clinical practice, and the scientific community is progressively moving towards the development of more personalized therapeutic regimens. Radiotherapy (RT) remains a fundamental therapeutic treatment used for many neoplastic diseases, including breast cancer (BC), where high variability at the clinical and molecular level is known. The aim of this work is to apply the generalized linear quadratic (LQ) model to customize the radiant treatment plan for BC, by extracting some characteristic parameters of intrinsic radiosensitivity that are not generic, but may be exclusive for each cell type. We tested the validity of the generalized LQ model and analyzed the local disease-free survival rate (LSR) for breast RT treatment by using four BC cell cultures (both primary and immortalized), irradiated with clinical X-ray beams. BC cells were chosen on the basis of their receptor profiles, in order to simulate a differential response to RT between triple negative breast and luminal adenocarcinomas. The MCF10A breast epithelial cell line was utilized as a healthy control. We show that an RT plan setup based only on α and β values could be limiting and misleading. Indeed, two other parameters, the doubling time and the clonogens number, are important to finely predict the tumor response to treatment. Our findings could be tested at a preclinical level to confirm their application as a variant of the classical LQ model, to create a more personalized approach for RT planning.

Adaptive radiation therapy of breast cancer by repeated imaging during irradiation

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

Characterization of irregular electron beam for boost dose after whole breast irradiation

Irradiating a tumor bed with boost dose after whole breast irradiation helps reducing the probability of local recurrence. However, the success of electron beam treatment with a small area aiming to cover a superficial lesion is a dual challenge as it requires an adequate dosimetry beside a double check for dose coverage with an estimation of various combined uncertainty of tumor location and losing lateral electron equilibrium within small field dimensions.

Aim of work

this work aims to measure the electron beam fluence within different field dimensions and the deviation from measurement performed in standard square electron applicator beam flatness and symmetry, then to calculate the average range of the correction factor required to overcome the loss of lateral electron equilibrium.

Material and method

the electron beam used in this work generated from the linear accelerator model ELEKTA Precise and dosimetry system used were a pair of PTW Pin Point ion chambers for electron beam dosimetry at standard conditions and assessment of beam quality at a reference depth of measurement, with an automatic water phantom, then a Roos ion chamber was used for absolute dose measurement, and PTW 2Darray to investigate the beam fluence of four applicators 6, 10, 14 and 20 cm² and 4 rectangular cutouts 6 × 14, 8 × 14, 6 × 17 and 8 × 17 cm², the second part was clinical application which was performed in a precise treatment planning system and examined boost dose after whole breast irradiation.

Results

revealed that lower energy (6MeV and 8MeV) showed the loss of lateral electron equilibrium and deviation from measurements of a standard applicator more than the high energy (15 MeV) which indicated that the treatment of superficial dose with 6MeV required higher monitor unit to allow for the loss of lateral electron equilibrium and higher margin as well.

Comparing Breast Conservation Surgery Seromas Contoured by Radiation Therapists versus those Contoured by a Radiation Oncologist in Radiation Therapy Planning for Early-Stage Breast Cancer

INTRODUCTION

In the management of early-stage breast cancer using radiation therapy, computed tomography (CT) simulation is used to identify the breast conservation surgery (BCS) seroma as a proxy for the tumour bed. The delineation or contouring of the seroma is generally a task performed by a radiation oncologist (RO). With increasing patient numbers and other demands placed on ROs, the scope of practice for radiation therapists (RTs) is continually expanding, and the need for skills transfer from one profession to another has been investigated in recent years. This study aims to compare the BCS seroma volumes contoured by RTs with those contoured by ROs to add evidence in support of expanding the RTs' role in the treatment planning process in the management of early-stage breast cancer.

METHODS

A study was undertaken using the CT-simulation (CT-sim) data sets of patients with early-stage breast cancer treated in 2013. The CT-sim data sets had BCS seromas contoured by 1 of 5 ROs as part of routine clinical management. This study involved 4 RTs who each used the patient information to identify and contour breast seromas on 50 deidentified CT-sim data sets. Metrics used to compare RT versus RO contours included volume size, overlap between volumes, and geographical distance from the centre of volumes.

RESULTS

There were 50 CT-sim data sets with 1 RO contour and 4 RT contours analysed. The contour volumes of the 4 RTs and the ROs were assessed. Although there were 50 CT-sim data sets presented to each RT, analysis was carried out on 45, 43, 46, and 45 CT-sim data sets. There were no comparisons made where contours were not delineated. The contour volumes of the 4 RTs and the ROs were assessed with an interclass correlation coefficient, with a result of excellent reliability (0.975, 95% [0.963, 0.985]). The DICE similarity coefficient was used to compare the overlap of each RT contour with the RO contour; the results were favourable with mean (95% CI) DSCs 0.685, 0.640, 0.678, and 0.681, respectively. Comparing the RT and RO geographical centre of the seroma volumes, good to excellent reliability between the RTs and ROs was demonstrated (95% CI mean RO vs RT distances (mm): 3.75, 4.99, 7.71, and 3.39). There was no statistically significant difference between the distances (P = 0.65).

CONCLUSION

BCS seromas contoured by RTs compared well with those contoured by an RO. This research has provided further evidence to support RTs in assuming additional contouring responsibilities in radiation therapy planning for patients with early-stage breast cancer.

Dosimetric analysis of breast cancer tumor bed boost: An interstitial brachytherapy vs. external beam radiation therapy comparison for deeply seated tumors

PURPOSE

To dosimetrically compare interstitial brachytherapy (MIBT) vs. EBRT (3DCRT and high-energy electron beams) for deep-seated tumor bed boosts (depth ≥4 cm) in early-stage breast cancer.

METHODS AND MATERIALS

Planning CTs of fifteen left-side breast cancer patients previously treated with MIBT boost chosen for this study. MIBT, 3DCRT (three-field technique), and enface high-energy electron (15-18 MeV) plans retrospectively generated on these images. To minimize intrapatient target contour inconsistency, due to a technical limitation for transferring identical contours from brachytherapy to EBRT planning system, spherical volumes delineated as hypothetical CTVs (CTV-H) (depth ≥4 cm with considering the geometry of the brachytherapy implant) instead of original lumpectomy cavities (which had irregular contours). In EBRT, PTV-H=CTV-H+5 mm. To account for beam penumbra, additional PTV-H to beam-edge margins added (3DCRT = 5 mm; electron = 10 mm). Included organs at risk (OARs) were ipsilateral breast, skin, ribs, lung, and heart. Prescribed dose-fractionations were 12 Gy/3fractions (MIBT) and 16 Gy/8fractions (EBRT) (BED = 24 Gy, breast cancer Alpha/Beta = 4 Gy). Biologically equivalent DVH parameters for all techniques compared.

RESULTS

Mean CTV-H depth was 6 cm. Normal breast V_25%-V_100%; skin V_10%-V_90%; rib V_25%-V_75%; lung V_5%-V_25%; heart V_10%; mean lung dose; ribs/lung D_max were lower in MIBT vs. 3CDRT. MIBT reduced breast V_25%-V_125%; skin V_25%-V_125%; rib V_25%-V_75% and V_100%; lung V_25%-V_90%; heart V_10%-V_50%; skin/ribs/lung D_max compared to electrons. In contrast, breast V_125%-V_250% and V_175%-V_250% were increased in MIBT vs. 3DCRT and electron plans, respectively. Electron plans had the minimum mean heart dose.

CONCLUSIONS

From a dosimetric point of view, in deeply-seated lumpectomy beds, MIBT boost better protects OARs from exposure to medium and high doses of radiation compared to 3DCRT and high energy electron beams (except more ipsilateral breast hot spots).

Investigation of electron boost radiotherapy in patients with breast cancer: Is a direct electron field optimal?

PURPOSE

Historically, electron boost dose mainly was delivered by a direct field in adjuvant radiotherapy of breast cancer. In this prospective study, we investigated direct electron field, in terms of optimal coverage of tumour bed volume following localization using ultrasound and surgical clips.

MATERIAL AND METHODS

First, for all 24 patients, a breast sonographer drew perimeter of tumour bed on the breast skin. Then an electron boost field was outlined on the demarcated territory, and a lead wire marker compatible with CT scan was placed on the field borders by a 2cm margin. After CT scan simulation, all patients underwent adjuvant whole breast irradiation with 3D-conformal radiotherapy to 50Gy in 25 fractions. Then for boost radiotherapy, lead wire in CT images was countoured as electron boost field. Also, the tumour bed was contoured based on surgical clips (true clinical target volume and true planning target volume). Electron treatment planning was done for electron boost field. Finally isodose coverages for true planning target volume investigated.

RESULTS

On average, 16.68% of clips planning target volume (true planning target volume; range: 0.00 to 95%) received 90% oor more of the prescribed dose when the electron treatment plan was made. Isodose curves does not provide adequate coverage on the tumour bed (clips planning target volume) when electron boost treatment planning was generated for electron boost field (en face electron field). In fact, a part of target (planning target volume-c) is missed and more doses is absorbed in normal tissue.

CONCLUSIONS

Electron boost treatment planning (an en face electron field) following tumour bed localization using ultrasonography does not provide an optimized coverage of tumour bed volume.

Effects of online cone-beam computed tomography with active breath control in determining planning target volume during accelerated partial breast irradiation

PURPOSE

To test if active breath control during cone-beam computed tomography (CBCT) could improve planning target volume during accelerated partial breast radiotherapy for breast cancer.

METHODS

Patients who were more than 40 years old, underwent breast-conserving dissection and planned for accelerated partial breast irradiation, and with postoperative staging limited to T1-2 N0 M0, or postoperative staging T2 lesion no larger than 3cm with a negative surgical margin greater than 2mm were enrolled. Patients with lobular carcinoma or extensive ductal carcinoma in situ were excluded. CBCT images were obtained pre-correction, post-correction and post-treatment. Set-up errors were recorded at left-right, anterior-posterior and superior-inferior directions. The differences between these CBCT images, as well as calculated radiation doses, were compared between patients with active breath control or free breathing.

RESULTS

Forty patients were enrolled, among them 25 had active breath control. A total of 836 CBCT images were obtained for analysis. CBCT significantly reduced planning target volume. However, active breath control did not show significant benefit in decreasing planning target volume margin and the doses of organ-at-risk when compared to free breathing.

CONCLUSION

CBCT, but not active breath control, could reduce planning target volume during accelerated partial breast irradiation.

Whole breast and excision cavity radiotherapy plan comparison: Conformal radiotherapy with sequential boost versus intensity-modulated radiation therapy with a simultaneously integrated boost

Introduction

A comparative study was conducted comparing the difference between (1) conformal radiotherapy (CRT) to the whole breast with sequential boost excision cavity plans and (2) intensity-modulated radiation therapy (IMRT) to the whole breast with simultaneously integrated boost to the excision cavity. The computed tomography (CT) data sets of 25 breast cancer patients were used and the results analysed to determine if either planning method produced superior plans.

Methods

CT data sets from 25 past breast cancer patients were planned using (1) CRT prescribed to 50 Gy in 25 fractions (Fx) to the whole-breast planning target volume (PTV) and 10 Gy in 5Fx to the excision cavity and (2) IMRT prescribed to 60 Gy in 25Fx, with 60 Gy delivered to the excision cavity PTV and 50 Gy delivered to the whole-breast PTV, treated simultaneously. In total, 50 plans were created, with each plan evaluated by PTV coverage using conformity indices, plan maximum dose, lung dose, and heart maximum dose for patients with left-side lesions.

Results

CRT plans delivered the lowest plan maximum doses in 56% of cases (average CRT = 6314.34 cGy, IMRT = 6371.52 cGy). They also delivered the lowest mean lung dose in 68% of cases (average CRT = 1206.64 cGy, IMRT = 1288.37 cGy) and V20 in 88% of cases (average CRT = 20.03%, IMRT = 21.73%) and V30 doses in 92% of cases (average CRT = 16.82%, IMRT = 17.97%). IMRT created more conformal plans, using both conformity index and conformation number, in every instance, and lower heart maximum doses in 78.6% of cases (average CRT = 5295.26 cGy, IMRT = 5209.87 cGy).

Conclusion

IMRT plans produced superior dose conformity and shorter treatment duration, but a slightly higher planning maximum and increased lung doses. IMRT plans are also faster to treat on a daily basis, with shorter fractionation.

Adjuvant radiotherapy in the management of axillary node negative invasive breast cancer: a qualitative systematic review

PURPOSE

To actualize and to detail guidelines used in technical radiotherapy and indications for innovative radiation technologies in early axillary node negative breast cancer (BC).

METHODS

Dosimetric and treatment planning studies, phase II and III trials, systematic reviews and retrospective studies were all searched (Medline(®) database). Their quality and clinical relevance were also checked against validated checklists. A level of evidence was associated for each result.

RESULTS

A total of 75 references were included. Adjuvant BC radiotherapy (50Gy/25 fractions/5 weeks followed by a tumor boost of 16Gy/8 fractions) is still the standard of care. Overall treatment time could be shortened for patients who present with low local relapse risk BC by using either hypofractionated whole breast irradiation; or accelerated partial breast irradiation. BC IMRT is not used in current practice.

CONCLUSION

Our group aimed to provide guidelines for technical and clinical applications of innovative BC radiation technologies.

Can ‘boost’ be avoided in pre-invasive and early breast cancer with free surgical margins after breast conservation surgery and irradiation?

Guidelines concerning early stage breast cancer do not clearly recommend tumour bed boost dose after breast conserving surgery and irradiation when the resection margins are negative. Because the number of these patients is expected to increase, we evaluated the results of our treatment scheme in which the additional tumour bed dose was omitted. One hundred consecutive individuals with ductal carcinoma in-situ or stage I or II cancer of the breast were identified for this retrospective analysis. The observed ipsilateral breast tumour recurrence and 10-year disease-free survival rates were 4% and 91% respectively. Univariate analysis indicated that triple receptor negative tumour is the most independent prognostic risk factor. In conclusion, the observed low rate of local recurrence and many long-term survivors in this study seem to legitimize the omission of the tumour bed boost dose after whole breast irradiation in women with early carcinoma of the breast and free breast conserving surgical margins.

Current technological clinical practice in breast radiotherapy; results of a survey in EORTC-Radiation Oncology Group affiliated institutions

PURPOSE

To evaluate the current technological clinical practice of radiation therapy of the breast in institutions participating in the EORTC-Radiation Oncology Group (EORTC-ROG).

MATERIALS AND METHODS

A survey was conducted between August 2008 and January 2009 on behalf of the Breast Working Party within the EORTC-ROG. The questionnaire comprised 32 questions on 4 main topics: fractionation schedules, treatment planning methods, volume definitions and position verification procedures.

RESULTS

Sixty-eight institutions out of 16 countries responded (a response rate of 47%). The standard fraction dose was generally 2Gy for both breast and boost treatment, although a 2.67 Gy boost fraction dose is routinely given in British institutions. The main boost modality was electrons in 55%, photons in 47% and brachytherapy in 3% of the institutions (equal use of photon and electron irradiation in 5% of the institutions). All institutions used CT-based treatment planning. Wide variations are seen in the definition of the breast and boost target volumes, with margins around the resection cavity, ranging from 0 to 30 mm. Inverse planned IMRT is available in 27% and breath-hold techniques in 19% of the institutions. The number of patients treated with IMRT and breath-hold varied per institution. Electronic portal imaging for patient set-up is used by 92% of the institutions.

CONCLUSIONS

This survey provides insight in the current practice of radiation technology used in the treatment of breast cancer among institutions participating in EORTC-ROG clinical trials.