Results Of Radiotherapy Research Articles

Accelerated three-dimensional conformal radiotherapy for early-stage glottic cancer in reducing dose to the internal carotid artery and pharyngeal constrictor muscles.

We evaluated clinical and dosimetric outcomes of radiotherapy using two anterior oblique portals (AOP), to reduce the dose to the bilateral internal carotid arteries (CAs) and pharyngeal constrictor muscle (PCM) during early-stage glottic cancer (ESGC) treatment. We identified patients with ESGC who underwent definitive radiotherapy between June 2014 and May 2020. Among the 66 patients, 32 (48%) underwent radiotherapy using AOP, and the remaining underwent typical radiotherapy using parallel opposed lateral portals (POLP). The median follow-up duration was 53 months. No significant differences were observed in the 5-year local failure (0%/9.4%), progression-free survival (90.6%/90.8%), and overall survival (90.6%/91.0%) rates between the two groups. The grade ≥2 acute mucositis incidence rate was significantly lower in the AOP group (44%/85%). Radiotherapy using AOP maintained an adequate dose coverage to the target while markedly reducing the CAs and PCM doses. Radiotherapy with AOP resulted in favorable clinical and dosimetric outcomes.

Long-Term Survival and Failure Outcomes of Single-Fraction Stereotactic Body Radiation Therapy in Early Stage NSCLC

IntroductionThis study aims to report our 13-year institutional experience with single-fraction stereotactic body radiation therapy (SF-SBRT) for early stage NSCLC. MethodsA single-institutional retrospective review of patients with biopsy-proven peripheral cT1-2N0M0 NSCLC undergoing definitive SF-SBRT between September 2008 and May 2022 was performed. All patients were treated to 27 Gy with heterogeneity corrections or 30 Gy without. Primary outcomes were overall survival and progression-free survival. Secondary outcomes included local failure, nodal failure, distant failure, and second primary lung cancer. ResultsAmong 263 eligible patients, the median age was 76 years (interquartile range [IQR]: 70–81 y) and median follow-up time was 27.2 months (IQR: 14.25–44.9 mo). Median tumor size was 1.9 cm (IQR: 1.4–2.6 cm), and 224 (85%) tumors were T1. There were 92 patients (35%) alive at the time of analysis with a median follow-up of 34.0 months (IQR: 16.6–50.0 mo). Two- and five-year overall survival was 65% and 26%, respectively. A total of 74 patients (28%) developed disease progression. Rates of five-year local failure, nodal failure, distant failure, and second primary lung cancer were 12.7%, 14.7%, 23.5%, and 12.0%, respectively. ConclusionsConsistent with multiple prospective randomized trials, in a large real-world retrospective cohort, SF-SBRT for peripheral early stage NSCLC was an effective treatment approach.

P125 - Clinical Outcomes of Metastasis-directed Stereotactic Ablative Radiation Therapy (MDT-SABR) as single intervention added to baseline systemic treatment for Oligometastatic Castration-Resistant Prostate Cancer (mCRPC)

P125 - Clinical Outcomes of Metastasis-directed Stereotactic Ablative Radiation Therapy (MDT-SABR) as single intervention added to baseline systemic treatment for Oligometastatic Castration-Resistant Prostate Cancer (mCRPC)

607P Single institutional outcomes of radiotherapy and systemic therapy for melanoma brain metastases in Japan

607P Single institutional outcomes of radiotherapy and systemic therapy for melanoma brain metastases in Japan

Conventionally fractionated radiation therapy is associated with long-term survival in dogs with infiltrative lipomas.

To describe radiotherapy outcomes for canine infiltrative lipomas and provide detailed radiotherapy planning data. 24 dogs from 2000 to 2020. In this retrospective study, dogs received 1 to 3 surgeries prior to conventionally fractionated radiotherapy for gross (18) or microscopic (8) infiltrative lipomas. Dogs received 45 to 51 Gray (Gy) in 15 to 20 daily fractions, with 71% of dogs receiving 48 Gy in daily 3-Gy fractions. Masses were regionally located as follows: limbs (7), trunk (13), head/neck (4). At analysis, 16/24 dogs were deceased, 5/24 were alive (median follow-up for alive dogs: 1,216 days [range, 741 to 1,870 days]), and 3/24 were lost to follow-up. One living dog had progressive disease 923 days after completing conventionally fractionated radiotherapy and received another surgery. The estimated median overall survival (OS) after completing radiotherapy was 4.8 years (1,760 days; 95% CI, 1,215 to 2,777 days; range, 23 to 3,499 days) for any cause of death, and no patients were reported to have been euthanized or died from their tumor. No statistically significant difference was found for dogs based on gross versus microscopic disease (gross OS, 4.8 years vs microscopic OS, 3.6 years; P = .45). Furthermore, the number of surgeries before radiotherapy did not impact survival (P = .96). The survival difference between females (median OS, 7.6 years; 95% CI, 963 days to not reached) versus males (median OS, 4.6 years; 95% CI, 335 to 2,245 days; P = .05) was statistically significant, although 4/5 living dogs were female. This study demonstrates lengthy survivals with radiotherapy, even with gross disease, for dogs with infiltrative lipomas.

EP07.05-09 Oncologic Outcomes of Stereotactic Body Radiotherapy in Early-Stage Non-Small Cell Lung Cancer Patients with Interstitial Lung Disease

EP07.05-09 Oncologic Outcomes of Stereotactic Body Radiotherapy in Early-Stage Non-Small Cell Lung Cancer Patients with Interstitial Lung Disease

Impact of Varying Chest Wall Target Volume Delineation on Postmastectomy Radiation Therapy Outcomes in Breast Cancer Patients with Implant-Based Reconstruction

Background: The target volume for post-mastectomy radiation therapy (PMRT) in breast cancer patients with reconstruction has been a subject of debate. Traditionally, the RT chest wall (CW) volume encompasses the entire implant. For patients with retropectoral implants, the deep lymphatic plexus dorsal part of the implant is no longer considered high risk and can be omitted. This study aimed to assess the radiation dose distribution and treatment outcomes associated with different CW delineation according to ESTRO ACROP guideline for patients who have undergone implant-based reconstruction. Methods: We conducted a retrospective review of breast cancer patients who underwent a mastectomy followed by two-stage implant-based breast reconstruction and adjuvant radiation therapy (RT) between 2007 and 2022. The expanders/implants were positioned retropectorally. The chest wall target volumes were categorized into two groups: the prepectoral group, which excluded the deep lymphatic plexus, and the whole expander group. Results: The study included 26 patients, with 15 in the prepectoral group and 11 in the whole expander group. No significant differences were observed in normal organ exposure between the two groups. There was a trend toward a lower ipsilateral lung mean dose in the prepectoral group (10.2 vs. 11.1 Gy, p = 0.06). Both groups exhibited limited instances of reconstruction failure and local recurrence. Conclusions: For patients undergoing two-stage expander/implant retropectoral breast reconstruction and PMRT, our data provided comparable outcomes and normal organ exposure for those omitting the deep lymphatic plexus.

Comparing the oncologic outcomes of proton therapy and intensity-modulated radiation therapy for head and neck squamous cell carcinoma

PurposeTo compare the oncologic outcomes between proton therapy and intensity-modulated radiation therapy (IMRT) for head and neck squamous cell carcinoma (HNSCC) patients undergoing curative radiotherapy (RT). Experimental DesignWe studied HNSCC patients who underwent curative-intent RT from 2015 to 2019, comparing the oncologic outcomes of proton therapy and IMRT. Our national retrospective HNSCC cohort study involved three institutes with proton therapy and 17 institutes (medical center levels) with IMRT in Taiwan. We utilized the Taiwan Cancer Registry Database to collect medical data for this study. We classified patients into two groups based on treatment method: Group 1 received IMRT, while Group 2 received proton therapy. 3:1 propensity score matching was performed to minimize the impact of potential confounders. Cox proportional hazards models were used to evaluate oncologic outcomes. ResultsThis study of 60,485 patients with HNSCC found that proton therapy was associated with better overall and cancer-specific survival and lower locoregional recurrence rates than IMRT. After matching, 982 patients were analyzed, with well-balanced factors. Proton therapy was a significant predictor of all-cause mortality, cancer-specific death, and locoregional recurrence (LRR). Patients who received proton therapy had significantly lower risks of all-cause mortality (adjusted hazard ratio, aHR = 0.43), cancer-specific death (aHR = 0.44), and LRR (aHR = 0.61) than those who received IMRT. ConclusionProton therapy is associated with superior outcomes in terms of overall survival, cancer-specific survival, and locoregional recurrence rates compared to IMRT in patients with HNSCC. These results provide valuable evidence for clinicians and patients in decision-making regarding the choice of radiation therapy for HNSCC.

Palliative radiotherapy is effective for both well- and poorly differentiated neuroendocrine neoplasms.

The outcomes of palliative radiation therapy (RT) for neuroendocrine neoplasms (NEN) are seldom reported. We investigated outcomes following palliative radiotherapy in a cohort of patients with NENs. We hypothesised that well-differentiated NEN will be less likely to have a clinical response than poorly differentiated NEN. Patients who received at least one course of palliative RT were identified using the New Zealand NETwork! Registry. Patients with Merkel cell carcinoma, pulmonary small cell carcinoma or asymptomatic patients were excluded. Clinical response to RT within 90 days and overall survival were analysed alongside clinical variables (fractionation, RT site, tumour differentiation and tumour primary site). The cohort comprised 79 patients, with 147 courses of palliative RT delivered. Clinical response was measurable for 100 courses, with clinical response rate of 76%. A course delivered to a well-differentiated NEN was associated with 2.02-fold (95% CI 0.67, 6.12; P = 0.21) increase in odds of a clinical response compared to a poorly differentiated NEN. Median overall survival from the first fraction of RT was 94 days (95% CI 80, 138 days). Overall survival was higher in well-differentiated NEN than in poorly differentiated NEN (HR 0.2, 95% CI 0.10-0.40, P-value < 0.001); 30-day mortality was 7%. There were significantly reduced odds of clinical response for non-bone sites, and for courses >10 fractions compared to a single fraction. Palliative RT is an appropriate option for management of symptoms in patients with both well- and poorly differentiated metastatic NEN.

Enhancing radiotherapy outcomes in rectal cancer: A systematic review of targeting hypoxia-induced radioresistance

IntroductionNeoadjuvant radiotherapy is successfully used in rectal cancer to improve overall survival. However, treatment response is both unpredictable and variable. There is strong evidence to show that the phenomenon of tumour hypoxia is associated with radioresistance, however the mechanism(s) behind this are poorly understood. Consequently, there have only been a small number of studies evaluating methods targeting hypoxia-induced radioresistance. The purpose of this systematic review is to evaluate the potential effectiveness of targeting hypoxia-induced radioresistance in rectal cancer and provide recommendations for future research in this area. MethodsA comprehensive literature search was performed following the PRISMA guidelines. This study was registered on the Prospero database (CRD42023441983). ResultsEight articles met the inclusion criteria. All studies identified were in vitro or in vivo studies, there were no clinical trials. Of the 8 studies identified, 5 assessed the efficacy of drugs which directly or indirectly targeted hypoxia and three that identified potential targets. There was conflicting in vivo evidence for the use of metformin to overcome hypoxia induced radioresistance. Vorinostat, atovaquone, and evofosfamide showed promising preclinical evidence that they can overcome hypoxia-induced radioresistance. DiscussionThe importance of investigating hypoxia-induced radioresistance in rectal cancer is crucial. However, to date, only a small number of preclinical studies exist evaluating this phenomenon. This systematic review highlights the importance of further research to fully understand the mechanism behind this radioresistance. There are promising targets identified in this systematic review however, substantially more pre-clinical and clinical research as a priority for future research is needed.

Disease control outcomes of stereotactic body radiation therapy or moderate hypo-fractionation for prostate cancer: Real-world experience at two Canadian centers.

Advantages of using stereotactic body radiation therapy to treat prostate cancer include short treatment times, decreased costs, and limited toxicity. Randomized trial outcomes comparing 5-fraction stereotactic body radiation therapy to conventionally fractionated radiotherapy or hypo-fractionated radiation therapy are pending. We report the 10-year experience with 5-fraction stereotactic body radiation therapy and hypo-fractionated radiation therapy at two Canadian centers. Patients with low- or intermediate-risk prostate cancer treated with stereotactic body radiation therapy alone (35-40 Gy in 5 fractions) or hypo-fractionated radiation therapy alone (60-62 Gy in 20 fractions) in the period of July 2010 and June 2020. The biochemical relapse-free survival, PSA nadir, interval time to PSA nadir, time to biochemical recurrence (2 ng/ml above PSA nadir) and overall survival were reviewed. Outcomes between treatment groups were compared after propensity-matching by patient baseline characteristics. Kaplan-Meier curves were used to assess biochemical relapse-free survival and overall survival. We identified 205 and 513 patients with low or intermediate-risk prostate cancer who were treated with stereotactic body radiation therapy or hypo-fractionation, respectively. Intermediate-risk category composed 81% and 95% of the stereotactic body radiation therapy and hypo-fractionated radiation therapy cohorts, respectively. After a median follow up of 58.6 months for the stereotactic body radiation therapy cohort and 45.0 months for the hypo-fractionated cohort, biochemical relapse-free survival and overall survival were not significantly different between treatment groups. The 5-year biochemical relapse-free survival rates were 92.1% and 93.6% and overall survival rates were 96.4% and 95.0% for the stereotactic body radiation therapy and hypo-fractionated cohorts, respectively, after propensity-matching. Stereotactic body radiation therapy resulted in a significantly lower PSA nadir (0.18 ng/ml) compared to hypo-fractionated radiation therapy (0.48 ng/ml) in patients with low-risk prostate cancer. Mean time to biochemical recurrence was not different between treatment groups. Stereotactic body radiation therapy is an effective treatment option for low and intermediate-risk prostate cancer with encouraging biochemical relapse-free survival and overall survival rates comparable with hypo-fractionated radiation therapy.

Novel Tumor Organoid-Based Mouse Model to Study Image Guided Radiation Therapy of Rectal Cancer After Noninvasive and Precise Endoscopic Implantation

PurposePreoperative (neoadjuvant) radiation therapy (RT) is an essential part of multimodal rectal cancer therapy. Recently, total neoadjuvant therapy (TNT) which combines simultaneous radio-chemotherapy with additional courses of chemotherapy (CTx) has emerged as an effective approach. TNT achieves a pathological complete remission in approximately 30% of resected patients, opening avenues for treatment strategies that avoid radical organ resection. Furthermore, recent studies have demonstrated that anti-PD-1 immunotherapy (IT) can induce clinical complete responses in patients with specific genetic alterations. Overall, there is significant potential to enhance outcomes through intensifying, personalizing, and de-escalating treatment approaches. However, the heterogeneous response rates to RT or TNT and strategies to sensitize patients without specific genetic changes to IT remain poorly understood. Materials and MethodsWe developed a novel orthotopic mouse model of rectal cancer which is based on precisely defined endoscopic injections of tumor organoids that reflect tumor heterogeneity. Subsequently, we employed endoscopic- and computed tomography-guided RT, and validated rectal tumor growth and response rates to therapy using small animal magnetic resonance imaging and endoscopic follow-up. ResultsRectal tumor formation was successfully induced in all mice following two organoid injections. Clinically relevant RT regimens with 5 × 5 Gy significantly delayed clinical signs of tumor progression and significantly improved survival. Consistent with human disease, rectal tumor progression correlated with the development of liver and lung metastases. Notably, longterm survivors after RT showed no evidence of tumor recurrence, as demonstrated by in vivo radiological tumor staging and histopathological examination. ConclusionsOur novel mouse model combines orthotopic tumor growth via non-invasive and precise rectal organoid injection and small animal RT. This model holds significant promise for investigating the impact of tumor cell-intrinsic aspects, genetic alterations of the host, or exogenous factors (e.g., nutrition or microbiota) on RT outcomes. Furthermore, it allows for the exploration of combination therapies involving CTx, IT or novel targeted therapies.

Combined Photon and Carbon Ion Radiation Therapy for Sinonasal Malignancies: Results of the HIT–SNT Prospective Phase 2 Trial

Radiation treatment of sinonasal malignancies is a challenging task due to proximity to critical structures of the head and neck and skull base. Local tumor control is highly dose-dependent, but dose application is limited due to accompanying toxicity and dose constraints. To evaluate the toxicity and efficacy of combined radiation treatment with intensity-modulated radiation therapy (IMRT) and carbon ion boost, we conducted a prospective phase 2 IMRT-Heidelberg Ion-Beam Therapy Sinonasal Tumors (HIT-SNT) trial. Between 2011 and 2019, we treated 35 patients with histologically proven, incompletely resected or inoperable adeno- (51%) or squamous cell carcinoma (49%) of the paranasal sinuses with combined IMRT (50 Gy) and carbon ion boost (24 Gy relative biologic effectiveness) to a total dose of 74 Gy. Acute mucositis Common Terminology Criteria for Adverse Events (CTCAE) grade 3 occurred in 12% of patients (n = 4) and was accompanied by odynophagia CTCAE grade 3. Except for 1 case of grade 3 weight loss, no other acute high-grade toxicity (grade 3-4) was observed. In a small patient cohort of 15 patients eligible for long-term follow-up we have seen no high-grade (grade ≥3) long-term side effects 2 years after radiation therapy. None of these patients suffered from therapy-associated vision or hearing loss. Secondary endpoints were 2-year overall survival, 2-year local progression-free survival, 2-year progression-free survival, and 2-year metastases-free survival with 79.4%, 61.8%, 61.8%, and 64.8%, respectively. To our knowledge, this is the first prospective data on toxicity and outcome of bimodal radiation therapy for the rare entity of sinonasal malignancies. Our study shows a low rate of CTCAE-reported acute toxicity with reasonable tumor control and survival rates after bimodal radiation therapy, which therefore remains a therapy approach to be further evaluated.

ROE (Radiotherapy Outcomes Estimator): An open-source tool for optimizing radiotherapy prescriptions

Background and objectivesRadiotherapy prescriptions currently derive from population-wide guidelines established through large clinical trials. We provide an open-source software tool for patient-specific prescription determination using personalized dose-response curves. MethodsWe developed ROE, a plugin to the Computational Environment for Radiotherapy Research to visualize predicted tumor control and normal tissue complication simultaneously, as a function of prescription dose. ROE can be used natively with MATLAB and is additionally made accessible in GNU Octave and Python, eliminating the need for commercial licenses. It provides a curated library of published and validated predictive models and incorporates clinical restrictions on normal tissue outcomes. ROE additionally provides batch-mode tools to evaluate and select among different fractionation schemes and analyze radiotherapy outcomes across patient cohorts. ConclusionROE is an open-source, GPL-copyrighted tool for interactive exploration of the dose-response relationship to aid in radiotherapy planning. We demonstrate its potential clinical relevance in (1) improving patient awareness by quantifying the risks and benefits of a given treatment protocol (2) assessing the potential for dose escalation across patient cohorts and (3) estimating accrual rates of new protocols.

Outcomes of palliative radiation therapy for cutaneous squamous cell carcinoma: A retrospective cohort study

Outcomes of palliative radiation therapy for cutaneous squamous cell carcinoma: A retrospective cohort study

Long-Term Outcomes Following Fairly Brief Androgen Suppression and Stereotactic Radiation Therapy in High-Risk Prostate Cancer: Update From the FASTR/FASTR-2 Trials

There is limited data on the long-term outcomes of ultrahypofractionated radiation therapy in high-risk prostate cancer. The FASTR and FASTR-2 trials were designed to assess the tolerability of stereotactic ablative radiation therapy (SABR) in this context. Herein, the long-term results are reported. Eligible patients had localized high-risk prostate cancer and were either ≥70 years old, had a score of ≥3 on the Vulnerable Elderly Scale, or declined standard therapy. Nineteen patients from a single institution were enrolled on FASTR between 2011 and 2015. They received 40 Gy to the prostate and 25 Gy to the pelvic lymph nodes in 5 weekly fractions, with 12 months of androgen deprivation therapy (ADT). Thirty patients from the same institution were enrolled on FASTR-2 between 2015 and 2017. They received 35 Gy to the prostate alone in 5 weekly fractions, with 18 months of ADT. Updated toxicity and outcomes were assessed retrospectively. Kaplan-Meier estimates were calculated for biochemical failure-free survival, freedom from distant metastases, prostate cancer-specific survival, and overall survival. Forty-four patients were eligible for analysis, 16 from FASTR and 28 from FASTR-2. Thirty-four patients (77%) were >70 years old. High-risk features included Gleason score ≥8 (n=20, 46%), T3-T4 disease (n=12, 27%), and baseline prostate-specific antigen > 20 (n=22, 50%). Median follow-up was 6.4 years. The 5-year cumulative incidence of late grade ≥3 genitourinary/gastrointestinal toxicity was 32% in FASTR and 11% in FASTR-2. At 5 years, the combined rates of biochemical failure-free survival, freedom from distant metastases, prostate cancer-specific survival, and overall survival were 72%, 90%, 92%, and 83%, respectively. SABR can be safely delivered in high-risk prostate cancer by optimizing technical delivery, particularly with adherence to strict dose constraints for organs at risk. The clinical outcomes in FASTR and FASTR-2 were largely comparable to more standard fractionation schemes plus ADT, but further modifications may improve disease control. Larger randomized trials are necessary to better understand the efficacy and tolerability of this approach.

Treatment outcomes of early-stage endometrial cancer patients: A propensity score matching of vaginal brachytherapy versus pelvic radiotherapy.

This study aimed to report the treatment outcomes of radiation therapy for early-stage endometrial cancer patients. In addition, this study intended to identify high-risk factors that require pelvic radiotherapy (PRT) in addition to vaginal brachytherapy (VBT) for intermediate-risk endometrial cancer patients. Patients with early-stage endometrial cancer receiving postoperative VBT alone or with PRT were included. Propensity score matching was used to balance the two study groups. The primary endpoint was locoregional recurrence (LRR). Age-adjusted Charlson comorbidity index and substantial lymphovascular space invasion were selected for subgroup analyses to identify the benefits of PRT over VBT alone. From 2005 to 2017, a total of 288 patients underwent analysis following propensity score matching. Of these, 144 received VBT and 144 received PRT. There was no significant difference in 5-year LRR between VBT and PRT for both intermediate (0% vs. 0%) and high-intermediate risk patients (3.5% VBT vs. 5.4% PRT; HR 0.54: 0.05-6.00; p = 0.616). The subgroup analyses revealed no significant factors favoring PRT over VBT. Patients with high comorbidities may have higher risks of non-cancer death after receiving PRT. Postoperative VBT alone is sufficient for early-stage intermediate-risk endometrial cancer patients.

Enhancing the sensitization of neuroblastoma to radiotherapy by the construction of a dual-channel parallel free radicals nanoamplifier

Radiation therapy (RT) has emerged as one of the most promising anti-tumor strategies for neuroblastoma. Nevertheless, the special tumor microenvironment (TME), including hypoxic and GSH-overexpressed TME, often greatly restricts the RT outcome. In this study, we demonstrated a dual-channel parallel radicals nanoamplifier (ATO@PAE-PEG-AS1411/Fe3+). The nanoamplifier was shaped into a bilayer shell-core structure, in which atovaquone-loaded poly (β-amino esters)-poly (ethylene glycol) (ATO@PAE-PEG) served as the core while Fe3+-absorbed AS1411 aptamer (AS1411/Fe3+) served as the shell. Taking advantage of the targeting ability of AS1411, ATO@PAE-PEG-AS1411/Fe3+ specifically accumulated in tumor cells, and then released ATO as well as Fe3+ in response to the acidic TME. The released ATO dramatically inhibited the mitochondrial respiration of tumor cells, thus sparing vast amounts of oxygen for the generation of free radicals during RT process, which was the first free radicals-amplifying pathway Meanwhile, the released Fe3+ could consume the tumor-overexpressed GSH through the redox reaction, thus effectively preserving the generated free radicals in RT process, which was the second free radicals-amplifying pathway. Taken together, our study demonstrates a dual-channel parallel free radicals-amplifying RT strategy, and it is expected this work will promote the clinical application prospects of RT treatment against neuroblastoma.

The Microvascular Network Density and Morphology Affect the Radiotherapy Outcome at the Microscale Level: A Computational Analysis.

Half of the cancer patients are treated with radiotherapy to obtain tumor control while minimizing radiation toxicity. In this context, hypoxia is known to determine treatment resistance, driving tumor relapse after treatment. Therefore, we investigated the role of microvasculature density and morphology in shaping the tissue oxygen distribution and consequently affecting the treatment outcome. We developed an advanced computational model to describe oxygen delivery in the vascular network and the surrounding tissue. A peculiar aspect of the model is its mesoscale mixed-dimensional approach, which allows the explicit inclusion of vascular network geometry and the description of the red blood cells' effect. The oxygen delivery is modeled considering both diffusive and convective phenomena. A 30 × 2GyRBE treatment is delivered in silico simulating photons, protons, and carbon ions. First, we estimated the surviving fraction by the classical linear quadratic model modified to account for the oxygen effect. Then, leveraging the 3D description of the surviving fraction at the microenvironment scale, we compute the local tumor control probability (LTCP) in different oxygenation states (reference, acute hypoxia, high oxygen consumption). We report correlations between the LTCP and the hypoxic volume fractions (with pO2 lower than 1 mmHg) starting with photons. These hypoxic regions are present locally, even in highly vascularized tissue, if the network is not uniformly distributed, as it might be in cancer. They are also present in tissue with low microvascular density, even with regular morphology. Interestingly, the domain considered is comparable to or smaller than the clinical imaging standard voxel dimension, and the average oxygen partial pressure in the tissue region fails to spot treatments with low LTCP, questioning whether these hypoxia areas are visible clinically via imaging. Protons have a similar effect, highlighting a similar behavior across the oxygenation levels at the microscale level. Finally, carbon ions seem more effective than photons and protons in the presence of hypoxia due to the lower oxygen effect at high LET. For this reason, the treatment with carbon ions results in high LTCPs, whatever vascular network is considered (density and morphology differences). These results show the effect of microvascular density and regularity on the radiotherapy outcome and they help us understand how the microvascular network morphology affects tumor oxygenation and the radiotherapy outcome.

Single high-dose radiation therapy and liquid fiducial markers can be used in dogs with incompletely resected soft tissue sarcomas.

To evaluate the outcome and effects of single high-dose radiation therapy with the aid of liquid fiducial markers in dogs following resection of soft tissue sarcomas (STSs). 36 client-owned dogs. Dogs with a histologic diagnosis of a grade II or III STS that underwent liquid fiducial guided single fraction, 20-Gy stereotactic radiation therapy following surgical excision of an STS between May 2017 and March 2019 were prospectively enrolled in this study. Data collected from the medical records included patient signalment, tumor-related information, treatment details, and outcome. Kaplan-Meier survival analysis was performed for overall survival time (OST) and disease-free interval (DFI). The median OST and DFI were not reached, so restricted mean OST and DFI were also calculated. 36 dogs were included in the study. All dogs underwent radiation therapy a mean of 36.1 days (range, 20 to 59 days) after surgery. Acute and delayed radiation toxicity effects occurred in 80.5% and 36.1% of dogs, respectively, all of which affected the skin. Tumor recurrence was noted in 24.3% of dogs with a median time to recurrence of 272 days (range, 14 to 843 days). The restricted mean OST was 1,556 days (range, 1,383 to 1,728 days) and restricted mean DFI was 1,330 days (range, 1,101 to 1,559 days). The results of this study showed that administering a single 20-Gy fraction of radiation in combination with a liquid fiducial marker to treat marginally or incompletely resected STS in the absence of gross disease resulted in similar OST and DFI compared to other previously reported radiation protocols.