Radiotherapy For Cancer Research Articles

Symmetry, separation, and stability: Physical properties for effective dosimetric space with a stabilized hyaluronic acid spacer.

The proximity of the rectum to the prostate in radiation therapy (RT) for prostate cancer presents a significant dosimetric challenge, leading to high rectal doses and resulting in detrimental side effects. Perirectal tissue spacing reduces rectal dose and gastrointestinal toxicities by mechanically separating these organs. A variety of materials have been explored for use as rectal spacers, most recently, a stabilized hyaluronic acid (HA) gel, which can be formed into deliberate a shape, and retains the definition of that shape, while remaining flexible, unlike polyethylene glycol (PEG) hydrogels. This study evaluates the dosimetric impact of the spacer, including shape symmetry, the degree of separation at different locations, and the temporal stability of the space. Our goal is to provide physics-informed guidance on the optimal use of this sculptable spacer. A secondary analysis was performed on data from a 13-center prospective randomized trial (NCT04189913), involving 136 patients with centrally-reviewed treatment plans conducted on CT/MR simulation scans before and after receiving HA spacer implants. Patients were treated with 60Gy in 20 fractions to the prostate. For this study, python software was utilized for automated processing of DICOM RTstruct and RTdose files, facilitating detailed analysis of the spacer's impact on anatomical displacement and dosimetric outcomes. Complete dose-volume histograms (DVHs) were reconstructed, and combined into composite population DVHs before and after implant, verified against trial-reported dose points. Patients were divided into similar groups of separation and symmetry, and differences in their composite DVHs were tested for significance. Stability of the spacer was studied by comparing serial MRI images and by computing the distance between contours at four axial planes, at simulation and 3-month follow-up, post RT. The introduction of the HA spacer significantly enhanced rectal sparing, as evidenced by a reduction in the mean rectal integral dose by over 6Gy. High rates of implant symmetry(>95%) were observed, indicating nearly optimal lateral spacer placement. In superior-inferior coverage, this study like many others, saw the spacing largest at the superior extent but becoming more variable inferiorly at the level of the prostate apex. This allowed study of the apex as a specific area for dosimetric concern. Stability assessments confirmed that the spacer maintained its position and dimensions between the simulation and the 3-month post-RT, implying stable geometry during treatment, with only minimal separation changes observed. Statistical analysis using the Kruskal-Wallis test revealed significant correlations of larger separations at the inferior and apical planes with improved dosimetric outcomes, including rV30Gy. The use of a stabilized HA spacer in prostate RT effectively enhances prostate-rectum separation, leading to significant rectal sparing without undesirable dose compromises. This study underscores the role of strategic placement and shape, specifically including>1cm separation from the base down to the prostate apex. When combined with the treatment planning techniques used in the trial to create a steep dosimetric gradient across the spacer, these findings elucidate the dosimetric outcomes that can be expected in the clinical implementation of HA spacer. This is particularly relevant in the evolution of hypofractionated treatment regimens for prostate cancer therapy.

A marginal structural model for normal tissue complication probability.

The goal of radiation therapy for cancer is to deliver prescribed radiation dose to the tumor while minimizing dose to the surrounding healthy tissues. To evaluate treatment plans, the dose distribution to healthy organs is commonly summarized as dose-volume histograms (DVHs). Normal tissue complication probability (NTCP) modeling has centered around making patient-level risk predictions with features extracted from the DVHs, but few have considered adapting a causal framework to evaluate the safety of alternative treatment plans. We propose causal estimands for NTCP based on deterministic and stochastic interventions, as well as propose estimators based on marginal structural models that impose bivariable monotonicity between dose, volume, and toxicity risk. The properties of these estimators are studied through simulations, and their use is illustrated in the context of radiotherapy treatment of anal canal cancer patients.

A marginal structural model for normal tissue complication probability.

The goal of radiation therapy for cancer is to deliver prescribed radiation dose to the tumor while minimizing dose to the surrounding healthy tissues. To evaluate treatment plans, the dose distribution to healthy organs is commonly summarized as dose-volume histograms (DVHs). Normal tissue complication probability (NTCP) modeling has centered around making patient-level risk predictions with features extracted from the DVHs, but few have considered adapting a causal framework to evaluate the safety of alternative treatment plans. We propose causal estimands for NTCP based on deterministic and stochastic interventions, as well as propose estimators based on marginal structural models that impose bivariable monotonicity between dose, volume, and toxicity risk. The properties of these estimators are studied through simulations, and their use is illustrated in the context of radiotherapy treatment of anal canal cancer patients.

Measurement of the distance between tumor micro-foci and gross tumor in rectal cancer pathological specimens: implication on margin distance of clinical target volume treated with high-dose radiotherapy for rectal cancer.

To measure the micro-foci distance away from gross tumor and to provide reference to create the clinical target volume (CTV) margin for boost radiotherapy in rectal adenocarcinoma. Twenty-eight rectal cancer surgical specimens of only total mesorectal excision were collected. The pathological specimens were retrospectively measured, and the nearest distance between the tumor micro-foci and gross tumor was microscopically measured. The "in vivo-in vitro" retraction factor was calculated as the ratio of the deepest thickness laterally and the vertical height superior/inferiorly of the rectal tumor measured in MRI and those measured in immediate pathological specimens. The retraction factor during pathological specimen processing was calculated as the distance ratio before and after dehydration in the lateral, superior, and inferior sides by the "knot marking method." The distances of tumor micro-foci were individually corrected with these two retraction factors. The mean "in vivo-in vitro" tumor retraction factors were 0.913 peripherally and 0.920 superior/inferiorly. The mean tumor specimen processing retraction factors were 0.804 peripherally, 0.815 inferiorly, and 0.789 superiorly. Of 28 patients, 14 cases (50.0%) had 24 lateral micro-foci, 8 cases (28.6%) had 13 inferior micro-foci, and 7 cases (25.0%) had 19 superior micro-foci. The 95th percentiles of the micro-foci distance for 28 patients were 6.44mm (peripheral), 5.54mm (inferior), and 5.42mm (superior) after retraction correction. The micro-foci distances of 95% of rectal adenocarcinoma patients examined were within 6.44mm peripherally, 5.54mm inferiorly, and 5.42mm superiorly. These findings provide reference to set the boost radiotherapy CTV margin for rectal cancer.

Surgical Margins After Neoadjuvant Radiation for Locally Advanced Vulvar Carcinoma: What is an Adequate Margin?

We aim to explore whether the surgical tumor free margin is important for overall survival (OS) and local control in patients who undergo neoadjuvant radiation (RT) for vulvar cancer. A retrospective review from 2004 to 2021 of patients who underwent RT followed by surgical resection was performed. Patients were categorized into groups based on margin status (no residual disease, >8mm, close margins defined as 1 to 7mm, or positive). Local control and OS were analyzed using the Kaplan-Meier with log rank test. Multivariate analysis was performed with cox hazards model. Eighty-three patients were included. A complete pathologic response (pCR) was found in 56% (n=46) of patients. The median follow-up time was 35 months (range: 4 to 216). The median OS for the entire cohort was 46 months (95% CI: 32.3-59.7). Having a pCR improved both OS and disease-free survival (DFS) compared with residual disease by 81 and 91 months, respectively (P<0.001). In the 2 patients with a margin >8mm, there was no statistical difference in survival between those with close margins (46 vs. 25mo, P=0.485). Factors that significantly impacted both OS and DFS were depth of invasion (DOI) and LVSI. On multivariate analysis of those with residual disease, there was no difference in OS or DFS by margin status but having a DOI >9mm showed decreased OS (HR: 3.654; 95% CI: 1.317-10.135). In this cohort, response to RT, not margin status drives survival and recurrence. Given residual disease, the optimal margin is not clear, as there were only 2 patients with >8mm margins. A close or positive margin had no impact on OS or local recurrence. A DOI >9mm significantly impacts both OS and local recurrence even when accounting for other factors.

Improvement of accumulated dose distribution in combined cervical cancer radiotherapy with deep learning–based dose prediction

PurposeDifficulties remain in dose optimization and evaluation of cervical cancer radiotherapy that combines external beam radiotherapy (EBRT) and brachytherapy (BT). This study estimates and improves the accumulated dose distribution of EBRT and BT with deep learning–based dose prediction.Materials and methodsA total of 30 patients treated with combined cervical cancer radiotherapy were enrolled in this study. The dose distributions of EBRT and BT plans were accumulated using commercial deformable image registration. A ResNet-101–based deep learning model was trained to predict pixel-wise dose distributions. To test the role of the predicted accumulated dose in clinic, each EBRT plan was designed using conventional method and then redesigned referencing the predicted accumulated dose distribution. Bladder and rectum dosimetric parameters and normal tissue complication probability (NTCP) values were calculated and compared between the conventional and redesigned accumulated doses.ResultsThe redesigned accumulated doses showed a decrease in mean values of V50, V60, and D2cc for the bladder (−3.02%, −1.71%, and −1.19 Gy, respectively) and rectum (−4.82%, −1.97%, and −4.13 Gy, respectively). The mean NTCP values for the bladder and rectum were also decreased by 0.02‰ and 0.98%, respectively. All values had statistically significant differences (p &amp;lt; 0.01), except for the bladder D2cc (p = 0.112).ConclusionThis study realized accumulated dose prediction for combined cervical cancer radiotherapy without knowing the BT dose. The predicted dose served as a reference for EBRT treatment planning, leading to a superior accumulated dose distribution and lower NTCP values.

Improvement of accumulated dose distribution in combined cervical cancer radiotherapy with deep learning-based dose prediction.

Difficulties remain in dose optimization and evaluation of cervical cancer radiotherapy that combines external beam radiotherapy (EBRT) and brachytherapy (BT). This study estimates and improves the accumulated dose distribution of EBRT and BT with deep learning-based dose prediction. A total of 30 patients treated with combined cervical cancer radiotherapy were enrolled in this study. The dose distributions of EBRT and BT plans were accumulated using commercial deformable image registration. A ResNet-101-based deep learning model was trained to predict pixel-wise dose distributions. To test the role of the predicted accumulated dose in clinic, each EBRT plan was designed using conventional method and then redesigned referencing the predicted accumulated dose distribution. Bladder and rectum dosimetric parameters and normal tissue complication probability (NTCP) values were calculated and compared between the conventional and redesigned accumulated doses. The redesigned accumulated doses showed a decrease in mean values of V50, V60, and D2cc for the bladder (-3.02%, -1.71%, and -1.19 Gy, respectively) and rectum (-4.82%, -1.97%, and -4.13 Gy, respectively). The mean NTCP values for the bladder and rectum were also decreased by 0.02‰ and 0.98%, respectively. All values had statistically significant differences (p < 0.01), except for the bladder D2cc (p = 0.112). This study realized accumulated dose prediction for combined cervical cancer radiotherapy without knowing the BT dose. The predicted dose served as a reference for EBRT treatment planning, leading to a superior accumulated dose distribution and lower NTCP values.

Stereotactic body radiation therapy for prostate cancer: a dosimetric comparison of IMRT and VMAT using flattening filter and flattening filter-free beams.

This retrospective study was performed to evaluate plan quality and treatment delivery parameters of stereotactic body radiation therapy (SBRT) for prostate cancer. The study utilized different isocentric modulated techniques: intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) using 6 MV flattening filter (FF) and 10 MV flattening filter-free beams (FFF). Fifteen retrospective prostate cancer patients were selected for this study. Sixty plans were created with an SBRT-prescribed dose of 36.25Gy delivered in five fractions. Planning target volume (PTV) coverage, plan quality indices, doses delivered to organs at risk (OARs), and treatment delivery parameters were compared for all plans. It turned out that VMAT plans, particularly those using the FFF beam, provided superior target conformality and a steeper dose gradient as compared to IMRT plans. Additionally, VMAT plans showed better OARs sparing compared to IMRT plans. However, IMRT plans delivered a lower maximum dose to the target than VMAT plans. Importantly, the VMAT plans resulted in reduced treatment delivery parameters, including beam on time (BOT), monitor unit (MU), and modulation factor (MF), compared to IMRT plans. Furthermore, a statistically significant difference was observed in BOT and mean body dose between FF and FFF beams, with FFF beams showing superior performance. Considering all results, VMAT using 10 MV (FFF) is suggested for treating prostate cancer patients with SBRT. This offers the fastest delivery in addition to maintaining the highest plan quality.

What's Changed in 75 Years of RadRes? - An Australian Perspective on Selected Topics.

Several scientific themes are reviewed in the context of the 75-year period relevant to this special platinum issue of Radiation Research. Two criteria have been considered in selecting the scientific themes. One is the exposure of the associated research activity in the annual meetings of the Radiation Research Society (RRS) and in the publications of the Society's Journal, thus reflecting the interest of members of RRS. The second criteria is a focus on contributions from Australian members of RRS. The first theme is the contribution of radiobiology to radiation oncology, featuring two prominent Australian radiation oncologists, the late Rod Withers and his younger colleague, Lester Peters. Two other themes are also linked to radiation oncology; preclinical research aimed at developing experimental radiotherapy modalities, namely microbeam radiotherapy (MRT) and Auger endoradiotherapy. The latter has a long history, in contrast to MRT, especially in Australia, given that the associated medical beamline at the Australian Synchrotron in Melbourne only opened in 2011. Another theme is DNA repair, which has a trajectory parallel to the 75-year period of interest, given the birth of molecular biology in the 1950s. The low-dose radiobiology theme has a similar timeline, predominantly prompted by the nuclear era, which is also connected to the radioprotector theme, although radioprotectors also have a long-established potential utility in cancer radiotherapy. Finally, two themes are associated with biodosimetry. One is the micronucleus assay, highlighting the pioneering contribution from Michael Fenech in Adelaide, South Australia, and the other is the γ-H2AX assay and its widespread clinical applications.

Uterine Anastomosis with Low Anterior Resection.

In this surgical teaching video, we demonstrate the technique of robot-assisted uterine anastomosis combined with low anterior resection in a 27-year-old patient with T2 node-positive rectal cancer. The patient had undergone uterine transposition for fertility preservation prior to upfront chemotherapy and radiation therapy for rectal cancer. In this video, we review the key steps of both surgical procedures. We emphasize robot trocar placement and docking, demonstrate optimal organ manipulation and tissue handling, and include key operative modifications and pearls for successful perioperative management.

Post-Operative Radiation in Early Breast Cancer with N1 Disease: 10-Year Follow-Up.

Post-operative radiotherapy for post-menopausal women with early breast cancer and N1 disease is controversial. Although locoregional control is improved, overall survival (OS) benefit is unclear. The clinical benefit of post-operative irradiation in this group of patients over 10 years was reviewed. We aimed to evaluate the OS, disease-free survival (DFS), and factors affecting OS and DFS. A retrospective review of 191 post-menopausal women with early breast cancer and N1 disease from 2004 to 2011 was performed. Demographics, post-operative histology, adjuvant treatment, OS, and DFS were evaluated. Post-operative radiation was given to 95 of 191 women (49.7%). Younger age at diagnosis (p < 0.001), a greater number of involved nodes (p = 0.004), lymphovascular invasion (LVI), and a higher tumor grade (p = 0.001) were more likely in women who received post-operative radiation. Nodal radiation did not improve 10-year DFS (p = 0.084) or OS (p = 0.203). Post-operative nodal radiation was associated with significant improvement in 10-year OS in women who received only hormonal therapy (p = 0.047) and no other systemic therapy. Women with unfavorable risk factors were more likely to receive post-operative radiation, likely due to a perceived higher risk of recurrence. Nodal radiation did not significantly improve 10-year DFS or OS in early breast cancer patients with N1 disease, and the benefit was not clearly demonstrated. However, in those who were on hormonal therapy, radiotherapy was beneficial in improving overall survival.

Radiotherapy and Testicular Function: A Comprehensive Review of the Radiation-Induced Effects with an Emphasis on Spermatogenesis.

This comprehensive review explores the existing literature on the effects of radiotherapy on testicular function, focusing mainly on spermatogenic effects, but also with a brief report on endocrine abnormalities. Data from animal experiments as well as results on humans either from clinical studies or from accidental radiation exposure are included to demonstrate a complete perspective on the level of vulnerability of the testes and their various cellular components to irradiation. Even relatively low doses of radiation, produced either from direct testicular irradiation or more commonly from scattered doses, may often lead to detrimental effects on sperm count and quality. Leydig cells are more radioresistant; however, they can still be influenced by the doses used in clinical practice. The potential resultant fertility complications of cancer radiotherapy should be always discussed with the patient before treatment initiation, and all available and appropriate fertility preservation measures should be taken to ensure the future reproductive potential of the patient. The topic of potential hereditary effects of germ cell irradiation remains a controversial field with ethical implications, requiring future research.

Complement C5a receptor 1 blockade reverses cognitive deficits following cranial radiation therapy for brain cancer.

Cranial radiation therapy (RT) for brain cancers leads to an irreversible decline in cognitive function without an available remedy. Radiation-induced cognitive deficits (RICD) are particularly a pressing problem for the survivors of pediatric and low grade glioma (LGG) patients who often live long post-RT. Radiation-induced elevated neuroinflammation and gliosis, triggered by the detrimental CNS complement cascade, lead to excessive synaptic and cognitive loss. Using intact and brain cancer-bearing mouse models, we now show that targeting anaphylatoxin complement C5a receptor (C5aR1) is neuroprotective against RICD. We used a genetic knockout, C5aR1 KO mouse, and a pharmacologic approach, employing the orally active, brain penetrant C5aR1 antagonist PMX205, to reverse RICD. Irradiated C5aR1 KO and WT mice receiving PMX205 showed significant neurocognitive improvements in object recognition memory and memory consolidation tasks. C5aR1 inhibition reduced microglial activation, astrogliosis, and synaptic loss in the irradiated brain. Importantly, C5aR1 inhibition in the syngeneic, orthotopic astrocytoma, and glioblastoma-bearing mice protected against RICD without interfering with the therapeutic efficacy of RT to reduce tumor volume in vivo . PMX205 is currently in clinical trials for amyotrophic lateral sclerosis (ALS). Thus, C5aR1 inhibition is a translationally feasible approach to address RICD, an unmet medical need.

Tracheal necrosis after sandwich immunotherapy and stereotactic body radiotherapy for lung cancer

Tracheal necrosis after sandwich immunotherapy and stereotactic body radiotherapy for lung cancer

Design, construction, and dosimetry of 3D printed heterogeneous phantoms for synchrotron brain cancer radiation therapy quality assurance

Objective. This study aims to design, manufacture, and test 3D printed quality assurance (QA) dosimetry phantoms for synchrotron brain cancer radiation therapy at the Australian synchrotron. Approach. Fabricated 3D printed phantoms from simple slab phantoms, a preclinical rat phantom, and an anthropomorphic head phantom were fabricated and characterized. Attenuation measurements of various polymers, ceramics and metals were acquired using synchrotron monochromatic micro-computed tomography (CT) imaging. Polylactic acid plus, VeroClear, Durable resin, and tricalcium phosphate were used in constructing the phantoms. Furthermore, 3D printed bone equivalent materials were compared relative to ICRU bone and hemihydrate plaster. Homogeneous and heterogeneous rat phantoms were designed and fabricated using tissue-equivalent materials. Geometric accuracy, CT imaging, and consistency were considered. Moreover, synchrotron broad-beam x-rays were delivered using a 3 Tesla superconducting multipole wiggler field for four sets of synchrotron radiation beam qualities. Dose measurements were acquired using a PinPoint ionization chamber and compared relative to a water phantom and a RMI457 Solid Water phantom. Experimental depth doses were compared relative to calculated doses using a Geant4 Monte Carlo simulation. Main results. Polylactic acid (PLA+) shows to have a good match with the attenuation coefficient of ICRU water, while both tricalcium phosphate and hydroxyapatite have good attenuation similarity with ICRU bone cortical. PLA+ material can be used as substitute to RMI457 slabs for reference dosimetry with a maximum difference of 1.84%. Percent depth dose measurement also shows that PLA+ has the best match with water and RMI457 within ±2.2% and ±1.6%, respectively. Overall, PLA+ phantoms match with RMI457 phantoms within ±3%. Significance and conclusion. The fabricated phantoms are excellent tissue equivalent equipment for synchrotron radiation dosimetry QA measurement. Both the rat and the anthropomorphic head phantoms are useful in synchrotron brain cancer radiotherapy dosimetry, experiments, and future clinical translation of synchrotron radiotherapy and imaging.

Feasibility of Left Anterior Descending Coronary Artery Sparing Radiation Therapy for Locally Advanced Lung Cancer

Efforts to mitigate radiotherapy (RT) associated cardiotoxicity have focused on constraining mean heart dose (MHD). However, recent studies have shown greater predictive power with cardiac substructure dose metrics such as the left anterior descending (LAD) coronary artery volume (V) receiving 15Gy (V15Gy) ≥10%. Herein, we investigated the feasibility of LAD radiation sparing in contemporary IMRT/VMAT lung cancer plans. Single institution retrospective analysis of 54 locally advanced lung cancer patients treated with thoracic RT between February 2018-August 2021. After excluding 33 (5=non-IMRT/VMAT or intentionally LAD-optimized; 28=LAD V15Gy<10%), 21 plans with LAD V15Gy ≥10% were identified for LAD re-optimization with intent to meet LAD V15Gy <10% while maintaining meeting organ-at-risk (OAR) metrics and target coverage with original plan parameters. Dosimetric variables were compared using paired t tests. Most (57.1%, 12/21) were treated with definitive RT, 8/21 (38.1%) with post-operative RT, and one with neoadjuvant RT. The median prescribed RT dose was 60Gy (range 50.4-66Gy) in 30 fractions (range 28-33). LAD re-optimized plans (vs original) led to significant reductions in mean LAD V15Gy (39.4% ±13.9% vs 9.4% ±13.0%; p<0.001) and mean LAD dose (12.9Gy ± 4.6Gy vs 7.6Gy ±2.8Gy; p<0.001). Most (85.7%; 18/21) LAD re-optimized plans achieved LAD V15Gy <10%. There were no statistically significant differences in overall lung, esophageal, or spinal cord dose metrics. Only one re-optimization (1/21) exceeded an OAR constraint that was initially met in the original plan. To our knowledge, this is the first report describing the feasibility of LAD-optimized lung cancer RT planning using the newly identified LAD V15 Gy constraint. We observed that LAD V15Gy <10% is achievable in more than 85% of plans initially exceeding this constraint, with minimal dosimetric tradeoffs. Our results support the feasibility of routine incorporation of the LAD as an OAR in modern thoracic IMRT/VMAT planning.

Efficacy of a nurse-led sexual rehabilitation intervention for women with gynaecological cancers receiving radiotherapy: results of a randomised trial.

The multicentre randomised SPARC trial evaluated the efficacy of a nurse-led sexual rehabilitation intervention on sexual functioning, distress, dilator use, and vaginal symptoms after radiotherapy for gynaecological cancers. Eligible women were randomised to the rehabilitation intervention or care-as-usual. Four intervention sessions were scheduled over 12 months, with concurrent validated questionnaires and clinical assessments. Primary outcome was the Female Sexual Function Index (FSFI). A generalised-mixed-effects model compared groups over time. In total, 229 women were included (n = 112 intervention; n = 117 care-as-usual). No differences in FSFI total scores were found between groups at any timepoint (P = 0.37), with 12-month scores of 22.57 (intervention) versus 21.76 (care-as-usual). The intervention did not significantly improve dilator use, reduce sexual distress or vaginal symptoms compared to care-as-usual. At 12 months, both groups had minimal physician-reported vaginal stenosis; 70% of women were sexually active and reported no or mild vaginal symptoms. After radiotherapy and brachytherapy, 85% (intervention) versus 75% (care-as-usual)of participants reported dilation twice weekly. Sexual rehabilitation for women treated with combined (chemo)radiotherapy and brachytherapy improved before and during the SPARC trial, which likely contributed to comparable study groups. Best practice involves a sexual rehabilitation appointment 1 month post-radiotherapy, including patient information, with dilator guidance, preferably by a trained nurse, and follow-up during the first year after treatment. NCT03611517.

The system of accounting and control of dose loads on the lacrimal apparatus during radiotherapy of thyroid cancer

The system of accounting and control of dose loads on the lacrimal apparatus during radiotherapy of thyroid cancer

611 Hydrogel Vue Spacer in Prostate Cancer Radiotherapy for Patients with Inflammatory Bowel Disease (IBD): Pilot Study

Abstract Introduction Patients with Inflammatory Bowel Disease and those with previous rectal surgery may have challenges when undergoing prostate radiotherapy due to increased rectal toxicity after radiotherapy which may preclude them from having radiotherapy for their prostate cancer. We need solutions that can minimize rectal toxicity while maintaining the efficacy of radiotherapy for patients. We report on our experience using SpaceOAR Hydrogel Spacer as a solution to minimize the radiation dose to the rectum and reduce toxicities. Aim To assess the benefits of SpaceOAR Hydrogel spacers following radiotherapy in patients who are at risk than average of rectal toxicity. Method We collected data from patients with IBD or previous rectal/bowel surgery who received radical radiotherapy with SpaceOAR Vue™ Hydrogel from period between Sep/2021 and Sep/2022. Data was collected including age, stage, baseline PSA, Gleason score, number of endoscopic assessment required and need for any surgical/medical intervention within one-year after completion of their radiotherapy. Results 16 patients were included in the study with one year follow up. The range of age is (62-82 years), the dose of radiotherapy varies between 6000-7400Gy and the initial PSA range was (6.1-89). 8 patients required endoscopic assessment within 1 year of treatment (As a part of their normal follow-up). was normal in all patients except in 3 patients who has mild colitis. Biochemical control at one year was excellent. Conclusions Results demonstrated that the use of Hydrogel spacer in patients with IBD or previous bowel surgery undergoing radical prostate cancer radiotherapy is safe and is a reasonable strategy.

Localized fine-tuning and clinical evaluation of deep-learning based auto-segmentation (DLAS) model for clinical target volume (CTV) and organs-at-risk (OAR) in rectal cancer radiotherapy

Background and purposeVarious deep learning auto-segmentation (DLAS) models have been proposed, some of which have been commercialized. However, the issue of performance degradation is notable when pretrained models are deployed in the clinic. This study aims to enhance precision of a popular commercial DLAS product in rectal cancer radiotherapy by localized fine-tuning, addressing challenges in practicality and generalizability in real-world clinical settings.Materials and methodsA total of 120 Stage II/III mid-low rectal cancer patients were retrospectively enrolled and divided into three datasets: training (n = 60), external validation (ExVal, n = 30), and generalizability evaluation (GenEva, n = 30) datasets respectively. The patients in the training and ExVal dataset were acquired on the same CT simulator, while those in GenEva were on a different CT simulator. The commercial DLAS software was first localized fine-tuned (LFT) for clinical target volume (CTV) and organs-at-risk (OAR) using the training data, and then validated on ExVal and GenEva respectively. Performance evaluation involved comparing the LFT model with the vendor-provided pretrained model (VPM) against ground truth contours, using metrics like Dice similarity coefficient (DSC), 95th Hausdorff distance (95HD), sensitivity and specificity.ResultsLFT significantly improved CTV delineation accuracy (p < 0.05) with LFT outperforming VPM in target volume, DSC, 95HD and specificity. Both models exhibited adequate accuracy for bladder and femoral heads, and LFT demonstrated significant enhancement in segmenting the more complex small intestine. We did not identify performance degradation when LFT and VPM models were applied in the GenEva dataset.ConclusionsThe necessity and potential benefits of LFT DLAS towards institution-specific model adaption is underscored. The commercial DLAS software exhibits superior accuracy once localized fine-tuned, and is highly robust to imaging equipment changes.