Arc Radiotherapy Research Articles

Dosimetric Effects of Dynamic Jaw Tracking and Collimator Angle Optimization in Non-Coplanar Cranial Arc Radiotherapy.

The stereotactic treatment of single cranial targets using noncoplanar volumetric modulated arc therapy (VMAT) allows for effective dose delivery to the target, while sparing normal brain tissue. In this study, the dosimetric effect of adding dynamic jaw tracking and automatic collimator angle selection in the optimization of single target cranial VMAT plans was investigated. Twenty-two cranial targets, previously treated with VMAT without dynamic jaw tracking and automatic collimator angle optimization (CAO) were chosen for replanning. Target volumes ranged from 0.441cc to 25.863cc with doses between 18Gy and 30Gy delivered in 1 to 5 fractions. Original plans were reoptimized with automatic CAO, keeping all other objectives the same (CAO plans). Next, original plans were reoptimized with both dynamic jaw tracking and CAO (DJT plans). Original, CAO, and DJT target doses were compared using the Paddick gradient index (GI) and the Paddick inverse conformity index (ICI), while normal tissue dose was compared using the volume of the normal brain receiving 5Gy, 10Gy, and 12Gy. The normal tissue volume was normalized to target size to allow cross comparison between plans. A one-sided t-test was performed to determine whether the changes in the plan metrics were statistically significant. CAO plans had improved GIs compared to the originals (p = 0.03) with insignificant changes in other plan metrics (p > 0.20). The addition of dynamic jaw tracking in DJT plans greatly improved ICIs and normal brain metrics (p < 0.01) compared to the CAO plans with minor improvement in ICIs (p = 0.07). The combined effect of adding dynamic jaw tracking and collimator optimization led to improvements in all metrics of the DJT plans when compared to the original (p < 0.02). The addition of dynamic jaw tracking and CAO led to improvements in both target and normal tissue dose metrics for single-target noncoplanar cranial VMAT plans.

Dosimetric evaluation study of IMRT and VMAT techniques for prostate cancer based on different multileaf collimator designs

The hypofractionated radiotherapy modality was established to reduce treatment durations and enhance therapeutic efficiency, as compared to conventional fractionation treatment. However, this modality is challenging because of rigid dosimetric constraints. This study aimed to assess the impact of multi-leaf collimator (MLC) widths (10 mm and 5 mm) on plan quality during the treatment of prostate cancer. Additionally, this study aimed to investigate the impact of the MLC mode of energy on the Agility flattening filter (FF), MLC Agility-free flattening filter (FFF), and MLCi2 for patients receiving hypofractionated radiotherapy. Two radiotherapy techniques; Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Radiotherapy (VMAT), were used in this research. In the present study, computed tomography simulations of ten patients (six plans per patient) with localized prostate adenocarcinoma were analyzed. Various dosimetric parameters were assessed, including monitor units, treatment delivery times, conformity, and homogeneity indices. To evaluate the plan quality, dose-volume histograms (DVHs) were estimated for each technique. The results demonstrated that the determined dosimetric parameters of planning target volume (PTV)p (such as D mean, conformity, and homogeneity index) showed greater improvement with MLC Agility FF and MLC Agility FFF than with MLCi2. Additionally, the treatment delivery time was reduced in the MLC Agility FF (by 31%) and MLC Agility FFF (by 10.8%) groups compared to the MLCi2 group. It is concluded that for both the VMAT and IMRT techniques, the smaller width (5 mm) MLCs revealed better planning target volume coverage, improved the dosimetric parameters for PTV, reduced the treatment time, and met the constraints for OARs. It is therefore recommended to use 5 mm MLCs for hypofractionated prostate cancer treatment due to better target coverage and better protection of OARs.

Correlation of oral mucosa dose and volume parameters with Grade 3 mucositis, in patients treated with volumetric modulated arc radiotherapy for oropharyngeal cancer?

Oral mucositis is the dose-limiting toxicity of chemoradiation in oropharyngeal cancer patients, which can be minimized by giving constraints to oral mucosa. However, the constraints defined in literature are extrapolated from chemoradiation in head and neck cancers as a whole. This study aims to determine oral mucosa dose-volume parameters that can predict grade≥3 acute oral mucositis in oropharyngeal cancer patients treated with volumetric modulated arc radiotherapy. This prospective study was done in 52 patients of locally advanced oropharyngeal cancer treated with Volumetric modulated arc radiotherapy. Dose-volume histogram data were extracted and then acute oral mucosa toxicity was analysed. Receiver operating characteristic analysis and logistic regression were carried out to determine predictive factors for grade≥3 mucositis. Grade≥3 acute oral mucositis occurred in 57.6% (30/52) patients in the study. V30Gy>53.35% (P=0.005) was an independent dosimetric factor related to grade≥3 acute toxicity. In the receiver operating characteristic curve, the area under V30Gy was 0.770 (P=0.001); the cut-off value of V30 was 46.23% (sensitivity, 0.80; specificity, 0.91). Dose-volume histogram analysis predicts V30>53.35% as independent factors for grade≥3 acute oral mucositis in patients with oropharyngeal cancers treated with Volumetric modulated arc radiotherapy. Studies in future with more patient number can further validate the above results.

Cardiac Morbidity Following Chemoradiation in Stage III Non-small Cell Lung Cancer Patients: A Population-Based Cohort Study

AimsTo assess the risk of cardiac toxicity following radical radiotherapy in advanced lung cancer patients. Materials and methodsPatients with a diagnosis of stage III non-small cell lung cancer (NSCLC) receiving chemoradiotherapy were extracted from a population-based cohort in Ontario, Canada. The primary outcome of cardiac toxicity, defined as cardiac events or congestive heart failure, was assessed at 1 and 5 years following chemoradiotherapy. Secondary outcomes included overall survival, survival in relationship to post-treatment cardiac events and the effect of radiotherapy technique on cardiac toxicity. ResultsIn total, 2031 NSCLC patients were included. The cumulative incidence of cardiac toxicity at 5 years was 20.3% (18.4–22.3). The median survival was 13.7 months in NSCLC patients who had a cardiac event post-chemoradiotherapy compared with 23.4 months in those who did not (P = 0.012). There was a trend towards increased cumulative cardiac toxicity (hazard ratio 3.37, P = 0.14) with three-dimensional conformal radiotherapy compared with intensity-modulated or volumetric arc radiotherapy techniques. ConclusionThe risk of cardiac events and congestive heart failure 5 years after radical thoracic radiotherapy appears high and survival is inferior at 1 year in those patients who experience a cardiac event post-treatment. More conformal radiotherapy techniques may help reduce cardiac toxicity. Further studies should investigate adaptive treatment planning and close monitoring and intervention in this high-risk group after chemoradiotherapy.

Direct emission spectrometry determination of fluorine in carbon materials: Argon dc arc and spark radiation sources

In this work, the procedure for direct atomic emission spectrometry (AES) determination of fluorine impurities in carbon materials was proposed. Two types of simple radiation sources with direct solid (powdered) sample introduction were studied: direct current arc (25A) and high-power low voltage spark (300 V, of 2348 μF). For each source, standard graphite extra high purity electrodes and argon discharge atmosphere were used. Red spectral region approach to non-metal AES determination was employed with analytical line F I 685.603 nm. The spectra were registered by compact tunable fiber-optic spectrometer with linear complementary metal oxide semiconductor array (CMOS) sensor and short-focus lens. Special measures were taken to counter red spectral region interferences, such as CN molecular bands and thermal radiation. The excitation of F in both types of radiation source was studied. A set of artificial graphite and NaF based standards was prepared for calibration and evaluated by two independent approaches: indirect dc arc AES and water extraction photometry. Limit of detection was determined for dc arc source was 5 μg/g, and for spark 20 μg/g of F. The whole cycle of measurement with each type of radiation source takes 10 min. As the power of dc arc is limited by generator capabilities, it is possible that even lower limit of detection is achievable with higher discharge current.

Image Guidance Volume-Modulated Arc Radiation Therapy Concurrently With Nab-Paclitaxel Plus Cisplatin for Patients With Locally Advanced Cervical Cancer: A Single-Arm Dose Escalation Trial

Nanoparticle albumin-bound (nab) paclitaxel has improved uptake by tumor cells in comparison to paclitaxel. The aim of this study was to determine the maximal tolerated dose (MTD) and the dose-limiting toxicity (DLT) of nab-paclitaxel plus cisplatin with concurrent image guidance volume modulated arc therapy for locally advanced cervical cancer (LACC). This single-arm phase 1 trial followed the standard 3+3 dose escalation design. Patients with histologically proven stage IB2-IVA LACC were eligible. Image guidance volume modulated arc therapy included 50.4 Gy in 28 fractions to the pelvis and 59.4 Gy simultaneous boost in 28 fractions to involved pelvic and para-aortic lymph nodes, and subsequent high-dose-rate intracavitary brachytherapy at a total dose of 30.0 Gy in 5 fractions, twice a week. Concurrent chemotherapy regimen included weekly cisplatin (40 mg/m2) and weekly nab-paclitaxel at escalating doses (10, 20, 33, 50, and 70 mg/m2 per week). Duration of the planned treatment was 8 weeks. Grade 4 hematologic toxicity and grade 3 or above nonhematologic toxicity were considered as DLT. MTD was defined as the highest dose with ≤33% DLT. A total of 22 patients were enrolled from September 2019 to August 2021. The most common adverse events were grade 1 to 3 leukopenia, diarrhea, and nausea/vomiting. A total of 4 patients (18.0%) experienced DLT: grade 3 hypokalemia at 33 mg/m2 (1 of 6 subjects), grade 3 deep vein thrombosis at 50 mg/m2 (1 of 6) and 70 mg/m2 (1 of 4), and grade 3 perineum edema at 70 mg/m2 (1 of 3). The estimated MTD was 50 mg/m2. Complete response was observed in 20 patients (90.9%). In patients undergoing concurrent IG-VAMT with nab-paclitaxel plus cisplatin for LACC, MTD of nab-paclitaxel was 50 mg/m2. Complete response rate was 90.9%.

Volumetric modulated arc radiotherapy with concomitant chemotherapy for the anal squamous carcinoma: A Welsh experience

Volumetric modulated arc radiotherapy with concomitant chemotherapy for the anal squamous carcinoma: A Welsh experience

Dynamic conformal arc radiotherapy for locally advanced lung cancer: a comparison with static-beam conformal radiotherapy.

This study investigated whether the dose distribution of lung cancer can be improved by dynamic arc conformal radiotherapy (dynamic CRT) compared with static multiple-beam radiotherapy (static CRT). A dummy study of static CRT and dynamic CRT was performed, designed to meet the predetermined dose constraints. A dose of 60 Gy in 30 fractions was administered using two dose prescription methods: dose prescribed to the isocenter (IC prescription), and dose prescribed to > 50% of the planning target volume (D50 prescription). Dose-volume parameters were compared between the plans. Among 20 patients with locally advanced lung cancer, dose conformity was significantly better with dynamic CRT than static CRT (median conformity index: 1.3 vs. 2.2; p < 0.01). As for the lung dose, compared with static CRT, dynamic CRT did not increase the percentage lung volume receiving ≥ 20 Gy (18.9% vs. 19.3%, p = 0.09). The maximum spinal cord dose was significantly reduced by dynamic CRT (static vs. dynamic CRT: 44.1 vs. 25.2 Gy, p < 0.001). With the change from IC to D50 prescription, the 95% isodose volume increased by 18.3 cc in static CRT and by 4.1 cc in dynamic CRT, while doses to the lung and spinal cord remained within the acceptable ranges. The dynamic CRT technique showed better target coverage and lower doses to the spinal cord in exchange for increased low-dose lung area, compared with static CRT. Dynamic CRT with D50 prescription instead of prescription to the isocenter has excellent dose distribution profiles without compromising doses to organs at risk for lung cancer at favorable locations.

Innovative Widefield Volumetric Arc Radiation Therapy (VMAT) Approach to Simultaneously Treat Extensive Skin Field Cancerization (ESFC) + In-Field Keratinocyte Carcinoma (KC) in Australian Patients: Report with 12 Month Follow-Up

<h3>Purpose/Objective(s)</h3> Patients with extensive skin field cancerization (ESFC) have large areas of diffuse hyperkeratotic actinic keratoses (AK), often with concomitant keratinocyte carcinoma (KC) or other cancer. Treatment can involve numerous interventions including cryotherapy, topical agents, and/or surgery, which can be ineffective or prohibitively invasive. The design of innovative widefield volumetric modulated arc radiation therapy (VMAT) protocols, has extended the high lesion cure rates of radiation to the treatment of patients with ESFC and in-field cancer. This is a report on treatment planning, and the efficacy, safety, and cosmetic outcomes of VMAT for the management of patients with ESFC + in-field cancer at facilities across five Australian states. <h3>Materials/Methods</h3> Twenty-six patients with ESFC plus a KC or lentigo melanoma (n=1), were prescribed widefield VMAT and prospectively enrolled in the National (Australian) Dermatology Radiation Oncology Registry (NDROR). Over 80% of patients had received up to 4 prior non-radiotherapy interventions. Fields included lower and upper limb, face, scalp, or trunk regions. Total widefield VMAT RT doses ranged from 45-50 Gy delivered in 25-30 daily fractions across 5-7 weeks. In-field cancer, defined as KC (cutaneous squamous cell carcinoma or basal cell carcinoma), or lentigo melanoma, were generally prescribed a simultaneous integrated boost (SIB) of 55Gy. 3-, 6-, and 12-month follow-up assessed the percentage of field disease clearance, lesion complete response, cosmesis using the Lovett's scale, and toxicity based on CTCAE. <h3>Results</h3> At 12-month follow-up, 88% of treated fields had achieved and maintained clinical success, defined as >90% clearance. A complete lesion response for boosted in-field cancer was observed in 96% of patients. Four percent of patients exhibited recurrence of original disease, whereas 15% of patients developed a new lesion. Cosmesis was rated as excellent or good in 96% of patients. Most patients exhibited grade 1-2 radiation-induced dermatitis during therapy, which resolved by 3-month follow-up. Nineteen percent (5/26) of patients discontinued treatment due to acute toxicities, though achieved complete responses without recurrence or new lesions, indicating a reduced dose and associated toxicity may be possible without compromising efficacy. <h3>Conclusion</h3> Widefield VMAT yielded promising clinical success in patients with ESFC plus in-field cancer, in addition to favorable cosmetic outcomes, and a manageable toxicity profile in most patients. Scheduled 24-month follow-up will be undertaken shortly to provide further insight into dosage and durability. These results demonstrate that widefield VMAT may be an excellent option for some patients with ESFC and in-field cancer, for whom other therapies have failed.

Can Perirectal Spacing Help Reduce GI Toxicity in Patients Undergoing Post-Prostatectomy Radiotherapy?

<h3>Purpose/Objective(s)</h3> To report single institutional feasibility of recto-vesical hyaluronic acid or hydrogel spacer insertion for patients undergoing post prostatectomy radiotherapy (PPRT). <h3>Materials/Methods</h3> Spacer insertion was considered in patients referred for PPRT following an intra or interfascial radical prostatectomy who had no radiological evidence of local recurrence (based on prostate specific membrane antigen positron emission tomography). The spacer was inserted into the perirectal fat between the bladder and anterior rectal wall using a transperineal approach under transrectal ultrasound guidance. Two gold seed fiducial markers were also inserted at the level of the vesico-urethral anastomosis for image guided radiation therapy as per institutional practice. Pre and post spacer computerized tomography planning scans, together with post spacer magnetic resonance imaging scans, were acquired for dosimetric comparison. The prostate bed clinical target volume (CTV) was delineated according to Australian guidelines and the CTV was uniformly expanded by 7mm to create the planning target volume (PTV). The prescribed dose to the prostate bed was 70.2Gy in 1.8 Gy fractions using volumetric arc radiation therapy. The PTV and rectal dosimetry for the two sets of planning scans (PTV 7mm/pre spacer and PTV 7mm/post spacer) were compared. <h3>Results</h3> Sixty-one patients were recruited between 9/18 to 10/21. Fifty-eight patients successfully underwent rectal spacer insertion without postoperative complications. We did not attempt spacer insertion in 3 patients as we were unable to hydrodissect the perirectal fat plane. Only 33 patients had pre spacer planning scans available for dosimetric comparison. The distance between the bladder and rectal wall was increased from ≤1mm to a median of 11mm (9-13) at its greatest extent. The rectal volume for all patients (N=61) receiving 42.2Gy (rV60%), 49.1Gy (rV70%), 56.2 Gy (rV80%), 63.2Gy (rV90%) and 70.2Gy (rV100%)] were 28.1%, 23%, 17.9%, 12.5% and 3.8% respectively. With spacing, a statistically significant reduction was seen on all rectal volume end points from rV60% to rV100% in the 33 patients with both pre and post planning scans (see Table 1). The median follow up was 10.5 months (3-31). The risk of any grade acute GI toxicity was 28% (grade 1 26% and grade 2 2%). The risk of late GI toxicity was 7% (all grade 1 proctitis). <h3>Conclusion</h3> More than 90% of our selected PPRT patients were able to achieve recto-vesical separation, with no surgical complications, resulting in a 43.7% reduction in rV90%. The reduction in acute and late grade 2 GI toxicity is of notable significance, albeit with short follow up. Table 1 Pre and Post Spacer Rectal Dosimetry

Risk-Adjusted Chemoradiation according to Human Papilloma Virus Status for Anal Cancer: A Pilot Registry Study

<h3>Purpose/Objective(s)</h3> Radiation with concurrent chemotherapy (CRT) represents standard definitive therapy for anal cancer. CRT protocols result in good local control, but are associated with significant acute and late morbidity. Whether radiation dose escalation beyond 55-60 Gy improves local control remains unknown. Most anal cancers are associated with HPV infection. Patients with HPV positive (+) cancers have better outcomes compared to those with HPV negative (-) disease. HPV+ anal cancer patients may not benefit from standard CRT. <h3>Materials/Methods</h3> Since 2019, we have instituted a REB-approved prospective registry study that tailored CRT for anal cancer according to HPV status in addition to disease stages. Patients with HPV+ T1, T2 and T3/T4 disease received a total dose of 45, 50.4 and 55.8 Gy respectively. Elective nodal radiation dose was 30.6 Gy. For HPV- disease, total doses for T1, T2 and T3/T4 disease were 50.4, 55.8 and 63 Gy respectively, and 36 Gy was given for N0 disease. Concurrent chemotherapy consisted of a single dose of mitomycin C (12 mg/m²) and daily oral capecitabine (825 mg/m² bid) on days of radiation only. Patients were planned following CT, PET/CT and MR simulation. Treatment was delivered using volumetric modulated arc radiotherapy (VMAT) with daily cone beam CT. We report results of an interim analysis, which was planned after the first consecutive cohort of patients had a minimum 18 months of follow-up from CRT. <h3>Results</h3> There were 20 patients with HPV+ (HPV16, 15; HPV18, 1; other HPV types, 3) tumor and 4 were HPV-. All HPV+ tumors demonstrated p16 immunoreactivity. In the HPV+ cohort, there were one T1 (1.6 cm), eleven T2 (2.1-4.8 cm), five T3 (5.1-5.8 cm) and three T4 (4-8.5 cm) lesions. Eight patients (N1a, 4; N1b, 1; N1c, 3) presented with nodal metastases. All HPV+ patients completed protocol RT without RT interruption. Two refused chemotherapy. Grade 2 acute toxicities were observed in all 20 patients and five had grade 3 acute toxicities (skin reactions, pain and anemia). Restaging MRI was done at a median of 170 days (103-204 days) from date of RT. There were two local failures. Both (T4N1c and T2N0) had persistent local disease. Of four patients with HPV- cancer, one (T2N1b) had persistent local disease and one (T2N1c) failed in the iliac nodes; one (T4N0) developed a perforated ischemic sigmoid at 14 months requiring surgery. The local failure rate of 4/24 (16.7%) in this registry study was similar to our historic local failure rate of 28/180 (15.6%) in a retrospective cohort of patients managed by CRT from 2001-2009. These patients were managed using the current RT protocol for HPV- disease but with two cycles of mitomycin C and 5-Fluorouracil. <h3>Conclusion</h3> Treatment de-escalation for HPV+ anal cancer appears safe and may result in similar local control rates compared to standard CRT protocols.

The Use of HA as Rectal Spacer in Prostate Cancer Patients Undergoing Hypofractionated RT: An Australian Experience

<h3>Purpose/Objective(s)</h3> To report the feasibility, post-operative complications and recto-prostatic separation achieved with hyaluronic acid (HA) inserted into the perirectal fat before definitive prostate radiotherapy (RT). <h3>Materials/Methods</h3> Fifty-seven patients with clinical stage T1-3 prostate cancer underwent transrectal ultrasound guided transperineal insertion of fiducial markers and HA into the perirectal space before volumetric arc RT between 7/2020 to 7/2021. Post insertion computerized tomography (CT) and magnetic resonance imaging (MRI) scans were obtained for treatment planning. HA feasibility, safety and recto-prostatic separation were assessed. The prescribed dose to the planning target volume (PTV) ranged from 60-62Gy in 20 fractions. <h3>Results</h3> The mean age was 74.7 years. The median PSA was 8.1 [Interquartile range (IQR)6.2-10.0]. The majority of patients had ISUP 2 adenocarcinoma (60%). The rest had ISUP 1 (11%) and ISUP 3 (30%). The disease risk was staged as early in 11%, favorable intermediate in 30%, unfavorable intermediate in 58% and high in 2%. Androgen deprivation therapy was delivered in 63%. HA insertion was completed with a 100% success rate. This was rated as ‘easy' to ‘very easy' 100% of the time. There were no device related complications, rectal perforation, serious bleeding, infections or allergic reactions. The mean prostate size was 43cc (IQR 30-55cc). Recto-prostatic separation at the base (measured 5mm below the prostate base), mid gland and apex (measured 5mm above the prostate apex) were 12mm (0.2), 11mm (0.2) and 0.9mm (0.1) respectively. The HA was also symmetrically placed in breadth at the mid gland in all patients. The mean rectal volume receiving 53Gy (rV53) was 3.2% (IQR 1.3-5.5) for patients receiving 60-62Gy. The median follow up was 13.5 months (IQR 9.5-17.5). The risk of any acute GU toxicity was 81%. The majority had grade 1 GU toxicity at 67% with urinary frequency, urgency and obstruction being the commonest reported side effects. The risk of any grade 2 GU toxicity was 14% with urinary obstruction (13%) and urgency (7%). The risk of any acute GI toxicity was 2%. Only 1 patient developed grade 1 GI toxicity with diarrhea. The risk of any late GU toxicity was 43%. The majority had grade 1 GU toxicity at 32% with urinary frequency, urgency and obstruction. The risk of any grade 2 GU toxicity was 11% with urinary obstruction (5%), urgency (5%) and incontinence (2%). The risk of any late GI toxicity was 2%. Only 1 patient had grade 1 GI toxicity with diarrhea. <h3>Conclusion</h3> HA was successfully inserted in all patients and was well tolerated. Recto-prostatic separation was symmetrical in length from the base to the apex and in breadth at the midgland. The risk of developing any acute GI toxicity was minimal at 2% with the use of HA. In addition, the risk of late GI toxicity was 2%, albeit with short follow up.

A Combined Hypofractionated Volumetric Modulated Arc Radiotherapy, Radio-Sensitising and Adjuvant Metronomic Chemotherapy Treatment for Canine Stage IV Nasal Tumours With Intracranial Extension

Radiation therapy has become the standard of care in the treatment of canine intranasal neoplasia, but because of the poor prognosis associated with stage IV nasal tumours and the proximity of the brain to the irradiation target, few data regarding the treatment of very advanced neoplasms are available. The aim of this pilot study was to evaluate the feasibility, safety and effectiveness of a combined treatment composed of definitive high-dose hypofractionated volumetric modulated arc radiotherapy on tumours with concurrent treatment of regional lymph nodes if positive or as prophylaxis, carboplatin radio-sensitising, and adjuvant metronomic chemotherapy for stage IV canine nasal tumours with intracranial extension.A pilot observational study was conducted in 7 dogs. Magnetic resonance imaging follow-up examinations revealed complete responses in 5 dogs and partial responses in 2. The median overall survival time, evaluated via Kaplan−Meier survival analysis, was 310 days with a 95% confidence interval of 210-400 days, whereas the median progression-free survival was 240 days with a 95% confidence interval of 190-290 days.Despite the proximity of highly sensitive organs at risk, no grade III or IV toxicities were observed, and volumetric modulated arc radiotherapy seemed to be a feasible treatment option for stage IV canine nasal tumours where conformal 3D radiotherapy has proven to give higher doses with severe damage to the surrounding unaffected tissues. Further studies are needed on the role of the sphenoid bone microscopic infiltration and regional lymph node involvement. The absence of severe toxicity could also lead to a dose escalation study and chemotherapy scheme.

Efficient dose-volume histogram-based pretreatment patient-specific quality assurance methodology with combined deep learning and machine learning models for volumetric modulated arc radiotherapy.

Weak correlation between gamma passing rates and dose differences in target volumes and organs at risk (OARs) has been reported in several studies. Evaluation on the differences between planned dose-volume histogram (DVH) and reconstructed DVH from measurement was adopted and incorporated into patient-specific quality assurance (PSQA). However, it is difficult to develop a methodology allowing the evaluation of errors on DVHs accurately and quickly. To develop a DVH-based pretreatment PSQA for volumetric modulated arc therapy (VMAT) with combined deep learning (DL) and machine learning models to overcome the limitation of conventional gamma index (GI) and improve the efficiency of DVH-based PSQA. A DL model with a three-dimensional squeeze-and-excitation residual blocks incorporated into a modified U-net was developed to predict the measured PSQA DVHs of 208 head-and-neck (H&N) cancer patients underwent VMAT between 2018 and 2021 from two hospitals, in which 162 cases was randomly selected for training, 18 for validation, and 28 for testing. After evaluating the differences between treatment planning system (TPS) and PSQA DVHs predicted by DL model with multiple metrics, a pass or fail (PoF) classification model was developed using XGBoost algorithm. Evaluation of domain experts on dose errors between TPS and reconstructed PSQA DVHs was taken as ground truth for PoF classification model training. The prediction model was able to achieve a good agreement between predicted, measured, and TPS doses. Quantitative evaluation demonstrated no significant difference between predicted PSQA dose and measured dose for target and OARs, except for Dmean of PTV6900 (p=0.001), D50 of PTV6000 (p=0.014), D2 of PTV5400 (p=0.009), D50 of left parotid (p=0.015), and Dmax of left inner ear (p=0.007). The XGBoost model achieved an area under curves, accuracy, sensitivity, and specificity of 0.89 versus 0.88, 0.89 versus 0.86, 0. 71 versus 0.71, and 0.95 versus 0.91 with measured and predicted PSQA doses, respectively. The agreement between domain experts and the classification model was 86% for 28 test cases. The successful prediction of PSQA doses and classification of PoF for H&N VMAT PSQA indicating that this DVH-based PSQA method is promising to overcome the limitations of GI and to improve the efficiency and accuracy of VMAT delivery.

The combination of volumetric arc radiation therapy and boost high-dose rate interstitial brachytherapy for T3N2c tongue cancer: a technical report.

Currently, tongue cancers are primarily managed by surgery, and interstitial brachytherapy is only recommended for a selected group of early state T1-2N0 patients who refuse surgery or are medically inoperable. In this report, a case with T3N2cM0 tongue cancer who has been effectively treated by the combination of concurrent chemoradiotherapy involving volumetric arc therapy and boost high-dose rate interstitial brachytherapy is presented. Of course, surgery remains the main treatment strategy for tongue cancer patients; however, the authors believe that if volumetric arc therapy is carefully planned to reduce the mandible dose as much as possible and high-dose rate interstitial brachytherapy with a mouthpiece that protects the mandible is combined, it is possible to treat T3N2 disease, and this can be considered for patients who want to preserve organ function.

Audit of radiation oncology practice: Lessons from a new private hospital in Delhi, India.

The objective of this audit was to analyze the radiotherapy (RT) practice in a newly established tertiary private hospital. With increasing radiation oncology (RO) facilities in private sector, this report is the first audit from a private health organization in India. The audit of all consecutively registered patients in RO has focused to extract data from the time of RT simulation planning till the completion of RT course. The patient and disease characteristics,RT-related treatment factors and compliance were analyzed in-depth. In this newly established RO department, the vendor-supplied equipment, e.g., RT planning system, treatment delivery (linear accelerator and brachytherapy), and RO information system (ROIS), are integrated with enterprise-wide hospital information system into unified paperless workflow management for the patient care records in a prospective manner. This analysis comprised consecutive 328 patients who consented for RT simulation and planning from April 20, 2018, to December 31, 2019. RT course compliance was 94.8% (311/328 patients), and treatment intent-wise: curative plus adjuvant in 60.2% and palliative RT in 36%. RT technique was conformal in all 100%, with volumetric arc radiotherapy (VMAT) delivered to 66.6% of patients. With overall median RT course duration of 29 days (range 1-81 days), the patients were delivered a median of 20 fractions. Compared to the previously published audit from an academic RO department in Delhi, this audit from a private hospital has shown (i) lesser waiting time, (ii) improved treatment compliance, (iii) utilization of higher techniques, and (iv) a lower duration of RT course.

Long Term Results of Elective Nodal Salvage Radiotherapy in Oligometastatic Prostate Cancer : A Mono-Institutional Series

Background The development of new metabolic diagnostic imaging PET is changing the history of metastatic prostate cancer (pCa), identifying situations of progression with a low disease burden; radiation treatment of metabolically active oligometastatic sites has been shown to be effective to prolong patient survival. In the scenario of oligometastatic disease to pelvic lymph nodes there is no uniform consensus on treatment volumes and radiotherapy doses to use. Methods We retrospectively assessed a series of 50 patients treated from 2015 to 2021 at our center who presented with recurrent pelvic lymph node pCa disease with 1-3 lymph-nodes lateralized to one side of the pelvis. Patients were treated with intensity modulated Rapid Arc radiotherapy (IMRT), limiting the treatment volume to the chain of the affected side only. During the follow-up, the patients who presented a biochemical recurrence of the disease were evaluated by PET. Results The biochemical progression-free survival and the metastatic progression-free survival were respectively 36% and 49% at 5 years. 22/50 patients presented a documented recurrence on PET. Only one patient presented a relapse within the irradiated volume and no patient presented a relapse on the contralateral pelvic lymph node chain. No patient had gastrointestinal toxicity &gt; grade 1 RTOG. Conclusion Treatment of patients with oligorecurrent (1-3 lesions) pelvic pCa, limiting the volume of irradiation to only one side of the affected lymph node chain, results in good biochemical disease control and presents a low risk of neoplastic contralateral progression.

Cranial Spinal Spreading of Canine Brain Gliomas after Hypofractionated Volumetric-Modulated Arc Radiotherapy and Concomitant Temozolomide Chemotherapy: A Four-Case Report.

Simple SummaryGliomas represent the second-most-common primary brain tumors in dogs. Surgery and radiotherapy are established treatment approaches with similar median survival time, whereas conventional chemotherapy is burdened by severe adverse effects. Spinal and leptomeningeal spread of gliomas have been described following radiotherapy treatment alone and the prognosis is generally inauspicious. In this work, a more aggressive radiotherapy protocol with concomitant radiosensitizing chemotherapy is represented but spinal-spread of the disease is reported, despite the fact that it was originally located exclusively in the brain area. This work suggests that the entire central nervous system should be investigated in diagnostic examinations and during the follow-up of canine gliomas. A radiotherapy dose-escalation trial and different chemotherapy dosages on a larger number of animals could estimate the optimal protocol to avoid spinal-spread while limiting radio-chemo toxicities. In the same context, prophylactic treatment to the spinal cord with a lower dose could also be the key to preventing recurrence across the cranial–spinal pathway and to improving quality of life.Gliomas are the second-most-common primary brain tumors in dogs. Surgery and radiotherapy are established treatment approaches with similar median survival time, whereas conventional chemotherapy is burdened by severe adverse effects. Spinal and leptomeningeal spread of gliomas have been described following radiotherapy treatment alone. The purpose of this study was to evaluate the outcome for four dogs with primary high-grade gliomas in the forebrain without evidence, at diagnosis, of neoplastic invasion along the spinal cord, that were treated with concomitant chemotherapy (temozolomide) and hypofractionated volumetric-modulated arc radiotherapy (VMAT-RT). Temozolomide was selected for its radiosensitive properties, and radiotherapy dose protocols of 37 Gy in 7 fractions or 42 Gy in 10 fractions were used. After an initial complete or partial response, tumors recurred across the cranial–spinal pathway. Post-mortem macroscopic examinations confirmed swollen spinal cord and hyperemic meningeal sleeve, with nodular lesions on the meningeal surface. Microscopically, infiltration of the spinal cord and meninges by neoplastic cells (with features of oligodendrogliomas) were observed. This work seems to suggest that the entire central nervous system should be investigated in diagnostic examinations of canine gliomas. Dose-escalation trials and/or spinal cord prophylaxis treatment could also be evaluated to prevent tumor progression.

Sexual health and quality of life: Study on prostate cancer patients treated with modern 6MV X-ray radiation therapy

This study aimed to compare the sexual quality of life through pre-defined parameters of prostate cancer (PCa) patients with pre-and-post- volumetric modulated arc radiation therapy (VMAT) and to examine their association with the radiation doses of the penile bulb (PB) and patient peculiarity. In this retrospective study, we analyzed medical record data of 100 patients who received definitive external radiation therapy (RT) and hormone therapy (HT) for prostate cancer (PCa) between June to December 2017. Sexual activities were analyzed by the patient-reported outcomes and clinician quality of life indices observed scale before and after treatment. The outcome of sexual activities was observed about patients' age, the volume of the prostate, the level of the testosterone, comorbidity, smoking habits, staging of the tumours, therapy technology, hormonal therapy (HT) and penile bulb (PB) radiation doses. 84 (84%) of all patients (n=100) after 2 years of radiation had a poor erectile grade, and 43 (75%) of previously potent (n=57) patients were impotent following treatment. However, sexual desire prevailed in 59 (76%) of patients who had desire before treatment.

Radiation Power of a Short High-Current Vacuum Arc at High Current Densities

The radiation of a vacuum arc was measured in the spectral region <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~\text {nm} \le \lambda \le 1100$ </tex-math></inline-formula> nm. The arc was initiated in the center of the cathode by breaking the current in the auxiliary circuit and was fed by the rectangular current pulse with a duration of 10 ms. The interelectrode gap was fixed at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$h = 4$ </tex-math></inline-formula> mm, and the butt <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2r =30$ </tex-math></inline-formula> -mm CuCr30 electrodes were used. The arc was stabilized by an external uniform axial magnetic field (AMF). The radiation was coming out of the vacuum chamber through quartz ultraviolet (KU)-1 quartz window. The radiation detector was a silicon photodiode with a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d =1.2$ </tex-math></inline-formula> mm. It was located on an axis intersecting the axis of symmetry of the discharge in the center of the interelectrode gap. The distance from the diode to the axis of symmetry was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L =1340$ </tex-math></inline-formula> mm. After amplification, the signal from the diode was recorded on an oscilloscope. The measurements were made in a range of currents from 10 to 25 kA in order to cover the modes with the anodic activity. It was found that under the conditions of these experiments, the anode activity begins to manifest itself at the end of the pulse, starting with currents exceeding 15 kA. As the current increases, the activity begins closer to the beginning of the pulse. Considering the type of the spectral sensitivity of the diode, two series of measurements were made—measurements without a filter and through a yellow filter ZhS-10 that cuts off radiation with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda \le400$ </tex-math></inline-formula> nm. The results obtained made it possible to analyze the dependence of the radiation power on the arc current. The results showed that at high current densities in the developed vacuum arc with anodic activity, a significant part of the power is transferred by radiation. At the end of a pulse with a current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 25$ </tex-math></inline-formula> kA, the radiation power is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {uv}}~\approx ~150$ </tex-math></inline-formula> kW, while in the discharge, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{a} ~\approx ~800$ </tex-math></inline-formula> kW is released. That is, at high current densities at the end of the pulse, the radiation power reaches almost 20% of the power released in the arc at this time. Estimates of lateral losses due to radiation are made.