Rotational Intensity-modulated Radiotherapy Research Articles

Comparative Dosimetry for Hippocampal-Avoidant Whole Brain Radiotherapy with Helical Tomotherapy and VMAT Planning Techniques

The advent of hippocampal-avoidant whole brain radiotherapy (HA-WBRT) has allowed for substantial improvements in cognition without compromising the efficacy of palliative whole brain radiotherapy. Volumetric modulated arc therapy (VMAT), a form of rotational intensity-modulated radiation therapy (IMRT), allows for rapid treatment delivery and minimizes fractional treatment time. However, given the intrinsic complexity of HA-WBRT planning, standard VMAT techniques require significant departmental resources and often fail to achieve planning objectives. We hypothesize that treatment planning and delivery on a helical tomotherapy (HT) unit improves OAR dosimetry compared to standard VMAT techniques. Patients with multiple brain metastases who received WBRT with palliative intent were included in this single institution dosimetric study. Treatment objectives and dose constraints for HA-WBRT from NRG CC001 were utilized. Three separate plans were generated for each patient including Dual-Arc Conventional VMAT (DAC), Split-Arc Partial-Field VMAT (SAPF), and HT for dosimetric comparison. VMAT plans were generated using 6-MV photon beams with a maximum dose rate of 600 MU/min with a 120-leaf MLC. DAC plans utilized 2 coplanar arcs each with jaw tracking. SAPF plans used four partial arcs, and the field size of each beam was reduced to allow the MLC to block the centrally located hippocampus without sacrificing the whole brain PTV coverage. HT plans with a dose rate of 1000MU/min and Helical Delivery mode used a 2.5cm dynamic Jaw setting. Mean differences in target volume coverage and OAR dosimetry between planning approaches were calculated. Two-tailed, paired Student's t-tests were employed to determine statistically significant differences between DAC, SAPF, and HT plans. A total of 15 treatment plans were generated for five patients (5 DAC, 5 SAPF, and 5 HT plans). HT was seen to significantly reduce hippocampal D100% compared to both DAC (∆-114.16 cGy, p = 0.001) and SAPF (∆-125.76 cGy, p < 0.001). Moreover, HT hippocampal D0.03cc was significantly lower than DAC (∆-80.26 cGy p = 0.003) and SAPF (∆-174.40 cGy, p < 0.001). At the same time, PTV coverage as determined by D98% was significantly higher compared to both DAC (∆ +372.66 cGy, p = <0.001) and SAPF (∆ +304 cGy, p = <0.001). Compared to both DAC and SAPF, HT planning for HA-WBRT provides significant improvements in target coverage and OAR sparing. Additional research is warranted to determine whether further reductions in dose to the hippocampi provide additional clinical benefit.

A PIN photodiode ionizing radiation detector with small angular dependence and low buildup

PurposeTo develop an improved PIN photodiode detector that has low angular dependence and small buildup. Show that the measured dose compares well with the dose calculated by a treatment planning system for static fields at oblique angles and rotationally delivered fields. MethodsCommercially available PIN photodiodes, VEMD1060X01, (Vishay Semiconductor, Shelton, CT), are fabricated into detectors that can be used for measurement of ionizing radiation. PIN photodiodes are soldered onto coaxial cables in an edge-on orientation and are mounted in a symmetrical package. Detector signals are measured with an electrometer with zero input bias voltage. Dose is measured from a Varian Trilogy (Varian Medical Systems, Milpitas, CA) linear accelerators 6 MV photon and 6 MeV electron beams. An Eclipse (Varian Medical Systems, Milpitas, CA) commercial treatment planning system Acuros and electron Monte Carlo algorithms are used for calculating dose expected in various irradiation geometries. ResultsThe single diode detector has an angular dependence between −1.1% and +1.2% and a buildup of 0.6 mm water equivalence. Measurements of dose at 0.3, 0.5, 1.0 and 1.5 cm depth from oblique static beams and from intensity modulated radiation therapy (IMRT) delivered beams agree with planning system calculations within ±1.5%. ConclusionsA clinically useable dose detector can be fabricated from a PIN type photodiode. This diode detector can be used to measure dose at the surface of a patient under a bolus if one is used. Measurements agree with calculations for static fields at oblique angles as well as rotational IMRT delivered beams.

Late hepatic toxicity after breast cancer intensity-modulated radiotherapy using helicoidal tomotherapy

PurposeHelical tomotherapy (HT) is a rotational intensity-modulated radiation therapy (IMRT) technique that allows target conformal irradiation and efficient organs at risk (OAR) sparing in the case of complex target volumes and specific anatomic considerations, but increases the “low-dose bath” to non-target volumes. The aim of this study was to analyze the delayed hepatotoxicity after rotational IMRT (HT) radiation therapy for non-metastatic breast cancer. Patients and methodsThis single-center retrospective study included all non-metastatic breast cancer patients with a normal pre-radiotherapy biological hepatic function who were treated with tomotherapy between January 2010 and January 2021 and for whom the dosimetric parameters for the whole liver were assessable. A logistic regression analysis was employed. The selected covariates for the multivariate analysis were those with a P-value that was less or equal to 0.20 in the univariate analysis. ResultsForty-nine patients were included in this study: 11 patients (22%) received Trastuzumab for 1 year in tumors with an HER2-expression; 27 patients (55%) received radiation therapy for cancer of the right or bilateral breasts; 43 patients (88%) received lymph node irradiation and 41 patients (84%) received a tumor bed boost. Mean and maximum doses to the liver were 2.8Gy [0.3–16.6] and 26.9Gy [0.7–51.7], respectively. With a median follow-up after irradiation was 5.4 years (range, 6 to 115 months), 11 patients (22%) had developed delayed low grade biological hepatic abnormalities: all patients had grade 1 delayed hepatotoxicity; 3 patients (6%) had additional grade 2 delayed hepatotoxicity. There was no hepatotoxicity at grade 3 or higher. According to the univariate and multivariate analysis, Trastuzumab was a significant predictive variable of late biological hepatotoxicity (OR=4.4 [1.01–20.18], P=0.04). No other variable was statistically associated with delayed biological hepatotoxicity. ConclusionDelayed hepatotoxicity after multimodal non-metastatic breast cancer management including rotational IMRT was negligible. Consequently, the liver doesn’t have to be considered like an organ-at-risk in the analysis of breast cancer radiotherapy but future prospectives studies are needed to confirm these findings.

TLD calibration and absorbed dose measurement in a radiation-induced liver injury model under a linear accelerator

The application of a thermoluminescent detector (TLD) for dose detection at the liver irradiation site in mice under linear accelerator precision radiotherapy and the use of a single high dose to irradiate the mouse liver to construct a biological model of a radiation-induced liver injury (RILD) in mice were to determine the feasibility of constructing a precision radiotherapy model in small animals under a linear accelerator. A 360° arc volumetric rotational intensity-modulated radiotherapy (VMAT) plan with a prescribed dose of 2 Gy was developed for the planned target volume (PTV) at the location of the TLD within solid water to compare the difference between the measured dose of TLD and the assessed parameters in the TPS system. The TLD was implanted in the livers of mice, and VMAT was planned based on TLD to compare the measured and prescribed doses. C57BL/6 J mice were randomly divided into control and 25-Gy radiation groups and were examined daily for changes in body weight. They were euthanized at 3 and 10 weeks after radiation, and the levels of liver serum enzymes such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were measured to observe any pathological histological changes in the irradiated areas of the mouse liver. The measured values of solid underwater TLD were within ± 3% of the Dmean value of the evaluation parameter in the TPS system. The mice in the 25-Gy radiation group demonstrated pathological signs of radiation-induced liver injury at the site of liver irradiation. The deviation in the measured and prescribed doses of TLD in the mouse liver ranged from − 1.5 to 6%; construction of an accurate model of RILD using the VMAT technique under a linear accelerator is feasible.

Characteristics of preplan-based three-dimensional individual template-guided brachytherapy compared to freehand implantation.

Image-guided adaptive intracavitary/interstitial brachytherapy (IC/IS IGABT) has exhibited superior dosimetry advantage and local control for locally advanced cervical cancer (LACC). Our group designed a type of cylindrical three-dimensional (3D) printed vaginal template combining an intracavitary applicator with straight and oblique interstitial needles according to the preplan on computed tomography images. This work aimed to research the consistency of the preplan with the treatment plan at every fraction to verify the practical guiding significance of the preplan. We also investigated the difference between 3D-printed template-guided implantation compared with freehand implantation for LACC. Twenty-six patients were treated with 3D-printed individual templates (3D template group), and 20 patients were treated by using freehand insertion (freehand group). Patients in the 3D template group would take a preplan one week before treatment to design and print the individual template, while the freehand group did not. All patients accepted volumetric rotational intensity-modulated radiotherapy at a dose of 49.4 Gy in 26 fractions and subsequent brachytherapy at a dose of 26 Gy in four fractions. All analyses were performed by utilizing SPSS 26. The insertion depth was decreased in fractions 1 and 4 compared with the preplan. None of the dose volume histogram parameters of fractions 1-3, nor the D2cc of bladder and bowel at fraction 4 were barely changed compared with the preplan. The D90 and D98 of the high-risk clinical target volume in the 3D template group were statistically higher than those in the freehand group (p < 0.01). The D2cc of the rectum, bladder, bowel, and sigmoid in the 3D template group were all lower than those in the freehand group (p < 0.01). The preplan in this research is consistent with treatment plans, which is important to ensure the feasibility of applying a 3D-printed template in brachytherapy. The 3D-printed individual guidance template was an effective method in brachytherapy for locally advanced cervical cancer.

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.

Radiation dose to the low axilla in patients treated for early-stage breast cancer by locoregional intensity-modulated radiotherapy (IMRT)

PurposeTo determine the dose received by the low axilla during locoregional radiotherapy (RT) for early-stage breast cancer and to assess the impact of the treatment technique (three-dimensional conformal radiotherapy (3D-CRT) or rotational IMRT (VMAT) or helical tomotherapy (HT). Materials and methodsThe dosimetric study was performed on patients receiving normofractionated (NFRT - 50Gy in 25 fractions) or hypofractionated (HFRT - 40Gy in 15 fractions) locoregional radiotherapy (breast or chest wall and internal mammary, supraclavicular and infraclavicular nodes±axillary nodes) by 3D-CRT or VMAT or HT at the Institut Curie Paris. Patients treated by breast-conserving surgery received a boost dose of 16Gy and 10Gy to the tumour bed, respectively. ResultsSixty-eight patients treated by RT from February 2017 to January 2019 were studied. The mean dose received by the low axilla when it was not part of the target volume was 30.8Gy, 41.0Gy and 44.4Gy by 3D-CRT, VMAT and HT, respectively for NFRT and 24.2Gy, 33.0Gy and 34.9Gy, respectively, for HFRT. With NFRT, 4.1% of the axilla received 95% (V95) of the prescribed dose by 3D-CRT compared to 24.5% and 33.6% by VMAT and HT, respectively; with HFRT, V95 was 3.9%, 19.5% and 24.1%, respectively. ConclusionThe axilla receives a non-negligible dose during locoregional radiotherapy; this dose is greater when VMAT or HT are used. Prospective studies must be conducted to assess the impact of this axillary dose in terms of morbidity, which currently remains unknown.

Evaluating cardiac substructure radiation exposure in breast rotational intensity modulated radiation therapy: Effects of cancer laterality, fractionation and deep inspiration breath-hold

PurposeRotational intensity-modulated radiation therapy currently has a growing role in breast cancer radiation therapy, since this radiation technique reduces cardiac radiation exposure while homogeneously covering target volumes. This study aims to evaluate radiation exposure of cardiac substructures across a broad spectrum of breast cancer cases differing by cancer laterality, fractionation regimen and addition of deep-inspiration breath hold. Materials and methodsCardiac substructures were delineated following guidelines endorsed by the European Society for Radiotherapy and Oncology (ESTRO) for forty-four breast cancer patients having undergone conserving surgery and adjuvant rotational intensity-modulated radiation therapy. Target volumes consisted of the whole breast with a boost, axillary and internal mammary nodes. Patients were treated using free-breathing technique for left-sided or right-sided, normofractionated or hypofractionated helical tomotherapy or volumetric modulated arc therapy, or using deep-inspiration breath hold for left-sided normofractionated volumetric modulated arc therapy. Mean and maximum doses to cardiac substructures were retrieved. Correlations were performed between mean- and maximum radiation doses to cardiac substructures. ResultsLeft-sided and right-sided irradiations were associated with different cardiac substructure exposure patterns despite comparable mean heart dose: 7.21Gy for left-sided normofractionated regimen, 6.28Gy for right-sided normofractionated regimen. Deep-inspiration breath hold reduced mean doses to almost all cardiac substructures for left-sided irradiation, but did not decrease maximum doses to coronary arteries. Correlations between mean- and maximum doses to cardiac substructures were usually moderate, but stronger for right-sided irradiation. ConclusionDespite comparable mean heart dose, cardiac substructure radiation exposure patterns with rotational intensity-modulated radiation therapy strongly depend on the breast side, which could trigger clinically different long-term cardiotoxicity events. Deep-inspiration breath hold improves cardiac substructure dosimetry. Mean- and maximum heart dose could probably not be used as surrogate markers for precise cardiac substructure evaluation. In a near future, clinical practice and cardiotoxicity studies could possibly gain by considering cardiac substructure in a more systematic manner, possibly relying on cardiac autosegmentation algorithms.

Safety and Efficacy of Ultra-hypofractionation in Node-positive Prostate Cancer

AimsThe safety and efficacy of stereotactic body radiotherapy (SBRT) in localised prostate cancer are now established through phase III randomised trials. Its utility in node-positive prostate cancer is restricted due to a lack of controlled studies specifically addressing this subgroup. Herein we report the safety and efficacy of SBRT in this subgroup. Materials and methodsIn total, 60 patients treated with SBRT to prostate and pelvis were analysed. All patients received neoadjuvant androgen deprivation therapy for at least 6 months and long-term adjuvant hormonal therapy (70% medical and 30% surgical). All patients were treated with daily image-guided rotational intensity-modulated radiotherapy. The dose delivered to the prostate and gross node was 35–37.5 Gy and 25 Gy in five fractions to the elective pelvic nodal region on alternate days. Acute and late toxicities were graded as per Radiation Therapy Oncology Group common toxicity criteria. ResultsForty-one (68%) patients had a Gleason score ≥8. The median prostate-specific antigen level at diagnosis was 39 ng/ml. Twenty (33%) patients had common iliac nodal uptake on initial prostate-specific membrane antigen positron emission tomography-computed tomography. After the median follow-up of 30 months, no acute or late Radiation Therapy Oncology Group grade ≥3 gastrointestinal toxicity was noted. Acute grade 2 genitourinary and gastrointestinal toxicities were 8.3% and 11.7%, respectively. Late grade 2 genitourinary and gastrointestinal toxicities were 3.3% and 8.3%, respectively. Late grade 3 genitourinary toxicity was seen in two (3.3%) patients. Three-year overall survival and biochemical failure-free survival was 89% and 77%, respectively. ConclusionSBRT to the prostate and pelvis is safe and efficacious in node-positive prostate cancer even with common iliac nodal involvement (stage M1a).

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

A straightforward estimation of cardiac substructure exposure for clinical practice: example of breast rotational intensity modulated radiation therapy

Introduction. Mean heart dose (MHD) is the most widely used dosimetric parameter for cardiac sparing during treatment planning. Specific cardiac substructure exposure could be more clinically important, but MHD cannot provide the radiation oncologist with precise insight at the substructural level. Materials. We propose a straightforward method for estimating cardiac substructure exposure based on linear regressions between mean dose delivered to cardiac substructures and MHD. We focused on breast irradiation with intensity modulated radiation therapy as an application example. Correlations between mean dose to cardiac substructures and MHD were statistically significant and usually moderate (r > 0.5) or strong (r > 0.7), allowing the use of such linear regression models to estimate cardiac substructure exposure from MHD for clinical practice. Conclusion. This method can be extrapolated to other clinical situations for daily practice, albeit with some restrictions.

Abstract P4-12-27: Dosimetric impact of axillary irradiation: Comparison between 3D-conformal radiotherapy and two types of intensity-modulated radiotherapy

Abstract The challenge with early breast cancer (EBC) management is finding balance between the most effective curative treatments with minimal long-term toxicity. De-escalade treatment modalities are emerging: sentinel lymph node biopsy instead of systematic axillary dissection, chemotherapy indications reduced with molecular signature, reduction of adjuvant trastuzumab duration, partial breast irradiation. Several trials, such as ACOSOG Z011 and AMAROS trials, demonstrated safety and tolerability of axillary RT instead of surgical approach. In this context, we aim to evaluate the dosimetric impact of axillary irradiation during adjuvant breast/chest wall radiotherapy (RT) for EBC and comparison between 3 techniques: three-dimensional conformal RT (3D), rotational intensity-modulated RT (IMRT) (VMAT) and helical IMRT with Tomotherapy® (HT). We selected all consecutive patients treated with RT including lymph node in our institution between February 2017 and November 2018. All patients received either 50Gy in 25 fractions or 40Gy in 15 fractions on the breast/chest wall and lymph node regions (IV, III, II, interpectoral, internal mammary chain+/- I, according to ESTRO Guidelines). In case of conservative surgery, patients received tumor bed boost (16Gy in 8 fractions in both arm); simultaneous integrated boost (SIB) was allowed (51.52Gy on breast and 63Gy on boost in 28 fractions and 42.3Gy on breast and 52.2Gy on boost in 18 fractions respectively). Dosimetric plan were performed on Eclipse TPS (3D and VMAT) or Tomotherapy® TPS (HT). We compared patients with axilla level I irradiation (group A) with patient without (group B); in group B, axilla level I (CTV) was retrospectively delineated. 68 patients, all female, were included in our dosimetric analysis. All patients received 95% of the prescribed dose on breast/chest wall and lymph node regions PTV (except 2 patients with 3D in group A, on the axilla level I). In B group, the axilla level I mean dose was superior with VMAT (44.7 and 36Gy) and HT (44.6 and 33.3Gy) compared with 3D (27.2 and 13.1Gy) with both treatment schedules respectively. This non-intentional axillary irradiation was heterogenous (table 1). Differences to organs at risk (OAR) doses between groups according treatment schedule are presented in table 2 (no comparison was calculated in 3D because only one patient in each schedules). HT was associated with additional doses to lungs and heart when the axilla level I was treated. This difference was not seen using VMAT. Our dosimetric work shows in group B that axilla level I receive a non-intentional dose, especially with IMRT. Although this irradiation is heterogenous, it is a non-negligible dose which could potentially have deleterious effect considering the morbidity of axillary treatment(s) already received by the patients. Willingly axillary irradiation (group A) is associated with increased doses to OAR with HT whereas it is not observed with VMAT. This suggest to wisely choose the IMRT technics according to patient medical history, especially cardiac and pulmonary morbidity. Table 1: Axilla level I dose according radiotherapy technics, with normo- (left column) and hypo-fractionated (right column) schedule, in group B.3DTomotherapy®VMATV953.11.433.723.431.121.4V8011.14.440.029.440.230.4V5028.516.445.43446.538.3Dmean27.213.144.633.344.736V95: volume of axilla level I that receive at least 95% of prescribed dose.V80: volume of axilla level I that receive at least 80% of prescribed dose.V50: volume of axilla level I that receive at least 50% of prescribed dose.Dmean: mean dose in Gy received by axilla level I region.3D: three-dimensional conformal radiotherapy.VMAT: rotational intensity-modulated radiotherapy Table 2: Additional dose to organs at risk according to radiotherapy technics, with normo- (left column) and hypo-fractionated (right column) schedules, in group A compared with group B.Tomotherapy®VMATHeart Dmean+2.1Gy+0.4Gy-2.2Gy-0.3GyHeart Dmax+11.7Gy+6.6Gy-10.6Gy-1GyIpsilateral lung V20-1.7%+3.2Gy-2.2%-3.5%Ipsilateral lung V30-1.1%+0.5%-1.7%-0.3%Controlateral lung V5+17.2%+1.1%-17.2%+4.2%Dmean: mean dose.Dmax: maximal dose.V20: lung volume receiving at least 20Gy.V30: lung volume receiving at least 30Gy.V5: lung volume receiving at least 5Gy. Citation Format: Louisa Marie Abbassi, Alexandre Arsène-Henry, Youlia M Kirova. Dosimetric impact of axillary irradiation: Comparison between 3D-conformal radiotherapy and two types of intensity-modulated radiotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-27.

The Limits of the Linear Quadratic (LQ) Model for Late Cardiotoxicity Prediction: Example of Hypofractionated Rotational Intensity Modulated Radiation Therapy (IMRT) for Breast Cancer

The Limits of the Linear Quadratic (LQ) Model for Late Cardiotoxicity Prediction: Example of Hypofractionated Rotational Intensity Modulated Radiation Therapy (IMRT) for Breast Cancer

Protontherapy versus best photon for mediastinal Hodgkin lymphoma: Dosimetry comparison and treatment using ILROG guidelines

The purpose of this work was reducing treatment-related toxicity for Hodgkin lymphomas using practical procedure inspired by the ILROG guidelines. Reporting the first case of localized Hodgkin lymphoma treated with protontherapy in France. A 24-year-old female with mediastinal, bulky, localized, mixed-cellularity, classic Hodgkin lymphoma required an involved-site radiation therapy after complete response following polychemotherapy. Three-dimensional conformal radiation therapy was not acceptable due to high doses to breasts, heart and lungs. We realized a four-dimensional computed tomography (CT) to evaluate target movements and another CT with gating and breath-hold technique. Delineation was performed on both CT using the initial fluorodeoxyglucose positron-emission tomography/CT. One dosimetric plan with rotational intensity-modulated radiation therapy with a helical Tomotherapy© was realized and compared to another one with conformational protontherapy. Ninety-five percent of the planning target volume was covered by 98 and 99% of the prescribed dose with protontherapy and helical Tomotherapy©. Protontherapy provided the best organ at risk protection. Lung and heart protections were better with protontherapy: lung mean dose (3.7Gy vs. 8.4Gy) and median dose (0.002Gy vs. 6.9Gy), heart mean dose (2.6Gy vs. 3.7Gy). Breast sparing was better for both breasts using protontherapy: right breast mean dose (2.4Gy vs. 4.4Gy) and left (1.9Gy vs. 4.6Gy). The biggest difference was seen with low doses, which were better with protontherapy: volume of lung receiving 5Gy was 17.5% vs. 54.2% with Helical Tomotherapy©. In view of these results, we decided to treat our patient with protontherapy using respiratory assessment. We delivered 30Gy (15 fractions) using protontherapy with one direct anterior field using pencil beam scanning and deep inspiration breath-hold technique. We observed only grade 1 skin erythema during treatment and no toxicity during early follow-up.

Radiotherapy in the Management of Childhood Rhabdomyosarcoma

Rhabdomyosarcoma is the most common soft-tissue sarcoma of childhood, comprising over 50% of cases. It is considered to be an embryonal tumour of skeletal muscle cell origin, frequently occurring at genitourinary and head and neck sites, although it can arise throughout the body and at sites where there is no skeletal muscle. For most cases, multimodality therapy is required to achieve the best results, incorporating induction ifosfamide, vincristine and actinomycin D-based chemotherapy and local therapy (radiotherapy and/or surgery). Recent reports from the European Paediatric Soft Tissue Sarcoma Group (EpSSG) RMS 2005 study have shown significant improvements in outcomes; high-risk rhabdomyosarcoma having a 3-year event-free survival and overall survival of about 68% and 80%, respectively. The more routine use of radiotherapy is considered to be a contributing factor to these improved results, but does also often result in significant long-term sequelae for survivors. Despite an increasing number of rhabdomyosarcoma treated with advanced radiotherapy techniques, including protons, brachytherapy and rotational intensity-modulated radiotherapy, in an effort to reduce the frequency of late complications, there remain a number of unanswered questions. Future planned collaborative group studies, such as the EpSSG Frontline and Relapsed Rhabdomyosarcoma (FaR-RMS) study, are looking to address these questions, investigating the potential benefits of preoperative radiotherapy, dose escalation and the irradiation of metastatic sites.

Irradiation mammaire locorégionale gauche avec modulation d’intensité rotationnelle et inspiration profonde : comparaison dosimétrique

PurposeAdjuvant left-sided breast cancer locoregional radiotherapy can be accounted for long-term cardiac toxicity. The deep inspiration breath hold techniques can reduce cardiac doses. Only a few studies have investigated rotational intensity-modulated radiotherapy with deep inspiration breath hold. Material and methodsWe conducted a dosimetric study comparing rotational intensity-modulated radiotherapy in free breathing with deep inspiration breath hold for irradiation of left breast cancer and locoregional lymph nodes. Doses to organs at risk were compared, as well as doses to coronary arteries, left anterior descending coronary artery region, and aortic valve. ResultsThe data from nine patients were included in the study. Treatment plans were comparable for target volumes. The deep inspiration breath hold delivery technique, compared with free breathing, reduced radiation dose to the heart (mean dose 4.8Gy vs. 6.6Gy, p=0.008; dose in 2% of the volume 16.8Gy vs. 23.3Gy, p=0.008; volume receiving 25Gy 0.8% vs. 2,2%, p=0.008; volume receiving 30Gy 0.4% vs. 1.2%, p=0.009), as well as to the right coronary artery (mean dose 6Gy vs. 8.9Gy, p=0.028), to the left anterior descending artery (mean dose 9.6Gy vs. 14.6Gy, p=0.021), to the left anterior descending coronary artery region (dose in 2% of the volume 17.4Gy vs. 24.6Gy, p=0.021), and to the aortic valve (mean dose 4.8Gy vs. 7Gy, p=0.028). Other doses to organs at risk were similar. ConclusionRotational intensity-modulated radiotherapy with deep inspiration breath hold is associated with better sparing of the heart, on the right and left anterior descending coronary arteries, and on the aortic valve, compared with free breathing techniques, for adjuvant left breast cancer locoregional irradiation.

Early Results of Extreme Hypofractionation Using Stereotactic Body Radiation Therapy for High-risk, Very High-risk and Node-positive Prostate Cancer

AimsStereotactic body radiotherapy (SBRT) in low- and intermediate-risk prostate cancer has shown encouraging results. However, its use in high-risk patients is limited due to lack of data regarding adequate radiotherapy dose, need for pelvic nodal treatment and androgen deprivation therapy. Herein we report our experience of SBRT in this subgroup. Materials and methodsAnalysis of a prospectively maintained database of 68 consecutive patients of the National Comprehensive Cancer Network (NCCN) high-risk, very high-risk and node-positive adenocarcinoma prostate treated with SBRT was undertaken. All patients were treated with rotational intensity-modulated radiotherapy with daily image guidance. The dose delivered to the prostate and gross node was 35–37.5 Gy in 5 alternate day fractions. Node-positive patients received 25 Gy to pelvic nodal regions until the common iliac nodes. Treatment was delivered in 7–10 days. All patients received long-term androgen deprivation therapy (79% medical and 21% surgical). ResultsMost patients (65%) had a Gleason score ≥ 8. The median prostate-specific antigen was 42. Twenty patients were high risk (30%), 11 (16%) very high risk and 37 (54%) node positive. No acute Radiation Therapy Oncology Group grade ≥ 3 genitourinary or gastrointestinal toxicity was noted. Acute grade 2 genitourinary and gastrointestinal toxicity were 12% and 3%, respectively. Late grade 3 genitourinary and gastrointestinal toxicity was 3% and 0%, respectively. There was no increase in acute or late gastrointestinal toxicity with prophylactic pelvic nodal radiotherapy. Prior transurethral resection of prostate (n = 11) did not increase toxicity. At a median follow-up of 18 months, 97% patients were alive and 94% were biochemically controlled. ConclusionSBRT is safe in the treatment of high-risk, very high-risk and node-positive prostate cancer, even with prophylactic pelvic radiotherapy or prior transurethral resection of prostate. Longer follow-up is required to determine efficacy.

Safety and efficacy of intensity-modulated radiotherapy in the management of spermatic cord sarcoma

PurposeSpermatic cord sarcoma is a rare disease, which management remains controversial due to the lack of guidelines. The standard therapeutic approach is surgical: wide soft-tissue resection with radical inguinal orchidectomy, The diagnosis is made during the analysis of the specimen. The high rate of local recurrence indicates adjuvant radiotherapy of the tumor bed. The aim of this series is to determine the efficacy and safety of postoperative intensity-modulated radiotherapy for spermatic cord sarcomas. Patients and methodsOur series included five consecutive cases of spermatic cord sarcoma treated between 2011 and 2014. The indications for radiotherapy were: R1 status after initial surgery, R1 status after wide en bloc resection and orchiectomy, high French federation of cancer centers (FNCLCC) grade, tumor size over 5cm, tumor resection during surgery. ResultsMedian age at diagnosis was 66years (range 46–84years). Median follow-up was 18months (range 6–28months). Four patients had repeat surgery after incomplete removal. All surgeries were orchidectomy with primary ligation of testicular vessels. One patient did not have an in sano margin after the second surgical procedure. The median tumor size was 60mm (range 30–150mm). No recurrence was observed during the follow-up. ConclusionNo grade 4 toxicities were reported and the most frequent acute toxicity was dermatitis. No recurrence was reported after adjuvant intensity-modulated radiotherapy. The treatment is feasible and well tolerated and seems to provide encouraging results regarding locoregional control of the disease. Dynamic or rotational intensity-modulated radiotherapy is now recommended to decrease acute toxicities while improving the efficacy of this approach.

Twenty Fraction Prostate Radiotherapy with Intra-prostatic Boost: Results of a Pilot Study

AimsFor patients with high-risk, locally bulky prostate cancer, an intra-prostatic boost to tumour volumes (dose-painting) offers a risk-adapted dose escalation. We evaluated the feasibility of hypofractionated dose-painting radiotherapy and the associated toxicity. The possibility to streamline a radiobiologically optimised planning protocol was also investigated. Materials and methodsTwenty-eight patients were treated using a dose-painting approach; boost volumes were identified with functional magnetic resonance imaging scans. The prostate dose outside the boost volume was 60 Gy in 20 fractions, and the maximum integrated boost dose was set to 68 Gy, provided that the dose constraints to the organs at risk could be fulfilled. Rotational intensity-modulated radiotherapy was used with daily image guidance and fiducial markers. ResultsThe boost dose was escalated to 68 Gy for 25 patients (median dose 69 Gy, range 68–70 Gy); for three patients the boost dose was 67 Gy, due to the proximity of the urethra and/or the rectum. The mean normal tissue complication probability for rectal bleeding was 4.7% (range 3.4–5.8%) and was 3.5% for faecal incontinence (range 2.3–5.0%). At a median follow-up of 38 months (range 32–45) there was no grade 3 toxicity. Two patients developed grade 2 genitourinary toxicity (7.1%) and none developed grade 2 gastrointestinal toxicity. The mean prostate-specific antigen (PSA) for 23 patients who had stopped the adjuvant hormone therapy with a normal testosterone was 0.27 ng/ml (0.02–0.72) at follow-up; two patients have suppressed PSA and testosterone after stopping 3 year adjuvant hormone and three patients have relapsed (one pelvic node, two PSA only) at 36, 12 and 42 months, respectively. ConclusionsA hypofractionated radiotherapy schedule, 60 Gy in 20 fractions with intra-prostatic boost dose of 68 Gy, can be achieved without exceeding dose constraints for organs at risk. Hypofractionated dose-painting escalated radiotherapy has an acceptable safety profile. The same planning protocol was used in a phase II single-arm trial (BIOPROP20: ClinicalTrials.gov identifier NCT02125175) and will further be used in a large phase III randomised trial (PIVOTALboost): patients will be randomised standard radiotherapy (60 Gy in 20 fractions) with or without lymph node radiotherapy versus dose-painting radiotherapy with or without lymph node radiotherapy; the trial will be opened for recruitment in summer 2017.

Squamous-cell carcinoma of the anus: progress in radiotherapy treatment.

Chemoradiotherapy is the standard-of-care treatment of squamous-cell carcinoma of the anus (SCCA), and this has not changed in decades. Radiation doses of 50-60 Gy, as used in many phase III trials, result in substantial late morbidities and fail to control larger and node-positive tumours. Technological advances in radiation therapy are improving patient outcomes and quality of life, and should be applied to patients with SCCA. Modern techniques such as intensity-modulated radiotherapy (IMRT), rotational IMRT, image-guided radiotherapy using cone-beam CT, and stereotactic techniques have enabled smaller margins and highly conformal plans, resulting in decreased radiation doses to the organs at risk and ensuring a shorter overall treatment time. In this Perspectives article, the use of novel approaches to target delineation, optimized radiotherapy techniques, adaptive radiotherapy, dose-escalation with external-beam radiotherapy (EBRT) or brachytherapy, and the potential for modified fractionation are discussed in the context of SCCA.