Fractionated Radiotherapy Regimen Research Articles

Henri Coutard (1876–1950): A Pioneer of Fractionated Radiotherapy Regimens

Henri Coutard (1876–1950): A Pioneer of Fractionated Radiotherapy Regimens

RBIO-05. MITOTIC ENRICHMENT AS AN EFFICIENT RADIOSENSITIZATION STRATEGY FOR INTRACRANIAL TUMORS

Abstract Radiotherapy remains one of the most effective modalities for anticancer treatment and part of standard of care for many primary and metastatic brain tumors. Boosting the efficacy of radiotherapy is therefore a logical avenue to improve patient survival. We have developed a radiosensitization strategy called ‘induction of mitotic enrichment’. It has long been known that the radiosensitivity of a cell depends on the phase of the cell cycle and that mitotic cells are especially vulnerable. Enriching the tumor for mitotic cells by arresting them during division prior to each radiotherapy fraction should therefore render the tumor population more sensitive to irradiation. Ideally, induction of mitotic enrichment should be reversible and non-cytotoxic to prevent healthy tissue toxicity and be compatible with clinically applied fractionated radiotherapy regimens. We have now identified an orally available targeted tubulin polymerization inhibitor that can achieve repeated and reversible mitotic enrichment for up to 10 hours prior to radiotherapy, without causing cytotoxicity in vitro or healthy tissue toxicity in vivo. This tubulin inhibitor (ABT-751) efficiently radiosensitizes a range of preclinical tumor models representing adult and pediatric, primary and metastatic brain tumors. Importantly, ABT-751 also improves survival in mouse models of adult glioblastoma (GBM), but only in a mitotic enrichment setup when given several hours prior to radiotherapy to allow accumulation in mitosis. Of note, induction of mitotic enrichment does not exacerbate healthy tissue toxicity. To conclude, induction of mitotic enrichment by ABT-751 radiosensitizes adult GBM to fractionated radiotherapy. We are currently expanding our preclinical development of mitotic enrichment as a radiosensitization strategy to other targets and cancers and have designed a phase 0/I trial for adult GBM to demonstrate induction of mitotic enrichment and tolerability when combined with radiotherapy. We expect to start enrollment in this trial soon.

Assessing Patterns of Practice in Early-Stage Lung Cancer Radiation Therapy: Findings from a Large Statewide Consortium Study on Hypofractionation

There are many different acceptable radiation dose and fractionation regimens for the treatment of early-stage non-small cell lung cancer (NSCLC), including hypofractionation (HypoRT). There are limited data supporting when to use HypoRT. We investigated which factors led physicians to choose HypoRT rather than stereotactic body radiation therapy (SBRT) or conventional fractionation (CRT) for early-stage NSCLC patients in a statewide consortium. We examined patients with T1-3N0M0 NSCLC treated at multiple institutions in a statewide consortium from January 2012-July 2022. We classified treatments as SBRT if 5 fractions or fewer, HypoRT if 6-20 fractions, and CRT if 1.8-2 Gy per fraction (Gy/Fx) for 25 or greater fractions. We excluded patients between 20 and 25 fractions as most appeared to be CRT that did not finish treatment (5% of total). We then performed a classification tree using age, race, gender, smoking status, T stage, PTV within 2cm of esophagus, PTV within 2cm of heart, and concurrent chemotherapy as covariates with a three-variable output (SBRT, HypoRT, and CRT). We excluded ECOG as it was not significant on initial analysis and was missing for 100 patients. We also reran the classification tree without CRT as an output to better discriminate between SBRT and HypoRT. A total of 418 patients were included in the analysis. 184 patients had T1, 123 with T2, and 111 with T3 tumors. In total, 228 patients underwent SBRT (median 50 Gy), 51 patients HypoRT (median 60 Gy), and 139 CRT (median 63 Gy). Covariates significant for discriminating between all three treatment regimens included T2, T3 vs T1, PTV within 2cm of the esophagus, and T3 vs T2. 94% of T1 patients were treated with SBRT. Among T2 and T3 patients, those within 2cm of the esophagus were significantly more likely to be treated with CRT or HypoRT (80% vs 15%). Patients with T3 tumor not within 2cm of the esophagus, were more likely to be treated with CRT or HypoRT than the T2 patients (85% vs 36%). Patients treated with CRT were also more likely to receive chemotherapy, particularly for T3 tumors (80% received concurrent chemotherapy). Excluding CRT as an output variable, proximity to the heart became significant in addition to the other previously described covariates. Notably, the branch with the highest likelihood of HypoRT were patients with T2/T3 tumors within 2 cm of both the esophagus and heart (94% HypoRT vs 6% SBRT). Patients with tumors not close to central structures but with T3 rather than T2 tumors were more likely to be treated with HypoRT as well (62% vs 38%). Based on this large prospective real-world data of early-stage NSCLC, larger tumors and those located near central structures are more likely to be treated with HypoRT. The patient's age, performance status, race, and smoking status were not significant in this analysis. Additional analysis on outcomes and toxicity related to treatments is underway.

Differential Response to Radiation Fractionation in Head and Neck Cancer Patient-Derived Xenografts

Despite optimal management with conventionally fractionated radiotherapy, head and neck cancer (HNC) mortality is driven by locoregional failure. With the increasing development of hypofractionated regimens in other malignancies, we sought to investigate the sensitivity of patient HNC to radiation fractionation using murine patient-derived xenografts (PDXs). We developed PDXs from three HNC patients who underwent primary surgical resection and enrolled on our IRB-approved (PRO00040992) prospective HNC tumor bank by implanting freshly resected tumors subcutaneously in the flank of NSG-SGM3 mice. PDXs from each patient were randomized to receive no radiation, 2 Gy x 5 fractions delivered daily (conventional arm) or 10 Gy in a single fraction (hypofractionation arm). Tumor volume was measured until 15 days post-RT, when mice were sacrificed. Bulk RNA sequencing analysis was performed on PDX tumors after intervention. Three PDX tumors from three unique patients (P006, P010 and P016) were successfully developed and irradiated per protocol. Unique responses to radiation were seen with each tumor: P010 showed equal sensitivity to both the conventional and hypofractionated regimens; P006 showed intermediate sensitivity to the conventional regimen with high sensitivity to hypofractionation, and P016 was resistant to conventional fractionation but showed sensitivity to hypofractionation. Concurrent with the patient-specific PDX response to fractionation, principal component analysis demonstrated that each patient PDX had a unique signature of differentially expressed genes in response to the conventional and hypofractionated regimens. HNC PDXs show differential tumor and genomic response to radiation fractionation regimens. A precision approach to radiation fractionation for HNC may improve tumor control outcomes in HNCs.

P03.11.B MITOTIC ENRICHMENT AS AN EFFICIENT RADIOSENSITIZATION STRATEGY FOR INTRACRANIAL TUMORS

Abstract BACKGROUND Radiotherapy remains one of the most effective modalities for anticancer treatment and part of standard of care for many primary and metastatic brain tumors. Boosting the efficacy of radiotherapy is therefore a logical avenue to improve patient survival. We have developed a radiosensitization strategy called ‘induction of mitotic enrichment’. It has long been known that the radiosensitivity of a cell depends on the phase of the cell cycle and that mitotic cells are especially vulnerable. Enriching the tumor for mitotic cells by arresting them during division prior to each radiotherapy fraction should therefore render the tumor population more sensitive to irradiation. Ideally, induction of mitotic enrichment should be reversible and non-cytotoxic to prevent healthy tissue toxicity and be compatible with clinically applied fractionated radiotherapy regimens. MATERIAL AND METHODS Mitotic enrichment in vitro is established using flow cytometry and radiosensitization is assessed using colony formation assays. In vivo, several independent luciferase-tagged orthotopic brain tumor models are used to investigate mitotic enrichment (phospho-histone 3 immunohistochemistry), tumor growth, survival and healthy tissue toxicity (body weight, blood liver enzymes, γH2AX and cleaved-caspase 3 immunohistochemistry). Pharmacokinetic studies are quantified using LC-MS/MS. All experiments on primary brain tumors included serum-free neurosphere culture models. RESULTS We have now identified an orally available targeted tubulin polymerization inhibitor that can achieve repeated and reversible mitotic enrichment for up to 10 hours prior to radiotherapy, without causing cytotoxicity in vitro or healthy tissue toxicity in vivo. This tubulin inhibitor (ABT-751) efficiently radiosensitizes a range of preclinical tumor models representing adult and pediatric, primary and metastatic brain tumors. Importantly, ABT-751 also improves survival in mouse models of adult glioblastoma (GBM), but only in a mitotic enrichment setup when given several hours prior to radiotherapy to allow accumulation in mitosis. Of note, induction of mitotic enrichment does not exacerbate healthy tissue toxicity. CONCLUSION Induction of mitotic enrichment by ABT-751 radiosensitizes adult GBM to fractionated radiotherapy. We are currently expanding our preclinical development of mitotic enrichment as a radiosensitization strategy to other targets and cancers and have designed a phase 0/I trial for adult GBM to demonstrate induction of mitotic enrichment and tolerability when combined with radiotherapy. We expect to start enrollment in this trial soon.

Radiotherapy for Mobile Spine and Sacral Chordoma: A Critical Review and Practical Guide from the Spine Tumor Academy.

Chordomas are rare tumors of the embryologic spinal cord remnant. They are locally aggressive and typically managed with surgery and either adjuvant or neoadjuvant radiation therapy. However, there is great variability in practice patterns including radiation type and fractionation regimen, and limited high-level data to drive decision making. The purpose of this manuscript was to summarize the current literature specific to radiotherapy in the management of spine and sacral chordoma and to provide practice recommendations on behalf of the Spine Tumor Academy. A systematic review of the literature was performed using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) approach. Medline and Embase databases were utilized. The primary outcome measure was the rate of local control. A detailed review and interpretation of eligible studies is provided in the manuscript tables and text. Recommendations were defined as follows: (1) consensus: approved by >75% of experts; (2) predominant: approved by >50% of experts; (3) controversial: not approved by a majority of experts. Expert consensus supports dose escalation as critical in optimizing local control following radiation therapy for chordoma. In addition, comprehensive target volumes including sites of potential microscopic involvement improve local control compared with focal targets. Level I and high-quality multi-institutional data comparing treatment modalities, sequencing of radiation and surgery, and dose/fractionation schedules are needed to optimize patient outcomes in this locally aggressive malignancy.

Can knowledge based treatment planning of VMAT for post-mastectomy locoregional radiotherapy involving internal mammary chain and supraclavicular fossa improve performance efficiency?

To validate and evaluate the performance of knowledge-based treatment planning for Volumetric Modulated Arc Radiotherapy for post-mastectomy loco-regional radiotherapy. Two knowledge-based planning (KBP) models for different dose prescriptions were built using the Eclipse RapidPlanTM v 16.1 (Varian Medical Systems, Palo Alto, USA) utilising the plans of previously treated patients with left-sided breast cancer who had undergone irradiation of the left chest wall, internal mammary nodal (IMN) region and supra-clavicular fossa (SCF). Plans of 60 and 73 patients were used to generate the KBP models for the prescriptions of 40 Gy in 15 fractions and 26 Gy in 5 fractions, respectively. A blinded review of all the clinical plans (CLI) and KBPs was done by two experienced radiation oncology consultants. Statistical analysis of the two groups was also done using the standard two-tailed paired t-test or Wilcoxon signed rank test, and p<0.05 was considered significant. A total of 20 metrics were compared. The KBPs were found to be either better (6/20) or comparable (10/20) to the CLIs for both the regimens. Dose to heart, contralateral breast,contralateral lung were either better or comparable in the KBP plans except of ipsilateral lung. Mean dose (Gy) for the ipsilateral lung are significantly (p˂0.001) higher in KBP though the values were acceptable clinically. Plans were of similar quality as per the result of the blinded review which was conducted by slice-by-slice evaluation of dose distribution for target coverage, overdose volume and dose to the OARs. However, it was also observed that treatment times in terms of monitoring units (MUs) and complexity indices are more in CLIs as compared with KBPs (p<0.001). KBP models for left-sided post-mastectomy loco-regional radiotherapy were developed and validated for clinical use. These models improved the efficiency of treatment delivery as well as work flow for VMAT planning involving both moderately hypo fractionated and ultra-hypo fractionated radiotherapy regimens.

Abstract 1718: Characterization of infiltrating immune cells after irradiation using 10x genomics single cell sequencing

Abstract Background: Radiation therapy is delivered to approximately 50% of all cancer patients. It has long been known that radiation causes not only DNA strand breaks, apoptosis, and necrosis, but also immunogenic modulation. Lately, there has been renewed interest in the potential of irradiation in colorectal cancer, not only as an adjuvant and palliative treatment, but also as an immune stimulant. Materials and Methods: CT26 murine colorectal carcinoma cells were subcutaneously implanted on the flank of BALB/c mice. Tumors were exposed to sham, single dose or fractionated radiotherapy regimens via a 300kV, 10mA X-ray with additional filtration to give a radiation quality of 2.3mm Cu half-value layer (HVL). Mice were anaesthetized, restrained and delivered a single uniform dose of radiation at a rate of 0.696Gy/min with the whole mouse being lead shielded except for a 1cm hole in the lead above the tumor site. Tumors were harvested at different timepoints post irradiation and dissociated into single cell suspensions. The tumor microenvironment and immune response within the tumors were analyzed with flow cytometry comparing the different treatment regimens. The individual CD45+ cell profile was investigated using 10x gene expression. 10x sequencing was demultiplexed using CellRanger and data analyzed using Seurat and ACTINN. Results: Following the initial cytotoxicity, flow cytometry showed a clear immune stimulatory effect of radiotherapy with immune cells infiltrating the irradiated tumors. The level of infiltration was dependent on the treatment scheduling. For single cell assessments, we observed approximately 8000 reads/cell and T-SNE cluster analysis using Seurat identified 16 clusters in control and treated samples. Identification of clusters by ACTINN demonstrated that CD8+ T-cells were increased 8-fold in irradiated samples whereas monocytes numbers decreased 3-fold. In irradiated tumors, the main population of CD8+ T-cells with increased numbers also expressed NKG7. Conclusion: These data provide evidence that radiotherapy can enhance immune cell trafficking to locally treated CT26 tumors. Furthermore, 10x genomics single cell sequencing revealed increased levels of cytotoxic T-cells expressing NKG7, a protein implicated in enhanced killing of extracellular targets. This response could prime the tumors such that they may be exploited by immune modulating drugs. Citation Format: Frida Ponthan, Valentina Ubertini, Gary Beale. Characterization of infiltrating immune cells after irradiation using 10x genomics single cell sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1718.

Differential effects of radiation fractionation regimens on glioblastoma

BackgroundRadiotherapy (RT) is a mainstay of treatment for patients with glioblastoma (GB). Early clinical trials show that short course hypofractionation showed no survival benefit compared to conventional regimens with or without temozolomide chemotherapy (TMZ) but reduces the number of doses required. Concerns around delayed neurological deficits and reduced cognition from short course hypofractionated RT remain a concern. The aim of this study was to evaluate the effect of increased interfractional time using two different radiation fractionation regimens on GB.MethodsThe radiobiological effect of increasing doses 0–20 Gy x-ray photon RT on Gl261 and CT2A GB cell lines was compared by colony forming assay, DNA damage by alkaline comet assay, oxidative stress, DNA damage, cell cycle, and caspase-3/7 by MUSE® flow cytometric analyses, and protein expression by western blot analyses. Conventional (20 Gy/10 fractions) and hypofractionated (20 Gy/4 fractions spaced 72 h apart) RT regimens with and without TMZ (200 mg/kg/day) were performed in syngeneic Gl261 and CT2A intracranial mouse models using the Small Animal Radiation Research Platform (Xstrahl Inc.).ResultsX-ray photon radiation dose-dependently increased reactive oxygen species, DNA damage, autophagy, and caspase 3/7-mediated apoptotic cell death. While the conventional fractionated dose regimen of 20 Gy/10 f was effective at inducing cell death via the above mechanism, this was exceeded by a 20 Gy/4 f regimen which improved median survival and histopathology in Gl261-tumor bearing mice, and eradicated tumors in CT2A tumors with no additional toxicity.ConclusionsSpacing of hypofractionated RT doses 72 h apart showed increased median survival and tumor control via increased activation of RT-mediated cell death, with no observed increased in radiotoxicity. This supports further exploration of differential RT fractionated regimens in GB clinical trials to reduce delayed neurological radiotoxicity.

Limited-Stage Small-Cell Lung Cancer: Current Progress and the Next Frontier

Limited-stage (LS) small-cell lung cancer (SCLC) is defined as disease confined to a tolerable radiation portal without extrathoracic metastases. Despite clinical research over two decades, the prognosis of LS-SCLC patients remains poor. The current standard of care for LS-SCLC patients is concurrent platinum-based chemotherapy with thoracic radiotherapy (RT). Widespread heterogeneity on the optimal radiation dose and fractionation regimen among physicians highlights the logistical challenges of administering BID regimens. Prophylactic cranial irradiation (PCI) is recommended to patients following a good initial response to chemoradiation due to improved overall survival from historical trials and the propensity for LS-SCLC to recur with brain metastases. However, PCI utilization is being debated due to the greater availability of magnetic resonance imaging (MRI) and data in extensive-stage SCLC regarding close MRI surveillance in lieu of PCI while spurring novel RT techniques, such as hippocampal-avoidance PCI. Additionally, novel treatment combinations incorporating targeted small molecule therapies and immunotherapies with or following radiation for LS-SCLC have seen recent interest and some concepts are being investigated in clinical trials. Here, we review the landscape of progress, limitations, and challenges for LS-SCLC including current standard of care, novel radiation techniques, and the integration of novel therapeutic strategies for LS-SCLC.

Abstract PO-003: Mitotic enrichment as an efficient radiosensitization strategy

Abstract Radiotherapy remains one of the most effective modalities for anticancer treatment. Boosting the efficacy of radiotherapy is therefore a logical avenue to improve patient survival. We have developed a radiosensitization strategy called ‘induction of mitotic enrichment’. It has long been known that the radiosensitivity of a cell depends to a large extent on the phase of the cell cycle and that especially mitotic cells are especially vulnerable. Enriching the tumor for mitotic cells by arresting them during division prior to each radiotherapy fraction should therefore render the tumor population more sensitive to irradiation. Ideally, induction of mitotic enrichment should be reversible and non-cytotoxic to prevent healthy tissue toxicity and be compatible with clinically applied fractionated radiotherapy regimens. We have now identified an orally available targeted tubulin polymerization inhibitor that can achieve repeated and reversible mitotic enrichment for up to 10 hours prior to radiotherapy, without causing cytotoxicity in vitro or healthy tissue toxicity in vivo. Most importantly, this tubulin inhibitor efficiently radiosensitizes a range of preclinical glioblastoma models in vitro and in vivo and significantly improves survival, but only in a mitotic enrichment setup when given several hours prior to radiotherapy to allow accumulation in mitosis. We have initiated development of mitotic enrichment for GBM, the most common primary malignant brain tumor. Their location and highly aggressive nature renders GBM among the most deadly and devastating of human malignancies. Despite extensive treatment involving surgery and adjuvant chemo-radiotherapy, prognosis is still dismal and novel treatment strategies are urgently needed. Of all available adjuvant therapies, radiotherapy contributes most to extending overall survival. Increasing the efficacy of existing radiotherapeutic regimens therefore offers a logical rationale to improve the survival of GBM patients. We are currently also expanding our preclinical development of mitotic enrichment as a radiosensitization strategy to other mitotic targets and different cancers for which radiotherapy is a mainstay treatment and have thus far achieved promising results in vitro. In parallel, we are preparing a phase 0 trial to demonstrate induction of mitotic enrichment in human GBM. Citation Format: Mark C. de Gooijer, Paul L.G. Slangen, Hilal Çolakoğlu, Ceren H. Çitirikkaya, Amal El Ouazani, Ronak Shah, Gerben R. Borst, Olaf van Tellingen. Mitotic enrichment as an efficient radiosensitization strategy [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-003.

Resistance of Hypoxic Cells to Ionizing Radiation Is Mediated in Part via Hypoxia-Induced Quiescence.

Double strand breaks (DSBs) are highly toxic to a cell, a property that is exploited in radiation therapy. A critical component for the damage induction is cellular oxygen, making hypoxic tumor areas refractory to the efficacy of radiation treatment. During a fractionated radiation regimen, these hypoxic areas can be re-oxygenated. Nonetheless, hypoxia still constitutes a negative prognostic factor for the patient’s outcome. We hypothesized that this might be attributed to specific hypoxia-induced cellular traits that are maintained upon reoxygenation. Here, we show that reoxygenation of hypoxic non-transformed RPE-1 cells fully restored induction of DSBs but the cells remain radioresistant as a consequence of hypoxia-induced quiescence. With the use of the cell cycle indicators (FUCCI), cell cycle-specific radiation sensitivity, the cell cycle phase duration with live cell imaging, and single cell tracing were assessed. We observed that RPE-1 cells experience a longer G1 phase under hypoxia and retain a large fraction of cells that are non-cycling. Expression of HPV oncoprotein E7 prevents hypoxia-induced quiescence and abolishes the radioprotective effect. In line with this, HPV-negative cancer cell lines retain radioresistance, while HPV-positive cancer cell lines are radiosensitized upon reoxygenation. Quiescence induction in hypoxia and its HPV-driven prevention was observed in 3D multicellular spheroids. Collectively, we identify a new hypoxia-dependent radioprotective phenotype due to hypoxia-induced quiescence that accounts for a global decrease in radiosensitivity that can be retained upon reoxygenation and is absent in cells expressing oncoprotein E7.

Assessment of Toxic Effects Associated With Dose-Fractionated Radiotherapy Among Patients With Cancer and Comorbid Collagen Vascular Disease

The adoption of alternative fractionated radiotherapy regimens for the treatment of patients with cancer and comorbid collagen vascular disease (CVD) is controversial among oncologists because of concerns about potentially severe toxic effects; however, the association between fractionated radiotherapy and toxic effects in the modern era has not been well studied. To compare acute and late toxic effects among patients with cancer and comorbid CVD who received dose-fractionated radiotherapy. This retrospective cohort study examined 197 adult patients with cancer and CVD who received radiotherapy at a single-institution tertiary academic center over a 12-year period (February 1, 2007, to April 30, 2019), with a median follow-up of 23 months (range, 0-108 months). Data were analyzed from February 1 to August 31, 2020. Three dose-fractionated radiotherapy regimens: conventional fractionation (CF; ≤2 Gy per fraction), moderate hypofractionation (MH; >2 Gy to <5 Gy per fraction), and ultrahypofractionation (UH; ≥5 Gy per fraction). The main outcomes were the incidence and severity of acute and late radiotherapy-associated toxic effects, which were assessed separately by dose-fractionation regimen. Toxic effects occurring within 90 days after radiotherapy completion were considered acute, and toxic effects occurring after that 90-day period were considered late. Secondary goals were to identify covariates associated with toxic effects and to characterize the incidence of CVD symptom flares (defined as worsening clinical symptoms and/or worsening results [transient or permanent] on associated blood tests compared with baseline, as documented by managing physicians) after radiotherapy. Of 197 patients with cancer and comorbid CVD (mean [SD] age, 69 [12] years; 134 women [68.0%]; and 149 White participants [75.6%]), 80 patients (40.6%) received CF radiotherapy, 55 patients (27.9%) received MH radiotherapy, and 62 patients (31.5%) received UH radiotherapy. The most common CVD diagnoses were rheumatoid arthritis (74 patients [37.6%]), psoriasis (54 patients [27.4%]), systemic lupus erythematosus (34 patients [17.3%]), and scleroderma (8 patients [4.1%]). The most common radiotherapy sites were the breast (48 patients [24.4%]), thorax (25 patients [12.7%]), central nervous system (24 patients [12.2%]), and prostate (23 patients [11.7%]). Data on acute toxic effects were available for 188 patients (95.4%) and missing for 9 patients (4.6%). Data on late toxic effects were available for 142 patients (72.1%) and missing for 55 patients (27.9%). Over 12 years, the unadjusted incidences of severe acute toxic effects associated with CF, MH, and UH radiotherapy were 5.4% (95% CI, 0.3%-10.5%), 7.4% (95% CI, 0.4%-14.4%), and 1.7% (95% CI, 0%-5.0%), respectively. The incidences of severe late toxic effects associated with CF, MH, and UH radiotherapy were 8.3% (95% CI, 1.3%-15.3%), 0%, and 2.2% (95% CI, 0%-6.4%), respectively. No significant associations were found between severe acute or late toxic effects by dose fractionation regimen. In the multivariable analysis, MH radiotherapy was associated with a lower likelihood of developing late toxic effects (odds ratio [OR], 0.21; 95% CI, 0.05-0.83; P = .03) compared with CF radiotherapy. Those who received UH radiotherapy had a lower likelihood of experiencing late toxic effects (OR, 0.22; 95% CI, 0.04-1.21; P = .08). A total of 19 of 80 patients (23.8%), 15 of 55 patients (27.3%), and 10 of 62 patients (16.1%) experienced CVD symptom flares after receiving CF, MH, and UH radiotherapy, respectively (P = .33). In this study, the incidences of unadjusted severe toxic effects over 12 years were less than 10% and were not significantly associated with dose fractionation. When clinically indicated, patients with cancer and comorbid CVD may not require immediate exclusion from the receipt of currently used hypofractionated radiotherapy regimens.

Moderately Hypofractionated Radiotherapy with Simultaneous Integrated Boost in Prostate Cancer: A Comparative Study with Conventionally Fractionated Radiation.

Background To report 5-year clinical outcomes and toxicity in organ-confined prostate cancer (PCa) for low- and intermediate-risk patients treated with a moderately hypofractionated schedule of radiotherapy (RT) delivered with simultaneous integrated boost (SIB) compared to a conventionally fractionated RT regimen. Methods Data of 384 patients with PCa treated between August 2006 and June 2017 were retrospectively reviewed. The treatment schedule consisted of hypofractionated RT (HYPO FR) with SIB up to 70 Gy to the prostate gland and 63 Gy to seminal vesicles delivered in 28 fractions or in conventionally fractionated RT (CONV FR) up to a total dose of 80 Gy in 40 fractions. Patient allocation to treatment was based on the time period considered. For intermediate-risk patients, androgen deprivation was given for a median duration of 6 months. The 5-year biochemical relapse-free survival (bRFS), cancer-specific survival (CSS), and overall survival (OS) were assessed. Furthermore, we evaluated gastrointestinal (GI) and genitourinary (GU) toxicities. Uni- and multivariate Cox regression analyses were used to test the impact of clinical variables on both outcome and toxicity. Results A total of 198 patients was treated with hypofractionated RT and 186 with the conventional schedule. At a median follow-up of 5 years, no significant differences were observed in terms of GI toxicity and outcome between the two groups. Early GU toxicity was significantly increased in HYPO FR, while late GU toxicity was significantly higher in CONV FR. In HYPO FR, a biochemical relapse occurred in 12 patients (6.1%), and 9 patients (4.5%) reported a clinical relapse (4 local, 2 locoregional, and 3 systemic recurrence). In CONV FR, 15 patients (8.1%) experienced a biochemical relapse and 11 patients (5.9%) showed a clinical relapse (5 local, 4 locoregional, and 3 systemic recurrences). Early grades 1-2 GU and GI toxicities were observed in 60 (30.3%) and 37 (18.7%) patients, respectively, in the hypofractionated group and in 33 (17.7%) and 27 (14.5%) patients, respectively, in the conventionally fractionated RT group. Late GU and GI toxicities occurred in 1 (0.51%) and 8 (4.1%) patients, respectively, in HYPO FR. In CONV FR, 5 (2.7%) and 6 (3.2%) patients experienced late GU and GI toxicities, respectively. The 5-year OS, bRFS, and CSS were 98.9%, 94.1%, and 99.5%, respectively, in HYPO FR, and 94.5%, 92.1%, and 99.0%, respectively, in CONV FR. Conclusions Results obtained in this study showed that moderately hypofractionated RT employing SIB can be an effective approach providing valuable clinical outcomes with an acceptable toxicity profile.

Distribution of Cytokeratin 17 in the Parenchymal Elements of Rat's Submandibular Glands Subjected to Fractionated Radiotherapy.

Objectives The aim of this research was to study the intensity of cytokeratin 17 (CK17) in the parenchymal elements of rat’s submandibular salivary glands subjected to fractionated radiotherapy regimen that used for treatment of head and neck malignancy. Materials and Methods Twenty male albino rats were divided into two equal groups (normal and irradiated). The irradiated group received a radiation dose of 5 Grays daily for 5 days using therapeutic X-ray beam. Six months later, submandibular gland was dissected out and prepared for both histological and immunohistochemical studies. Results Submandibular gland of irradiated group showed two different types of histological alterations. The first alteration showed severe gland atrophy replaced by either fibrous or fatty tissues. In some sections, the gland exhibited proliferating activity in the form of profuse amounts of mitotic figures. Immunohistochemical examination of control glands displayed a mild cytoplasmic expression of CK17 of duct cells as well as serous acini. The staining pattern was either diffused or concentrated at the basal part of the cell with negative expression at its apical part. Statistical Analysis Expression of CK17 in submandibular gland of irradiated group displayed a highly significant differences (P < 0.001) in both intercalated and striated ducts. Many serous acini displayed a highly significant differences (P < 0.001) whereas, mucous acini were negatively stained. Conclusions The intensity and diffusion of CK17 expression in our results foretell the pathological effect of radiotherapy on the intermediate filaments of salivary gland parenchyma that interfered with production and/or secretion of saliva leading to xerostomia.

External beam radiation dose escalation for high grade glioma.

External beam radiation dose escalation for high grade glioma.

Development and Radiation Response Assessment in A Novel Syngeneic Mouse Model of Tongue Cancer: 2D Culture, 3D Organoids and Orthotopic Allografts.

Oral squamous cell carcinoma (OSCC) are aggressive cancers that contribute to significant morbidity and mortality in humans. Although numerous human xenograft models of OSCC have been developed, only a few syngeneic models of OSCC exist. Here, we report on a novel murine model of OSCC, RP-MOC1, derived from a tongue tumor in a C57Bl/6 mouse exposed to the carcinogen 4-nitroquinoline-1-oxide. Phenotypic characterization and credentialing (STR profiling, exome sequencing) of RP-MOC1 cells was performed in vitro. Radiosensitivity was evaluated in 2D culture, 3D organoids, and in vivo using orthotopic allografts. RP-MOC1 cells exhibited a stable epithelial phenotype with proliferative, migratory and invasive properties. Exome sequencing identified several mutations commonly found in OSCC patients. The LD50 for RP-MOC1 cells in 2D culture and 3D organoids was found to be 2.4 Gy and 12.6 Gy, respectively. Orthotopic RP-MOC1 tumors were pan-cytokeratin+ and Ki-67+. Magnetic resonance imaging of orthotopic RP-MOC1 tumors established in immunocompetent mice revealed marked growth inhibition following 10 Gy and 15 Gy fractionated radiation regimens. This radiation response was completely abolished in tumors established in immunodeficient mice. This novel syngeneic model of OSCC can serve as a valuable platform for the evaluation of combination strategies to enhance radiation response against this deadly disease.

Synergistic effect of cisplatin chemotherapy combined with fractionated radiotherapy regimen in HPV-positive and HPV-negative experimental pharyngeal squamous cell carcinoma

HPV infection renders oropharyngeal squamous cell carcinomas more radiosensitive, which results in a favorable prognosis for HPV-positive patients treated with radiation alone or with concurrent platinum-based chemotherapy. The degree of radiosensitivity in fractionated regimens has not yet been fully explored; therefore, in this study, the radiosensitivity of HPV-negative tumors (FaDu) was compared to that of HPV-positive tumors (2A3) subjected to concurrent cisplatin chemotherapy and fractionated versus isoeffective single-dose tumor irradiation in immunodeficient mice. HPV-positive tumors were approximately 5 times more radiosensitive than HPV-negative tumors, irrespective of the irradiation regimen. In both tumor models, concurrent cisplatin chemotherapy and the fractionated regimen induced significant tumor radiosensitization, with a 3- to 4-fold increase in the tumor growth delay compared to that of single-dose irradiation. Furthermore, the degree of radiosensitization induced by cisplatin chemotherapy concurrent with the fractionated irradiation regimen was much higher in HPV-positive tumors, where a synergistic antitumor effect was observed. Specifically, after combined therapy, a 26% higher survival rate was observed in mice with HPV-positive tumors than in mice with HPV-negative tumors. These data suggest that HPV-positive tumors are more radiosensitive to fractionated regimen than to single-dose irradiation with concurrent cisplatin chemotherapy acting synergistically to irradiation.

Influence of Radiotherapy Fractionation Schedule on the Tumor Vascular Microenvironment in Prostate and Lung Cancer Models.

Background. The tumor vasculature acts as an interface for the primary tumor. It regulates oxygenation, nutrient delivery, and treatment efficacy including radiotherapy. The response of the tumor vasculature to different radiation doses has been disparately reported. Whereas high single doses can induce endothelial cell death, improved vascular functionality has also been described in a various dose range, and few attempts have been made to reconcile these findings. Therefore, we aimed at comparing the effects of different radiation fractionation regimens on the tumor vascular microenvironment. Methods: Lewis lung and prostate PC3 carcinoma-derived tumors were irradiated with regimens of 10 × 2 Gy, 6 × 4 Gy, 3 × 8 Gy or 2 × 12 Gy fractions. The tumor vasculature phenotype and function was evaluated by immunohistochemistry for endothelial cells (CD31), pericytes (desmin, α-SMA), hypoxia (pimonidazole) and perfusion (Hoechst 33342). Results: Radiotherapy increased vascular coverage similarly in all fractionation regimens in both models. Vessel density appeared unaffected. In PC3 tumors, hypoxia was decreased and perfusion was enhanced in proportion with the dose per fraction. In LLC tumors, no functional changes were observed at t = 15 days, but increased perfusion was noticed earlier (t = 9–11 days). Conclusion: The vascular microenvironment response of prostate and lung cancers to radiotherapy consists of both tumor/dose-independent vascular maturation and tumor-dependent functional parameters.

Variability in the Sequencing of Palliative Radiation with Targeted Therapy in the Treatment of Metastatic NSCLC: A Single Institutional Patterns of Care Analysis

The treatment of metastatic non-small cell lung cancer (NSCLC) varies on an individual basis but increasingly involves the use of palliative radiation in combination with molecularly targeted agents. There are currently no accepted guidelines for how to sequence or integrate palliative radiation with targeted therapies. Due to uncertainties regarding the timing and sequencing of these therapies, we sought to describe current patterns of care with respect to how these modalities are integrated in practice for patients with metastatic NSCLC. The medical records of 96 consecutive patients who were treated with palliative radiation for metastatic NSCLC from June 2011 to December 2018 at a tertiary care-based comprehensive cancer center were reviewed. Subjects who received molecularly targeted therapies, including immuno-oncology agents, within thirty days of receiving palliative radiation comprised the primary population of the analysis. The timing of when radiation was delivered in relation to treatment with targeted therapy was documented, as well as clinical and treatment-related variables such as age, gender, performance status, and radiation dose. Only patients treated with external-beam techniques were included. Logistical regression was used to determine variables that influenced the likelihood of starting molecular targeted therapy in the pre-irradiation versus concurrent/post-irradiation setting. A total of 50 patients were identified that satisfied inclusion criteria with 59 courses of radiation treatments. The most commonly treated regions with palliative radiation were the brain (n=34), followed by the spine (n=11), and lung (n=11). The proportion of metastatic NSCLC patients treated by both palliative radiation and molecularly targeted agents have increased over time with 7 patients in 2011-2014 and 43 patients in 2015-2018. The most common targeted agents were tyrosine kinase inhibitors (n=31) followed by immunotherapy (n=25) and other biologic agents (n=3). The most commonly used radiation fractionation regimen was 30 Gy in 10 fractions (31%). Eighty-one percent (81%) of the patients started targeted therapy prior to initiation of radiation therapy, five percent (5%) during radiation therapy and fourteen percent (14%) post completion of radiation therapy. A significant proportion of patients (52%) experienced overlap of palliative radiation and molecularly targeted therapy. While significant variability exists in the timing of palliative radiation with molecularly targeted therapies, the most common sequence identified was a sequential approach using the latter followed by the former. Additional data on how to optimally integrate palliative radiation with molecularly targeted therapies is needed.