Contouring Guidelines for the Axillary Lymph Nodes for the Delivery of Radiation Therapy in Breast Cancer: Evaluation of the RTOG Breast Cancer Atlas

Prediction of the axillary lymph-node metastatic burden of breast cancer by 18F-FDG PET/CT-based radiomics

BACKGROUND

The axillary lymph-node metastatic burden is closely associated with treatment decisions and prognosis in breast cancer patients. This study aimed to explore the value of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT)-based radiomics in combination with ultrasound and clinical pathological features for predicting axillary lymph-node metastatic burden in breast cancer.

METHODS

A retrospective analysis was conducted and involved 124 patients with pathologically confirmed early-stage breast cancer who had undergone 18F-FDG PET/CT examination. The ultrasound, PET/CT, and clinical pathological features of all patients were analysed, and radiomic features from PET images were extracted to establish a multi-parameter predictive model.

RESULTS

The ultrasound lymph-node positivity rate and PET lymph-node positivity rate in the high nodal burden group were significantly higher than those in the low nodal burden group (χ2 = 19.867, p < 0.001; χ2 = 33.025, p < 0.001). There was a statistically significant difference in the PET-based radiomics score (RS) for predicting axillary lymph-node burden between the high and low lymph-node burden groups. (-1.04 ± 0.41 vs. -1.47 ± 0.41, t = -4.775, p < 0.001). The ultrasound lymph-node positivity (US_LNM) (odds ratio [OR] = 3.264, 95% confidence interval [CI] = 1.022-10.423), PET lymph-node positivity (PET_LNM) (OR = 14.242, 95% CI = 2.960-68.524), and RS (OR = 5.244, 95% CI = 3.16-20.896) are all independent factors associated with high lymph-node burden (p < 0.05). The area under the curve (AUC) of the multi-parameter (MultiP) model was 0.895, which was superior to those of US_LNM, PET_LNM, and RS models (AUC = 0.703, 0.814, 0.773, respectively), with statistically significant differences (Z = 2.888, 3.208, 3.804, respectively; p = 0.004, 0.002, < 0.001, respectively). Decision curve analysis indicated that the MultiP model provided a higher net benefit for all patients.

CONCLUSION

A MultiP model based on PET-based radiomics was able to effectively predict axillary lymph-node metastatic burden in breast cancer.

TRIAL REGISTRATION

This study was registered with ClinicalTrials.gov (registration number: NCT05826197) on May 7, 2023.

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.

Comparing breath hold versus free breathing irradiation for left-sided breast radiotherapy by PlanIQ™

BACKGROUND

Breast cancer is the most widespread cancer in women and young women worldwide. Moving towards customised radiotherapy, balancing the use of the available technology with the best treatment modality may not be an easy task in the daily routine. This study aims to evaluate the effectiveness of introducing IQ-feasibility into clinical practice to support the decision of free-breathing (FB) versus breath-hold (BH) left-sided breast irradiations, in order to optimise the technology available and the effectiveness of the treatment.

METHODS

Thirty-five patients who received 3D radiotherapy treatment of the left breast in deep-inspiration BH were included in this retrospective study. Computed tomography scans in FB and BH were acquired for each patient; targets contoured in both imaging datasets by an experienced radiation oncologist, and organs at risk delineated using automatic segmentation software were exported to PlanIQ™ (Sun Nuclear Corp.) to generate feasibility dose volume histogram (FDVHs). The dosimetric parameter of BH versus FB FDVH, and BH clinical dataset versus BH FDVH were compared.

RESULTS

A total of 30 patients out of 35 patients analysed, presented for the BH treatments a significant reduction (p < 0.05) in the heart mean dose ([Formula: see text]), volume receiving 5 Gy ([Formula: see text]) and 20 Gy ([Formula: see text]), of 35.7%, 54.5%, and 2.1%, respectively; for the left lung, a lower reduction was registered and significant only for [Formula: see text] (21.4%, p = 0.046). For the remaining five patients, the FDVH cut-off points of heart and lung were superimposable with differences of less than 1%. Heart and left lung dosimetric parameters of the BH clinical plans are located in the difficult zone of the FDVH and differ significantly (p < 0.05) from the corresponding parameters of the FDVH curves delimiting this buffer area between the impossible and feasible zones, respectively.

CONCLUSION

The use of PlanIQTM as a decision-support tool for the FB versus BH treatment delivery modality allows customisation of the treatment technique using the most appropriate technology for each patient enabling accurate management of available technologies.

Comparison of helical and TomoDirect techniques with simultaneous integrated boost in early breast cancer patients

Background

The aim of the study was to perform dosimetric comparisons of helical (H) and TomoDirect (TD) plans for whole-breast irradiation (WBI) with simultaneous integrated boost (SIB) in early-stage breast cancer patients undergoing breast conserving surgery.

Materials and methods

Fifty patients, 25 with left-side and 25 with right-side tumors, were determined for a treatment planning system for a total dose of 50.4Gy in 1.8Gy per fraction to WBI, with a SIB of 2.3Gy per fraction delivered to the tumor bed. The planning target volume (PTV) doses and the conformity (CI) and homogeneity indices (HI) for PTVbreast and PTVboost, as well as organ-at-risk (OAR) doses and treatment times, were compared between the H and TD plans.

Results

All plans met the PTV coverage criteria for the H plan, except for mean V107 of PTVbreast for TD plan. The H plan yielded better homogeneity and conformity of dose distribution compared to the TD plan. The ipsilateral mean lung doses were not significantly different between the two plans. The TD plans is advantageous for mean doses to the heart, contralateral breast and lung, spinal cord, and esophagus than the H plans. In both the H and TD plans, the right-sided breast patients had lower heart dose parameters than the left-sided breast patients. The TD plan is superior to the H plan in sparing the contralateral breast and lung by decreasing low-dose volumes.

Conclusions

While the OAR dose advantages of TD are appealing, shorter treatment times or improved dose homogeneity and conformity for target volume may be advantageous for H plan.

Dosimetric Comparison of Hypofractionated Regimen in Breast Cancer Using Two Different Techniques: Intensity-Modulated Radiation Therapy (IMRT) and Volumetric-Modulated Arc Therapy (VMAT)

INTRODUCTION

Breast cancer treated with adjuvant hypofractionation radiotherapy with two different techniques, i.e., volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) and their effects in terms of loco-regional control and adverse effects in terms of cutaneous, pulmonary, and cardiac outcomes are compared.

MATERIALS AND METHODS

This is a prospective non-randomized observational study. VMAT and IMRT plan for 30 breast cancer patients who were supposed to receive adjuvant radiotherapy were prepared using a hypofractionation schedule. The plans were dosimetrically evaluated.

OBJECTIVE

Dosimetric comparative analysis of IMRT and VMAT in hypofractionated radiotherapy in breast cancer is done and tested whether VMAT has a dosimetric advantage over IMRT. These patients were recruited for a clinical assessment of toxicities. They were followed up for at least three months.

RESULT

On dosimetric analysis, planning target volume (PTV) coverage (PTV_ V95) of both VMAT (96.41 ± 1.31) and IMRT (96.63 ± 1.56) were similar with significantly lower monitor units required with VMAT plans (1,084.36 ± 270.82 vs 1,181.55 ± 244.50, p = 0.043). Clinically, all patients tolerated hypofractionation through VMAT (n = 8) and IMRT (n = 8) satisfactorily in the short term. No cardiotoxicity or appreciable falls in pulmonary function test parameters were observed. Acute radiation dermatitis poses challenges similar to standard fractionation or any other delivery technique.

CONCLUSION

PVT dose, homogeneity, and conformity indices were similar in both VMAT and IMRT groups. In VMAT, there was high-dose sparing of some critical organs like the heart and lungs at the cost of the low-dose baths to these organs. Increased risk of secondary cancer will require a decade-long follow-up study to indict the VMAT technique. As we move toward precision in oncology, "one-size-fits-all" can never be an acceptable dictum. Each patient is unique and therefore we must offer, and the patient must "choose wisely."

Deep learning empowered volume delineation of whole-body organs-at-risk for accelerated radiotherapy

In radiotherapy for cancer patients, an indispensable process is to delineate organs-at-risk (OARs) and tumors. However, it is the most time-consuming step as manual delineation is always required from radiation oncologists. Herein, we propose a lightweight deep learning framework for radiotherapy treatment planning (RTP), named RTP-Net, to promote an automatic, rapid, and precise initialization of whole-body OARs and tumors. Briefly, the framework implements a cascade coarse-to-fine segmentation, with adaptive module for both small and large organs, and attention mechanisms for organs and boundaries. Our experiments show three merits: 1) Extensively evaluates on 67 delineation tasks on a large-scale dataset of 28,581 cases; 2) Demonstrates comparable or superior accuracy with an average Dice of 0.95; 3) Achieves near real-time delineation in most tasks with <2 s. This framework could be utilized to accelerate the contouring process in the All-in-One radiotherapy scheme, and thus greatly shorten the turnaround time of patients.

Mapping of PET/CT-based regional nodes distribution of recurrent/advanced breast cancer and comparison with current delineation atlas

OBJECTIVE

To localize the distribution of regional nodes in recurrent/advanced breast cancer patients based on 18-fludeoxyglucose (FDG) positron emission tomography/CT (PET/CT) images and validate the coverage of clinical target volumes (CTVs) for regional nodes with current contouring guidelines.

METHODS

We enrolled 154 recurrent/advanced breast cancer patients with FDG-avid regional nodes who underwent PET/CT between January 2018 and June 2020. Involvement of lymph node regions including axillary lymph node level I-III (ALN-I, ALN-II, ALN-III), Rotter's nodes (RN), medial supraclavicular (SC-M), lateral supraclavicular (SC-L) and internal mammary nodes (IMN) was recorded respectively. Coverage of the CTVs in different atlases and the locations of out-of-field were evaluated.

RESULTS

A total of 348 lymph node regions containing disease were identified, including ALN-I 109, ALN-II 46, ALN-III 36, RN 17, SC-M 68, SC-L 36 and IMN 36. Recurrent ALNs mainly located cranially and ventrally to the axillary vein (AV). Ipsilateral cervical nodes were simultaneously affected in 33/76 SC positive patients. RADCOMP (306/348) and RUIJIN (291/348) guidelines had higher coverage compared with RTOG (205/348) and ESTRO (202/348) guidelines (p < 0.001, respectively). In primary non-metastastic and recurrent patients, major missings located in SC-L (7/7, 17/17) and IMN (7/10, 15/19) for RTOG guideline while SC-L (7/7, 17/17) for ESTRO guideline (p < 0.001, respectively). Among recurrent patients, SC-M (22/31) was another major missing area for ESTRO guideline (p < 0.001).

CONCLUSION

The current guidelines effectively cover most regional nodes in postoperative breast cancer patients. SC-L and IMN were the major missing regions. Recurrent ALNs were most often seen in cranial and ventral to the AV. The CTV of patients with clinically positive SC was recommended to extend up to the hyoid level. The CTVs should be adjusted based on risks of recurrence individually.

ADVANCES IN KNOWLEDGE

The difference of regional nodes delineation between current guidelines mainly located in SC and IMN regions. High axilla including subclavicular nodes and the RN above AV for recurrent patients and the region between cricoid and hyoid for positive SC patients should be meticulously contoured.

Radiation Oncology: Future Vision for Quality Assurance and Data Management in Clinical Trials and Translational Science

The future of radiation oncology is exceptionally strong as we are increasingly involved in nearly all oncology disease sites due to extraordinary advances in radiation oncology treatment management platforms and improvements in treatment execution. Due to our technology and consistent accuracy, compressed radiation oncology treatment strategies are becoming more commonplace secondary to our ability to successfully treat tumor targets with increased normal tissue avoidance. In many disease sites including the central nervous system, pulmonary parenchyma, liver, and other areas, our service is redefining the standards of care. Targeting of disease has improved due to advances in tumor imaging and application of integrated imaging datasets into sophisticated planning systems which can optimize volume driven plans created by talented personnel. Treatment times have significantly decreased due to volume driven arc therapy and positioning is secured by real time imaging and optical tracking. Normal tissue exclusion has permitted compressed treatment schedules making treatment more convenient for the patient. These changes require additional study to further optimize care. Because data exchange worldwide have evolved through digital platforms and prisms, images and radiation datasets worldwide can be shared/reviewed on a same day basis using established de-identification and anonymization methods. Data storage post-trial completion can co-exist with digital pathomic and radiomic information in a single database coupled with patient specific outcome information and serve to move our translational science forward with nimble query elements and artificial intelligence to ask better questions of the data we collect and collate. This will be important moving forward to validate our process improvements at an enterprise level and support our science. We have to be thorough and complete in our data acquisition processes, however if we remain disciplined in our data management plan, our field can grow further and become more successful generating new standards of care from validated datasets.

Incidental irradiation of the regional lymph nodes during deep inspiration breath-hold radiation therapy in left-sided breast cancer patients: a dosimetric analysis

Background

Radiotherapy using the deep inspiration breath-hold (DIBH) technique compared with free breathing (FB) can achieve substantial reduction of heart and lung doses in left-sided breast cancer cases. The anatomical organ movement in deep inspiration also cause unintended exposure of locoregional lymph nodes to the irradiation field.

Methods

From 2017–2020, 148 patients with left-sided breast cancer underwent breast conserving surgery (BCS) or mastectomy (ME) with axillary lymph node staging, followed by adjuvant irradiation in DIBH technique. Neoadjuvant or adjuvant systemic therapy was administered depending on hormone receptor and HER2-status.

CT scans in FB and DIBH position with individual coaching and determination of the breathing amplitude during the radiation planning CT were performed for all patients. Intrafractional 3D position monitoring of the patient surface in deep inspiration and gating was performed using Sentinel and Catalyst HD 3D surface scanning systems (C-RAD, Catalyst, C-RAD AB, Uppsala, Sweden). Three-dimensional treatment planning was performed using standard tangential treatment portals (6 or 18 MV). The delineation of ipsilateral locoregional lymph nodes was done on the FB and the DIBH CT-scan according to the RTOG recommendations.

Results

The mean doses (D_mean) in axillary lymph node (AL) level I, II and III in DIBH were 32.28 Gy (range 2.87–51.7), 20.1 Gy (range 0.44–53.84) and 3.84 Gy (range 0.25–39.23) vs. 34.93 Gy (range 10.52–50.40), 16.40 Gy (range 0.38–52.40) and 3.06 Gy (range 0.21–40.48) in FB (p < 0.0001). Accordingly, in DIBH the D_mean for AL level I were reduced by 7.59%, whereas for AL level II and III increased by 22.56% and 25.49%, respectively.

The D_mean for the supraclavicular lymph nodes (SC) in DIBH was 0.82 Gy (range 0.23–4.11), as compared to 0.84 Gy (range 0.22–10.80) with FB (p = 0.002). This results in a mean dose reduction of 2.38% in DIBH.

The D_mean for internal mammary lymph nodes (IM) was 12.77 Gy (range 1.45–39.09) in DIBH vs. 11.17 Gy (range 1.34–44.24) in FB (p = 0.005). This yields a mean dose increase of 14.32% in DIBH.

Conclusions

The DIBH technique may result in changes in the incidental dose exposure of regional lymph node areas.

Breast Cancer, Version 3.2022, NCCN Clinical Practice Guidelines in Oncology

The therapeutic options for patients with noninvasive or invasive breast cancer are complex and varied. These NCCN Clinical Practice Guidelines for Breast Cancer include recommendations for clinical management of patients with carcinoma in situ, invasive breast cancer, Paget disease, phyllodes tumor, inflammatory breast cancer, and management of breast cancer during pregnancy. The content featured in this issue focuses on the recommendations for overall management of ductal carcinoma in situ and the workup and locoregional management of early stage invasive breast cancer. For the full version of the NCCN Guidelines for Breast Cancer, visit NCCN.org.

Evaluation of clinically involved lymph nodes with deformable registration in breast cancer radiotherapy

OBJECTIVES

Modern radiotherapy (RT) techniques require careful delineation of the target. There is no particular RT contouring guideline for patients receiving neoadjuvant chemotherapy (NACT). In this study, we examined the distribution of pre-chemotherapy clinically positive nodal metastases.

METHODS

We explored the coverage rate of the RTOG breast contouring guideline by deformable fusion of 18-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) scan. We retrospectively evaluated neoadjuvant chemotherapy patients. All PET-CT images were imported into the planning software. We combined the planning CT and the CT images of PET-CT with rigid and then a deformable registration. We manually contoured positive lymph nodes on the CT component of the PET-CT data set and transferred them to planning CT after fusion. We evaluated whether previously contoured lymphatic CTVs, according to the RTOG breast atlas, include GTV-LNs.

RESULTS

All breast cancer patients between October 2018 and February 2021 were evaluated from the electronic database. There were 142 radiologically defined positive lymph nodes in 31 patients who were irradiated after NACT. Most LNs (70%) were in the level I axilla. Only 71.1% (n:101) of the whole lymph nodes in 10 patients were totally covered, 22.5% (n:32) partially covered and 6.4% %(n:9) totally undercovered.

CONCLUSIONS

The extent of regional nodal areas in the RTOG atlas may be insufficient to cover positive lymph nodes adequately. For patients with nodal involvement undergoing neoadjuvant chemotherapy, PET-CT image fusions can be helpful to be sure that positive lymph nodes are in the treatment volume.

ADVANCES IN KNOWLEDGE

RTOG contouring atlas may be insufficient to cover all involved lymph nodes after NACT. For patients with nodal involvement undergoing neoadjuvant chemotherapy, PET-CT image fusions may help to be sure that positive lymph nodes are in the treatment volume.

Mapping of Level I Axillary Lymph Nodes in Patients with Newly Diagnosed Breast Cancer: Optimal Target Delineation and Treatment Techniques for Breast and Level I Axilla irradiation

PURPOSE

To map the locations of level I axilla (Ax-L1) lymph nodes (LNs), evaluate the clinical target volume (CTV) coverage defined by the Radiation Therapy Oncology Group (RTOG) breast cancer atlas, and assess the optimal techniques for whole-breast and Ax-L1 irradiation (WBI + Ax-L1).

MATERIALS AND METHODS

We identified 76 newly diagnosed breast cancer patients with 1-4 positive LNs confirmed by axillary dissection. The locations of 116 involved Ax-L1 LNs on diagnostic computed tomography (CT) were mapped onto simulated CT images of a standard patient. Ax-L1 LN coverage by the RTOG atlas was evaluated, and a modified Ax-L1 CTV with better coverage was proposed. Treatment plans were designed for WBI + Ax-L1 with high tangential simplified intensity-modulated radiation therapy (HT-sIMRT) and volumetric modulated arc therapy (VMAT), and for WBI + RTOG Ax-L1 with VMAT with a prescription dose of 50 Gy in 25 fractions, respectively. The differences in dosimetric parameters were compared.

RESULTS

The RTOG atlas missed 29.3% of LNs. Modification by extending 1 cm caudal and 0.5 cm anterior to the RTOG-defined CTV borders allowed the modified Ax-L1 CTV to encompass 90.5% of LNs. All plans met the required prescription dose to WBI and Ax-L1. The mean dose and V20 and V5 of the ipsilateral lung were 11.7Gy, 23.0%, 38.1% for HT-sIMRT WBI + Ax-L1, and 8.9 Gy, 16.4%, 32.5% for VMAT WBI + Ax-L1 plans, respectively. The mean heart doses in the left-sided plans were 3.2Gy and 3.0Gy, respectively. The V30 of the humeral head and minimum dose to the axillary-lateral thoracic vessel junction were 2.0% vs 1.8%, and 45.5Gy vs 45.7Gy for VMAT WBI + Ax-L1 and VMAT WBI + RTOG Ax-L1 plans, respectively.

CONCLUSIONS

A modified Ax-L1 CTV with expansion of the caudal and anterior borders might provide better coverage. Compared with HT-sIMRT WBI + Ax-L1, VMAT WBI+ Ax-L1 provided an adequate dose to Ax-L1 with decreasing the doses to most normal tissues. Coverage of modified Ax-L1 did not increase the dose to organs-at-risk compared with coverage of RTOG Ax-L1.

Effects of Tumor-Rib Distance and Dose-Dependent Rib Volume on Radiation-Induced Rib Fractures in Patients with Breast Cancer

This study aimed to investigate the effects of tumor-rib distance and dose-dependent rib volume on radiation-induced rib fractures (RIRFs) in patients with breast cancer. We retrospectively included 510 women with breast cancer who underwent surgical resection with adjuvant radiotherapy. The tumor-rib distance was measured using preoperative computed tomography (CT) images. Postoperative chest wall thickness and dose-dependent rib volumes, which are absolute rib volumes receiving >20 Gy (V20), 30 Gy (V30), 40 Gy (V40), 45 Gy (V45), and 50 Gy (V50), were measured from the stimulation CT images for radiation treatment planning. We assessed the relationship of RIRF with tumor-rib distance, postoperative chest wall thickness, and dose-dependent rib volumes. Patients with high values of tumor-rib distance and postoperative chest wall thickness had significantly lower risks of RIRF than those with low values. Patients with high values of V20, V30, V40, V45, and V50 had significantly higher risks of RIRF than those with low values. In a multivariate analysis, tumor-rib distance and all five dose-dependent rib volumes, as well as osteoporosis and radiation field, were independent risk factors for RIRF. Tumor-rib distance and dose-dependent rib volume were independent risk factors for RIRF in patients with breast cancer.

Comparison of the distribution of lymph node metastases compared to healthy lymph nodes in breast cancer

Background

Current literature lacks a comparison of lymph node metastases and non-pathological lymph nodes distribution in breast cancer patients. The aim of the current retrospective study was to generate a comprehensive atlas of the lymph node system.

Methods

143 breast cancer patients underwent F-18-FDG-PET/CT (PET/CT) imaging for staging purposes and were diagnosed with regional lymph node metastases. Based on the PET/CT data set a total of 326 lymph node metastases and 1826 non-pathological lymph nodes were detected and contoured manually in the patient collective. Using rigid and deformable registration algorithms all structures were transferred to a template planning CT of a standard patient. Subsequently, a 3D-atlas of the distribution of lymph node metastases and non-pathological lymph nodes were generated and compared to each other.

Results

Both, lymph node metastases and non-pathological lymph nodes, accumulated in certain areas (“hot-spots”) within the lymphatic drainage system. However large differences regarding the distribution patterns were detected: lymph node metastases hot spots occurred in close proximity to the subclavian vein in level I-III, whereas the non-pathological lymph nodes accumulated mostly (within a wider range) in level I. In level II and III lymph node metastases exceeded clearly the areas in which non-pathological lymph nodes occurred.

Conclusion

Lymph node metastases and non-pathological lymph node distribution within the lymph node system differ clearly. Based on our results, an individual adjustment of the CTV in order to include visible lymph nodes in level II and III should be discussed.

The Impact of Post-Mastectomy Radiotherapy on Survival Outcomes in Breast Cancer Patients Who Underwent Neoadjuvant Chemotherapy

Simple Summary

The benefits of post-mastectomy radiotherapy (PMRT) may vary depending on patients’ responses to neoadjuvant chemotherapy (NAC), although PMRT is useful for patients who underwent NAC. One can consider omitting PMRT in patients who have achieved pathologic complete response or who have minimal residual disease, with a neoadjuvant response index value of 0.7–1.0.

Abstract

This study aimed to determine whether post-mastectomy radiotherapy (PMRT) is beneficial for the prognosis of patients who achieved pathologic complete response (pCR), or who had minimal residual disease, after undergoing neoadjuvant chemotherapy (NAC). Patients who underwent a total mastectomy between 2006 and 2018, after NAC, were included. Patients who did not receive PMRT were matched using 1:3 propensity score matching (PSM). Kaplan–Meier survival curves were used to compare locoregional recurrence-free survival (LRRFS) and overall survival (OS). A total of 368 patients were included after 1:3 PSM. PMRT improved the LRRFS (p = 0.016) and OS (p = 0.017) rates of patients who underwent NAC. However, PMRT did not affect the prognosis of patients with pCR (LRRFS: p = 0.999; OS: p = 0.453). In addition, PMRT had a limited effect on LRRFS and OS in patients who responded well to NAC, with a neoadjuvant response index (NRI) value of 0.7–1.0 (LRRFS: p = 0.568; OS: p = 0.875). PMRT improved the OS of patients with a large residual tumor burden, such as nodal metastases or pathologic stage II/III. The benefits of PMRT vary depending on the patients’ response to NAC, although PMRT is useful for treating patients who underwent NAC. PMRT can be omitted, not only in patients with pCR, but also in good responders with an NRI value of 0.7–1.0.

Tricks and tips for target volume definition and delineation in breast cancer: Lessons learned from ESTRO breast courses

Delineation of target and 'organ at risk' volumes is a critical part of modern radiation therapy planning, the next essential step after deciding the indication, patient discussion and image acquisition. Adoption of volume-based treatment planning for non-metastatic breast cancer has increased greatly along with the use of improved planning techniques, essential for modern therapy. However, identifying the volumes on a planning CT is no easy task. The current paper is written by ESTRO's breast course faculty, providing tricks and tips for target volume definition and delineation for optimal postoperative breast cancer irradiation.

Geometric contour variation in clinical target volume of axillary lymph nodes in breast cancer radiotherapy: an AIRO multi-institutional study

OBJECTIVES

To determine interobserver variability in axillary nodal contouring in breast cancer (BC) radiotherapy (RT) by comparing the clinical target volume of participating single centres (SC-CTV) with a gold-standard CTV (GS-CTV).

METHODS

The GS-CTV of three patients (P1, P2, P3) with increasing complexity was created in DICOM format from the median contour of axillary CTVs drawn by BC experts, validated using the simultaneous truth and performance-level estimation and peer-reviewed. GS-CTVs were compared with the correspondent SC-CTVs drawn by radiation oncologists, using validated metrics and a total score (TS) integrating all of them.

RESULTS

Eighteen RT centres participated in the study. Comparative analyses revealed that, on average, the SC-CTVs were smaller than GS-CTV for P1 and P2 (by -29.25% and -27.83%, respectively) and larger for P3 (by +12.53%). The mean Jaccard index was greater for P1 and P2 compared to P3, but the overlap extent value was around 0.50 or less. Regarding nodal levels, L4 showed the highest concordance with the GS. In the intra-patient comparison, L2 and L3 achieved lower TS than L4. Nodal levels showed discrepancy with GS, which was not statistically significant for P1, and negligible for P2, while P3 had the worst agreement. DICE similarity coefficient did not exceed the minimum threshold for agreement of 0.70 in all the measurements.

CONCLUSIONS

Substantial differences were observed between SC- and GS-CTV, especially for P3 with altered arm setup. L2 and L3 were the most critical levels. The study highlighted these key points to address.

ADVANCES IN KNOWLEDGE

The present study compares, by means of validated geometric indexes, manual segmentations of axillary lymph nodes in breast cancer from different observers and different institutions made on radiotherapy planning CT images. Assessing such variability is of paramount importance, as geometric uncertainties might lead to incorrect dosimetry and compromise oncological outcome.

Clinical feasibility of deep learning-based auto-segmentation of target volumes and organs-at-risk in breast cancer patients after breast-conserving surgery

Background

In breast cancer patients receiving radiotherapy (RT), accurate target delineation and reduction of radiation doses to the nearby normal organs is important. However, manual clinical target volume (CTV) and organs-at-risk (OARs) segmentation for treatment planning increases physicians’ workload and inter-physician variability considerably. In this study, we evaluated the potential benefits of deep learning-based auto-segmented contours by comparing them to manually delineated contours for breast cancer patients.

Methods

CTVs for bilateral breasts, regional lymph nodes, and OARs (including the heart, lungs, esophagus, spinal cord, and thyroid) were manually delineated on planning computed tomography scans of 111 breast cancer patients who received breast-conserving surgery. Subsequently, a two-stage convolutional neural network algorithm was used. Quantitative metrics, including the Dice similarity coefficient (DSC) and 95% Hausdorff distance, and qualitative scoring by two panels from 10 institutions were used for analysis. Inter-observer variability and delineation time were assessed; furthermore, dose-volume histograms and dosimetric parameters were also analyzed using another set of patient data.

Results

The correlation between the auto-segmented and manual contours was acceptable for OARs, with a mean DSC higher than 0.80 for all OARs. In addition, the CTVs showed favorable results, with mean DSCs higher than 0.70 for all breast and regional lymph node CTVs. Furthermore, qualitative subjective scoring showed that the results were acceptable for all CTVs and OARs, with a median score of at least 8 (possible range: 0–10) for (1) the differences between manual and auto-segmented contours and (2) the extent to which auto-segmentation would assist physicians in clinical practice. The differences in dosimetric parameters between the auto-segmented and manual contours were minimal.

Conclusions

The feasibility of deep learning-based auto-segmentation in breast RT planning was demonstrated. Although deep learning-based auto-segmentation cannot be a substitute for radiation oncologists, it is a useful tool with excellent potential in assisting radiation oncologists in the future.

Trial registration Retrospectively registered.

Retrospective Study on Left-Sided Breast Radiotherapy: Dosimetric Results and Correlation with Physical Factors for Free Breathing and Breath Hold Irradiation Techniques

Objectives: In breast radiotherapy, the proximity of the target to sensitive structures together with the uncertainty introduced by respiratory movement, make this treatment one of the most studied to increase its effectiveness. Dosimetric and physical variables play an important role and the study of their correlation and impact on treatment is fundamental. This retrospective study aims to highlight the dosimetric differences of 2 different clinical data sets of patients receiving left-sided breast irradiation in free breathing (FB) or breath hold (BH). Methods: A total of 155 left breast carcinoma patients receiving whole-breast irradiation in FB (73 patients) and BH (82 patients) were enrolled in this study. The dosimetric parameters of the target, heart, left and right lung and right breast were evaluated and compared, and possible correlations were studied in both groups. Results: No significant difference (P > .05) was found in the target dosimetry; a clear advantage in BH for both high and low doses received by the heart, with reductions of the dosimetric parameters between 27.1% and 100% (P < .003); for the left lung reductions decreased with increasing dose (-22.4% and -13.4% for doses of 5 and 20 Gy, respectively, P < .003). Conclusion: Significant correlations for BH treatments were registered between the volumes of the target and left lung, and the dosimetric parameters of the heart and left lung. BH treatment brings significant dosimetric advantages to organs at risk for a wide range of patients with different anatomy, target volumes and lung capacity, with additional benefits for small-sized breasts and important lung capacity.

Single click automated breast planning with iterative optimization

Purpose

To present the development of an in‐house coded solution for treatment planning of tangential breast radiotherapy that creates single click plans by emulating the iterative optimization process of human dosimetrists.

Method

One hundred clinical breast cancer patients were retrospectively planned with an automated planning (AP) code incorporating the hybrid intensity‐modulated radiotherapy (IMRT) approach. The code automates all planning processes including plan generation, beam generation, gantry and collimator angle determination, open segments and dynamic IMRT fluence and calculations. Thirty‐nine dose volume histogram (DVH) metrics taken from three international recommendations were compared between the automated and clinical plans (CP), along with median interquartile analysis of the DVH distributions. Total planning time and delivery QA were also compared between the plan sets.

Results

Of the 39 planning metrics analyzed 23 showed no significant difference between clinical and automated planning techniques. Of the 16 metrics with statistically significant variations, 2 were improved in the clinical plans in comparison to 14 improved in the AP plans. Automated plans produced a greater number of ideal plans against international guidelines as per EviQ (AP:77%, CP:68%), RTOG 1005 (AP:80%, CP:71%), and London Cancer references (AP:80%, CP:75%). Delivery QA results for both techniques were equivalent. Automated planning techniques resulted in an average reduction in planning time from 23 to 5 minutes.

Conclusion

We have introduced an automated planning code with iterative optimization that produces equivalent quality plans to manual clinical planning. The resultant change in workflow results in a reduction in treatment planning times.

Feasibility of using calibrated cone-beam computed tomography scans to validate the heart dose in left breast post-mastectomy radiotherapy

Objective

In post-mastectomy radiotherapy, high-conformal techniques are a valid method for determining the dose distribution around a target. However, the proximity of critical structures is a reason for concern. This study aims to evaluate the feasibility of using calibrated cone-beam computed tomography (CBCT) scans as a valid tool for a timely heart dose evaluation.

Methods

A retrospective analysis was conducted on 170 retrospective CBCT scans of 17 patients who underwent high-conformal post-mastectomy irradiation. The delivered doses that were calculated using personalized calibrated CBCT were compared with the doses planned, using the dose–volume histogram dosimetric parameters.

Results

The heart volume that was evaluated using CBCT presented a mean increase of 6%; this discrepancy impacted the heart dose in 4 of 17 patients, with an absolute increase of V25 Gy (range, 2.5%–7.6%) and an increase in the mean dose (range, 1.1–3.4 Gy). The dose for the target, ipsilateral lung, and contralateral breast remained unchanged.

Conclusion

Using CBCT to monitor the dose that is delivered to the heart is feasible, allowing for a timely shift to an adaptive plan if clinically necessary.

PET/CT of breast cancer regional nodal recurrences: an evaluation of contouring atlases

BACKGROUND

To validate the Radiation Therapy Oncology Group (RTOG) and European Society for Radiotherapy and Oncology (ESTRO) breast cancer nodal clinical target volumes (CTVs) and to investigate the Radiotherapy Comparative Effectiveness Consortium (RADCOMP) Posterior Neck volume in relation to regional nodal recurrences (RNR).

METHODS

From a population-based database, 69 patients were identified who developed RNR after curative treatment for breast cancer. RNRs were detected with 18-fluorodeoxyglucose-positron emission tomography-computed tomography (PET/CT). All patients were treatment-naïve for RNR when imaged. The RTOG and ESTRO nodal CTVs and RADCOMP Posterior Neck volumes were contoured onto a template patient's CT. RNRs were contoured on each PET/CT and deformed onto the template patient's CT. Each RNR was represented by a 5 mm diameter epicentre, and categorized as 'inside', 'marginal' or 'outside' the CTV boundaries.

RESULTS

Sixty-nine patients with 226 nodes (median 2, range 1-11) were eligible for inclusion. Thirty patients had received adjuvant tangent and regional nodal radiotherapy, 16 tangent-only radiotherapy and 23 no adjuvant radiotherapy. For the RTOG CTVs, the RNR epicentres were 70% (158/226) inside, 4% (8/226) marginal and 27% (60/226) outside. They included the full extent of the RNR epicentres in 38% (26/69) of patients. Addition of the RADCOMP Posterior Neck volume increased complete RNR coverage to 48% (33/69) of patients. For the ESTRO CTVs, the RNR epicentres were 73% (165/226) inside, 2% (4/226) marginal and 25% (57/226) outside. They included the full extent of the RNR epicentres in 57% (39/69) of patients. Addition of the RADCOMP Posterior Neck volume increased complete RNR coverage to 70% (48/69) of patients.

CONCLUSIONS

The RTOG and ESTRO breast cancer nodal CTVs do not fully cover all potential areas of RNR, but the ESTRO nodal CTVs provided full coverage of all RNR epicentres in 19% more patients than the RTOG nodal CTVs. With addition of the RADCOMP Posterior Neck volume to the ESTRO CTVs, 70% of patients had full coverage of all RNR epicentres.

Impact of positioning errors in the dosimetry of VMAT left-sided post mastectomy irradiation

Background

Volumetric modulated arc therapy (VMAT) adopted in post-mastectomy radiation therapy (PMRT) has the capacity to achieve highly conformal dose distributions. The research aims to evaluate the impact of positioning errors in the dosimetry of VMAT left-sided PMRT.

Methods

A total of 18 perturbations where introduced in 11 VMAT treatment plans that shifted the isocenter from its reference position of 3, 5, 10 mm in six directions. The thoracic wall and supraclavicular clinical target volumes (CTVs), the heart and the left lung dose volume histograms (DVHs) of 198 perturbed plans were calculated. The absolute differences (∆) of the mean dose (Dm) and DVH endpoints Vx and Dy (percentage volume receiving x Gy, and dose covering y% of the volume, respectively) were used to compare the dosimetry of the reference vs perturbed plans.

Results

Isocenter shifts in the anterior and lateral directions lead to maximum disagreement between the CTVs dosimetry of perturbed vs reference plans. Isocenter shifts of 10 mm shown a decrease of D95, D98 and Dm of 12.8, 18.0, and 2.9% respectively, for the CTVs. For 5 mm isocenter shifts, these differences decreased to 3.2, 5.2, and 0.9%, respectively, and for 3 mm shifts to 1.0, 1.7, and 0.6%, respectively. For the organs at risk (OARs), only isocenter shifts in the right, posterior and inferior directions worsen the plan dosimetry, nevertheless not negligible lung ∆ V20 of + 2.6%, and heart ∆ V25 of + 1.6% persist for 3 mm shifts.

Conclusions

Inaccuracy in isocenter positioning for VMAT left-sided PMRT irradiation may impact the dosimetry of the CTVs and OARs to a different extent, depending on the directions and magnitude of the perturbation. The acquired information could be useful for planning strategies to guarantee the accuracy of the treatment delivered.

Comparison of Nodal Target Volume Definition in Breast Cancer Radiation Therapy According to RTOG Versus ESTRO Atlases: A Practical Review From the TransAtlantic Radiation Oncology Network (TRONE)

Regional nodal irradiation has gained interest in recent years with the publication of several important randomized trials and the availability of more conformal techniques. Target volume delineation represents a critical step in the radiation planning process. Adequate coverage of the microscopic tumor spread to regional lymph nodes must be weighed against exposure of critical structures such as the heart and lungs. Among available guidelines for delineating the clinical target volume for the breast/chest wall and regional nodes, the Radiation Therapy Oncology Group and European Society for Radiotherapy and Oncology guidelines are the most widely used internationally. These guidelines have been formulated based on anatomic boundaries of areas historically covered in 2-dimensional field-based radiation therapy but have not been validated by patterns-of-failure studies. In recent years, an important body of data has emerged from mapping studies documenting patterns of local and regional recurrence. We aim to review, discuss, and compare contouring guidelines for breast cancer radiation therapy in the context of contemporary data on locoregional relapse to improve their implementation in modern practice.

An Update on Regional Nodal Irradiation: Indication, Target Volume Delineation, and Radiotherapy Techniques

Background

Tremendous changes have occurred in the treatment of breast cancer. This paper reviews and unifies the available data on modern axillary management of breast cancer patients with focus on the target volume delineation for regional nodal irradiation according to the most important contouring guidelines, the European Society for Radiotherapy and Oncology (ESTRO) and the Radiation Therapy and Oncology Group (RTOG).

Summary

The use of extensive radiotherapy target volumes (level I, II, III, IV) is probably not necessary for all patients to reproduce the clinical benefit shown in the available randomized trials (EORTC, MA.20, AMAROS, Z0011). Nevertheless, given the results in the MA.20 trial, where the patients received more modern systemic therapies and high irradiation doses in the medial paraclavicular region (level IV) and level II, it can be justified to include these regions completely in selected high-risk patients.

Key Messages

High-tangent irradiation results in a similar dose distribution in axillary levels I and II compared to the AMAROS treatment field design in some patients. This supports earlier assumptions that irradiation may have accounted for the good results after sentinel lymph node dissection alone in the Z0011 trial. The ESTRO and RTOG clinical target volume (CTV) definitions cover sufficiently the metastatic lymph node hotspots, with a better coverage for the ESTRO CTV. Further, contouring according to the ESTRO would spare a significantly larger part of the healthy lymphatic system, making it our preferred contouring atlas. Modern radiotherapy techniques, such as deep inspiration breath hold, should be cautiously employed in patients treated according to the inclusion criteria of the Z0011 as it will result in a lower dose to the axillary levels.

Mapping of Metastatic Level I Axillary Lymph Nodes in Patients with Newly Diagnosed Breast Cancer

PURPOSE

We examined the distribution of pretreatment nodal metastases to the level I axilla (Ax-L1) to assess the appropriateness of current breast atlases and provide guidelines in relationship to easily identifiable anatomic landmarks for accurate delineation of this lymph node (LN) basin.

METHODS AND MATERIALS

Patients with newly diagnosed breast cancer and biopsy-proven metastatic Ax-L1 LNs were identified. We related the location of each LN to its most adjacent rib and its distance from the bottom of the humeral head, axillary vessels, and a line connecting the anterior aspects of the pectoralis and latissimus dorsi muscles (P-L line). LNs were mapped onto a representative planning computed tomography scan, and their distribution was used to validate the current Radiation Therapy Oncology Group, European Society for Radiotherapy and Oncology, and Radiotherapy Comparative Effectiveness breast atlases. Furthermore, we examined metastases to a subregion encompassing the superolateral Ax-L1, irradiation of which correlates highly with lymphedema.

RESULTS

We identified 106 eligible patients with 107 biopsied LNs. All LNs fell between the second and fifth ribs (mean, 3.8 ± 0.56). Mean distance from the inferior aspect of the humeral head was 4.3 ± 1.6 cm (range, 0.3-8.4). Mean distance from the inferior aspect of the axillary vessels was 2.9 ± 1.5 cm (range, -0.6 to 5.4). Mean distance from the P-L line was 0.01 ± 1.9 cm (range, -2.2 to 2.4); negative and positive values denote medial or lateral to the P-L line. A Radiation Therapy Oncology Group-compliant Ax-L1 consensus contour, created from contours by 4 attending breast radiation oncologists, partially or fully missed 45% of mapped LNs. European Society for Radiotherapy and Oncology- and Radiotherapy Comparative Effectiveness-compliant Ax-L1 similarly missed 46% and 34% of mapped LNs, respectively. LNs were most frequently missed in the lateral direction. The superolateral Ax-L1 encompassed 9.3% of the mapped LNs.

CONCLUSIONS

A significant percentage of at-risk Ax-L1 tissue falls outside current contouring atlases. We propose expansion of the recommended Ax-L1 borders, most notably in the lateral direction.

Adjuvant whole breast radiotherapy with simultaneous integrated boost to tumor bed with intensity modulated radiotherapy technique in elderly breast cancer patients

Background

Adjuvant whole breast radiotherapy is the standard of care for breast cancer patients after partial mastectomy. Intensity-modulated radiation therapy (IMRT) has been reported to reduce acute toxicities compared to conventional radiotherapy. IMRT with simultaneous integrated boost (SIB) technique can deliver higher doses to tumor bed and irradiate whole breast with a lower dose level to shorten overall treatment duration. This study presents the long-term results of adjuvant IMRT with SIB in elderly breast cancer patients who received partial mastectomy.

Methods

From January 2007 to January 2018, 93 elder breast cancer patients (≥65-year-old) who received IMRT with SIB technique after partial mastectomy were reviewed retrospectively. The axillary areas were managed with either sentinel lymph node biopsies or axillary lymph node dissection. The dose to whole breast was 50.4 Gy in 28 fractions in all patients and the dose to tumor bed was 61.6 to 66.4 Gy in 28 fractions. The primary end point is locoregional control. Secondary end points include: overall survival, breast cancer-specific survival, distant-metastases-free survival, disease-free survival, and acute and chronic toxicities.

Results

The median follow-up was 56.1 months. One patient had ipsilateral breast tumor recurrence, 3 patients had regional lymph node recurrence, and 9 patients had distant metastases. Death occurred in 5 patients, including 3 patients died of breast cancer progression. Five-year overall survival is 96.3% and 5-year locoregional recurrence-free survival is 96.4%. The 5-year breast cancer specific survival and 5-year distant metastases-free survival is 97.5% and 87.2%, respectively. Seven patients developed second primary cancer after RT. Eighty-one point seven percent patients had acute grade 1 dermatitis while 18.3% suffered from grade 2 dermatitis. The incidence of grade 1 pneumonitis and grade 1 stomatitis was 4.3% and 8.6%, respectively.

Conclusions

Adjuvant IMRT with SIB technique is a safe and effective treatment strategy for elderly breast cancer patients after partial mastectomy.

Evaluation of interfraction setup variations for postmastectomy radiation therapy using EPID-based in vivo dosimetry

Postmastectomy radiation therapy is technically difficult and can be considered one of the most complex techniques concerning patient setup reproducibility. Slight patient setup variations — particularly when high‐conformal treatment techniques are used — can adversely affect the accuracy of the delivered dose and the patient outcome. This research aims to investigate the inter‐fraction setup variations occurring in two different scenarios of clinical practice: at the reference and at the current patient setups, when an image‐guided system is used or not used, respectively. The results were used with the secondary aim of assessing the robustness of the patient setup procedure in use. Forty eight patients treated with volumetric modulated arc and intensity modulated therapies were included in this study. EPID‐based in vivo dosimetry (IVD) was performed at the reference setup concomitantly with the weekly cone beam computed tomography acquisition and during the daily current setup. Three indices were analyzed: the ratio R between the reconstructed and planned isocenter doses, γ% and the mean value of γ from a transit dosimetry based on a two‐dimensional γ‐analysis of the electronic portal images using 5% and 5 mm as dose difference and distance to agreement gamma criteria; they were considered in tolerance if R was within 5%, γ% > 90% and γmean < 0.4. One thousand and sixteen EPID‐based IVD were analyzed and 6.3% resulted out of the tolerance level. Setup errors represented the main cause of this off tolerance with an occurrence rate of 72.2%. The percentage of results out of tolerance obtained at the current setup was three times greater (9.5% vs 3.1%) than the one obtained at the reference setup, indicating weaknesses in the setup procedure. This study highlights an EPID‐based IVD system's utility in the radiotherapy routine as part of the patient’s treatment quality controls and to optimize (or confirm) the performed setup procedures’ accuracy.

Predictors of Cardiac Sparing in Deep Inspiration Breath-Hold for Patients With Left Sided Breast Cancer

Purpose: The purpose of this study was to evaluate patient-related non-dosimetric predictors of cardiac sparing with the use of deep inspiration breath-hold (DIBH) in patients with left-sided breast cancer undergoing irradiation (RT).

Materials and Methods: We retrospectively reviewed charts and treatment plans of one-hundred and three patients with left-sided breast cancer. All patients had both free-breathing (FB) and DIBH (with body surface tracking) plans available. (MHD) and V4 (heart volume receiving at least 4 Gy) were extracted from dose volume histograms. Fisher's exact and Chi-square tests were used to identify predictors of reductions in MHD and V4 after DIBH.

Results: One-hundred and three patients were identified and most underwent mastectomy. MHD and V4 decreased significantly in DIBH plans (0.74 ± 0.25 Gy vs. 1.72 ± 0.98 Gy, p < 0.0001 for MHD; 4 ± 4.98 cc vs. 20.79 ± 18.2 cc, p < 0.0001 for V4). Body mass index (BMI), smoking and timing of CT simulation (spring/winter vs. summer/fall) were significant predictors of reduction in MHD whereas BMI, field size, chemotherapy, axillary dissection, and timing of CT simulation predicted reduction in V4. On multivariate analysis, BMI, and timing of CT simulation remained significant predictors of the heart-sparing effect of DIBH.

Conclusions: In the setting of limited resources, identifying patients who will benefit the most from DIBH is extremely important. Prior studies have identified multiple dosimetric predictors of cardiac sparing and hereby we identified new non-dosimetric factors such as BMI and timing of treatments.

Contouring consensus guidelines in breast cancer radiotherapy: Comparison and systematic review of patterns of failure

Adequate coverage of sites harbouring potential microscopic disease is paramount, where the clinical decision has been made to include regional lymph node radiotherapy for patients with breast cancer. This must be achieved in balance with minimising dose to normal tissues. Several international consensus guidelines detailing clinical target volumes (CTVs) are available, but there is currently no agreement as to which is most appropriate for a given clinical situation. Contouring guidelines are beneficial for routine practice and essential for clinical trial quality assurance. The aims of this study were as follows: to provide a single point of comparison of four commonly used contouring guidelines, including one used in a current Trans-Tasman Radiation Oncology Group trial; and to undertake a systematic review of existing studies which map sites of breast cancer recurrence against contouring guidelines. Two international consensus guidelines (European Society for Radiotherapy and Oncology, and Radiation Therapy Oncology Group) were compared with two clinical trial guidelines (TROG 12.02 PET LABRADOR and the Proton/Photon trial NCT02603341 RADCOMP). Comprehensive literature search for patterns of failure studies was undertaken using Embase and Pubmed. We detail the small but significant differences between the breast consensus guidelines, particularly the supraclavicular (SCF) and internal mammary chain CTVs. Seven series were found mapping recurrence patterns. These results are discussed in the context of the contouring guidelines. Several studies found the SCF CTV is the area at greatest risk of geographical 'miss'. This review will facilitate further discussion about guideline selection and modification, particularly for future clinical trials in Australia and New Zealand.

How Histopathologic Tumor Extent and Patterns of Recurrence Data Inform the Development of Radiation Therapy Treatment Volumes in Solid Malignancies

The ability to deliver highly conformal radiation therapy using intensity-modulated radiation therapy and particle therapy provides for new opportunities to improve patient outcomes by reducing treatment-related morbidities following radiation therapy. By reducing the volume of normal tissue exposed to radiation therapy (RT), while also allowing for the opportunity to escalate the dose of RT delivered to the tumor, use of conformal RT delivery should also provide the possibility of expanding the therapeutic index of radiotherapy. However, the ability to safely and confidently deliver conformal RT is largely dependent on our ability to clearly define the clinical target volume for radiation therapy, which requires an in-depth knowledge of histopathologic extent of different tumor types, as well as patterns of recurrence data. In this article, we provide a comprehensive review of the histopathologic and radiographic data that provide the basis for evidence-based guidelines for clinical tumor volume delineation.

Recent advances in radiation oncology

Radiotherapy (RT) is very much a technology-driven treatment modality in the management of cancer. RT techniques have changed significantly over the past few decades, thanks to improvements in engineering and computing. We aim to highlight the recent developments in radiation oncology, focusing on the technological and biological advances. We will present state-of-the-art treatment techniques, employing photon beams, such as intensity-modulated RT, volumetric-modulated arc therapy, stereotactic body RT and adaptive RT, which make possible a highly tailored dose distribution with maximum normal tissue sparing. We will analyse all the steps involved in the treatment: imaging, delineation of the tumour and organs at risk, treatment planning and finally image-guidance for accurate tumour localisation before and during treatment delivery. Particular attention will be given to the crucial role that imaging plays throughout the entire process. In the case of adaptive RT, the precise identification of target volumes as well as the monitoring of tumour response/modification during the course of treatment is mainly based on multimodality imaging that integrates morphological, functional and metabolic information. Moreover, real-time imaging of the tumour is essential in breathing adaptive techniques to compensate for tumour motion due to respiration. Brief reference will be made to the recent spread of particle beam therapy, in particular to the use of protons, but also to the yet limited experience of using heavy particles such as carbon ions. Finally, we will analyse the latest biological advances in tumour targeting. Indeed, the effectiveness of RT has been improved not only by technological developments but also through the integration of radiobiological knowledge to produce more efficient and personalised treatment strategies.

Deep-Inspiration Breath-Hold Radiation Therapy in Breast Cancer: A Word of Caution on the Dose to the Axillary Lymph Node Levels

PURPOSE

To assess the differences in unintended regional nodal irradiation between free breathing (FB) and deep-inspiration breath-hold (DIBH) during tangential field irradiation.

METHODS AND MATERIALS

We randomly chose 32 patients from our database who underwent both DIBH and FB treatment planning. Contouring of the axillary lymph node levels (LI, LII, and LIII) was performed retrospectively according to the Radiation Therapy Oncology Group contouring atlas. We assessed the center of mass of each level and the planning target volume, as well as the dose distribution (Dmean, Dmedian, Dmax, Dmin, V30, and V40) in the lymph node levels I-III. Subsequently center of mass movement and dose changes due to deep inspiration treatment planning were calculated.

RESULTS

All lymph node levels showed significant (P<.001) movement in anterior and cranial directions due to DIBH. The overall median movement (range) in the x (lateral), y (anterior-posterior), and z (cranio-caudal) directions was 0.1 cm (0.0-1.1 cm), 0.9 cm (0.1-2.0 cm), and 1.2 cm (0.0-2.6 cm), respectively. Movement of the planning target volume showed significant correlation (r=0.72, r=0.63, r=0.63; P<.05) with levels I-III. The average Dmean during FB/DIBH was as follows: LI 33.9 Gy/30.8 Gy (P<.001), LII 23.7 Gy/24.1 Gy (P=.74), and LIII 14.0 Gy/15.6 Gy (P=.14). V30 was as follows: LI 63.8%/56.5% (P<.001), LII 44.6%/45.5% (P=.76), and LIII 24.2%/27.8% (P<.05). V40 was as follows: LI 58.9%/51.0% (P<.001), LII 39.3%/40.1% (P=.79), and LIII 20.4%/23.9% (P<.05).

CONCLUSIONS

Deep-inspiration breath-hold results in a significant dose reduction in level I. Only minor changes in dose distribution were recorded for levels II and III. Thus, DIBH seems to have an impact on unintended regional nodal irradiation as compared with FB.

Supine MRI for regional breast radiotherapy: imaging axillary lymph nodes before and after sentinel-node biopsy

Regional radiotherapy (RT) is increasingly used in breast cancer treatment. Conventionally, computed tomography (CT) is performed for RT planning. Lymph node (LN) target levels are delineated according to anatomical boundaries. Magnetic resonance imaging (MRI) could enable individual LN delineation. The purpose was to evaluate the applicability of MRI for LN detection in supine treatment position, before and after sentinel-node biopsy (SNB). Twenty-three female breast cancer patients (cTis-3N0M0) underwent 1.5 T MRI, before and after SNB, in addition to CT. Endurance for MRI was monitored. Axillary levels were delineated. LNs were identified and delineated on MRI from before and after SNB, and on CT, and compared by Wilcoxon signed-rank tests. LN locations and LN-based volumes were related to axillary delineations and associated volumes. Although postoperative effects were visible, LN numbers on postoperative MRI (median 26 LNs) were highly reproducible compared to preoperative MRI when adding excised sentinel nodes, and higher than on CT (median 11, p  <  0.001). LN-based volumes were considerably smaller than respective axillary levels. Supine MRI of LNs is feasible and reproducible before and after SNB. This may lead to more accurate RT target definition compared to CT, with potentially lower toxicity. With the MRI techniques described here, initiation of novel MRI-guided RT strategies aiming at individual LNs could be possible.

Variability in axillary lymph node delineation for breast cancer radiotherapy in presence of guidelines on a multi-institutional platform

AIM

To quantify the variability between radiation oncologists (ROs) when outlining axillary nodes in breast cancer.

MATERIAL AND METHODS

For each participating center, three ROs with different levels of expertise, i.e., junior (J), senior (S) and expert (E), contoured axillary nodal levels (L1, L2, L3 and L4) on the CT images of three different patients (P) of an increasing degree of anatomical complexity (from P1 to P2 to P3), according to contouring guidelines. Consensus contours were generated using the simultaneous truth and performance level estimation (STAPLE) method.

RESULTS

Fifteen centers and 42 ROs participated. Overall, the median Dice similarity coefficient was 0.66. Statistically significant differences were observed according to the level of expertise (better agreement for J and E, worse for S); the axillary level (better agreement for L1 and L4, worse for L3); the patient (better agreement for P1, worse for P3). Statistically significant differences in contouring were found in 18% of the inter-center comparison. Less than a half of the centers could claim to have a good agreement between the internal ROs.

CONCLUSIONS

The overall intra-institute and inter-institute agreement was moderate. Central lymph-node levels were the most critical and variability increased as the complexity of the patient's anatomy increased. These findings might have an effect on the interpretation of results from multicenter and even mono-institute studies.

Deep inspiration breathhold for left-sided breast cancer patients with unfavorable cardiac anatomy requiring internal mammary nodal irradiation

PURPOSE

The purpose of this study was to evaluate the utility of moderate deep inspiration breathhold (mDIBH) in reducing heart exposure in left breast cancer patients who have unfavorable cardiac anatomy and need internal mammary lymph node (IMLN) radiation therapy (RT).

METHODS AND MATERIALS

We used maximum heart distance (MHD), defined as the maximum distance of the heart within the treatment field, >1 cm as a surrogate for unfavorable cardiac anatomy. Twenty-two left breast cancer patients with unfavorable cardiac anatomy requiring IMLN-RT underwent free-breathing (FB) and mDIBH computed tomography simulation and planning. Three-dimensional partially wide tangents (3D-PWTs) and intensity modulated RT plans were generated. Dose-volume histograms were used to compare heart and lung dosimetric parameters. Duration of treatment delivery was recorded for all fractions.

RESULTS

MHD decreased significantly in mDIBH scans. mDIBH significantly reduced mean heart dose (222.7 vs 578.4 cGy; P < .0001) and percentage of left lung receiving doses ≥20 Gy (V20; 31.93 vs 38.41%; P = .0006) in both 3D-PWT and intensity modulated RT plans. The change in MHD after breathhold reliably predicted mean heart dose reduction after mDIBH. Radiation was effectively delivered in 11.31 ± 3.40 minutes with an average of 10.06 ± 2.74 breathholds per fraction.

CONCLUSIONS

mDIBH is efficient and can effectively decrease mean heart dose in patients with unfavorable cardiac anatomy who need IMLN-RT, thus simplifying planning and delivery for them. The reduction in mean heart dose is proportional to the reduction in maximum heart distance.

Effects of Millimetric Shifts in Breast Cancer Radiotherapy on the Radiation Dose Distribution

BACKGROUND

This study aimed to facilitate decision-making in cases of breast cancer radiotherapy shifts by simulating millimetric shifts and analyzing their effects on dose distribution.

METHODS

The study included 30 patients with left side breast cancer who were treated with three dimensional conformal radiotherapy (3D-CRT) in the Radiation Oncology Department in Hatay Public Hospital, between January 2013 and April 2015. A treatment plan shifting at three axes with six different measures was simulated.

RESULTS

The biggest difference in values was (+3mm shift) 476cGy, with a 7.7 % change for heart and 25.6% for spinal cord. The shifts in values respectively for CTV min, mean, max were -4.8%, 2.5%, 4%. The differences for lymphatic min, mean, max were 21.3%, 20.3%, -12.2%.

CONCLUSION

The most important thing is not the treatment plan quality, but its practicality. The treatment plan must be practical and its practice must be controlled rigidly.