Locoregional Breast Irradiation Research Articles

Automated dose evaluation on daily cone-beam computed tomography for breast cancer patients

Background and purposeOur goal was to develop a workflow to automatically evaluate delivered dose on daily cone beam computed tomography (CBCT) in all breast cancer patients to assess dosimetric impact of anatomical changes and guide decision-making for offline plan adaptation. Materials and methodsThe workflow automatically processes the daily CBCTs of all breast cancer patients receiving local and locoregional radiotherapy. The planning-CT is registered to the CBCT to create a synthetic CT and propagate contours. A forward dose calculation is performed, and DVH parameters are extracted and printed in a report. We evaluated the workflow on a group level and in a subset of 30 patients on a patient-specific level, including comparison to clinical evaluation on additional planning-CT in 10 patients. Results7454 fractions in 647 patients were analyzed over a period of seven months. Median breast clinical target volume V95% was ≥ 95 % for 97 % of the patients. The workflow would have provided useful additional insights for decision-making for the requirement of plan adaptation, based on debatable disagreement with the clinical decision in half of the cases with an additional planning-CT. The workflow also identified cases with suboptimal coverage not identified in the clinical procedure. ConclusionWe developed a fully automated workflow for dose evaluation on daily CBCT for local and locoregional breast radiotherapy. We have demonstrated its potential for aiding decision-making for plan adaptation in patients with changing anatomy and its capability to highlight patients that may receive suboptimal treatment and require closer clinical evaluation of treatment quality.

3131: Development of an automated VMAT-technique for left locoregional breast radiotherapy including IMN

3131: Development of an automated VMAT-technique for left locoregional breast radiotherapy including IMN

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.

Correlation between Thyroid Radiation Dose and Thyroid Function after Adjuvant Hypofractionated Locoregional Radiotherapy in Breast Cancer Patients

Radiotherapy (RT) is used quite often among breast cancer patients, and because these patients now live longer than they used to, long-term treatment-related adverse effects, such as hypothyroidism, are becoming increasingly relevant. Radiation-induced hypothyroidism is a late side effect of radiation to the thyroid gland, which could develop months to years after radiotherapy. However, there is no sufficient data on hypothyroidism in patients with breast cancer who receive locoregional RT, which usually affects a portion of the thyroid gland. In this prospective study, we tried to correlate between the radiation dose received by the thyroid gland and the incidence of thyroid dysfunction in breast cancer patients treated with hypofractionated locoregional radiotherapy, as well as establishing potential planning objectives that could help in sparing the thyroid gland. Our study included 109 women who received 3-D conformal loco-regional breast radiotherapy, these patients had normal thyroid function prior to start of radiotherapy. Patients had follow-up thyroid function tests 6 months after finishing radiotherapy. Based on dose volume histograms (DVH), the percentages of the thyroid volume, and ipsilateral thyroid lobe, receiving 5, 10, 15, 20, 25, 30, 35, and 40 Gy (V5, V10, V15, V20, V25, V30, V35, and V40 respectively), in addition to the mean and maximum thyroid doses, were estimated. Follow-up assessment of thyroid function and statistical analysis unveiled incidence of radiotherapy induced hypothyroidism to be 8.3%. Possible risk factors included high maximum radiation dose and V40 to the thyroid gland and the ipsilateral thyroid lobe, as well as high mean dose and smaller volume of the ipsilateral thyroid lobe. The likelihood of hypothyroidism was significantly increased with V40 of >5% of the thyroid gland, and V40 of >11% of the ipsilateral thyroid lobe. Further study is recommended for larger populations and longer follow-up periods.

Évaluation prospective des dysthyroïdies radio-induites après irradiation mammaire et sus-claviculaire

PurposeThe thyroid is an endocrine gland playing a major role in metabolism and development by the secretion of T4 and T3 thyroid hormones. Due to its anatomical position, it is often included in the target volume for the irradiation of certain tumours and thus receives significant doses (10 to 80Gy). The treatment of breast cancer requires in most cases a breast irradiation associated or not with a lymph node irradiation. The aim of our study was to investigate prospectively the frequency of thyroid disorders in patients with breast cancer treated by radiation, with or without irradiation of the supra- and subclavicular lymph nodes. Material and methodsThis prospective multicentre study (institut Godinot, institut de cancérologie Strasbourg Europe and institut de cancérologie de Lorraine) concerned adult patients with non-metastatic breast carcinoma treated by adjuvant irradiation. They were included in a non-randomized way between February 2013 and June 2015 and divided into two groups according to treatment: (i) breast radiotherapy associated with irradiation of the supra- and subclavicular lymph nodes (group 1), or (ii) breast irradiation alone (group 2). The dose – volume histogram of the thyroid was systematically edited by the physics department. Each patient had a consultation with an endocrinologist at the beginning of the treatment and was monitored by blood analyses including TSH, T4L, antithyroglobulin and antiperoxidase antibodies every 6 months until the 60th month after the end of radiotherapy. Data were described by numbers and percentages for qualitative variables; by means, medians, standard deviation and ranges for quantitative variables. Statistical associations were tested by Chi2, Fisher's, Student's, or analysis of variance tests depending on the conditions of application. Survival analyses were performed by log rank tests and Cox models. ResultsThis study initially included 500 patients, 245 in group 1 and 252 in group 2 (three patients were later excluded for false inclusion). Thyroid abnormalities occurred in 76 patients, representing an incidence of 15.3%. The mean time of the first occurrence of thyroid disorders was 24.3 months. It was more frequent in group 1 with a prevalence of 19.2% against 11.5% in group 2 (P=0.01745). A maximal radiation dose delivered to the thyroid gland greater than 20Gy (odds ratio [OR]: 1.82; P=0.018) or 30Gy (OR: 1.89; P=0.013) was significantly associated with a higher incidence of thyroid disorders, as was a mean dose greater than 30Gy (OR: 5.69; P=0.049). A percentage of thyroid volume receiving 30Gy (V30) greater than 50% (P=0.006) or greater than 62.5% (P=0.021) was significantly associated with an increased incidence of thyroid disorder and more precisely, hypothyroidism (P=0.0007). In multivariate analysis, no factor associated with the occurrence of thyroid disorder was identified. However, in the subgroup analysis concerning group 1 (receiving supraclavicular irradiation), a maximal radiation dose greater than 30Gy appeared to be a risk factor for the occurrence of thyroid disorders (P=0.040). ConclusionThyroid disorder, and in particular hypothyroidism, may be a late side effect of locoregional breast radiotherapy. Patients receiving this treatment should have a biological monitoring of thyroid function.

Is there a role for adjuvant therapy in radiation-induced angiosarcoma of the breast? A case report and review of the literature.

Angiosarcoma (AS) of the breast is very rare, accounting for 1% of all soft tissue breast tumors. AS may present as primary tumors of the breast or as secondary lesions usually associated with previous radiotherapy. Commonly, secondary AS affects older women (median age 67-71 years) with a clinical history of breast cancer. The preferred site of onset of RIAS is the edge of radiation fields, where radiation doses and tumor necrosis may be heterogeneous, resulting in a DNA damage and instability. Radical surgery is the treatment of choice, but no clear consensus exists on surgical management of breast AS. We describe an atypical case of relapsed RIAS after radical mastectomy, treated with new surgery and, considering the higher risk of recurrence, subsequent adjuvant chemotherapy with weekly paclitaxel. The frequency of radiation-induced angiosarcomas (RIAS) after breast-conserving surgery and radiotherapy has been increased to 0.14-0.5% among long survivors. Nevertheless, even if RIAS continues to be prognostically an extremely unfavorable cancer due to a high rate of recurrence, distant spread, and median overall survival (OS) of about 60 months, the benefits of loco-regional breast radiotherapy are clearly higher than the risk in developing angiosarcoma.

P108 Should we delineate brachial plexus in hypofractionated locoregional breast radiotherapy to reduce the risk of brachial plexopathy?

P108 Should we delineate brachial plexus in hypofractionated locoregional breast radiotherapy to reduce the risk of brachial plexopathy?

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

AimsInclusion 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 methodsLeft-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. ResultsTwenty-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. ConclusionVMAT(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.

Do We Need to Delineate the Humeral Head in Breast Cancer Patients?

Simple SummaryHumeral heads can be unintentionally exposed during breast radiotherapy, particularly when regional lymph nodes are targeted. The aim of this study was to analyze late adverse events involving the humeral head occurring after adjuvant locoregional breast radiotherapy. We included 159 breast cancer patients locoregionally irradiated in an adjuvant setting with helical tomotherapy. After a median delay of 48 months, 10 patients (6.06% (3.20–10.92%) of breasts treated) presented clinical events such as localized bone pain, shoulder functional limitation and humeral head fracture. The average mean and maximum doses to humeral heads were 9.18 Gy and 24.41 Gy, respectively, and were not statistically associated with humeral head adverse events. We found that clinical adverse events involving the humeral head after adjuvant helical tomotherapy for breast cancer were rare, and the radiation exposure was low. No correlation was found between dosimetric parameters and late toxicity.Humeral heads can be unintentionally exposed during breast radiotherapy, particularly when regional lymph nodes are targeted. Moreover, rotational intensity-modulated radiation therapy techniques, such as helical tomotherapy (HT), increase the low-dose bath, the consequences of which are subject to debate. The aim of this study was to analyze late adverse events involving humeral heads occurring after adjuvant locoregional breast radiotherapy with HT. This single-center retrospective study included 159 breast cancer patients locoregionally irradiated, including the regional lymph nodes, in an adjuvant setting with HT at Institut Curie (Paris, France), between January 2010 and 2016. After a median delay of 48 months, six patients (3.8%) developed localized bone pain, three (1.9%) developed a shoulder functional limitation and one (0.6%) developed a traumatic humeral head fracture. The average mean and maximum doses to humeral heads were 9.18 Gy and 24.41 Gy, respectively, and were not statistically associated with humeral head adverse events. Adverse events were statistically more frequent after mastectomy than after breast-conserving surgery. Berg’s level 1 and 2/3 irradiation, and right-sided radiotherapy were associated with an increased maximum dose. In summary, clinical adverse events were rare, and radiation exposure to humeral heads was low. No correlation was found between dosimetric parameters and late toxicity.

Long-Term Survival and Toxicity in Patients Treated With Radiotherapy for Neuroendocrine Breast Cancer: A Single-Center Experience

<h3>Purpose/Objective(s)</h3> Neuroendocrine breast cancer (NEBC) is an uncommon histotype of breast carcinoma. Due to their rarity, no recommendation has been made for their management; in daily practice, the same guidelines as for ductal invasive carcinoma apply for NEBC. However, the place of radiotherapy in the management of resectable NEBC is still debated since multiple epidemiological studies failed to demonstrate any clinical benefit, probably due to a lack of statistical power. We aimed to report the long-term survival and toxicity in patients treated with radiotherapy for NEBC at our institute. <h3>Materials/Methods</h3> All NEBC patients referred between 1995 and 2005 to the Department of Radiation Oncology at our institute for local or locoregional breast radiotherapy, as a complement to surgery, were identified. The whole breast or the chest wall was irradiated to 50 Gy in 25 fractions. For patients treated with breast-conserving surgery, a 16 Gy tumor bed boost could be delivered for those younger than 50 years at the time of diagnosis, narrow surgical margins or pathological criteria of aggressiveness. Regional lymph nodes were irradiated to 46 Gy in 23 fractions depending on the clinical and pathological findings, according to local guidelines. Adjuvant chemotherapy was delivered based on clinical and histological considerations and relied on anthracyclines and taxanes. A five-year hormone-therapy by tamoxifen or aromatase inhibitor was indicated in the case of hormone receptor positivity. Patients were followed every 6 months to 5 years and annually thereafter. <h3>Results</h3> 18 patients were treated with normofractionated breast radiotherapy for locoregional management of NEBC. With a median follow-up of 5.7 years, three patients died of their cancers, two patients had local recurrences and three patients developed distant metastases. There was no regional relapse, contralateral breast cancer or second non-breast cancer. Five-year overall and metastasis-free survivals were both 88% [73%-100%], whereas 5-year locoregional and local controls were both 100%. In univariate analysis only, pathological tumor size was significantly associated with overall survival and metastasis-free survival (HR = 1.26 [95% CI: 1.00-1.58], <i>P</i> = 0.04 and HR = 1.13 [95% CI: 1.00-1.28], <i>P</i> = 0.04, respectively). No patients developed grade ≥2 toxicity. Two patients experienced a grade 1 fibrosis, 2 patients had a grade 1 breast pain on the last clinical evaluation and 1 patient had a persistent grade 1 breast oedema. <h3>Conclusion</h3> Radiotherapy appears effective and well-tolerated for locoregional management of resectable neuroendocrine breast cancers, as a complement to surgery.

Pertuzumab and Trastuzumab Combination with Concomitant Locoregional Radiotherapy for the Treatment of Breast Cancers with HER2 Receptor Overexpression

Simple SummaryThis retrospective study demonstrates that the combination of locoregional breast RT with dual HER2 blockade by pertuzumab/trastuzumab was very well tolerated, suggesting that RT can be safely administered to patients with HER2-positive breast cancer during dual HER2 blockade. Excellent locoregional control was achieved in irradiated patients.Background: The combination of pertuzumab and trastuzumab dual HER2 blockade with concomitant curative dose locoregional breast radiotherapy in patients with metastatic breast cancer is an important part of treatment strategy. Methods: This was a retrospective study conducted at the Institut Curie on all patients treated concomitantly with pertuzumab/trastuzumab and locoregional breast radiotherapy. Toxicity was evaluated according to the NCICTCAEv4.0. Overall survival, progression-free survival and locoregional recurrence-free survival were evaluated in metastatic patients who were initially well controlled by chemotherapy, for whom local treatment was decided by the multidisciplinary team. Results: Fifty-five patients treated between October 2013 and December 2019 were included, with a median follow-up of 4.1 years. The median age was 53 years (range: 28–81). All patients received curative dose radiotherapy (RT) concomitantly with pertuzumab and trastuzumab (Pertu/Trastu). The median radiation dose was 50 Gy. Safety evaluation did not reveal any significant adverse effects, with 3 cases of grade 3 radiodermatitis (5.4%), but no significant gastrointestinal or cardiac toxicity. The mean difference in LVEF before any chemotherapy and after radiotherapy was −2.43% (p < 0.01). Conclusions: This study demonstrates that the combination of locoregional breast RT with dual HER2 blockade by Pertu/Trastu was very well tolerated, suggesting that RT can be safely administered to patients with HER2-positive breast cancer.

121MO Acute toxicity associated with a 3-week versus a standard 5-week regimen for locoregional breast radiotherapy delivered in the UNICANCER HypoG-01 phase III trial

In most countries, the 5-week normofractionated (NF) locoregional radiotherapy (RT) is still the standard of care for breast cancer with an indication for regional lymph node irradiation. HypoG-01 (NCT03127995) is a randomized phase 3 clinical trial evaluating the safety and efficacy of a 3-week moderate hypofractionated (HF)-RT against NF-RT regimen. Here, we report for the first time the acute toxicity results, a secondary endpoint of the trial.

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

BackgroundDeep-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. MethodPatients 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. Results16 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. ConclusionThis 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.

Deep Inspiration Breath-Hold (DIBH) for Locoregional Breast Irradiation using Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Proton Therapy (IMPT): A Dosimetric Comparison to Cardiac Substructure

Conventional breast irradiation with tangent fields poses cardiotoxicity risks but recent techniques significantly reduce heart exposure, such as rotational intensity modulated radiation therapy or proton therapy. This study evaluates the potential of deep inspiration breath-hold (DIBH) combination with volumetric modulated arc therapy (VMAT) and intensity modulated proton therapy (IMPT) for further cardiac sparing, at the cardiac substructure level. Following breast conserving surgery, 14 left-sided breast cancer patients treated with free breathing (FB)-VMAT (n = 7) or DIBH-VMAT (n = 7) were retrospectively included. Patients were treated to a dose of 51.8Gy to the whole left breast, 50.4 Gy to the axillary and internal mammary nodes, and 63 Gy to the tumor bed. Pencil beam scanning plans were generated on the initial simulation FB or DIBH computed tomography scans with similar PTV coverage constraints. The endpoint was the mean dose to the heart, to the cardiac cavities, to the left ventricle walls and to the coronary arteries. Table 1 presents the mean doses to cardiac substructures using VMAT and IMPT, with or without DIBH. When combined with VMAT, DIBH significantly reduces dose to nearly all cardiac substructures and to all coronary artery segments. In contrast, when combined with IMPT, DIBH does not show any dosimetric benefit. FB-IMPT significantly spares cardiac substructures compared with DIBH-VMAT. Contrasting with VMAT irradiation where DIBH significantly reduces doses delivered to nearly all cardiac substructures, DIBH does not seem to demonstrate a dosimetric benefit when combined with IMPT. DIBH is thus probably unnecessary for locoregional breast irradiation with IMPT.Abstract 2091; TableStructureVMAT (mean dose Gy)IMPT (mean dose Gy)Free BreathingDIBHp valueFree BreathingDIBHp valueHeart7.123.500.010.800.320.05Left ventricle7.403.19<0.010.090.220.09Anterior wall12.475.23<0.010.260.720.18Apical wall12.384.390.010.400.880.20Lateral wall6.603.37<0.010.040.160.02Inferior wall4.131.65<0.02<0.010.010.47Septal wall6.622.77<0.030.020.010.36Right ventricle7.053.55<0.040.790.070.14Left auricle3.971.910.02<0.01<0.010.08Right auricle3.892.440.040.060.030.13Left main coronary artery6.342.85<0.010.02<0.010.37Left anterior descending artery21.198.32<0.012.481.650.47Proximal segment12.995.170.040.190.290.63Mid segment24.1010.88<0.014.003.130.68Distal segment23.528.370.012.151.380.35Circumflex artery5.122.540.03<0.01<0.010.11Proximal segment7.343.090.02<0.010.010.22Distal segment4.532.410.06<0.01<0.010.10Right coronary artery5.402.870.010.030.060.62Proximal segment6.454.580.220.060.140.59Mid segment4.152.270.050.01<0.010.29Distal segment3.011.170.01<0.01<0.010.36Posterior descending segment6.151.560.01<0.01<0.010.18Author Disclosure: P. Loap: None. F. Goudjil: None. B. Baron: None. M. Ribeiro: None. A. Fourquet: None. Y. Kirova: None. Open table in a new tab

Evaluation of organ motion-based robust optimisation for VMAT planning for breast and internal mammary chain radiotherapy

AimsIn patients undergoing locoregional radiotherapy (RT) for breast cancer including the internal mammary chain (IMC), VMAT has been shown to be superior to tangential-field radiotherapy in terms of target coverage and minimising dose to heart and lungs. In this study we describe and validate organ motion-based robust optimisation for generating breast and locoregional lymph node VMAT plans that are robust to inter-fractional changes. Materials and methodsIn this retrospective study of five patients with left-sided breast cancer requiring locoregional breast radiotherapy including the IMC, non-robust plans were generated in the nominal scenario (planning-CT) and corresponding robust plans were created by optimising over a range of simulated CTs representing worst-case scenario shape changes to the breast. Both plans were re-calculated on CBCT images (n = 67) acquired prior to RT to generate estimates of delivered fractional dose. Plan robustness to inter-fractional changes was assessed in terms of the estimated target coverage and OAR dose. ResultsOrgan motion-based robust optimisation was able to generate clinically acceptable treatment plans in the nominal scenario on the planning CT with no significant differences to OAR dose between the robust and non-robust planning techniques. All plans (robust and non-robust) achieved the mandatory target coverage requirements. Estimates of delivered dose demonstrated a significant improvement in breast target coverage for the robust plans compared to non-robust plans. For the breast CTV, 92% of the robust plans achieved the optimal D98% > 95% clinical goal as compared to 71% of the non-robust plans (p < 0.01). 94% of robust plans achieved acceptable superficial breast coverage, as compared to 55% for the non-robust technique. ConclusionsOrgan motion-based robust optimisation VMAT is able to produce clinically acceptable organ-at-risk sparing plans for locoregional breast radiotherapy (including the IMC) that are robust to inter-fractional changes, therefore reducing the likelihood of reactive adaptive re-planning.

PO-1116 Set-up in locoregional breast irradiation: reduced margins for subclavicular and axilar lymph nodes.

PO-1116 Set-up in locoregional breast irradiation: reduced margins for subclavicular and axilar lymph nodes.

Deep inspiration breath hold level variability and deformation in locoregional breast irradiation

PurposeThe purpose of this study was to evaluate the dosimetric effect of breath hold level variability and deformation on breast, chest wall, internal mammary chain (IMC) nodes, and heart. Methods and materialsLeft-sided post-lumpectomy (n = 12) and postmastectomy (n = 3) patients underwent deep inspiration breath hold (DIBH) and exhale breath hold (EBH) computed tomography (CT) scans. Forward-planned locoregional breast plans were created on the DIBH scan. Two effects were modeled assuming no setup uncertainties: residual motion within the gating window and systematically shallow breath hold levels (BHLs). Real-time position management (RPM) was used to monitor BHL at simulation and during treatment. The RPM data were scaled to simulate BHL variation within symmetric gating window widths of ±1, 3, 5, and 7 mm; the dosimetric impact of this motion was simulated in the treatment planning system. Systematically “shallow” BHL errors were modeled using deformable image registration to map the patient trajectory from DIBH to EBH (n = 12). The deformable vector fields were scaled to produce synthetic CT scans modeling patient position during breath holds 1, 3, 5, and 7 mm shallower than simulator BHL. The original treatment plans were applied to the synthetic CTs and dose was recalculated. ResultsAcceptable plan quality was maintained for most patients with motion within gating windows up to ±7 mm. Patients with shallow median BHLs experienced loss of coverage at simulated gating windows ±5 mm or larger. At systematic 3 mm shallow BHL error, 4/12 patients had clinical target volume IMC V80% < 99%; this increased to 11/12 patients at 5 mm. Change in heart dose from systematic BHL errors was negligible. ConclusionsMotion within gating windows has minimal dosimetric impact for most BHL variability; however, loss of IMC coverage can occur even for small gating windows when BHLs are systematically shallow. This can be mitigated by restricting lower BHL tolerances or accounting for known uncertainties in planning.

PO-0829: Robustness of IMRT and VMAT for interfraction motion in locoregional breast irradiation

PO-0829: Robustness of IMRT and VMAT for interfraction motion in locoregional breast irradiation

PO-1006: A breath-hold friendly, hybrid 3DCRT/IMRT technique for locoregional breast irradiation

PO-1006: A breath-hold friendly, hybrid 3DCRT/IMRT technique for locoregional breast irradiation

Concurrent administration of trastuzumab with locoregional breast radiotherapy: long-term results of a prospective study.

This single-center prospective study aims to assess the outcomes and the toxicities related to the concurrent administration of trastuzumab (T) with adjuvant locoregional radiotherapy (RT) in localized breast cancer. Data of 308 patients were analyzed. T was delivered every 3 weeks (loading dose of 8 mg/kg, then 6 mg/kg) for 1 year. Left ventricular ejection fraction (LVEF), measured by echocardiography or myocardial scintigraphy, was considered as impaired when below 55%. Toxicities were assessed according to the Common Terminology Criteria for Adverse Events version 3.0. Univariate and multivariate analyses were carried out using the Cox model. Median follow-up was 50.2 months (13.0-126.0). Median age at diagnosis was 52 years (25-83). Internal mammary node (IMN) RT was performed in 227 patients (73.7%). After completion of RT, 26 patients (8.4%) presented an impaired LVEF: 17 (5.5%) of grade 1, 7 (2.3%) of grade 2, and 2 (0.6%) of grade 3. At 48 months, locoregional control rate was 95% [95% CI 92; 98], and overall survival rate was 98% [95% CI 96; 100]. In univariate analysis, neither the treated breast side (p = 0.655) nor IMN RT (p = 0.213) exposed patients to LVEF alteration. In multivariate analysis, clinical lymph node involvement was associated with an increased risk of locoregional and distant recurrence (p = 0.016 and p = 0.007, respectively). In this prospective study, the toxicities of concurrent T with locoregional breast RT were acceptable and the outcomes favorable. Longer follow-up is warranted to confirm these results.