A Dosimetric Comparison of Breast Radiotherapy Techniques to Treat Locoregional Lymph Nodes Including the Internal Mammary Chain

Practice of Tumor Bed Boost in Patients after Oncoplastic Breast-Conserving Surgery

The practice of boost to the tumor bed after treatment with oncoplastic breast-conserving surgery (BCS) remains variable. Using a survey, the present study evaluated the current practice of tumor bed boost administered in women after oncoplastic BCS. Actively practicing radiation oncologists across India were sent a questionnaire on the practice of adjuvant whole-breast radiotherapy and tumor bed boost after oncoplastic BCS via email and encouraged to participate. Of the 54 radiation oncologists who participated, most (98.1%) used a linear accelerator for radiotherapy. Hypofractionation was preferred by 59.26%, standard fractionation by 7.41%, and the remaining selected the fractionation strategy based on various patient factors. In addition, 83.33% participants reported that they always planned tumor boost, 51.85% preferred photons for the boost, and 75.93% administered sequential boost. The most common dose for the boost was 12.5 Gy in five fractions (40.74%). Most participants (77.78%) revealed that they used a combination of methods for identifying the tumor bed. With respect to clip placement, most surgeons (96%) at the participants' centers placed ≥ 4 clips at the tumor site, with both the base and margins being preferred by surgeons (81.48%) for placement. Finally, 12.96% participants revealed that the surgeons always involved them during surgical planning, whereas 7.4% participants reported that they always included the surgeons during radiotherapy planning, suggesting that radiation oncologists and oncoplastic surgeons do not involve each other during surgical and radiotherapy planning, possibly leading to suboptimal treatment. This may be attributed to the absence of guidelines regarding boost practices after oncoplastic BCS.

Spot-scanning proton therapy for early breast cancer in free breathing versus deep inspiration breath-hold

BACKGROUND AND PURPOSE

Proton therapy for breast cancer is usually given in free breathing (FB). With the use of deep inspiration breath-hold (DIBH) technique, the location of the heart is displaced inferiorly, away from the internal mammary nodes and, thus, the dose to the heart can potentially be reduced. The aim of this study was to explore the potential benefit of proton therapy in DIBH compared to FB for highly selected patients to reduce exposure of the heart and other organs at risk. We aimed at creating proton plans with delivery times feasible with treatment in DIBH.

MATERIAL AND METHODS

Sixteen patients with left-sided breast cancer receiving loco-regional proton therapy were included. The FB and DIBH plans were created for each patient using spot-scanning proton therapy with 2-3 fields, robust and single field optimization. For the DIBH plans, minimum monitor unit per spot and spot spacing were increased to reduce treatment delivery time.

RESULTS

All plans complied with target coverage constraints. The median mean heart dose was statistically significant reduced from 1.1 to 0.6 Gy relative biological effectiveness (RBE) by applying DIBH. No statistical significant difference was seen for mean dose and V17Gy RBE to the ipsilateral lung. The median treatment delivery time for the DIBH plans was reduced by 27% compared to the FB plans without compromising the plan quality.

INTERPRETATION

The median absolute reduction in dose to the heart was limited. Proton treatment in DIBH may only be relevant for a subset of these patients with the largest reduction in heart exposure.

Proton Reirradiation for High-Risk Recurrent or New Primary Breast Cancer

Radiotherapy is an integral component of multidisciplinary breast cancer care. Given how commonly radiotherapy is used in the treatment of breast cancer, many patients with recurrences have received previous radiotherapy. Patients with new primary breast cancer may also have received previous radiotherapy to the thoracic region. Curative doses and comprehensive field photon reirradiation (reRT) have often been avoided in these patients due to concerns for severe toxicities to organs-at-risk (OARs), such as the heart, lungs, brachial plexus, and soft tissue. However, many patients may benefit from definitive-intent reRT, such as patients with high-risk disease features such as lymph node involvement and dermal/epidermal invasion. Proton therapy is a potentially advantageous treatment option for delivery of reRT due to its lack of exit dose and greater conformality that allow for enhanced non-target tissue sparing of previously irradiated tissues. In this review, we discuss the clinical applications of proton therapy for patients with breast cancer requiring reRT, the currently available literature and how it compares to historical photon reRT outcomes, treatment planning considerations, and questions in this area warranting further study. Given the dosimetric advantages of protons and the data reported to date, proton therapy is a promising option for patients who would benefit from the added locoregional disease control provided by reRT for recurrent or new primary breast cancer.

Proton Beam Therapy for Early Breast Cancer: A Systematic Review and Meta-analysis of Clinical Outcomes

PURPOSE

Adjuvant proton beam therapy (PBT) is increasingly available to patients with breast cancer. It achieves better planned dose distributions than standard photon radiation therapy and therefore may reduce the risks. However, clinical evidence is lacking.

METHODS AND MATERIALS

A systematic review of clinical outcomes from studies of adjuvant PBT for early breast cancer published in 2000 to 2022 was undertaken. Early breast cancer was defined as when all detected invasive cancer cells are in the breast or nearby lymph nodes and can be removed surgically. Adverse outcomes were summarized quantitatively, and the prevalence of the most common ones were estimated using meta-analysis.

RESULTS

Thirty-two studies (1452 patients) reported clinical outcomes after adjuvant PBT for early breast cancer. Median follow-up ranged from 2 to 59 months. There were no published randomized trials comparing PBT with photon radiation therapy. Scattering PBT was delivered in 7 studies (258 patients) starting 2003 to 2015 and scanning PBT in 22 studies (1041 patients) starting 2000 to 2019. Two studies (123 patients) starting 2011 used both PBT types. For 1 study (30 patients), PBT type was unspecified. Adverse events were less severe after scanning than after scattering PBT. They also varied by clinical target. For partial breast PBT, 498 adverse events were reported (8 studies, 358 patients). None were categorized as severe after scanning PBT. For whole breast or chest wall ± regional lymph nodes PBT, 1344 adverse events were reported (19 studies, 933 patients). After scanning PBT, 4% (44/1026) of events were severe. The most prevalent severe outcome after scanning PBT was dermatitis, which occurred in 5.7% (95% confidence interval, 4.2-7.6) of patients. Other severe adverse outcomes included infection, pain, and pneumonitis (each ≤1%). Of the 141 reconstruction events reported (13 studies, 459 patients), the most prevalent after scanning PBT was prosthetic implant removal (34/181, 19%).

CONCLUSIONS

This is a quantitative summary of all published clinical outcomes after adjuvant PBT for early breast cancer. Ongoing randomized trials will provide information on its longer-term safety compared with standard photon radiation therapy.

Fully automated volumetric modulated arc therapy technique for radiation therapy of locally advanced breast cancer

BACKGROUND

This study aimed to evaluate an a-priori multicriteria plan optimization algorithm (mCycle) for locally advanced breast cancer radiation therapy (RT) by comparing automatically generated VMAT (Volumetric Modulated Arc Therapy) plans (AP-VMAT) with manual clinical Helical Tomotherapy (HT) plans.

METHODS

The study included 25 patients who received postoperative RT using HT. The patient cohort had diverse target selections, including both left and right breast/chest wall (CW) and III-IV node, with or without internal mammary node (IMN) and Simultaneous Integrated Boost (SIB). The Planning Target Volume (PTV) was obtained by applying a 5 mm isotropic expansion to the CTV (Clinical Target Volume), with a 5 mm clip from the skin. Comparisons of dosimetric parameters and delivery/planning times were conducted. Dosimetric verification of the AP-VMAT plans was performed.

RESULTS

The study showed statistically significant improvements in AP-VMAT plans compared to HT for OARs (Organs At Risk) mean dose, except for the heart and ipsilateral lung. No significant differences in V95% were observed for PTV breast/CW and PTV III-IV, while increased coverage (higher V95%) was seen for PTV IMN in AP-VMAT plans. HT plans exhibited smaller values of PTV V105% for breast/CW and III-IV, with no differences in PTV IMN and boost. HT had an average (± standard deviation) delivery time of (17 ± 8) minutes, while AP-VMAT took (3 ± 1) minutes. The average γ passing rate for AP-VMAT plans was 97%±1%. Planning times reduced from an average of 6 h for HT to about 2 min for AP-VMAT.

CONCLUSIONS

Comparing AP-VMAT plans with clinical HT plans showed similar or improved quality. The implementation of mCycle demonstrated successful automation of the planning process for VMAT treatment of locally advanced breast cancer, significantly reducing workload.

Locoregional breast radiotherapy including IMN: optimizing the dose distribution using an automated non-coplanar VMAT-technique

BACKGROUND

Volumetric Modulated Arc Therapy (VMAT) offers better conformity, homogeneity and sparing of the heart and ipsilateral lung for locoregional radiotherapy in left-sided breast cancer compared to three-dimensional conformal radiotherapy (3D-CRT). However, conventional coplanar VMAT (cVMAT) can result in higher doses to the normal tissue on the contralateral side. This study investigates a non-coplanar VMAT-technique (ncVMAT) to mitigate this issue.

MATERIAL AND METHODS

CT series of 20 left sided breast cancer patients were included for planning of locoregional breast radiotherapy including internal mammary nodes (IMN). Three treatment plans; 3D-CRT, cVMAT and ncVMAT, were generated for each patient with a prescription dose of 40.05 Gy in 15 fractions. Both VMAT-techniques consisted of a single arc in the axial plane, while ncVMAT included an additional arc in the sagittal plane. All plans were optimized to cover the clinical target volume (CTV) by 38.05 Gy for the breast and 36.05 Gy for lymph nodes, with as low as possible dose to organs at risk.

RESULTS

Full CTV coverage was achieved for all plans. Both cVMAT and ncVMAT delivered more conformal and homogeneous target doses than 3D-CRT. Doses to the heart and ipsilateral lung were significantly lower with ncVMAT compared to both cVMAT and 3D-CRT. ncVMAT reduced doses to both the contralateral breast and lung compared to cVMAT and achieved levels similar to 3D-CRT for the contralateral breast and moderately higher doses for the contralateral lung. Delivery of high doses (>30 Gy) to the contralateral side was completely avoided with ncVMAT, contrary to the results for cVMAT and 3D-CRT.

CONCLUSION

ncVMAT reduced doses to the heart and ipsilateral lung as compared to both cVMAT and 3D-CRT. All contralateral dose metrics were reduced with the novel ncVMAT technique compared to cVMAT, and the mean contralateral breast doses were similar to 3D-CRT.

Dose delivery reproducibility for PBS proton treatment of breast cancer patients with and without mask immobilization

BACKGROUND

Setup reproducibility of the tissue in the proton beam path is critical in maintaining the planned clinical target volume (CTV) dose coverage and sparing the organs at risk (OAR). In this study, we retrospectively evaluated radiation therapy dose reproducibility for proton pencil beam scanning (PBS) treatment of breast cancer patients with and without mask immobilization.

METHODS

Ninety-four patients treated between January 2019 and September 2022 with at least one verification CT scan (V-CT) in treatment position were included for this study. All patients were set up with arms up using the Orfit AIO patient positioning system, with (69 patients) or without (25 patients) mask immobilization in chin, neck, shoulder, upper arm, and chest areas. Two to three enface or near enface single field uniform dose PBS beams were optimized using a commercial treatment planning system. Prescription doses were 25 to 60 GyRBE in 5 to 45 fractions. Treatment plan doses re-calculated on V-CTs were compared to the corresponding planned doses. Cumulative doses were also calculated for patients with at least 3 V-CTs by deform and weighted sum doses from V-CTs to corresponding P-CTs. CTV D95%, ipsilateral-lung V40%, esophagus D0.01cc, and heart mean dose were evaluated and reported as percentages of prescription doses. Differences were large dose deteriorations (LDD) if: (1) CTV (V-CT/cumulative D95%) - (Planned D95%) < - 5%; or (2) Ipsilateral-lung (V-CT/cumulative V40%) - (Planned V40%) > 5%; or (3) Esophagus (V-CT/cumulative D0.01cc) - (Planned D0.01cc) > 10%; or (4) Heart (V-CT/cumulative mean) - (Planned mean) > 1.5%.

RESULTS

On average, V-CT/cumulative and planned CTV/OAR dose parameter differences were less than 2.2%/1.7% and 3.4%/3.7% for masked and maskless patients, respectively. The percentages of patients with at least one CTV or OAR V-CT/cumulative dose LDD were 20.3%/25.0% and 72.0%/54.0% for masked and maskless patients, respectively.

CONCLUSIONS

On average, masked/maskless setups achieved delivered and planned CTV/OAR dose parameters agreed within 2.2%/3.7% for PBS treatment of breast cancer patients in this study. Maskless patients had higher rate of CTV/OAR LDDs compared to masked patients. Dosimetric differences large enough to raise clinical concerns in either group were able to be addressed with replannings.

Proton Therapy in the Adolescent and Young Adult Population

BACKGROUND

Adolescent and young adult cancer patients are at high risk of developing radiation-associated side effects after treatment. Proton beam radiation therapy might reduce the risk of these side effects for this population without compromising treatment efficacy.

METHODS

We review the current literature describing the utility of proton beam radiation therapy in the treatment of central nervous system tumors, sarcomas, breast cancer and Hodgkin lymphoma for the adolescent and young adult cancer population.

RESULTS

Proton beam radiation therapy has utility for the treatment of certain cancers in the young adult population. Preliminary data suggest reduced radiation dose to normal tissues, which might reduce radiation-associated toxicities. Research is ongoing to further establish the role of proton therapy in this population.

CONCLUSION

This report highlights the potential utility of proton beam radiation for certain adolescent young adult cancers, especially with reducing radiation doses to organs at risk and thereby potentially lowering risks of certain treatment-associated toxicities.

Recent advances progress in radiotherapy for breast cancer after breast-conserving surgery: a review

Adjuvant radiotherapy after breast-conserving surgery has become an integral part of the treatment of breast cancer. In recent years, the development of radiotherapy technology has made great progress in this field, including the comparison of the curative effects of various radiotherapy techniques and the performance of the segmentation times. The choice of radiotherapy technology needs to be co-determined by clinical evidence practice and evaluated for each individual patient to achieve precision radiotherapy. This article discusses the treatment effects of different radiotherapy, techniques, the risk of second cancers and short-range radiation therapy techniques after breast-conserving surgery such as hypo fractionated whole breast irradiation and accelerated partial breast irradiation. The choice of radiotherapy regimen needs to be based on the individual condition of the patient, and the general principle is to focus on the target area and reduce the irradiation of the normal tissues and organs. Short-range radiotherapy and hypofractionated are superior to conventional radiotherapy and are expected to become the mainstream treatment after breast-conserving surgery.

Can knowledge based treatment planning of VMAT for post-mastectomy locoregional radiotherapy involving internal mammary chain and supraclavicular fossa improve performance efficiency?

Introduction

To validate and evaluate the performance of knowledge-based treatment planning for Volumetric Modulated Arc Radiotherapy for post-mastectomy loco-regional radiotherapy.

Material and methods

Two knowledge-based planning (KBP) models for different dose prescriptions were built using the Eclipse RapidPlanTM v 16.1 (Varian Medical Systems, Palo Alto, USA) utilising the plans of previously treated patients with left-sided breast cancer who had undergone irradiation of the left chest wall, internal mammary nodal (IMN) region and supra-clavicular fossa (SCF). Plans of 60 and 73 patients were used to generate the KBP models for the prescriptions of 40 Gy in 15 fractions and 26 Gy in 5 fractions, respectively. A blinded review of all the clinical plans (CLI) and KBPs was done by two experienced radiation oncology consultants. Statistical analysis of the two groups was also done using the standard two-tailed paired t-test or Wilcoxon signed rank test, and p&lt;0.05 was considered significant.

Results

A total of 20 metrics were compared. The KBPs were found to be either better (6/20) or comparable (10/20) to the CLIs for both the regimens. Dose to heart, contralateral breast,contralateral lung were either better or comparable in the KBP plans except of ipsilateral lung. Mean dose (Gy) for the ipsilateral lung are significantly (p˂0.001) higher in KBP though the values were acceptable clinically. Plans were of similar quality as per the result of the blinded review which was conducted by slice-by-slice evaluation of dose distribution for target coverage, overdose volume and dose to the OARs. However, it was also observed that treatment times in terms of monitoring units (MUs) and complexity indices are more in CLIs as compared with KBPs (p&lt;0.001).

Discussion

KBP models for left-sided post-mastectomy loco-regional radiotherapy were developed and validated for clinical use. These models improved the efficiency of treatment delivery as well as work flow for VMAT planning involving both moderately hypo fractionated and ultra-hypo fractionated radiotherapy regimens.

Implementation of automated personalised breast radiotherapy planning techniques with scripting in Raystation

OBJECTIVE

Implement scripted automatic breast planning (AP) for breast techniques within Raystation.

METHODS

Manual plans (MPs) were re-planned and compared with AP plans for whole breast (WB), partial breast (PB), hybrid volumetric modulated arc therapy simultaneous integrated boost (VMAT SIB) and VMAT nodal plans.

RESULTS

WB AP plans took 7 min comparing well to MP. One WB AP failed a mandatory dose constraint. Small statistically significant differences showed improved coverage for AP at expense of slightly hotter plans, however absolute differences were small (mean differences < 1% or D _0.5cc<0.2 Gy). PB AP plans took 9 min, showing improved coverage (V _24.7Gy97.6 vs 96.4 %). One PB AP case failed a mandatory constraint. Other dosimetric differences were non-significant. SIB AP plans took 14 min with one case failing a mandatory constraint with minor differences compared with MP except larger V _42.8Gy (3 vs 1.5 %) and more MU. VMAT AP plans took 12 min and were hotter for PTVp_4000 but had higher nodal coverage. Contra_Lung V _2.5Gy was higher (8.8 %) than MP plans (6.5 %).

CONCLUSION

Automatic planning of modern breast techniques has been successfully introduced using a commercial planning system. AP plans are very similar to MP, requiring little manual interaction for most cases with significant timesaving potential.

ADVANCES IN KNOWLEDGE

Scripted breast plans produced within minutes for WB, PB, SIB and VMAT. Successfully introduced into large busy department. Plans similar to manual plans, requiring little manual interaction.

Dose and organ displacement comparisons with breast conservative radiotherapy using abdominal and thoracic deep-inspiration breath-holds: A comparative dosimetric study

Deep-inspiration breath-hold (DIBH) reduces the radiation dose to the heart and lungs during breast radiotherapy in cancer. However, there is not enough discussion about suitable breathing methods for DIBH. Therefore, we investigated the radiation doses and organ and body surface displacement in abdominal DIBH (A-DIBH) and thoracic DIBH (T-DIBH). Free-breathing, A-DIBH, and T-DIBH computed tomography images of 100 patients were used. After contouring the targets, heart, and lungs, radiotherapy plans were created. We investigated the heart and lung doses, the associations between the heart and left lung displacements, and the thorax and abdominal surface displacements. No significant differences were observed in the target dose indices. However, the heart and lung doses were significantly lower in A-DIBH than in T-DIBH for all the indices; the mean heart and lung doses were 1.69 and 3.48 Gy, and 1.91 and 3.55 Gy in A-DIBH and T-DIBH, respectively. The inferior displacement of the heart and the left lung was more significant in A-DIBH. Therefore, inferior expansion of the heart and lungs may be responsible for the respective dose reductions. The abdominal surface displaced more than the thoracic surface in both A-DIBH and T-DIBH, and thoracic surface displacement was greater in T-DIBH than in A-DIBH. Moreover, A-DIBH can be identified because abdominal surface displacement was greater in A-DIBH than in T-DIBH. In conclusion, A-DIBH and T-DIBH could be distinguished by comparing the abdominal and thoracic surfaces of A-DIBH and T-DIBH, thereby ensuring the implementation of A-DIBH and reducing the heart and lung doses.

A Randomised Phase II Clinical Trial Comparing the Deliverability and Acute Toxicity of Wide Tangent versus Volumetric Modulated Arc Therapy to the Breast and Internal Mammary Chain

AIMS

Inclusion of the internal mammary chain in the radiotherapy target volume (IMC-RT) improves disease-free and overall survival in higher risk breast cancer patients, but increases radiation doses to heart and lungs. Dosimetric data show that either modified wide-tangential fields (WT) or volumetric modulated arc therapy (VMAT) together with [AQ1]voluntary deep inspiration breath hold (vDIBH) keep mean heart doses below 4 Gy in most patients. However, the impact on departmental resources has not yet been documented. This phase II clinical trial compared the time taken to deliver IMC-RT using either WT and vDIBH or VMAT and vDIBH, together with planning time, dosimetry, set-up reproducibility and toxicity.

MATERIALS AND METHODS

Left-sided breast cancer patients requiring IMC-RT were randomised to receive either WT(vDIBH) or VMAT radiotherapy. The primary outcome was treatment time, powered to detect a minimum difference of 75 min (5 min/fraction) between techniques. The population mean displacement, systematic error and random error for cone beam computed tomography chest wall matches in three directions of movement were calculated. Target volume and organ at risk doses were compared between groups. Side-effects, including skin (Radiation Therapy Oncology Group), lung and oesophageal toxicity (Common Terminology Criteria for Adverse Events v 4.03) rates, were compared between the groups over 3 months. Patient-reported outcome measures, including shoulder toxicity at baseline, 6 months and 1 year, were compared.

RESULTS

Twenty-one patients were recruited from a single UK centre between February 2017 and January 2018. The mean (standard deviation) total treatment time per fraction for VMAT treatments was 13.2 min (1.7 min) compared with 28.1 min (3.3 min) for WT(vDIBH). There were no statistically significant differences in patient set-up errors in between groups. The average mean heart dose for WT(vDIBH) was 2.6 Gy compared with 3.4 Gy for VMAT(vDIBH) (P = 0.13). The mean ipsilateral lung V17Gy was 32.8% in the WT(vDIBH) group versus 34.4% in the VMAT group (P = 0.2). The humeral head (mean dose 16.8 Gy versus 2.8 Gy), oesophagus (maximum dose 37.3 Gy versus 20.1 Gy) and thyroid (mean dose 22.0 Gy versus 11.2 Gy) all received a statistically significantly higher dose in the VMAT group. There were no statistically significant differences in skin, lung or oesophageal toxicity within 3 months of treatment. Patient-reported outcomes of shoulder toxicity, pain, fatigue, breathlessness and breast symptoms were similar between groups at 1 year.

CONCLUSION

VMAT(vDIBH) and WT(vDIBH) are feasible options for locoregional breast radiotherapy including the IMC. VMAT improves nodal coverage and delivers treatment more quickly, resulting in less breath holds for the patient. This is at the cost of increased dose to some non-target tissues. The latter does not appear to translate into increased toxicity in this small study.

Radiotherapy of Breast Cancer—Professional Guideline 1st Central-Eastern European Professional Consensus Statement on Breast Cancer

The international radiotherapy (RT) expert panel has revised and updated the RT guidelines that were accepted in 2020 at the 4th Hungarian Breast Cancer Consensus Conference, based on new scientific evidence. Radiotherapy after breast-conserving surgery (BCS) is indicated in ductal carcinoma in situ (stage 0), as RT decreases the risk of local recurrence (LR) by 50–60%. In early stage (stage I-II) invasive breast cancer RT remains a standard treatment following BCS. However, in elderly (≥70 years) patients with stage I, hormone receptor-positive tumour, hormonal therapy without RT can be considered. Hypofractionated whole breast irradiation (WBI) and for selected cases accelerated partial breast irradiation are validated treatment alternatives to conventional WBI administered for 5 weeks. Following mastectomy, RT significantly decreases the risk of LR and improves overall survival of patients who have 1 to 3 or ≥4 positive axillary lymph nodes. In selected cases of patients with 1 to 2 positive sentinel lymph nodes axillary dissection can be substituted with axillary RT. After neoadjuvant systemic treatment (NST) followed by BCS, WBI is mandatory, while after NST followed by mastectomy, locoregional RT should be given in cases of initial stage III–IV and ypN1 axillary status.

Influence of respiratory movement during post mastectomy radiotherapy on targets and heart for breast cancer

BACKGROUND/AIM

This study aimed to compare the dosimetric consequences of respiratory movement in volumetric-modulated arc therapy (VMAT) and three-dimensional conformal radiation therapy (3D-CRT) during postmastectomy radiation therapy, including internal mammary nodes (IMNs).

MATERIALS AND METHODS

Respiratory motion was implemented to a phantom using a dynamic device. The plans were delivered during cranial-caudal and ventral-dorsal movement in 5-mm (R05) and 10-mm (R10) amplitudes.

RESULTS

At the IMN, the dose errors were -2.8% (R05) and -6.2% (R10) for 3D-CRT and -4.9% (R05) and -8.5% (R10) for VMAT. The dose errors in chest wall were -.5% (R05) and -6.0% (R10) for 3D-CRT and -1.9% (R05) and -5.3% (R10) for VMAT. The left anterior descending doses showed significantly small absolute values. The gamma pass rates of VMAT were higher than those of 3D-CRT.

CONCLUSIONS

The benefit of VMAT technique in dose distribution was maintained, except in occasional instances of large breathing motion.

Comparison of organs at risk doses between deep inspiration breath-hold and free-breathing techniques during radiotherapy of left-sided breast cancer: A Meta-Analysis

After radiotherapy (RT) of left-sided breast cancer patients, organs at risk (OARs) such as heart, left anterior descending (LAD) coronary artery, and left lung could be affected by radiation dose in the long term. The objective of this study was to perform a comprehensive meta-analysis and determine OARs dose reduction during left-sided breast cancer treatment using different RT modalities combined with deep inspiration breath-hold (DIBH) relative to free-breathing (FB). PubMed, Scopus, EMBASE, ProQuest, Google Scholar, and Cochrane Library electronic databases were used to search for studies until June 6, 2021. Nineteen eligible studies were selected and analyzed using the RevMan 5.3 statistical software package. The pooled weighted mean difference (MD) with their 95% confidence intervals for each of the three OAR mean doses were determined using a random-effects meta-analysis model to assess the dose reductions. From a total of 189 studies, 1 prospective study, 15 retrospective studies, and 3 randomized control trials (RCTs) with an overall of 634 patients were included. Reduction of doses to the heart (weighted MD = -1.79 Gy; 95% CI (-2.28, -1.30); P = 0.00001), LAD (weighted MD = -8.34 Gy; 95% CI (-11.06, -5.61); P = 0.00001), and left-lung (weighted MD = -0.90 Gy; 95% CI (-1.19, -0.61); P = 0.00001) were observed using DIBH combinations relative to FB combination. This study emphasizes that during the treatment of left-sided breast/chest wall (CW) ± supraclavicular (SCV) ± infraclavicular (ICV) ± internal mammary chain (IMC) lymph nodes (LN) ± axillary (Ax)/ cancer patients, different RT modalities combined with DIBH techniques are better options to reduce dose to OARs compared to FB, which benefits to minimize the long-term complications.

Proton therapy for early breast cancer patients in the DBCG proton trial: planning, adaptation, and clinical experience from the first 43 patients

BACKGROUND

The Danish Breast Cancer Group (DBCG) Proton Trial randomizes breast cancer patients selected on high mean heart dose (MHD) or high lung dose (V20Gy/V17Gy) in the photon plan between photon and proton therapy. This study presents the proton plans and adaptation strategy for the first 43 breast cancer patients treated with protons in Denmark.

MATERIAL AND METHODS

Forty-four proton plans (one patient with bilateral cancer) were included; 2 local and 42 loco-regional including internal mammary nodes (IMN). Nineteen patients had a mastectomy and 25 a lumpectomy. The prescribed dose was either 50 Gy in 25 fractions (n = 30) or 40 Gy in 15 fractions (n = 14) wherefrom five received simultaneous integrated boost to the tumor bed. Using 2-3 en face proton fields, single-field optimization, robust optimization and a 5 cm range shifter ensured robustness towards breathing motion, setup- and range uncertainties. An anatomical evaluation was performed by evaluating the dose after adding/removing 3 mm and 5 mm tissue to/from the body-outline and used to define treatment tolerances for anatomical changes.

RESULTS

The nominal and robust criteria were met for all patients except two. The median MHD was 1.5 Gy (0.5-3.4 Gy, 50 Gy) and 1.1 Gy (0.0-1.5 Gy, 40 Gy). The anatomical evaluations showed how 5 mm shrinkage approximately doubled the MHD while 5 mm swelling reduced target coverage of the IMN below constraints. Ensuring 3-5 mm robustness toward swelling was prioritized but not always achieved by robust optimization alone emphasizing the need for a distal margin. Twenty-eight patients received plan adaptation, eight patients received two, and one received five.

CONCLUSION

This proton planning strategy ensured robust treatment plans within a pre-defined level of acceptable anatomical changes that fulfilled the planning criteria for most of the patients and ensured low MHD.

Hadrontherapy techniques for breast cancer

Radiotherapy plays a key role in breast cancer treatment, and recent technical advances have been made to improve the therapeutic window by limiting the risk of radiation-induced toxicity or by increasing tumor control. Hadrontherapy is a form a radiotherapy relying on particle beams; compared with photon beams, particle beams have specific physical, radiobiological and immunological properties, which can be valuable in diverse clinical situations. To date, available hadrontherapy techniques for breast cancer irradiation include proton therapy, carbon ion radiation therapy, fast neutron therapy and boron neutron capture therapy. This review analyzes the current rationale and level of evidence for each hadrontherapy technique for breast cancer.

What Can Proton Beam Therapy Achieve for Patients with Pectus Excavatum Requiring Left Breast, Axilla and Internal Mammary Nodal Radiotherapy?

AIMS

Exposure of the heart to radiation increases the risk of ischaemic heart disease, proportionate to the mean heart dose (MHD). Radiotherapy techniques including proton beam therapy (PBT) can reduce MHD. The aims of this study were to quantify the MHD reduction achievable by PBT compared with volumetric modulated arc therapy in breath hold (VMAT-BH) in patients with pectus excavatum (PEx), to identify an anatomical metric from a computed tomography scan that might indicate which patients will achieve the greatest MHD reductions from PBT.

MATERIALS AND METHODS

Sixteen patients with PEx (Haller Index ≥2.7) were identified from radiotherapy planning computed tomography images. Left breast/chest wall, axilla (I-IV) and internal mammary node (IMN) volumes were delineated. VMAT and PBT plans were prepared, all satisfying target coverage constraints. Signed-rank comparisons of techniques were undertaken for the mean dose to the heart, ipsilateral lung and contralateral breast. Spearman's rho correlations were calculated for anatomical metrics against MHD reduction achieved by PBT.

RESULTS

The mean MHD for VMAT-BH plans was 4.1 Gy compared with 0.7 Gy for PBT plans. PBT reduced MHD by an average of 3.4 Gy (range 2.8-4.4 Gy) compared with VMAT-BH (P < 0.001). PBT significantly reduced the mean dose to the ipsilateral lung (4.7 Gy, P < 0.001) and contralateral breast (2.7 Gy, P < 0.001). The distance (mm) at the most inferomedial extent of IMN volume (IMN to heart distance) negatively correlated with MHD reduction achieved by PBT (Spearman's rho -0.88 (95% confidence interval -0.96 to -0.67, P < 0.001)).

CONCLUSION

For patients with PEx requiring left-sided breast and IMN radiotherapy, a clinically significant MHD reduction is achievable using PBT, compared with the optimal photon technique (VMAT-BH). This is a patient group in whom PBT could have the greatest benefit.

Radiation-Induced Toxicity Risks in Photon Versus Proton Therapy for Synchronous Bilateral Breast Cancer

Purpose

This study compares photon and proton therapy plans for patients with synchronous bilateral early breast cancer and estimates risks of early and late radiation-induced toxicities.

Materials and Methods

Twenty-four patients with synchronous bilateral early breast cancer receiving adjuvant radiation therapy using photons, 3-dimensional conformal radiation therapy or volumetric modulated arc therapy, were included and competing pencil beam scanning proton therapy plans were created. Risks of dermatitis, pneumonitis, acute esophageal toxicity, lung and breast fibrosis, hypothyroidism, secondary lung and esophageal cancer and coronary artery events were estimated using published dose-response relationships and normal tissue complication probability (NTCP) models.

Results

The primary clinical target volume V95% and/or nodal clinical target volume V90% were less than 95% in 17 photon therapy plans and none of the proton plans. Median NTCP of radiation dermatitis ≥ grade 2 was 18.3% (range, 5.4-41.7) with photon therapy and 58.4% (range, 31.4-69.7) with proton therapy. Median excess absolute risk (EAR) of secondary lung cancer at age 80 for current and former smokers was 4.8% (range, 0.0-17.0) using photons and 2.7% (range, 0.0-13.6) using protons. Median EAR of coronary event at age 80, assuming all patients have preexisting cardiac risk factors, was 1.0% (range, 0.0-5.6) with photons and 0.2% (range, 0.0-1.3) with protons.

Conclusion

Proton therapy plans improved target coverage and reduced risk of coronary artery event and secondary lung cancer while increasing the risk of radiation dermatitis.

Proton reirradiation for recurrent or new primary breast cancer in the setting of prior breast irradiation

BACKGROUND AND PURPOSE

Late local recurrences and second primary breast cancers are increasingly common. Proton beam therapy (PBT) reirradiation (reRT) may allow safer delivery of a second definitive radiotherapy (RT) course. We analyzed outcomes of patients with recurrent or new primary breast cancer who underwent reRT.

MATERIALS AND METHODS

In an IRB-approved retrospective study, patient/tumor characteristics, treatment parameters, outcomes, and toxicities were collected for all consecutive patients with recurrent or new primary non-metastatic breast cancer previously treated with breast or chest wall RT who underwent PBT reRT.

RESULTS

Forty-six patients received reRT using uniform (70%) or pencil beam (30%) scanning PBT. Median first RT, reRT, and cumulative doses were 60 Gy (range 45-66 Gy), 50.4 Gy(RBE) (40-66.6 Gy(RBE)), and 110 Gy(RBE) (96.6-169.4 Gy(RBE)), respectively. Median follow-up was 21 months. There were no local or regional recurrences; 17% developed distant recurrence. Two-year DMFS and OS were 92.0% and 93.6%, respectively. Nine of 13 (69.2%) patients who underwent implant or flap reconstruction developed capsular contracture, 3 (23.1%) requiring surgical intervention. One (7.7%) patient developed grade 3 breast pain requiring mastectomy after breast conserving surgery. No acute or late grade 4-5 toxicities were seen. Increased body mass index (BMI) was protective of grade ≥ 2 acute toxicity (OR = 0.84, 95%CI = 0.70-1.00).

CONCLUSION

In the largest series to date of PBT reRT for breast cancer recurrence or new primary after prior definitive breast or chest wall RT, excellent locoregional control and few high-grade toxicities were encountered. PBT reRT may provide a relatively safe and highly effective salvage option. Additional patients and follow-up are needed to correlate composite normal tissue doses with toxicities and assess long-term outcomes.

Mammary Chain Irradiation in Left-Sided Breast Cancer: Can We Reduce the Risk of Secondary Cancer and Ischaemic Heart Disease with Modern Intensity-Modulated Radiotherapy Techniques?

Introduction

The aim of the present study was to estimate the impact of the addition of internal mammary chain (IMC) irradiation in node-positive left-sided breast cancer (BC) patients undergoing regional nodal irradiation (RNI) and comparatively evaluate excess relative and absolute risks of radiation-induced lung cancer/BC and ischaemic heart disease for intensity-modulated radiotherapy (IMRT) versus 3D conformal radiotherapy (3D-CRT).

Methods

Four treatment plans were created (3D-CRT and IMRT -/+ IMC) for each of the 10 evaluated patients, and estimates of excess relative risk (ERR) and 10-year excess absolute risk (EAR) were calculated for radiation-induced lung cancer/BC and coronary events using linear, linear-exponential and plateau models.

Results

The addition of IMC irradiation to RNI significantly increased the dose exposure of the heart, lung and contralateral breast using both techniques, increasing ERR for secondary lung cancer (58 vs. 44%, p = 0.002), contralateral BC (49 vs. 31%, p = 0.002) and ischaemic heart disease (41 vs. 27%, p = 0.002, IMRT plans). IMRT significantly reduced the mean cardiac dose and mean lung dose as compared to 3D-CRT, decreasing ERR for major coronary events (64% 3D-CRT vs. 41% IMRT, p = 0.002) and ERR for secondary lung cancer (75 vs. 58%, p = 0.004) in IMC irradiation, without a significant impact on secondary contralateral BC risks.

Conclusion

Although IMC irradiation has been shown to increase survival rates in node-positive BC patients, it increased dose exposure of organs at risk in left-sided BC, resulting in significantly increased risks for secondary lung cancer/contralateral BC and ischaemic heart disease. In this setting, the adoption of IMRT seems advantageous when compared to 3D-CRT.

Proton Therapy for Breast Cancer: A Consensus Statement From the Particle Therapy Cooperative Group Breast Cancer Subcommittee

Radiation therapy plays an important role in the multidisciplinary management of breast cancer. Recent years have seen improvements in breast cancer survival and a greater appreciation of potential long-term morbidity associated with the dose and volume of irradiated organs. Proton therapy reduces the dose to nontarget structures while optimizing target coverage. However, there remain additional financial costs associated with proton therapy, despite reductions over time, and studies have yet to demonstrate that protons improve upon the treatment outcomes achieved with photon radiation therapy. There remains considerable heterogeneity in proton patient selection and techniques, and the rapid technological advances in the field have the potential to affect evidence evaluation, given the long latency period for breast cancer radiation therapy recurrence and late effects. In this consensus statement, we assess the data available to the radiation oncology community of proton therapy for breast cancer, provide expert consensus recommendations on indications and technique, and highlight ongoing trials' cost-effectiveness analyses and key areas for future research.

Radiation Oncologists' Approach to Internal Mammary Lymph Node Radiotherapy in Breast Cancer: The Turkish Society for Radiation Oncology Breast Cancer Study Group (TROD 06-005 Survey Study)

Background

This study aimed to examine the practice patterns of radiation oncologists in Turkey regarding radiotherapy to the regional lymph nodes, including internal mammary lymph nodes (IMNs), and identify the factors influencing their clinical decisions in breast cancer patients.

Methods

A nationwide, 19-point questionnaire was sent to the physician members of the Turkish Society for Radiation Oncology (TROD).

Results

In total, 165 radiation oncologists completed the survey, corresponding to a 27% response rate. Regional radiotherapy was used in 64.2% of the patients with 1-3 axillary lymphatic involvement and unfavorable prognostic factors. In contrast, 61.2% of the respondents indicated that IMN should be included in the target volume for regional radiotherapy when the patient had one positive node after axillary lymph node dissection (ALND) in the inner quadrant and central region tumors. However, 71.5% of the respondents chose to include the IMN in the non-inner quadrant and non-central region tumors for patients with four or more positive nodes after ALND. The decision to offer internal mammary lymph node radiotherapy (IMNRT) varied widely and significantly among respondents, years in practice, and the rates of dedicating their clinical time to patients with breast cancer.

Conclusion

The results of this survey revealed significant national variation in attitudes regarding the treatment of IMN. Thus, this study may also help document the impact of future studies on clinical practice.

Technical Note: Clinical modeling and validation of breast tissue expander metallic ports in a commercial treatment planning system for proton therapy

PURPOSE

To validate breast tissue expander metallic port (MP) models in a commercial treatment planning system (TPS) in proton pencil beam scanning (PBS) treatments for breast cancer patients with breast tissue expanders.

METHODS AND MATERIALS

Three types of MPs taken out of a Mentor CPX4, a Natrelle 133, and a PMT Integra breast tissue expanders and a 650 cc saline filled Mentor CPX4 expander were placed on top of acrylic slabs, and scanned using a Siemens Somatom Definition AS Open RT CT scanner. Structure templates for each of the MPs were designed within Eclipse TPS. The CT numbers for the metallic parts were overridden to reflect measured or calculated relative proton stopping powers (RPSPs). Mock targets were contoured in acrylic to represent postmastectomy chest-wall radiation therapy (PMRT) targets. Plans with different beam incident angles were optimized using the Eclipse TPS to deliver uniform prescription dose to the target using Hitachi Probeat-V PBS beams. Eclipse calculated doses and an in-house Monte Carlo (MC) code calculated doses were compared to the measured Gafchromic EBT3 film doses in acrylic.

RESULTS

TPS/MC and film dose comparison results showed that (1) 3%/2 mm/10% threshold Gamma pass rates were better than 90.8% in the acrylic target region for all plans; (2) comparing TPS and film doses for the individual beam plans in the MP dose shadow areas, the area with dose difference above 5% ([ΔA] 5%) ranged from 1.1 to 5.0 cm² , and the maximum dose difference ([ΔD] 0.01 cm² ) ranged from 12.5% to 25.0%; (3) comparing MC and film doses for the individual beam plans in the MP dose shadow areas, the (ΔA) 5% varied from 1.1 to 2.9 cm² and (ΔD) 0.01 cm² varied from 8.5% to 24.2%; (4) for a plan composed of three individual beams treating through the Mentor CPX4 expander, the TPS (ΔA) 5% was less than 0.13 cm² , and the (ΔD) 0.01 cm² was less than 6% in the MP dose shadow areas.

CONCLUSIONS

It is feasible to treat patients with tissue expanders using multiple PBS beams using a structure template with CT number overridden to represent the measured/calculated RPSP for MPs for PBS treatment planning. MC dose was more accurate than analytical dose in the areas with high dose gradient caused by the density heterogeneity of the breast tissue expander MPs.

A dosimetric and radiobiological evaluation of VMAT following mastectomy for patients with left-sided breast cancer

Background

To compare the dosimetric, normal tissue complication probability (NTCP), secondary cancer complication probabilities (SCCP), and excess absolute risk (EAR) differences of volumetric modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) for left-sided breast cancer after mastectomy.

Methods and materials

Thirty patients with left-sided breast cancer treated with post-mastectomy radiation therapy (PMRT) were randomly enrolled in this study. Both IMRT and VMAT treatment plans were created for each patient. Planning target volume (PTV) doses for the chest wall and internal mammary nodes, PTV1, and PTV of the supraclavicular nodes, PTV2, of 50 Gy were prescribed in 25 fractions. The plans were evaluated based on PTV1 and PTV2 coverage, homogeneity index (HI), conformity index, conformity number (CN), dose to organs at risk, NTCP, SCCP, EAR, number of monitors units, and beam delivery time.

Results

VMAT resulted in more homogeneous chest wall coverage than did IMRT. The percent volume of PTV1 that received the prescribed dose of VMRT and IMRT was 95.9 ± 1.2% and 94.5 ± 1.6%, respectively (p < 0.001). The HI was 0.11 ± 0.01 for VMAT and 0.12 ± 0.02 for IMRT, respectively (p = 0.001). The VMAT plan had better conformity (CN: 0.84 ± 0.02 vs. 0.78 ± 0.04, p < 0.001) in PTV compared with IMRT. As opposed to IMRT plans, VMAT delivered a lower mean dose to the ipsilateral lung (11.5 Gy vs 12.6 Gy) and heart (5.2 Gy vs 6.0 Gy) and significantly reduced the V₅, V₁₀, V_20, V_30, and V₄₀ of the ipsilateral lung and heart; only the differences in V₅ of the ipsilateral lung did not reach statistical significance (p = 0.409). Although the volume of the ipsilateral lung and heart encompassed by the 2.5 Gy isodose line (V_2.5) was increased by 6.7% and 7.7% (p < 0.001, p = 0.002), the NTCP was decreased by 0.8% and 0.6%, and SCCP and EAR were decreased by 1.9% and 0.1% for the ipsilateral lung. No significant differences were observed in the contralateral lung/breast V_2.5, V_5, V₁₀, V₂₀, mean dose, SCCP, and EAR. Finally, VMAT reduced the number of monitor units by 31.5% and the treatment time by 71.4%, as compared with IMRT.

Conclusions

Compared with IMRT, VMAT is the optimal technique for PMRT patients with left-sided breast cancer due to better target coverage, a lower dose delivered, NTCP, SCCP, and EAR to the ipsilateral lung and heart, similar doses delivered to the contralateral lung and breast, fewer monitor units and a shorter delivery time.

Comprehensive nodal breast VMAT: solving the low-dose wash dilemma using an iterative knowledge-based radiotherapy planning solution

Introduction

Aimed to develop a simple and robust volumetric modulated arc radiotherapy (VMAT) solution for comprehensive lymph node (CLN) breast cancer without increase in low‐dose wash.

Methods

Forty CLN‐breast patient data sets were utilised to develop a knowledge‐based planning (KBP) VMAT model, which limits low‐dose wash using iterative learning and base‐tangential methods as benchmark. Another twenty data sets were employed to validate the model comparing KBP‐generated ipsilateral VMAT (ipsi‐VMAT) plans against the benchmarked hybrid (h)‐VMAT (departmental standard) and bowtie‐VMAT (published best practice) methods. Planning target volume (PTV), conformity/homogeneity index (CI/HI), organ‐at‐risk (OAR), remaining‐volume‐at‐risk (RVR) and blinded radiation oncologist (RO) plan preference were evaluated.

Results

Ipsi‐ and bowtie‐VMAT plans were dosimetrically equivalent, achieving greater nodal target coverage (P < 0.05) compared to h‐VMAT with minor reduction in breast coverage. CI was enhanced for a small reduction in breast HI with improved dose sparing to ipsilateral‐lung and humeral head (P < 0.05) at immaterial expense to spinal cord. Significantly, low‐dose wash to OARs and RVR were comparable between all plan types demonstrating a simple VMAT class solution robust to patient‐specific anatomic variation can be applied to CLN breast without need for complex beam modification (hybrid plans, avoidance sectors or other). This result was supported by blinded RO review.

Conclusions

A simple and robust ipsilateral VMAT class solution for CLN breast generated using iterative KBP modelling can achieve clinically acceptable target coverage and OAR sparing without unwanted increase in low‐dose wash associated with increased second malignancy risk.

Cardiac substructure exposure in breast radiotherapy: a comparison between intensity modulated proton therapy and volumetric modulated arc therapy

INTRODUCTION

Proton therapy for breast cancer treatment reduces cardiac radiation exposure. Left-sided breast cancer patients with indication for internal mammary chain (IMC) irradiation are most at risk of radiation-induced cardiotoxicity. This study aims to evaluate in this situation the potential dosimetric benefit of intensity modulated proton therapy (IMPT) over volumetric modulated arc therapy (VMAT) at the cardiac substructure level.

MATERIALS AND METHODS

Cardiac substructures were retrospectively delineated according to ESTRO guidelines on the simulation CT scans of fourteen left-sided breast cancer patients having undergone conserving surgery and adjuvant locoregional free-breathing (FB-) or deep inspiration breath-hold (DIBH-) VMAT with internal mammary chain irradiation. IMPT treatment was re-planned on the simulation CT scans. Mean doses to cardiac substructures were retrieved and compared between VMAT treatment plans and IMPT simulation plans. Pearson correlation coefficients were calculated between mean doses delivered to cardiac substructures using these two techniques.

RESULTS

Mean doses to all cardiac substructures were significantly lower with IMPT than with VMAT. Regardless of the irradiation technique, the most exposed cardiac substructure was the mid segment of the left anterior descending coronary artery (LADCA). Pearson correlation coefficients between mean doses to cardiac substructures were usually weak and statistically non-significant for IMPT; mean heart dose (MHD) only correlated with mean doses delivered to the right ventricle, to the mid segment of the right coronary artery (RCA) and, to a lesser extent, to the LADCA.

CONCLUSION

The dosimetric benefit of IMPT over conformal photon therapy was consistently observed for all cardiac substructures. MHD may not be a reliable dosimetric parameter for precise cardiac exposure evaluation when planning IMPT.

Side Effects 15 Years after Lymph Node Irradiation in Breast Cancer: Randomized EORTC Trial 22922/10925

BACKGROUND

Uncertainty about the benefit/risk ratio of regional lymph node irradiation led to varying clinical protocols. We investigated long-term late side effects after internal mammary and medial supraclavicular (IM-MS) lymph node irradiation to improve shared decision-making.

METHODS

The multicentre EORTC trial (ClinicalTrials.gov, NCT00002851) randomized stage I-III breast cancer patients with involved axillary nodes and/or a medially located primary tumor. We analyzed late side effects, both longitudinally at every follow-up and cross-sectionally at 5-year intervals. All statistical tests were 2-sided.

RESULTS

Between 1996 and 2004, 46 departments from 13 countries accrued 4004 patients. Median follow-up was 15.7 years. Longitudinal follow-up data showed cumulative incidence rates at 15 years of 2.9% (95% confidence interval [CI] = 2.2%-3.8%) vs. 5.7% (95% CI = 4.7%-6.9%) (P<.001) for lung fibrosis, of 1.1% (95% CI = 0.7%-1.7%) vs. 1.9% (95% CI = 1.3%-2.6%) (P=.07) for cardiac fibrosis, and of 9.4% (95% CI = 8.0%-10.8%) vs. 11.1% (95% CI = 9.6%-12.7%) (P=.04) for any cardiac disease, when treated without or with IM-MS lymph node irradiation. There was no evidence for differences between left- and right-sided breast cancer (Wald chi-square test of treatment by breast side interaction, P=.33 and P=.35, for cardiac fibrosis and for any cardiac disease, respectively). The cumulative incidence probabilities of cross-sectionally reported side effects with a score of 2 or greater at 15 years were 0.1% (95% CI = 0.0%-0.5%) vs. 0.8% (95% CI = 0.4%-1.4%) for pulmonary (P=.02), 1.8% (95% CI = 1.1%-2.8%) vs. 2.6% (95% CI = 1.8%-3.7%) for cardiac (P=.15), and 0.0% (95% CI not evaluated) vs. 0.1% (95% CI = 0.0%-0.4%) for oesophageal (P=.16), respectively. No difference was observed in the incidence of second malignancies, contralateral breast cancer or cardiovascular deaths.

CONCLUSIONS

The incidence of late pulmonary side effects was statistically significantly higher after IM-MS lymph node irradiation, as were some of the cardiac events, without a difference between left- and right-sided treatments. Absolute rates and differences were very low, without increased non-breast cancer related mortality, even before introducing heart-sparing techniques.

Outcomes of and treatment planning considerations for a hybrid technique delivering proton pencil-beam scanning radiation to women with metal-containing tissue expanders undergoing post-mastectomy radiation

BACKGROUND

Following mastectomy, immediate breast reconstruction often involves the use of temporary tissue expanders (TEs). TEs contain metallic ports (MPs), which complicate proton pencil-beam scanning (PBS) planning. A technique was implemented for delivering PBS post-mastectomy radiation (PMRT) to patients with TEs and MPs.

METHODS

A protocol utilizing a hybrid single- and multi-field optimization (SFO, MFO) technique was developed. Plans were robustly optimized using a Monte Carlo algorithm. A CTV_eval structure including chest wall (CW) and regional nodal (RNI) targets and excluding the TE was evaluated. Organ at risk (OAR) dosimetry and acute toxicities were analyzed.

RESULTS

Twenty-nine women were treated with this technique. A 2-field SFO technique was used superior and inferior to the MP, with a 3 or 4-field MFO technique used at the level of the MP. Virtual blocks were utilized so that beams did not travel through the MP. A port-to-CW distance of 1 cm was required. Patients underwent daily image-guidance to ensure the port remained within a 0.5 cm internal planning volume (ITV). Median RT dose to CTV_eval was 50.4 Gy (45.0-50.4). Median 95% CTV_eval coverage was 99.5% (95-100). Optically stimulated luminescent dosimeter (OSLD) readings were available for 8 patients and correlated to the dose measurements in the treatment planning system (TPS); median OSLD ratio was 0.99 (range, 0.93-1.02).

CONCLUSIONS

Delivering PMRT with PBS for women with metal-containing TEs using a hybrid SFO/MFO technique is feasible, reproducible, and achieves excellent dose distributions. Specialized planning and image-guidance techniques are required to safely utilize this treatment in the clinic.

Clinical and technical considerations for mediastinal Hodgkin lymphoma protontherapy based on a single-center early experience

PURPOSE

Protontherapy for mediastinal Hodgkin lymphoma reduces cardiac, lung and breast exposure, which may limit radiation-induced adverse events. While this technique is already widely implemented in the United-States, clinical experience is still limited in France. This study analyses the practice of mediastinal Hodgkin lymphoma protontherapy at the Institut Curie to implement this technique at a larger scale.

MATERIALS AND METHODS

Data from all mediastinal Hodgkin lymphoma patients from the hematology department of the Institut Curie who were subsequently evaluated at the Protontherapy Center of Orsay (CPO) of Institut Curie for adjuvant protontherapy were retrieved. We analyzed why these patients were ultimately treated with protontherapy or not.

RESULTS

Between January 2018 and January 2021, twenty mediastinal Hodgkin lymphoma patients from the hematology department of the Institut Curie have been screened for protontherapy at the CPO. Four of them (20%) were ultimately treated with proton beams. Treatment was well tolerated without grade 3-4 adverse events. With a median follow-up of two years, none of these patients relapsed. The others sixteen patients were not treated with protontherapy due to multiple reasons including: lack of treatment room disponibility, accessibility difficulties, psychiatric disorder, and anatomic or dosimetric considerations.

CONCLUSION

Despite notable dosimetric superiority over photon radiotherapy and excellent clinical tolerance, lack of availability of protontherapy facilities limit implementation of mediastinal Hodgkin lymphoma protontherapy. Additionally, strict selection criteria must be defined.

Split-VMAT technique to control the deep inspiration breath hold time for breast cancer radiotherapy

BACKGROUND

To improve split-VMAT technique by optimizing treatment delivery time for deep-inspiration breath hold (DIBH) radiotherapy in left-sided breast cancer patients, when automatic beam-interruption devices are not available.

METHODS

Ten consecutive patients were treated with an eight partial arcs (8paVMAT) plan, standard of care in our center. A four partial arcs (4paVMAT) plan was also created and actual LINAC outputs were measured, to evaluate whether there was a dosimetric difference between both techniques and potential impact on the delivered dose. Subsequently, ten other patients were consecutively treated with a 4paVMAT plan to compare the actual treatment delivery time between both techniques. The prescribed dose was 40.05 Gy/15 fractions on the PTV breast (breast or thoracic wall), lymph nodes (LN) and intramammary lymph node chain (IMN). Treatment delivery time, PTVs coverage, conformity index (CI), organs at risk (OAR) dose, monitor units (MU), and gamma index were compared.

RESULTS

Both split-VMAT techniques resulted in similar dose coverage for the PTV Breast and LN, and similar CI. For PTV IMN we observed a 5% increased coverage for the volume receiving ≥ 36 Gy with 4paVMAT, with an identical volume receiving ≥ 32 Gy. There was no difference for the OAR sparing, with the exception of the contralateral organs: there was a 0.6 Gy decrease for contralateral breast mean (p ≤ 0.01) and 1% decrease for the volume of right lung receiving ≥ 5 Gy (p = 0.024). Overall, these results indicate a modest clinical benefit of using 4paVMAT in comparison to 8paVMAT. An increase in the number of MU per arc was observed for the 4paVMAT technique, as expected, while the total number of MU remained comparable for both techniques. All the plans were measured with the Delta4 phantom and passed the gamma index criteria with no significant differences. Finally, the main difference was seen for the treatment delivery time: there was a significant decrease from 8.9 to 5.4 min for the 4paVMAT plans (p < .05).

CONCLUSIONS

This study is mainly of interest for centers who are implementing the DIBH technique without automatic beam-holding devices and who therefore may require to manually switch the beam on and off during breast DIBH treatment. Split-VMAT technique with 4 partial arcs significantly reduces the treatment delivery time compared to 8 partial arcs, without compromising the target coverage and the OAR sparing. The technique decreases the number of breath holds per fraction, resulting in a shorter treatment session.

Excluding Lung Tissue from the PTV during Internal Mammary Irradiation. A Safe Technique for OAR-Sparing?

Simple Summary

The planning treatment volume (PTV) during internal mammary irradiation (IMNI) regularly overlaps with lung tissue and is often in close proximity to the heart. Thus, exclusion of lung tissue from the PTV is a potential technique to spare the organs at risk (OARs) during adjuvant breast cancer irradiation. Using an innovative dose recalculation and accumulation algorithm, we evaluated the safety of exclusion of lung tissue from the PTV. According to our data, exclusion of lung tissue from the PTV to spare the OARs leads to significant dose reduction in the target volume and can, therefore, not be recommended.

Abstract

The current study aims to determine whether exclusion of lung tissue from planning treatment volume (PTV) is a valid organ at risk (OAR)-sparing technique during internal mammary irradiation (IMNI). Twenty patients with left-sided breast cancer undergoing adjuvant radiotherapy including IMNI after mastectomy or lumpectomy with daily ConeBeam CT (CBCT; median n = 28) were enrolled in the current study. The daily dose distribution of the patients was estimated by recalculating treatment plans on CBCT-scans based on a standard PTV (PTV margin: 5mm-STD) and a modified PTV, which excluded overlapping lung tissue (ExLung). Using 3D-deformable dose accumulation, the dose coverage in the target volume was estimated in dependence of the PTV-margins. The estimated delivered dose in the IMN-CTV was significantly lower for the ExLung PTV compared to the STD PTV: ExLung: V95%: 76.6 ± 22.9%; V90%: 89.6 ± 13.2%, STD: V95%: 95.6 ± 7.4%; V90%: 99.1 ± 2.7%. Daily CBCT imaging cannot sufficiently compensate the anatomic changes and intrafraction movement throughout the treatment. Therefore, to ensure adequate delivery of the prescribed dose to the IMN-CTV, exclusion of lung tissue from the PTV to spare the OARs is not recommended.

Dosimetric Comparison of Radiation Techniques for Comprehensive Regional Nodal Radiation Therapy for Left-Sided Breast Cancer: A Treatment Planning Study

Purpose

How modern cardiac sparing techniques and beam delivery systems using advanced x-ray and proton beam therapy (PBT) can reduce incidental radiation exposure doses to cardiac and pulmonary organs individually or in any combination is poorly investigated.

Methods

Among 15 patients with left-sided breast cancer, partial wide tangential 3D-conformal radiotherapy (3DCRT) delivered in conventional fractionation (CF) or hypofractionated (HF) schedules; PBT delivered in a CF schedule; and volumetric modulated arc therapy (VMAT) delivered in an HF schedule, each under continuous positive airway pressure (CPAP) and free-breathing (FB) conditions, were examined. Target volume coverage and doses to organs-at-risk (OARs) were calculated for each technique. Outcomes were compared with one-way analysis of variance and the Bonferroni test, with p-values <0.05 considered significant.

Results

Target volume coverage was within acceptable levels in all interventions, except for the internal mammary lymph node D95 (99% in PBT, 90% in VMAT-CPAP, 84% in VMAT-FB, and 74% in 3DCRT). The mean heart dose (MHD) was the lowest in PBT (<1 Gy) and VMAT-CPAP (2.2 Gy) and the highest in 3DCRT with CF/FB (7.8 Gy), respectively. The mean lung dose (MLD) was the highest in 3DCRT-CF-FB (20 Gy) and the lowest in both VMAT-HF-CPAP and PBT (approximately 5-6 Gy). VMAT-HF-CPAP and PBT delivered a comparable maximum dose to the left ascending artery (7.2 and 6.13 Gy, respectively).

Conclusions

Both proton and VMAT in combination with CPAP can minimize the radiation exposure to heart and lung with optimal target coverage in regional RT for left-sided breast cancer. The clinical relevance of these differences is yet to be elucidated. Continued efforts are needed to minimize radiation exposures during RT treatment to maximize its therapeutic index.

Identifying Surrogates for Heart and Ipsilateral Lung Dose to Guide Field Placement and Treatment Modality Selection during Virtual Simulation of Breast Radiotherapy

AIMS

Virtual simulation (VSim) of tangential photon fields is a common method of field localisation for breast radiotherapy. Heart and ipsilateral lung dose is unknown until the dosimetric plan is produced. If heart and ipsilateral lung tolerance doses are exceeded, this can prolong the pre-treatment pathway, particularly if a change of technique is required. The aim of this study was to identify predictive surrogates for heart and ipsilateral lung dose during VSim to aid optimum field placement and treatment modality selection.

MATERIALS AND METHODS

Computed tomography data from 50 patients referred for left breast/chest wall radiotherapy were retrospectively analysed (model-building cohort). The prescribed dose was 40.05 Gy in 15 fractions using a tangential photon technique. The heart and ipsilateral lung contours were duplicated, cropped to within the field borders and labelled heart-in-field (HIF) and ipsilateral lung-in-field (ILF). The percentage of HIF (%HIF) and ILF (%ILF) was calculated and correlated with mean heart dose (MHD) and volume of the ipsilateral lung receiving 18 Gy (V18Gy). Linear regression models were calculated. A validation cohort of 10 left- and 10 right-sided cases with an anterior supraclavicular fossa (SCF) field, and 10 left- and 10 right-sided cases including the internal mammary nodes using a wide tangential technique and anterior SCF field, tested the predictive model. Threshold values for %HIF and %ILF were calculated for clinically relevant MHD and ipsilateral lung V18Gy tolerance doses.

RESULTS

For the model-building cohort, the median %HIF and MHD were 2.6 (0.4-16.7) and 2.3 (1.2-8) Gy. The median %ILF and ipsilateral lung V18Gy were 12.1 (2.8-33.6) and 12.6 (3.3-35) %. There was a statistically significant strong positive correlation of %HIF with MHD (r2 = 0.97, P < 0.0001) and of %ILF with ipsilateral lung V18Gy (r2 = 0.99, P < 0.0001). For the validation cohort, the median %HIF and MHD were 3.9 (0.6-8) and 2.5 (1.4-4.7) Gy. The median %ILF and ipsilateral lung V18Gy were 20.1 (12.4-32.0) and 20.9 (12.4-34.4) %. The validation cohort confirmed that %HIF and %ILF continue to be predictive surrogates for heart and ipsilateral lung dose during VSim of left- and right-sided cases when including the SCF ± internal mammary nodes with a three-field photon technique.

DISCUSSION

The ability to VSim breast radiotherapy (±nodal targets) and accurately predict the heart and ipsilateral lung doses on the dosimetric plan will ensure that tolerance doses are not exceeded, and identify early in the pre-treatment pathway those cases where alternative techniques or modalities should be considered.

Volumetric arc therapy: A viable option for right-sided breast with comprehensive regional nodal irradiation in conjunction with deep inspiration breath hold

PURPOSE

Deep inspiration breath hold (DIBH) is an innovative technique routinely used for left-sided breast radiotherapy to significantly reduce harmful dose to the heart and ipsilateral lung. Currently, there is scant literature exploring DIBH for right-sided whole breast and regional nodal irradiation (WB & RNI). The purpose of this study is to examine if DIBH produces a clinically significant reduction in organ at risk (OAR) dose for right-sided WB + RNI, whilst comparatively analysing the use of volumetric arc therapy (VMAT) versus tangential inverse modulated radiotherapy (t-IMRT).

METHODS AND MATERIALS

Ten patients, previously treated for left sided breast cancer (with a FB and DIBH CT scan), were selected from our database to be retrospectively replanned to the right breast and nodal regions. Planning target volumes (PTV) were marked to include the whole right breast and regional nodes, encompassing the supraclavicular fossa (SCF) and internal mammary nodes (IMN). PTVs and OARs were contoured on the Pinnacle workstation according to the Radiation Therapy Oncology Group (RTOG) guidelines. VMAT and t-IMRT plans were generated to a prescribed dose of 50 Gy in 25 fractions on both the DIBH and FB data sets for dosimetric analysis.

RESULTS

Coverage of the right breast (mean, D95%) and SCF (D95%) were significantly improved with VMAT in comparison to t-IMRT, with no statistically significant variation on the IMN PTV (D95%). The use of DIBH did not impact PTV coverage compared with FB. VMAT reduced dose to the ipsilateral lung (mean, V20Gy), combined lungs (mean, V20Gy) and liver (D2cc); conversely dose to the heart (mean), left lung (mean, V5Gy) and contralateral breast (mean) were increased. For both techniques DIBH significantly improved dose to OARs including the ipsilateral lung (mean, V20Gy, V5Gy), total lung (mean, V20Gy), heart (mean, V25Gy) and liver (D2cc) when compared to FB.

CONCLUSION

DIBH could be considered for patients treated with right-sided WB and RNI due to a significant decrease in heart, ipsilateral lung, total lung and liver doses. VMAT significantly improves PTV coverage over t-IMRT whilst reducing dose to the ipsilateral lung and liver, albeit to the detriment of the left lung, contralateral breast and heart. The increase in heart dose can be mitigated by the use of DIBH. We recommend if VMAT is utilised for superior target volume coverage, DIBH should also be implemented to reduce OAR toxicity. RÉSUMÉ:   BUT: La retenue respiratoire profonde (DIBH) est une technique innovante couramment utilisée pour la radiothérapie du cÔté gauche du sein afin de réduire de manière significative la dose nocive pour le cŒur et le poumon ipsilatéral (13-15). Actuellement, il existe peu d'ouvrages sur la DIBH pour l'irradiation du sein entier du cÔté droit et des nodules régionaux (WB+RNI). L'objectif de cette étude est d'examiner si la DIBH produit une réduction cliniquement significative de la dose d'organe à risque (OAR) pour la WB+RNI du cÔté droit, tout en analysant comparativement l'utilisation de l'arcthérapie volumétrique (VMAT) par rapport à la radiothérapie par modulation d'intensité tangentielle (t-IMRT). MéTHODOLOGIE ET MATéRIEL: Dix scans tomodensitométriques avec un ensemble de données DIBH et de respiration libre (FB) ont été sélectionnés de manière rétrospective. Les volumes cibles de planification (PTV) ont été marqués pour inclure le sein droit entier et les ganglions régionaux, englobant la fosse supraclaviculaire (SCF) et les ganglions mammaires internes (IMN). Les PTV et les OAR ont été définis sur la station de travail Pinnacle conformément aux directives du groupe de radiothérapie oncologique (RTOG) (17). Les plans t-IMRT et VMAT ont été générés pour une dose prescrite de 50Gy en 25 fractions sur les ensembles de données DIBH et FB pour l'analyse dosimétrique. RéSULTATS: La couverture du sein droit (moyenne, D95%) et du SCF (D95%) a été significativement améliorée avec la VMAT par rapport à la t-IMRT, sans variation statistiquement significative sur la PTV IMN (D95%). L'utilisation de la DIBH n'a pas eu d'impact sur la couverture du PTV par rapport à la FB. La VMAT a réduit la dose dans le poumon ipsilatéral (moyenne, V20Gy), les poumons combinés (moyenne, V20Gy) et le foie (D2cc) ; à l'inverse, la dose dans le cŒur (moyenne), le poumon gauche (moyenne, V5Gy) et le sein controlatéral (moyenne) a été augmentée. Pour les deux techniques, la DIBH a amélioré de manière significative la dose aux OAR, y compris le poumon ipsilatéral (moyenne, V20Gy, V5Gy), le poumon total (moyenne, V20Gy), le cŒur (moyenne, V25Gy) et le foie (D2cc), par rapport à la respiration libre.

CONCLUSION

La DIBH pourrait être envisagé pour les patients traités par WB+RNI du cÔté droit en raison d'une diminution significative des doses dans le cŒur, le poumon ipsilatéral, le poumon total et le foie. La VMAT améliore considérablement la couverture de la PTV par rapport à la t-IMRT tout en réduisant la dose dans le poumon ipsilatéral et le foie, mais au détriment du poumon gauche, du sein controlatéral et du cŒur. L'augmentation de la dose au cŒur peut être atténuée par l'utilisation de la DIBH. Nous recommandons, si la VMAT est utilisée pour une couverture supérieure du volume cible, de mettre également en Œuvre la DIBH pour réduire la toxicité aux OAR.

Selection criteria for early breast cancer patients in the DBCG proton trial - The randomised phase III trial strategy

BACKGROUND AND PURPOSE

Adjuvant radiotherapy of internal mammary nodes (IMN) improves survival in high-risk early breast cancer patients but inevitably leads to more dose to heart and lung. Target coverage is often compromised to meet heart/lung dose constraints. We estimate heart and lung dose when target coverage is not compromised in consecutive patients. These estimates are used to guide the choice of selection criteria for the randomised Danish Breast Cancer Group (DBCG) Proton Trial.

MATERIALS AND METHODS

179 breast cancer patients already treated with loco-regional IMN radiotherapy from 18 European departments were included. If the clinically delivered treatment plan did not comply with defined target coverage requirements, the plan was modified retrospectively until sufficient coverage was reached. The choice of selection criteria was based on the estimated number of eligible patients for different heart and lung dose thresholds in combination with proton therapy capacity limitations and dose-response relationships for heart and lung.

RESULTS

Median mean heart dose was 3.0 Gy (range, 1.1-8.2 Gy) for left-sided and 1.4 Gy (0.4-11.5 Gy) for right-sided treatment plans. Median V17Gy/V20Gy (hypofractionated/normofractionated plans) for ipsilateral lung was 31% (9-57%). The DBCG Radiotherapy Committee chose mean heart dose ≥ 4 Gy and/or lung V17Gy/V20Gy ≥ 37% as thresholds for inclusion in the randomised trial. Using these thresholds, we estimate that 22% of patients requiring loco-regional IMN radiotherapy will be eligible for the trial.

CONCLUSION

The patient selection criteria for the DBCG Proton Trial are mean heart dose ≥ 4 Gy and/or lung V17Gy/V20Gy ≥ 37%.

Voluntary versus ABC breath-hold in the context of VMAT for breast and locoregional lymph node radiotherapy including the internal mammary chain

BACKGROUND

Deep-inspiration breath-hold (DIBH) reduces radiation dose to the heart in patients undergoing locoregional breast radiotherapy. In the context of tangential irradiation of the breast/ chest wall, a voluntary breath hold (vDIBH) technique has been shown to be as reproducible as a machine-assisted breath hold technique using the active breathing co-ordinator (ABC™, Elekta, Crawley, UK, ABC_DIBH). This study compares set-up reproducibility for vDIBH versus ABC_DIBH in patients undergoing volumetric-modulated arc radiotherapy (VMAT) for breast cancer, both with and without wax bolus.

METHOD

Patients with breast cancer requiring pan regional lymph node VMAT +/- wax bolus in breath-hold were CT scanned in vDIBH and ABC_DIBH. Patients were randomised to receive one technique for fractions 1-7 and the other for fractions 8-15. Daily cone beam computed tomography (CBCT) was performed and registered to planning-CT using bony anatomy. Within-patient comparisons of mean daily chest wall position were made using a paired t-test. Population, systematic (∑) and random errors (α) were estimated. Intrafraction reproducibility was assessed by comparing chest wall position and diaphragm movement between consecutive breath holds on CBCT.

RESULTS

16 patients were recruited. All completed treatment with both techniques (9 patients with wax bolus, 7 patients without). CBCT derived ∑ were 2.1-6.4 mm (ABC_DIBH) and 2.1-4.9 mm (vDIBH), α were 1.7-2.6 mm (ABC_DIBH) and 2.2-2.7 mm (vDIBH) and mean daily chest wall displacements (MD) were 0.0-1.5 mm (ABC_DIBH) and -0.1-1.6 vDIBH (all p non-significant). Chest wall and diaphragm position was equivalent between consecutive breath holds in ABC and vDIBH (median difference 1.0 mm and 0.8 mm respectively, non p significant) demonstrating equivalent intrafraction reproducibility.

CONCLUSION

This study demonstrates that a simple voluntary breath hold technique is feasible in combination with VMAT (+/- bolus) and is as reproducible as ABC_DIBH with VMAT for the irradiation of the breast and axillary and IMC lymph nodes in breast cancer patients.

When the World Throws You a Curve Ball: Lessons Learned in Breast Cancer Management

In the care of patients with operable breast cancer, there has been a shift toward increasing use of neoadjuvant therapy. There are benefits to neoadjuvant therapy, such as monitoring for response, as well as an increased rate of breast conservation and reduction of potential morbidity associated with breast surgery, including axillary management. Among patients with highly proliferative tumors, such as HER2-positive or triple-negative breast cancer, those with residual disease are at higher risk of recurrence, which informs the recommended systemic therapy in the adjuvant setting. For instance, in patients with residual disease after neoadjuvant chemotherapy and HER2-targeted therapy, there is a role for adjuvant trastuzumab emtansine for those with residual disease at the time of surgery. The same holds true regarding the role of adjuvant capecitabine in patients with residual disease after neoadjuvant chemotherapy. With the added complexities of treating patients in the era of the COVID-19 outbreak, additional considerations are critical, including initiation of surgery within an appropriate time from completion of neoadjuvant therapy. National consensus guidelines on time to surgery must be developed to improve measurement and comparison across systems. In addition, there is emerging radiation treatment management research addressing a number of factors, including hypofractionation, role of proton beam therapy, safe omission of radiotherapy, and preoperative radiotherapy with or without drug combination. In this article, the multidisciplinary approach of treating patients with operable breast cancer is highlighted, with updates and future considerations described.