Dosimetric and radiobiological advantages from deep inspiration breath-hold and free breath technique for left-sided breast radiation using 3DCRT, IMRT and Rapid Arc methods-a complete assessment

The verification and use of the best treatment approach using 3D conformal radiation therapy (3DCRT), intensity modulated radiation therapy (IMRT) and Rapid Arc methods for left breast radiation with dosimetric and radiobiological characteristics. The use of custom-built Python software for the estimation and comparison of volume, mean dose, maximum dose, monitor units and normal tissue integral dose along with radiobiological parameters such as NTCP, tumor control probability, equivalent uniform dose and LKB's effective volume from 3DCRT, IMRT and Rapid Arc planning with deep inspiration with breath holding (DIBH) and free breadth (FB) techniques. Volume growth of three-fourth in DIBH compared with FB causes a decrease in cardiac doses and complications because the left lung expands, pulling the heart away from the chest wall and the treatment area. A tiny area of the left lung was exposed during treatment, which reduced the mean dose. There was little difference in the treatment approaches because the spinal cord was immobile in both techniques. Rapid Arc is the unmatched modality for left-sided breast irradiation with significant patient breath-hold, as shown by the comparison of dosimetric and radiobiological parameters from treatment techniques with a deep inspiration breath-hold approach.

Fetal dose assessment in a pregnant patient with brain tumor: A comparative study of proton PBS and 3DCRT/VMAT radiation therapy techniques

PURPOSE

The treatment of brain tumors in pregnant patients poses challenges, as the out-of-field dose exposure to the fetus can potentially be harmful. A pregnant patient with prior radiation treatment was presented with a brain tumor at our clinic. This work reports on our pre-treatment study that compared fetal dose exposure between intensity-modulated proton therapy (IMPT) using pencil beam scanning (PBS) and conventional photon 3D conformal radiation therapy (3DCRT) and volumetric-modulated arc therapy (VMAT), and the subsequent pregnant patient's radiation treatment.

MATERIALS AND METHODS

Pre-treatment measurements of clinical plans, 3DCRT, VMAT, and IMPT, were conducted on a phantom. Measurements were performed using a device capable of neutron detections, closely following AAPM guidelines, TG158. For photon measurements, fetus shielding was utilized. On patient treatment days, which was determined to be proton treatment, shielding was used only during daily imaging for patient setup. Additionally, an in vivo measurement was conducted on the patient.

RESULTS

Measurements showed that IMPT delivered the lowest fetal dose, considering both photon and neutron out-of-field doses to the fetus, even when shielding was implemented for photon measurements. Additionally, the proton plans demonstrated superior treatment for the mother, a reirradiation case.

CONCLUSION

The patient was treated with proton therapy, and the baby was subsequently delivered at full term with no complications. This case study supports previous clinical findings and advocates for the expanded use of proton therapy in this patient population.

Long-Term Outcomes After Concurrent Once- or Twice-Daily Chemoradiation in Limited-Stage Small Cell Lung Cancer: A Brief Report From the CONVERT Trial

PURPOSE

CONVERT was a phase 3 international randomized clinical trial comparing once-daily (OD) and twice-daily (BD) radiation therapy (RT). This updated analysis describes the 6.5-year outcomes of these regimens delivered with conformal techniques.

METHODS AND MATERIALS

CONVERT (NCT00433563) randomized patients 1:1 between OD RT (66 Gy/33 fractions/6.5 weeks) and BD RT (45 Gy/30 fractions/3 weeks), both delivered with concurrent cisplatin/etoposide. Three-dimensional conformal RT was mandatory, intensity-modulated RT was permitted, and elective nodal irradiation was not allowed. Prophylactic cranial irradiation was delivered at the discretion of treating clinicians. RT treatment planning was subject to central quality assurance.

RESULTS

Five hundred forty-seven patients were recruited at 73 centers. The median follow-up for the surviving cohort (n = 164) was 81.2 months. The median survival for the OD and BD arms were 25.4 months (95% CI, 21.1-30.9) and 30.0 months (95% CI, 25.3-36.5; hazard ratio, 1.13; 95% CI, 0.92-1.38; P = .247). Performance status and tumor volume were associated with survival on multivariate analysis. No treatment-related deaths occurred subsequent to the initial analysis performed in 2017. Regarding late toxicity, 7 patients in the OD arm developed grade 3 esophagitis, 4 of which went on to develop stricture or fistulation, compared with no patients in the BD arm. Grade 3 pulmonary fibrosis occurred in 2 and 3 patients in the OD and BD arms, respectively.

CONCLUSIONS

As the CONVERT trial did not demonstrate the superiority of OD RT and this regimen had a slightly worse toxicity profile after 80 months of follow-up, 45 Gy BD should remain the standard of care in limited stage small cell lung cancer.

Long-Term Prospective Outcomes of Intensity Modulated Radiotherapy for Locally Advanced Lung Cancer: A Secondary Analysis of a Randomized Clinical Trial

Importance

The optimal radiotherapy technique for unresectable locally advanced non-small cell lung cancer (NSCLC) is controversial, so evaluating long-term prospective outcomes of intensity-modulated radiotherapy (IMRT) is important.

Objective

To compare long-term prospective outcomes of patients receiving IMRT and 3-dimensional conformal radiotherapy (3D-CRT) with concurrent carboplatin/paclitaxel for locally advanced NSCLC.

Design, Setting, and Participants

A secondary analysis of a prospective phase 3 randomized clinical trial NRG Oncology-RTOG 0617 assessed 483 patients receiving chemoradiotherapy (3D-CRT vs IMRT) for locally advanced NSCLC based on stratification.

Main Outcomes and Measures

Long-term outcomes were analyzed, including overall survival (OS), progression-free survival (PFS), time to local failure, development of second cancers, and severe grade 3 or higher adverse events (AEs) per Common Terminology Criteria for Adverse Events, version 3. The percentage of an organ volume (V) receiving a specified amount of radiation in units of Gy is reported as V(radiation dose).

Results

Of 483 patients (median [IQR] age, 64 [57-70] years; 194 [40.2%] female), 228 (47.2%) received IMRT, and 255 (52.8%) received 3D-CRT (median [IQR] follow-up, 5.2 [4.8-6.0] years). IMRT was associated with a 2-fold reduction in grade 3 or higher pneumonitis AEs compared with 3D-CRT (8 [3.5%] vs 21 [8.2%]; P = .03). On univariate analysis, heart V20, V40, and V60 were associated with worse OS (hazard ratios, 1.06 [95% CI, 1.04-1.09]; 1.09 [95% CI, 1.05-1.13]; 1.16 [95% CI, 1.09-1.24], respectively; all P < .001). IMRT significantly reduced heart V40 compared to 3D-CRT (16.5% vs 20.5%; P < .001). Heart V40 (<20%) had better OS than V40 (≥20%) (median [IQR], 2.5 [2.1-3.1] years vs 1.7 [1.5-2.0] years; P < .001). On multivariable analysis, heart V40 (≥20%), was associated with worse OS (hazard ratio, 1.34 [95% CI, 1.06-1.70]; P = .01), whereas lung V5 and age had no association with OS. Patients receiving IMRT and 3D-CRT had similar rates of developing secondary cancers (15 [6.6%] vs 14 [5.5%]) with long-term follow-up.

Conclusions and Relevance

These findings support the standard use of IMRT for locally advanced NSCLC. IMRT should aim to minimize lung V20 and heart V20 to V60, rather than constraining low-dose radiation bath. Lung V5 and age were not associated with survival and should not be considered a contraindication for chemoradiotherapy.

Trial Registration

ClinicalTrials.gov Identifier: NCT00533949.

[Photon field junction for external beam radiotherapy of breast cancer involving axillary and supraclavicular lymph nodes]

We present evaluation of junction of coplanar external beam photon fields and its portal dosimetric analysis for breast cancer with positive lymph nodes. In our work, we compared twelve patients affected by breast cancer with axillary and supraclavicular lymph nodes, using conformal external beam plans from a dosimetric point of view. 3-3 plans were prepared per patient. Three methods were used for the conformal technique to investigate the potential of lymph nodes treatment field's collimations. During the evaluation of the portal dosimetry images, it was concluded that the junction plane at isocenter appeared as a discrete coldline, when fitted the regional field with or without collimation manually and by the software. However, the coverage of the isocenter plane is strongly influenced by the linear accelerator and the fitted field edges. Based on our results, in order to avoid uncertainties arising from field junctions and the overdosed areas of the target volume, it is more appropriate to choose another advanced irradiation technique such as intensity-modulated radiation therapy.

Use of Zernike moments to characterize dose conformity for radiotherapy treatment plans

Dose conformity is an essential parameter used in radiotherapy and radiosurgery that measures the correspondence of the dose distribution derived from a Treatment Planning System (TPS) with the actual volume to be treated, the Planning Treatment Volume (PTV). The present work uses a method based on the expansion of dose distributions and PTVs by three-dimensional Zernike polynomials and further comparison of their moments to define a general criterion of dose conformity. To carry on this study, data coming from 20 patients comprising 80 datasets exported from the TPS, which included imaging data (PTVs) and dose distributions corresponding to different treatment modalities: three-dimensional conformal radiotherapy, intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT), were used. The expansions in Zernike polynomials were obtained up to order 6 and reconstructed dose distributions and PTVs were obtained and compared, and several definitions for a general dose conformity index were proposed. Results indicate agreement between the proposed dose conformity index and the Conformation Number CN. The proposed method allows for a systematic approach to the analysis of dose distributions with further extensions in AI applications.

Secondary neutron dosimetry for conformal FLASH proton therapy

BACKGROUND

Cyclotron-based proton therapy systems utilize the highest proton energies to achieve an ultra-high dose rate (UHDR) for FLASH radiotherapy. The deep-penetrating range associated with this high energy can be modulated by inserting a uniform plate of proton-stopping material, known as a range shifter, in the beam path at the nozzle to bring the Bragg peak within the target while ensuring high proton transport efficiency for UHDR. Aluminum has been recently proposed as a range shifter material mainly due to its high compactness and its mechanical properties. A possible drawback lies in the fact that aluminum has a larger cross-section of producing secondary neutrons compared to conventional plastic range shifters. Accordingly, an increase in secondary neutron contamination was expected during the delivery of range-modulated FLASH proton therapy, potentially heightening neutron-induced carcinogenic risks to the patient.

PURPOSE

We conducted neutron dosimetry using simulations and measurements to evaluate excess dose due to neutron exposure during UHDR proton irradiation with aluminum range shifters compared to plastic range shifters.

METHODS

Monte Carlo simulations in TOPAS were performed to investigate the secondary neutron production characteristics with aluminum range shifter during 225 MeV single-spot proton irradiation. The computational results were validated against measurements with a pair of ionization chambers in an out-of-field region ( ≤ $\le$ 30 cm) and with a Proton Recoil Scintillator-Los Alamos rem meter in a far-out-of-field region (0.5-2.5 m). The assessments were repeated with solid water slabs as a surrogate for the conventional range shifter material to evaluate the impact of aluminum on neutron yield. The results were compared with the International Electrotechnical Commission (IEC) standards to evaluate the clinical acceptance of the secondary neutron yield.

RESULTS

For a range modulation up to 26 cm in water, the maximum simulated and measured values of out-of-field secondary neutron dose equivalent per therapeutic dose with aluminum range shifter were found to be( 0.57 ± 0.02 ) mSv/Gy $(0.57\pm 0.02)\ \text{mSv/Gy}$ and( 0.46 ± 0.04 ) mSv/Gy $(0.46\pm 0.04)\ \text{mSv/Gy}$ , respectively, overall higher than the solid water cases (simulation:( 0.332 ± 0.003 ) mSv/Gy $(0.332\pm 0.003)\ \text{mSv/Gy}$ ; measurement:( 0.33 ± 0.03 ) mSv/Gy $(0.33\pm 0.03)\ \text{mSv/Gy}$ ). The maximum far out-of-field secondary neutron dose equivalent was found to be (8.8 ± 0.5 $8.8 \pm 0.5$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ and (1.62 ± 0.02 $1.62 \pm 0.02$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ for the simulations and rem meter measurements, respectively, also higher than the solid water counterparts (simulation: (3.3 ± 0.3 $3.3 \pm 0.3$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ ; measurement: (0.63 ± 0.03 $0.63 \pm 0.03$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ ).

CONCLUSIONS

We conducted simulations and measurements of secondary neutron production under proton irradiation at FLASH energy with range shifters. We found that the secondary neutron yield increased when using aluminum range shifters compared to conventional materials while remaining well below the non-primary radiation limit constrained by the IEC regulations.

Lung cancer reirradiation: Exploring modifications to utilization, treatment modalities and factors associated with outcomes

BACKGROUND

Patients treated for lung cancer (LC) often experience locoregional failure after initial treatment. Due to technological advances, thoracic reirradiation (re-RT) has become a viable treatment option. We sought to investigate the use of thoracic re-RT in LC patients over a time period characterized by technological advances in a large, multi-center cohort.

METHODS AND MATERIALS

LC patients treated with thoracic re-RT in two University Hospitals from 2010-2020 were identified. Clinical variables and RT data were extracted from the medical records and treatment planning systems. Overall survival (OS) was calculated from the last day of re-RT until death or last follow up.

RESULTS

296 patients (small cell LC n=30, non-small cell LC n=266) were included. Three-dimensional conformal radiation therapy was the RT technique used most frequently (63%), and 86% of all patients were referred for re-RT with palliative treatment intent. During the second half of the study period, the use of thoracic re-RT increased in general, more patients received curative re-RT, and there was an increased use of stereotactic body radiation therapy (SBRT). Median time between initial RT and re-RT was 18 months (range 1-213 months). Only 83/296 patients had combined treatment plans that allowed for registration of combined doses to organs at risk (OAR). Most of the combined doses to OAR were below recommendations from guidelines. Multivariate analysis showed superior OS (p<0.05) in patients treated with curative intent, SBRT or intensity modulated radiation therapy or had excellent performance status prior to re-RT.

CONCLUSIONS

The use of re-RT increased in the second half of the study period, although 2020 did not follow the trend. The use of SBRT and IMRT became more frequent over the years, yet the majority received palliative re-RT. Combined dose plans were only created for one third of the patients.

Dosimetric parameters predict radiation-induced temporal lobe necrosis in nasopharyngeal carcinoma patients: A systematic review and meta-analysis

This systematic review examines the role of dosimetric parameters in predicting temporal lobe necrosis (TLN) risk in nasopharyngeal carcinoma (NPC) patients treated with three-dimensional conformal RT (3D-CRT), intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). TLN is a serious late complication that can adversely affect the quality of life of NPC patients. Understanding the relationship between dosimetric parameters and TLN can guide treatment planning and minimize radiation-related complications. A comprehensive search identified relevant studies published up to July 2023. Studies reporting on dosimetric parameters and TLN in NPC patients undergoing 3D-CRT, IMRT, and VMAT were included. TLN incidence, follow-up duration, and correlation with dosimetric parameters of the temporal lobe were analyzed. The review included 30 studies with median follow-up durations ranging from 28 to 110 months. The crude incidence of TLN varied from 2.3 % to 47.3 % and the average crude incidence of TLN is approximately 14 %. Dmax and D1cc emerged as potential predictors of TLN in 3D-CRT and IMRT-treated NPC patients. Threshold values of >72 Gy for Dmax and >62 Gy for D1cc were associated with increased TLN risk. However, other factors should also be considered, including host characteristics, tumor-specific features and therapeutic factors. In conclusion, this systematic review highlights the significance of dosimetric parameters, particularly Dmax and D1cc, in predicting TLN risk in NPC patients undergoing 3D-CRT, IMRT, and VMAT. The findings provide valuable insights that can help in developing optimal treatment planning strategies and contribute to the development of clinical guidelines in this field.

A phantom study investigating effective strategies for reducing fetal dose in pregnant patients with head and neck cancer

PURPOSE

To measure the out-of-field doses for various treatment planning techniques and assess the impact on fetal dose with and without the use of custom shielding.

MATERIALS AND METHODS

A total of six treatment plans were generated with different treatment techniques such as 3-dimensional conformal radiation therapy (3DCRT), intensity modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT), utilizing both 6 MV flattened beams and flattening filter-free (FFF) beams. The measurements were carried out both out-of-field at the surface and at depth to assess the dose reduction achieved by removing the flattening filter and incorporating shielding.

RESULTS

The custom-made frame shielding can effectively reduce the surface dose with a maximum reduction of 15.2% observed in VMAT plans and achieve a maximum reduction of 100% for cone beam computed tomography (CBCT) imaging. Out-of-field dose measurements conducted at depth, positioned 58 cm inferior to the target isocenter, reveal that the shielding effectiveness consistently remains the greatest for 3DCRT technique. A maximum reduction of 21% is observed when utilizing a flattening filter-free beam.

CONCLUSION

The results of this study indicate that the 3DCRT technique exhibits the least amount of scatter radiation both near and far from the treatment isocenter, which is the most suitable approach for radiation therapy of pregnant patients. In cases where meeting dose constraints for critical organs becomes challenging, VMAT technique emerges as the most suitable treatment technique for reducing out-of-field doses. Additionally, a flattening filter-free beam significantly reduces out-of-field doses due to lower contributions from head scatter.

Effect of prescription isodose line on tissue sparing in linear accelerator-based stereotactic radiosurgery treating multiple brain metastases using dynamic conformal arcs

PURPOSE

Linear accelerator-based stereotactic radiosurgery (SRS) has become a mainstay for simultaneous management of multiple intracranial targets. Recent improvements in treatment planning systems (TPS) have enabled treatment of multiple brain metastases using dynamic conformal arcs (DCA) and a single treatment isocenter. However, as the volume of healthy tissue receiving at least 12 Gy (V12) is linked to the probability of developing radionecrosis, balancing target coverage while minimizing V12 is a critical factor affecting SRS plan quality. Current TPS allow users to adjust various parameters influencing plan optimization. The purpose of this work is to quantify the effect of negative margins on V12 for cranial SRS plans managing multiple brain metastases.

METHODS

Using the Brainlab Elements v3.0 TPS (Brainlab, Munich, Germany), we calculated V10, V12, V15, monitor units, and conformity index for seventeen SRS plans treating 2-10 metastases on our Elekta Versa HD (Elekta, Stockholm, Sweden) linear accelerator. We compared plans optimized using 70%-90% prescription isodose lines (IDL) in 5% increments.

RESULTS

Irrespective of the number of treated metastases, optimization at a lower prescription IDL reduced V10, V12, and V15 and increased MU compared to the 90% IDL (p < 0.01). However, comparing the 70% and 75% IDL optimizations, there was little difference in tissue sparing. The conformity index showed no consistent trends at different IDLs due to a significant spread in case data.

CONCLUSION

For our plans treating up to 10 metastases, diminishing returns for tissue sparing at IDLs below 80% paired with increasing treatment MU and dosimetric hot spot made optimization at lower IDLs less favorable. In our clinic, after consulting with a physician, it was determined that optimization at the 80% IDL achieved the best balance of V12, treatment MU, and maximum dose. Clinics implementing LINAC-based SRS programs may consider using similar evaluations to develop their own clinical protocols.

Feasibility of determining external beam radiotherapy dose using LuSy dosimeter

INTRODUCTION

Radiation dose measurement is an essential part of radiotherapy to verify the correct delivery of doses to patients and ensure patient safety. Recent advancements in radiotherapy technology have highlighted the need for fast and precise dosimeters. Technologies like FLASH radiotherapy and magnetic-resonance linear accelerators (MR-LINAC) demand dosimeters that can meet their unique requirements. One promising solution is the plastic scintillator-based dosimeter with high spatial resolution and real-time dose output. This study explores the feasibility of using the LuSy dosimeter, an in-house developed plastic scintillator dosimeter for dose verification across various radiotherapy techniques, including conformal radiotherapy (CRT), intensity-modulated radiation therapy (IMRT), volumetric-modulated arc therapy (VMAT), and stereotactic radiosurgery (SRS).

MATERIALS AND METHODS

A new dosimetry system, comprising a new plastic scintillator as the sensing material, was developed and characterized for radiotherapy beams. Treatment plans were created for conformal radiotherapy, IMRT, VMAT, and SRS and delivered to a phantom. LuSy dosimeter was used to measure the delivered dose for each plan on the surface of the phantom and inside the target volumes. Then, LuSy measurements were compared against an ionization chamber, MOSFET dosimeter, radiochromic films, and dose calculated using the treatment planning system (TPS).

RESULTS

For CRT, surface dose measurement by LuSy dosimeter showed a deviation of -5.5% and -5.4% for breast and abdomen treatment from the TPS, respectively. When measuring inside the target volume for IMRT, VMAT, and SRS, the LuSy dosimeter produced a mean deviation of -3.0% from the TPS. Surface dose measurement resulted in higher TPS discrepancies where the deviations for IMRT, VMAT, and SRS were -2.0%, -19.5%, and 16.1%, respectively.

CONCLUSION

The LuSy dosimeter was feasible for measuring radiotherapy doses for various treatment techniques. Treatment delivery verification enables early error detection, allowing for safe treatment delivery for radiotherapy patients.

Post-operative intensity-modulated vs 3D conformal radiotherapy after conservative surgery for laryngeal tumours of the supraglottic region: a dosimetric analysis on 20 patients

Objective

To perform a dosimetric comparison between intensity modulated radiotherapy (IMRT) and 3D conformal radiotherapy in patients with locally advanced (stage III and IV) tumours of the supraglottic region treated with conservative surgery and post-operative radiotherapy.

Methods

An in-silico plan using a 3D conformal shrinking field technique was retrospectively produced for 20 patients and compared with actually delivered IMRT plans. Eighteen structures (arytenoids, constrictor muscles, base of tongue, floor of mouth, pharyngeal axis, oral cavity, submandibular glands and muscles of the swallowing functional units [SFU]) were considered.

Results

IMRT allowed a reduction of maximum and mean doses to 9 and 14 structures, respectively (p < .05).

Conclusions

IMRT achieved a reduction of unnecessary dose to the remnant larynx and the majority of surrounding SFUs. Further prospective analyses and correlations with functional clinical outcomes are required to confirm these dosimetric findings.

Current practices of craniospinal irradiation techniques in Turkey: a comprehensive dosimetric analysis

OBJECTIVE

This study evaluates various craniospinal irradiation (CSI) techniques used in Turkish centers to understand their advantages, disadvantages and overall effectiveness, with a focus on enhancing dose distribution.

METHODS

Anonymized CT scans of adult and pediatric patients, alongside target volumes and organ-at-risk (OAR) structures, were shared with 25 local radiotherapy centers. They were tasked to develop optimal treatment plans delivering 36 Gy in 20 fractions with 95% PTV coverage, while minimizing OAR exposure. The same CT data was sent to a US proton therapy center for comparison. Various planning systems and treatment techniques (3D conformal RT, IMRT, VMAT, tomotherapy) were utilized. Elekta Proknow software was used to analyze parameters, assess dose distributions, mean doses, conformity index (CI), and homogeneity index (HI) for both target volumes and OARs. Comparisons were made against proton therapy.

RESULTS

All techniques consistently achieved excellent PTV coverage (V95 > 98%) for both adult and pediatric patients. Tomotherapy closely approached ideal Dmean doses for all PTVs, while 3D-CRT had higher Dmean for PTV_brain. Tomotherapy excelled in CI and HI for PTVs. IMRT resulted in lower pediatric heart, kidney, parotid, and eye doses, while 3D-CRT achieved the lowest adult lung doses. Tomotherapy approached proton therapy doses for adult kidneys and thyroid, while IMRT excelled for adult heart, kidney, parotid, esophagus, and eyes.

CONCLUSION

Modern radiotherapy techniques offer improved target coverage and OAR protection. However, 3D techniques are continued to be used for CSI. Notably, proton therapy stands out as the most efficient approach, closely followed by Tomotherapy in terms of achieving superior target coverage and OAR protection.

Integrating cine EPID, dynamic delivery, and the off-axis Winston-Lutz test to enhance quality control in multiple brain metastasis stereotactic radiotherapy

PURPOSE

Stereotactic radiotherapy (SRT) has transformed cancer treatment, especially for brain metastases. Ensuring accurate SRT delivery is crucial, with the Winston-Lutz test being an important quality control tool. Off-axis Winston-Lutz (OAWL) tests are designed for accuracy assessment, but most are limited to fixed angles and hampered by local-field shifts caused by suboptimal Multi-Leaf Collimator (MLC) positioning. This study introduces a new OAWL approach for quality control in multi-brain-metastasis SRT. Utilizing cine Electronic Portal Imaging Device (EPID) images, it can be used with dynamic conformal arc (DCA) therapy. However, dynamic OAWL (DOAWL) is prone to more local-field shifts due to dynamic MLC movements. A two-step DOAWL is proposed: step 1 calculates local-field shifts using dynamic MLC movements in the beam-eye view data from the Treatment Planning System (TPS), while step 2 processes cine EPID images with an OAWL algorithm to isolate true deviations.

METHODS

Validation involved an anthropomorphic head phantom with metallic ball-bearings, Varian TrueBeam STx accelerator delivering six coplanar/non-coplanar DCA beams, cine EPID, and ImageJ's OAWL analysis algorithm.

RESULTS

Inherent local-field shifts ranged from 0.11 to 0.49 mm; corrected mean/max EPID-measured displacement was 0.34/1.03 mm. Few points exceeded 0.75/1.0-mm thresholds.

CONCLUSIONS

This two-step DOAWL test merges cine-EPID acquisitions, DCA, OAWL, and advanced analysis and offers effective quality control for multi-brain-metastasis SRT. Its routine implementation may also improve physicist knowledge of the treatment precision of their machines.

Sparing Swallowing-Related Structures Reduces Post-Radiotherapy Dysphagia in Oropharyngeal Cancer

OBJECTIVE

To identify swallowing-related structures (SRSs) predicting post-radiotherapy dysphagia in oropharyngeal carcinoma patients.

MATERIAL AND METHODS

Between September 2020 and October 2022, oropharyngeal cancer patients who had completed radiotherapy at least one year before without recurrence or residuals were selected. They underwent flexible endoscopic evaluation of swallowing (FEES) assessments and dysphagia grading. The mean radiation doses delivered to their SRSs were recalculated. The correlation between radiation doses to each SRS and FEES scores was analysed.

RESULTS

Twenty-nine participants, aged 51-73 years, were enrolled. Six patients had received two-dimensional radiotherapy, eight had undergone three-dimensional conformal radiotherapy, and fifteen had received intensity-modulated radiation therapy. Radiation doses to the inferior pharyngeal constrictor, cricopharyngeus and glottic larynx significantly predicted dysphagia for both semisolids (p = 0.023, 0.030 and 0.001) and liquid diets (p = 0.021, 0.013 and 0.002). The esophageal inlet significantly predicted swallowing outcomes for only the liquid diet (p = 0.007).

CONCLUSIONS

This study supports that SRS-sparing during radiotherapy for oropharyngeal cancers improves swallowing outcomes.

Validation of complex radiotherapy techniques using polymer gel dosimetry

Modern radiotherapy delivers highly conformal dose distributions to irregularly shaped target volumes while sparing the surrounding normal tissue. Due to the complex planning and delivery techniques, dose verification and validation of the whole treatment workflow by end-to-end tests became much more important and polymer gel dosimeters are one of the few possibilities to capture the delivered dose distribution in 3D. The basic principles and formulations of gel dosimetry and its evaluation methods are described and the available studies validating device-specific geometrical parameters as well as the dose delivery by advanced radiotherapy techniques, such as 3D-CRT/IMRT and stereotactic radiosurgery treatments, the treatment of moving targets, online-adaptive magnetic resonance-guided radiotherapy as well as proton and ion beam treatments, are reviewed. The present status and limitations as well as future challenges of polymer gel dosimetry for the validation of complex radiotherapy techniques are discussed.

A comparison of the incidence of ≥ grade 2 radiation pneumonitis between intensity-modulated radiotherapy and three-dimensional conformal radiotherapy in patients with unresectable non-small cell lung cancer treated with durvalumab after concurrent chemoradiotherapy

BACKGROUND

Intensity-modulated radiation therapy (IMRT) has been increasingly used as a new radiation modality for unresectable non-small cell lung cancer (NSCLC). The risk factors for radiation pneumonitis (RP) during consolidation durvalumab following concurrent chemoradiotherapy (CCRT) using IMRT have not been thoroughly investigated.

METHODS

This retrospective study analyzed medical record data from consecutive patients diagnosed with NSCLC who underwent CCRT and consolidation durvalumab at our institution between April 2018 and September 2022. Since we adopted IMRT for the treatment of NSCLC in April 2020, these patients were categorized into two groups: those treated with IMRT after April 2020 and those treated with three-dimensional conformal radiotherapy (3D-CRT) before April 2020.

RESULTS

A total of 31 patients underwent IMRT (the IMRT group), while 25 patients underwent 3D-CRT (the 3D-CRT group). In both groups, the total dose was 60 Gy in 30 fractions. The cumulative incidence of ≥ grade 2 RP at 12 months was significantly lower in the IMRT group than in the 3D-CRT group (27.0% vs. 64.0%, hazard ratio [HR]: 0.338, 95% confidence interval [CI]: 0.144-0.793, p = 0.013). In the multivariable analysis, V20 (≥ 25.6%, HR: 2.706, 95% CI: 1.168-6.269, p = 0.020) and radiotherapy technique (IMRT, HR: 0.414, 95% CI: 0.172-0.994, p = 0.048) were identified as significant risk factors for ≥ grade 2 RP.

CONCLUSIONS

IMRT is associated with a lower rate of ≥ grade 2 RP in patients with NSCLC who received CCRT followed by durvalumab.

Using standardized workflows and quantitative data-driven management to reduce time interval from simulation to treatment initiation

PURPOSE

External beam radiotherapy is a complex process, involving timely coordination among multiple teams. The aim of this study is to report our experience of establishing a standardized workflow and using quantitative data and metrics to manage the time-to-treatment initiation (TTI).

METHODS AND MATERIALS

Starting in 2014, we established a standard process in a radiation oncology-specific electronic medical record system (RO-EMR) for patients receiving external beam radiation therapy in our department, aiming to measure the time interval from simulation to treatment initiation, defined as TTI, for radiation oncology. TTI data were stratified according to the following treatment techniques: three-dimensional (3D) conformal therapy, intensity-modulated radiotherapy (IMRT), and stereotactic body radiotherapy (SBRT). Statistical analysis was performed with the Mann-Whitney test for the respective metrics of aggregate data for the initial period 2012- 2015 (PI) and the later period 2016-2019 (PII).

RESULT

Over 8 years, the average annual number of treatments for PI and PII were 1760 and 2357 respectively, with 3D, IMRT, and SBRT treatments accounting for 53, 29, 18% and 44, 34, 22%, respectively, of the treatment techniques. The median TTI for 3D, IMRT, and SBRT for PI and PII were 1, 6, 7, and 1, 5, 7 days, respectively, while the 90th percentile TTI for the three techniques in both periods were 5, 9, 11 and 4, 9, 10 days, respectively. From the aggregate data, the TTI was significantly reduced (p = 0.0004, p < 0.0001, p < 0.0001) from PI to PII for the three treatment techniques.

CONCLUSION

Establishing a standardized workflow and frequently measuring TTI resulted in shortening the TTI during the early years (in PI) and maintaining the established TTI in the subsequent years (in PII).

Clinical Implementation of "Plan of the Day" Strategy in Definitive Radiation Therapy of Cervical Cancer: Online Adaptation to Address the Challenge of Organ Filling Reproducibility

PURPOSE

Definitive pelvic intensity modulated radiation therapy (IMRT) in cervical cancer is susceptible to geographic miss due to daily positional and volumetric variations in target and organs at risk. Hence, despite evidence of reduced acute and late treatment-related toxicities, implementation of image-guided IMRT (IG-IMRT) with a reasonable safety margin to encompass organ motion is challenging.

METHODS AND MATERIALS

In this prospective, nonrandomized phase 2 study, patients with cervical cancer International Federation of Gynecology and Obstetrics (2009) stage IB2-IIIB between the ages of 18 and 65 years were treated with definitive pelvic chemoradiotherapy with a prespecified organ (bladder and rectum) filling protocol. Reproducibility of organ filling was assessed along with the implementation of daily comprehensive adaptive image-guided radiotherapy (IGRT), with a library of 3 IMRT (volumetric modulated arc therapy) plans with incremental expansions of clinical target volume (CTV) to planning target volume (PTV) (primary) margins (small, 0.7 cm; adequate, 1 cm; and large, 1.5 cm) and a backup motion robust 3-dimensional conformal radiotherapy plan; the appropriate plan is chosen based on pretreatment cone beam computed tomography (CBCT) ("plan of the day" approach).

RESULTS

Fifty patients with a median age of 49 years (IQR, 45-56 years) received definitive radiation therapy (45-46 Gy in 23-25 fractions to pelvis, with simultaneous integrated boost to gross nodes in 15 patients) with the aforementioned IGRT protocol. In the analysis of 1171 CBCT images (in 1184 treatment sessions), the mean planning computed tomography (CT) and CBCT bladder volumes were 417 and 373 cc, respectively. Significant interfractional variation in bladder volume was noted with a mean absolute dispersion of 29.5% with respect to planning CT; significant influential random factors were postchemotherapy sessions (P ≤ .001), pre-CBCT protocol duration (P = .001), and grades of chemotherapy induced nausea vomiting (P = .001). Significantly higher variation in bladder filling was noted in patients with older age (P = .014) and larger planning CT bladder volume (P ≤ .001). Time trend analysis of fraction-wise bladder volume revealed an absolute systemic reduction of 16.3% in bladder volume means from the first to the fifth week. Variation in rectal diameter was much less pronounced, with 19.2% mean dispersion and without any significant factors affecting it. Although in 19% and 2% of sessions large IMRT PTV and 3-dimensional conformal radiotherapy were necessary to cover the primary target, respectively, reduction in treated volume was possible in 43% of sessions with small PTV selection instead of standard adequate PTV (36% sessions). Plan of the day selection had a moderate to strong correlation with nonabsolute dispersion of bladder filling (Spearman ρ =0.4; P = .001) and a weak (but significant) correlation with grades of acute toxicities. The planned protocol was well tolerated with no radiation-induced local grade 3 toxicity.

CONCLUSIONS

Interfractional variation in organ filling (especially bladder) is inevitable despite fixed pretreatment protocol in definitive settings (intact cervix). Despite the logistical challenges, adaptive IGRT in the form of plan of the day based on incremental CTV-to-PTV margins is a relatively simple and feasible strategy to minimize geometric uncertainties in radical IG-IMRT of cervical cancer.

Correlation Between Dosimetric Parameters and Local Control in Definitive Radiotherapy for Head and Neck Cancers

BACKGROUND/AIM

Radiotherapy (RT) outcomes are generally reported based on stage, patient background, and concomitant chemotherapy. This study aimed to investigate the effects of the prescribed dose to gross tumor volume (GTV) and the calculation algorithm on local control in definitive RT for head and neck (H&N) cancers using follow-up images after RT.

PATIENTS AND METHODS

This study included 154 patients with H&N cancers treated by Volumetric Modulated Arc Therapy at the Kobe City Medical Center General Hospital. Patients were classified into those receiving definitive RT (70 Gy of irradiation) and those not receiving it. Follow-up images were used to categorize the patients into the responders and non-responders groups. In the non-responders group, follow-up images were imported into the treatment planning system, and the contours of the residual or recurrent areas (local failure) were extracted and fused with computed tomography-simulated images for treatment planning. Dose evaluation parameters included maximum dose, dose administered to 1% of the volume, dose administered to 50% of the volume, dose administered to 99% of the volume (D99%), and minimum dose (Dmin) administered to the GTV. The doses to the GTV were compared between responders and non-responders.

RESULTS

D99% exhibited significant differences between local failure and responders and between local failure and non-responders. Dmin showed significant differences between responders and non-responders and between responders and local failure.

CONCLUSION

This study emphasizes the importance of verifying dose distribution in all slices of treatment planning, highlighting the need for precise assessment of the dose to the GTV in head and neck cancers.

In vivo dose measurements for tangential field-in-field ultra-hypofractionated breast radiotherapy

INTRODUCTION

Ultra-hypofractionated radiotherapy (UHF-RT) mandates more accuracy in each part of the treatment cycle to maximize cure rates and minimize toxicities. In vivo dosimetry is a direct method for verifying overall treatment accuracy. This study evaluated uncertainties in the delivered dose of Hypofractionated (HF) and UHF Whole Breast Irradiation (WBI) and to analyze the accuracy of the workflow to pave the way for a wide-scale use of UHF-RT.

METHODS

Thirty-three breast cancer cases, including 16 HF-WBI and 17 UHF-WBI were treated with 3D conformal Radiotherapy (3D-CRT), where 79 fields were analyzed for dose verification. The measurement point was set at the beam entrance (1.5 cm depth). The expected dose at Dmax was calculated via TPS. Before in vivo measurements, diode detectors were tested and calibrated. We developed initial validation measurements for UHF-RT on an anthropomorphic breast phantom for the first time.

RESULTS

For RANDO phantom, the percentage difference between measured and calculated doses showed an average of -0.52 ± 5.4%, in addition to an excellent dose reproducibility within 0.6%. The overall in vivo measurements for studied cases showed that 83.5% of the measured doses were within ±5% and only 1.8% of the measured doses were greater than ±10% of the calculated doses. The percentage accuracy was slightly larger for UHF cohort (84.2%) compared to HF cohort (83.2%). The maximum percentage difference between them was less than 1%.

CONCLUSION

Breast in vivo dosimetry is an adequate tool for treatment verification that improves the accuracy of the treatment cycle. UHF-RT may contribute in reducing the long waiting lists, increasing patient convenience, and saving the available resources for breast cancer patients.

Radiation technique and outcomes following moderately hypofractionated treatment of low risk prostate cancer: a secondary analysis of RTOG 0415

BACKGROUND

While moderately hypofractionated radiotherapy (MHRT) for prostate cancer (PC) is commonly delivered by intensity modulated radiation therapy, IMRT has not been prospectively compared to three-dimensional conformal radiotherapy (3D-CRT) in this context. We conducted a secondary analysis of the phase III RTOG 0415 trial comparing survival and toxicity outcomes for low-risk PC following MHRT with IMRT versus 3D-CRT.

METHODS

RTOG 0415 was a phase III, non-inferiority trial randomizing low-risk PC patients to either MHRT or conventionally fractionated radiation with stratification by RT technique. A secondary analysis for differences in overall survival (OS), biochemical recurrence free survival (BRFS), or toxicity by EPIC scores and Common Terminology Criteria for Adverse Events (CTCAE) was performed.

RESULTS

1079 patients received the allocated intervention with a median follow up of 5.8 years. 79.1% of patients were treated with IMRT and radiation technique was balanced between arms. Across all patients, RT technique was not associated with significant differences in BRFS, OS, or rates of acute and late toxicities. For patients completing MHRT, there was a difference in the late GU toxicity distribution between 3D-CRT and IMRT but no difference in late grade 2 or greater GU or GI toxicity. Stratifying patients by RT technique and fractionation, no significant differences were observed in the minimal clinically important difference (MCID) in EPIC urinary and bowel scores following RT.

CONCLUSIONS

RT technique did not impact clinical outcomes following MHRT for low-risk PC. Despite different late GU toxicity distributions in patients treated with MHRT by IMRT or 3D-CRT, there was no difference in late Grade 2 or greater GU or GI toxicity or patient reported toxicity. Increases in late GU and GI toxicity following MHRT compared to CFRT, as demonstrated in the initial publication of RTOG 0415, do not appear related to a 3D-CRT treatment technique.

Longitudinal Costs of Image-Guided Intensity-Modulated Radiation Therapy Versus Three-Dimensional Conformal Radiation: Lessons From Phase III PARCER Trial for Shaping Resource-Stratified Guidelines in Low- and Middle-Income Countries

PURPOSE

The PARCER trial provided level I evidence for image-guided intensity-modulated radiation therapy (IG-IMRT) in patients with cervical cancer. Further information regarding long-term financial impact is imperative for adoption into the National Cancer Grid of India cervical cancer resource-stratified guidelines.

METHODS

Patient data from the PARCER trial were analyzed to evaluate the cost implications of transitioning to IG-IMRT. Lacking differences in outcomes between the three-dimensional conformal radiation (3D-CRT) and IG-IMRT, differences in treatment costs, adverse event incidence, and toxicity management costs were examined. The overall financial impact was estimated by adding the treatment costs, toxicity management, and wage loss. This was extrapolated nationally to determine if a transition to IG-IMRT would be feasible for the Indian health care system.

RESULTS

Of the 300 patients in the PARCER trial, 93 faced grades ≥2 adverse events (3D-CRT = 59, IG-IMRT = 34). Patients in the 3D-CRT and IG-IMRT arms spent an average of 2.39 years and 1.96 years in toxicity, respectively. The average toxicity management and the yearly financial impact per patient were, respectively, 1.50 and 1.44 times higher for 3D-CRT patients compared with IG-IMRT patients. Extrapolation to the national level showed that treatment with 3D-CRT led to a 2.88 times higher cost ratio when compared with treatment with IG-IMRT.

CONCLUSION

Although the initial costs of IG-IMRT are high, on the basis of longitudinal data, it is financially inefficient to treat with 3D-CRT. Resource-stratified guidelines should include longitudinal health intervention costs rather than solely initial costs for policy decisions to implement advanced radiation technology.

Safety of Three-Dimensional Conformal Radiotherapy on the Sheep with Pulmonary Cystic Echinococcosis: A Preliminary Study

PURPOSE

Radiotherapy showed the potential to effectively kill the cysts of pulmonary cystic echinococcosis (CE). However, little is known about its safety. This study was designed to investigate the safety of three-dimensional conformal radiotherapy (3D-CRT) on the normal lung tissue adjacent to the cyst and blood of sheep naturally infected with pulmonary CE.

METHODS

Twenty pulmonary CE sheep were randomly divided into control group (n = 5) and radiation groups with a dose of 30 Gray (Gy) (n = 5), 45 Gy (n = 5), and 60 Gy (n = 5), respectively. Animals in control group received no radiation. Heat shock protein 70 (Hsp70), tumor growth factor-β (TGF-β), matrix metalloproteinase-2 (MMP-2) and MMP-9 in the lung tissues adjacent to the cysts, which were considered to be closely related to the pathogenesis of CE, were evaluated after 3D-CRT. A routine blood test was conducted.

RESULTS

The results showed that there were multiple cysts of various sizes with protoscoleces in the lung tissues of sheep, and necrotic cysts were found after 3D-CRT. 3D-CRT significantly increased the mRNA level of Hsp70, enhanced the protein level of TGF-β and slightly increased the expression of MMP-2 and MMP-9 in lung tissues adjacent to the cysts. 3D-CRT did not significantly alter the amount of WBC, HB and PLT in sheep blood.

CONCLUSIONS

The results suggested that 3D-CRT may suppress the inflammation and induce less damage of the normal lung tissues and blood. We preliminarily showed that 3D-CRT under a safe dose may be used to treat pulmonary CE.