Consensus recommendations for a dynamic susceptibility contrast MRI protocol for use in high-grade gliomas

Despite the widespread clinical use of dynamic susceptibility contrast (DSC) MRI, DSC-MRI methodology has not been standardized, hindering its utilization for response assessment in multicenter trials. Recently, the DSC-MRI Standardization Subcommittee of the Jumpstarting Brain Tumor Drug Development Coalition issued an updated consensus DSC-MRI protocol compatible with the standardized brain tumor imaging protocol (BTIP) for high-grade gliomas that is increasingly used in the clinical setting and is the default MRI protocol for the National Clinical Trials Network. After reviewing the basis for controversy over DSC-MRI protocols, this paper provides evidence-based best practices for clinical DSC-MRI as determined by the Committee, including pulse sequence (gradient echo vs spin echo), BTIP-compliant contrast agent dosing (preload and bolus), flip angle (FA), echo time (TE), and post-processing leakage correction. In summary, full-dose preload, full-dose bolus dosing using intermediate (60°) FA and field strength-dependent TE (40-50 ms at 1.5 T, 20-35 ms at 3 T) provides overall best accuracy and precision for cerebral blood volume estimates. When single-dose contrast agent usage is desired, no-preload, full-dose bolus dosing using low FA (30°) and field strength-dependent TE provides excellent performance, with reduced contrast agent usage and elimination of potential systematic errors introduced by variations in preload dose and incubation time.

A modular phantom and software to characterize 3D geometric distortion in MRI

Magnetic resonance imaging (MRI) offers outstanding soft tissue contrast that may reduce uncertainties in target and organ-at-risk delineation and enable online adaptive image-guided treatment. Spatial distortions resulting from non-linearities in the gradient fields and non-uniformity in the main magnetic field must be accounted for across the imaging field-of-view to prevent systematic errors during treatment delivery. This work presents a modular phantom and software application to characterize geometric distortion (GD) within the large field-of-view MRI images required for radiation therapy simulation. The modular phantom is assembled from a series of rectangular foam blocks containing high-contrast fiducial markers in a known configuration. The modular phantom design facilitates transportation of the phantom between different MR scanners and MR-guided linear accelerators and allows the phantom to be adapted to fit different sized bores or coils. The phantom was evaluated using a 1.5 T MR-guided linear accelerator (MR-Linac) and 1.5 T and 3.0 T diagnostic scanners. Performance was assessed by varying acquisition parameters to induce image distortions in a known manner. Imaging was performed using T1 and T2 weighted pulse sequences with 2D and 3D distortion correction algorithms and the receiver bandwidth (BW) varied as 250-815 Hz pixel-1. Phantom set-up reproducibility was evaluated across independent set-ups. The software was validated by comparison with a non-modular phantom. Average geometric distortion was 0.94 ± 0.58 mm for the MR-Linac, 0.90 ± 0.53 mm for the 1.5 T scanner, and 1.15 ± 0.62 mm for the 3.0 T scanner, for a 400 mm diameter volume-of-interest. GD increased, as expected, with decreasing BW, and with the 2D versus 3D correction algorithm. Differences in GD attributed to phantom set-up were 0.13 mm or less. Differences in GD for the two software applications were less than 0.07 mm. A novel modular phantom was developed to evaluate distortions in MR images for radiation therapy applications.

Abstract 5487: A biologically-motivated mathematical model for forecasting chemoradiationresponse in high grade gliomas: Initial results

Introduction: Using patient-specific imaging data, we aimed to calibrate biologically-based mathematical models of tumor growth and treatment response to forecast the progression of high-grade glioma on an individual patient basis.

Methods: Four patients with partially resected or biopsy only, histologically confirmed high grade gliomas were imaged with T2-FLAIR, diffusion weighted (DW-) MRI, and post-contrast T1-weighted MRI at baseline (prior to chemoradiation), and at 1-, 3-, and 5-months following chemoradiation. Patients received standard of care radiotherapy (RT) with concurrent and adjuvant temozolomide. The gross tumor volume (GTV) defined as enhancing tumor and clinical tumor volume (CTV) defined as non-enhancing, T2-hyperintense region were expertly segmented from the post-contrast T1-weighted and T2-FLAIR images, respectively. The apparent diffusion coefficient (ADC) estimated from DW-MRI was used to assign tumor cell number within the GTV. Within the CTV, we interpolated the tumor cell number from 2% of the carrying capacity (at the periphery of the CTV) to the number of cells calculated at the periphery of the GTV. Using this data, a 3D mechanically-coupled, reaction-diffusion model was developed to describe the spatiotemporal evolution of tumor cell number due to proliferation, diffusion, and death due to chemoradiation on an individual patient basis. For each patient, model parameters were calibrated using their cellularity measurements from the entire time course (to evaluate how well the model describes the data) and separately from a subset of the time course (to evaluate how well the model predicts future data). For the prediction scenario, we then used the calibrated parameters in a forward evaluation of the model to predict future tumor growth at the final imaging visit. The model estimates of tumor cellularity where compared directly to the measured tumor distributions at the volume and voxel levels.

Results: For the model fit scenario, a strong level of voxel-wise correlation (Pearson correlation coefficients, PCC, ranging from 0.68 to 0.94) and agreement (concordance correlation coefficients, CCC, 0.76 to 0.99) were observed between the calibrated model and the measured cellularity for each patient. Additionally, Dice coefficients (measuring the degree of overlap between calibrated and observed values) ranged from 0.76 to 0.92 at all time points.

For the prediction scenario, a strong of voxel-wise correlation (PCC ranging from 0.61 to 0.90) and agreement (CCC ranging from 0.72 to 0.92) were observed between the predicted and estimated cellularity for each patient. A strong level of spatial agreement was also observed with Dice values ranging from 0.65 to 0.84 at all time points.

Conclusions: This preliminary study demonstrates that patient-specific imaging data can be used to calibrate a mathematical model that can accurately predict the spatio-temporal distribution of enhancing and non-enhancing glioma.

Funding: NCI U01 CA174706, CPRIT RR160005. AAPM Grant 2018

Citation Format: David Andrew Hormuth, Karine Al Feghali, Andrew M. Elliot, Caroline Chung, Thomas E. Yankeelov. A biologically-motivated mathematical model for forecasting chemoradiationresponse in high grade gliomas: Initial results [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5487.

25. EFFECT OF STEREOTACTIC RADIOSURGERY COMPARED TO WHOLE-BRAIN RADIOTHERAPY FOR LIMITED BRAIN METASTASIS ON LONG TERM COGNITION AND QUALITY OF LIFE: A POOLED ANALYSIS OF NCCTG N107C/CEC.3 AND N0574 (ALLIANCE) RANDOMIZED CLINICAL TRIALS

PURPOSE

We investigated the long term impact of SRS and WBRT in two large prospective phase III trials.

METHODS

Patients with 1–4 BMs +/- resection were randomized to SRS or WBRT. Cognitive deterioration was a drop of >1 standard deviation from baseline in >2/6 cognitive measures (CM). Quality of life (QOL) scores were scored 0–100 point scale. CM and QOL scores were modeled using baseline adjusted Linear Mixed Models (LMM) with uncorrelated random intercept for subject and random slopes for time. Differences in trend over time between groups and the effect of >2 cognitive scores with >2 SD change from baseline were assessed.

RESULTS

88 patients were included with median follow up of 24 months. We observed decreasing CM over time (SRS: 4/6; WBRT: 5/6). Mean CM was significantly higher in SRS for Total recall and Delayed Recall at 3, 6, 9, 12 months. More patients in WBRT arm declined 1 SD in >1 and >2 CM at the 3, 6, 9, and 12 months. A 1 SD decline in >3 CM at 1 year was 21% SRS vs 47% WBRT (p=0.02). SRS had fewer patients with a 2 SD decline in >1 CM at every time point. SRS had fewer patients with a 2 SD decline at >2 and >3 CM. WBRT had lower QOL at 3 months, but switched to SRS having lower QOL at 24 months for PWB, EWB, FWB, FactG, BR, and FactBR (p<0.05). A 2 SD decline in cognition decreased mean FWB by 6.4 units (95% CI: -11, -1.75; p=0.007) and decreased QOL by 5.1 units (95% CI: -7.7, -2.5; p<0.001).

CONCLUSIONS

We report the first pooled prospective study demonstrating the long term outcomes of patients with BMs after cranial radiation. WBRT was associated with worse cognitive outcomes. Impaired cognition is associated with worse QOL.

Radiation for Glioblastoma in the Era of Coronavirus Disease 2019 (COVID-19): Patient Selection and Hypofractionation to Maximize Benefit and Minimize Risk

We describe the institutional guidelines of a major tertiary cancer center with regard to using hypofractionated radiation regimens to treat glioblastoma as a measure to minimize exposure to coronavirus disease 2019 (COVID-19) while not sacrificing clinical outcomes. Our guidelines review level one evidence of various hypofractionated regimens, and recommend a multidisciplinary approach while balancing the risk of morbidity and mortality among individuals at high risk for severe illness from COVID-19 infection. We also briefly outline strategies our department is taking in mitigating risk among our cancer patients undergoing radiation.

Concurrent nivolumab and ipilimumab with brain stereotactic radiosurgery for brain metastases from non-small cell lung cancer: A phase I trial

2531

Background: Nivolumab (nivo) and ipilimumab (ipi) were found in the recent phase III CheckMate 227 trial to have an overall survival benefit over chemotherapy for advanced non-small cell lung cancer (NSCLC). However, patients (pts) with untreated brain metastasis (mets) were excluded from that trial. Because 30% of NSCLC pts develop brain mets, we tested nivo/ipi with concurrent stereotactic radiosurgery (SRS) for NSCLC pts with active brain mets. Methods: We report the safety data from the phase I portion of an ongoing phase I/II single-institution trial in which one treatment group was given SRS with nivo (3 mg/kg) every 2 weeks (wks) plus ipi (1 mg/kg) every 6 wks x 4 cycles, followed by maintenance nivo (480 mg) every 4 wks until disease progression, unacceptable toxicity, or withdrawal of consent. Brain SRS was delivered within 7 days of initiation of nivo/ipi. The primary endpoints were safety and 4-month (mo) intracranial progression-free survival (PFS). Dose-limiting toxicity (DLT) was defined as > 15% intracranial toxicity (>G3 hypophysitis / neurologic toxicity) or > 30% extracranial toxicity (>G3 non-dermatologic non-lab toxicity or >G4 dermatologic / lab toxicity), refractory to medical management, assessed at 8 wks after treatment initiation. Target accrual for phase I was 10 evaluable pts, with enrollment suspended after every 5 pts for DLT assessment. Results: Since June 15, 2018, 13 pts were enrolled and 10 were evaluable for DLT. The median follow-up time was 6.8 mo (range 1.2‒18). As of January 6, 2020, only 1 pt had DLT-defined toxicity and thus the predefined stopping criteria were not met. This pt had G3 seizure right after SRS that resolved within a week, and then had increased but asymptomatic CNS edema 4 wks later. Aside from DLTs, 3 pts (25%) developed treatment-related G3 (elevated liver function tests, fatigue, nausea, adrenal insufficiency, and myocarditis) or G4 events (pneumonitis/acute respiratory distress syndrome in 1 pt with confirmed influenza at 7 mos after treatment initiation). This pt subsequently died of hemophagocytic lymphohistiocytosis (considered possibly related to the study drugs). Median intracranial PFS time was 9.7 mo, and the 4-mo intracranial PFS rate was 75%. Extracranial objective response rate was 33% in the 12 evaluable pts with a median response duration of 9.1 mo. Conclusions: Concurrent SRS withnivo/ipi was safe for pts with active NSCLC brain mets. Preliminary analyses of efficacy were encouraging for durable intracranial and extracranial response. Clinical trial information: NCT02696993 .

Association Between Facility Volume and Overall Survival for Patients with Grade II Meningioma after Gross Total Resection

BACKGROUND

The role of adjuvant radiation after gross total resection (GTR) for grade II meningioma is evolving, prompting further evaluation in NRG-BN003, a phase 3 national trial. Furthermore, the relationship between facility volume and outcomes in patients with grade II meningioma after GTR has not been examined at a national level. We aim to assess overall survival (OS) of patients with grade II meningioma after GTR by surgical case volume and OS by receipt of adjuvant radiation.

METHODS

We used the National Cancer Database to identity 2823 patients diagnosed with grade II meningioma who underwent GTR. Propensity score matching was applied to balance covariates in patients with grade II meningioma after GTR stratified by adjuvant radiation status. Multivariable logistic regression was used to assess factors associated with radiation receipt. Kaplan-Meier and log-rank tests were used to assess OS by facility volume.

RESULTS

As facility volume increased, OS increased, with a 5-year OS of 72.8% for facilities with GTR grade II meningioma volumes of ≤8 cases per decade and 87.5% for >8 cases per decade (P < 0.0001). There was no difference in 5-year OS between GTR alone and GTR with adjuvant radiation (84.8% vs. 86.4%; P = 0.151). Covariates significantly associated with radiation receipt included facility location, facility volume, distance, and tumor size.

CONCLUSIONS

Treatment at higher surgical case volume facilities is associated with improved OS for GTR grade II meningioma. These facilities also have more patients receiving adjuvant radiation. However, we observed no difference in OS between adjuvant radiation and surgery alone.

Outcomes following stereotactic radiosurgery for small to medium-sized brain metastases are exceptionally dependent upon tumor size and prescribed dose

BACKGROUND

At our institution, we have historically treated brain metastasis (BM) ≤2 cm in eloquent brain with a radiosurgery (SRS) lower prescription dose (PD) to reduce the risk of radionecrosis (RN). We sought to evaluate the impact of this practice on outcomes.

METHODS

We analyzed a prospective registry of BM patients treated with SRS between 2008 and 2017. Incidences of local failure (LF) and RN were determined and Cox regression was performed for univariate and multivariate analyses (MVAs).

RESULTS

We evaluated 1533 BM ≤2 cm. Median radiographic follow-up post SRS was 12.7 months (1.4-100). Overall, the 2-year incidence of LF was lower for BM treated with PD ≥21 Gy (9.3%) compared with PD ≤15 Gy (19.5%) (sub-hazard ratio, 2.3; 95% CI: 1.4-3.7; P = 0.0006). The 2-year incidence of RN was not significantly higher for the group treated with PD ≥21 Gy (9.5%) compared with the PD ≤15 Gy group (7.5%) (P = 0.16). MVA demonstrated that PD (≤15 Gy) and tumor size (>1 cm) were significantly correlated (P < 0.05) with higher rates of LF and RN, respectively. For tumors ≤1 cm, when comparing PD ≤15 Gy with ≥21 Gy, the risks of LF and RN are equivalent. However, for lesions >1 cm, PD ≥21 Gy is associated with a lower incidence of LF without significantly increasing the risk of RN.

CONCLUSION

Our results indicate that rates of LF or RN following SRS for BM are strongly correlated with size and PD. Based on our results, we now, depending upon the clinical context, consider increasing PD to 21 Gy for BM in eloquent brain, excluding the brainstem.

Abstract ES10-2: Understanding breast cancer using a developmental perspective

Parallels among embryonic development, stem cells, and cancer have long been recognized. We identified, isolated, and characterized stem cells that first become committed to a mammary fate during embryogenesis; we refer to these cells as fetal mammary stem cells (fMaSCs). Lineage tracing, in vitro sphere formation, and in vivo transplantation studies by our group and many others all confirm that cells in the embryo are the bipotent progenitors of the mammary gland. There is debate, however, on whether such bipotent cells persist into the adult, or whether the luminal and basal lineages are maintained by unipotent progenitors. To gain insight into the relationships between fMaSCs and breast cancer, and to investigate their potential persistence in the adult, we have applied bulk and single cell RNA-sequencing (sc-RNA-seq) and single nucleus ATAC-sequencing (snATAC-seq) throughout mammary development. The results to be discussed demonstrate that fMaSC transcriptomes are heterogeneous, but all share co-expression of genes associated with luminal and basal cell fates. This fits a model in which the bipotent state is created by a balance of lineage specifiers. We also find that the fMaSC transcriptome is highly enriched in basal-like human breast cancers and identify potential embryonic pathways that correlate with poor prognosis. We used a variety of computational tools to infer the gene expression programs that ensue when fMaSCs commit to luminal and basal states. The data from scRNA-seq and snATAC-seq demonstrate that the transitions are gradual, not precipitous, and that luminal and basal cells exhibit significant transcriptomic and epigenetic heterogeneity. This challenges the notion that the mammary gland consists of discrete cell types defined by rigid transcriptomic parameters, and reveals a potential for intrinsic phenotypic plasticity of normal mammary cells. Using the combined databases, we identified Sox10 as a significantly differentially expressed cell state regulator. We show that tumors are heterogeneous with regard to Sox10 expression, and that locally invasive cells tend to express high Sox10 levels. Elevated Sox10 correlates with acquisition of a neural-crest like, EMT-related state. Implications for interception of metastasis by targeting neural crest-like cells will be discussed. Finally, we have generated a web resource that is available to the scientific community to enable the transcription and epigenetic characteristics of any gene of interest to be tracked through mammary development (https://wahl-labsalk.shinyapps.io/Mammary_snATAC/).

Citation Format: GM Wahl, Z Ma, C Chung, C Dravis, BT Spike, RR Giraddi, O Balcioglu, C Fan, B Hagos, R Heinz, Herrera-Valdez J, X Hou, J Hwang, R Lasken, G Luna, NE Lytle, EM Mehrabad, M Novotny, CM Perou, O Poirion, S Preissl, B Ren, T Reya, CL Trejo, KT Varley. Understanding breast cancer using a developmental perspective [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr ES10-2.

Phantom Validation of DCE-MRI Magnitude and Phase-Based Vascular Input Function Measurements

Accurate, patient-specific measurement of arterial input functions (AIF) may improve model-based analysis of vascular permeability. This study investigated factors affecting AIF measurements from magnetic resonance imaging (MRI) magnitude (AIF_MAGN) and phase (AIF_PHA) signals, and compared them against computed tomography (CT) (AIF_CT), under controlled conditions relevant to clinical protocols using a multimodality flow phantom. The flow phantom was applied at flip angles of 20° and 30°, flow rates (3-7.5 mL/s), and peak bolus concentrations (0.5-10 mM), for in-plane and through-plane flow. Spatial 3D-FLASH signal and variable flip angle T1 profiles were measured to investigate in-flow and radiofrequency-related biases, and magnitude- and phase-derived Gd-DTPA concentrations were compared. MRI AIF performance was tested against AIF_CT via Pearson correlation analysis. AIF_MAGN was sensitive to imaging orientation, spatial location, flip angle, and flow rate, and it grossly underestimated AIF_CT peak concentrations. Conversion to Gd-DTPA concentration using T1 taken at the same orientation and flow rate as the dynamic contrast-enhanced acquisition improved AIF_MAGN accuracy; yet, AIF_MAGN metrics remained variable and significantly reduced from AIF_CT at concentrations above 2.5 mM. AIF_PHA performed equivalently within 1 mM to AIF_CT across all tested conditions. AIF_PHA, but not AIF_MAGN, reported equivalent measurements to AIF_CT across the range of tested conditions. AIF_PHA showed superior robustness.

Radiotherapy in Leptomeningeal Disease: A Systematic Review of Randomized and Non-randomized Trials

Background: Leptomeningeal disease (LMD), also known as neoplastic meningitis, leptomeningeal carcinomatosis, or carcinomatous meningitis, is a rare cancer complication occurring in ~5% of cases and ultimately leads to significant morbidity and mortality. In the modern era, incidence of this condition continues to rise with longer survival of patients with advanced and even metastatic disease due to continued improvements in systemic therapies that are providing prolonged control of distant disease, but with limited effect in the central nervous system (CNS). Typical treatment strategies include optimal systemic therapy for the primary disease, as well as neuroaxis directed therapies, which may include intrathecal chemotherapy (ITC) or radiotherapy (RT). Methods: A systematic review of radiotherapy for LMD was performed. Medline, EMBASE, and Cochrane databases were searched from 1946 to 2018 for clinical trials, retrospective/prospective reviews, and case series with ≥2 human subjects that used radiation therapy techniques in the treatment of LMD. The outcome measures of interest included: characteristics of trial participants, inclusion/exclusion criteria, study type, number of participants, primary cancer histology, type of intervention for LMD, survival results if reported, length of follow up, and study conclusion. Results: Of 547 unique citations, 62 studies met the pre-specified eligibility criteria. These studies included 36 retrospective cohorts, 11 prospective series, 12 case series, and a single citation of guidelines, NCDB analysis, and a randomized control trial. Owing to study heterogeneity, meta-analyses of the endpoint data could not be performed. Conclusions: LMD is a devastating complication of cancer with reported survivals ranging from 2 to 4 months. Based on this systematic review, the recommendation for the treatment of LMD is for multimodality discussion of cases and treatment, including the use of radiotherapy, for LMD. However, with continued advances in systemic therapy as well as imaging advances, the landscape of LMD is evolving rapidly and the role of RT will likely also continue to evolve and advance. There is limited high-quality evidence to guide the optimal use of RT for the treatment of LMD, and there is a great need for prospective, histology specific investigation of the role of radiotherapy for LMD in the era of modern systemic therapies.

RTHP-23. PROSPECTIVE TRIAL OF CONVENTIONALLY FRACTIONATED DOSE CONSTRAINTS FOR RE-IRRADIATION OF PRIMARY BRAIN TUMORS

PURPOSE/OBJECTIVE

Dose constraints for re-irradiation of recurrent primary brain tumors are not well-established, especially for treatment volumes too large for stereotactic radiotherapy. This prospective trial was performed to test dose constraints for conventionally-fractionated re-irradiation of recurrent primary brain tumors

MATERIALS/METHODS

A single-institution, prospective trial of 21 adults with recurrent brain tumors was performed. Electronic dosimetry records from the first course of radiation (RT1) were obtained and deformed onto the simulation CT for the second course of radiation (RT2). Treatment plans for RT2 were developed that met protocol-assigned dose constraints for RT2 alone and the composite dose of RT1+RT2. Dose constraints were also based on histology and interval since RT1. The primary endpoint was the rate of symptomatic brain necrosis after RT2.

RESULTS

Twenty one adults enrolled from March 2017 to May 2018. Twelve had glioblastoma, four had oligodendroglioma, two had anaplastic astrocytoma, and one each had choroid plexus papilloma, hemangiopericytoma, and pleomorphic xanthroastrocytoma (PXA). Twenty patients were treated with VMAT and one was treated with proton CSI. Median RT1-RT2 interval was 45 months (range, 9–141 months). Median RT2 dose was 42.8 Gy (range, 17.5–60 Gy). Median PTV volume was 208 cc (range, 7–1537 cc). Median imaging followup was 9 months (range, 1–20 months). Two months after RT2, the patient with PXA developed a trapped temporal horn adjacent to the RT2 treatment volume; pathology from emergent resection revealed necrotic brain tissue. The patient recovered fully and lived another 18 months until dying of disease progression. No other patient developed symptomatic radionecrosis. Median overall survival from RT2 for all patients was 11 months (range, 3–20 months).

CONCLUSION

Re-irradiation can be performed with conventionally fractionated schemes. Given the low rate of symptomatic radionecrosis, the dose constraints described here are a starting point for future studies of conventionally fractionated re-irradiation.

NIMG-03. PROSPECTIVE PHASE II RANDOMIZED TRIAL COMPARING PROTON THERAPY VS. PHOTON IMRT FOR GBM: SECONDARY ANALYSIS COMPARISON OF PROGRESSION FREE SURVIVAL BETWEEN RANO VS. CLINICAL AND RADIOLOGICAL ASSESSMENT

PURPOSE

To compare tumor progression based on clinical radiological assessment and on Response Assessment in Neuro-Oncology (RANO) criteria between GBM patients treated with proton radiotherapy (PT) vs. photon intensity modulated radiotherapy (IMRT).

METHODS

Eligible patients were enrolled on the described prospective phase II trial and had MR imaging at baseline and follow-up beyond 12 weeks from treatment completion. ‘Clinical’ progression was based on a radiology report of progression in combination with changes in treatment due to suspected disease progression. A single blinded observer applied RANO criteria to determine the RANO-based tumor progression.

RESULTS

Of 90 enrolled patients, 66 were evaluable, with median follow-up of 19.8 (Range: 3.2–65.1) months; median of 22.6 months for PT (n=25) vs. 18.9 months for IMRT (n=41). Median time to progression (TTP) was 7.9 months based on clinical progression criteria (8.1 months IMRT, 6.3 months PT) and 7.2 months (7.3 months IMRT, 5.7 months PT) by RANO criteria (p=ns for all). Median ‘clinical’ progression-free survival (PFS) was 8.7 (Range: 6.4–11.1) months; 8.9 months IMRT vs. 8.7 months PT (p=0.065). Median RANO PFS was 8.3 (range, 5.8–11.6) months: 8.3 months IMRT vs. 6.9 months PT (p=0.226). There were 14 discrepant cases: 3 had progression based on ‘clinical’ but not RANO criteria, and 11 had progression based on RANO but not ‘clinical’ criteria.

CONCLUSION

Based on this secondary analysis of a randomized trial of PT vs. IMRT for GBM, there was no difference in tumor progression relative to treatment technique used. There was no statistical difference in PFS noted between clinical and RANO-based assessments, but RANO criteria identified progression more often than clinical assessment, and TTP was shortened with the use of RANO criteria alone. Further development of tumor assessment tools that improve consistency and accuracy of determining tumor progression are needed to guide therapeutic trials in GBM.

RTHP-18. PROSPECTIVE PHASE II RANDOMIZED TRIAL COMPARING PROTON THERAPY VS. PHOTON IMRT FOR NEWLY DIAGNOSED GBM: SECONDARY ANALYSIS COMPARISON OF GENDER AND NEUTROPHIL-LYMPHOCYTE RATIO (NLR) IN GBM OUTCOMES

BACKGROUND

While glioblastoma (GBM) is more prevalent in males, studies show that females with GBM tend to have longer overall survival (OS) than males. Pretreatment neutrophil to lymphocyte ratio (NLR) has also proven to be prognostic in GBM, with lower NLR having favorable outcomes. This secondary analysis of a prospective randomized trial of proton vs. photon intensity modulated radiotherapy aims to explore the interaction of gender and NLR on GBM outcomes.

METHODS

Analysis was performed on the full patient population. Kaplan-Meier methods estimated OS with censoring at last follow-up for those who were alive. Univariate (UVA) and multivariate (MVA)Cox proportional hazards models assessed predictors of OS.

RESULTS

Of 90 patients, 77 were included (43 males; 34 females) with median age of 52 years (range: 26–82 years). Median OS was longer for females than males (30.7 vs 18.2 months, p=0.004). On UVA, patients with NLR below median value (NLR= 3.1) tended to have longer OS than those above median, though not meeting statistical significance (23.1 vs. 17.9 months, p=0.051). Difference in OS was statistically significant in females (OS 36.4 months NLR >median vs. 16.7 months NLR< median, p=0.002), but not in males (OS 17.8 months NLR >median vs. 19.1 NLR< median, p=0.95). MVA analysis was consistent, with female gender predicting reduced hazard ratio (HR) (0.28, p=0.034) and females with below median NLR showing a reduced HR over those with above median (0.28, p=0.005). Again, males did not benefit (HR 0.90, p=0.77).

CONCLUSION

Consistent with prior publications, females and all patients with lower pre-treatment NLR with newly diagnosed GBM had longer OS. However, combining these two factors revealed that the benefits from lower pre-treatment NLR were conferred only in females with no impact on males. This different impact of NLR between genders may suggest innate immune differences in gender during response to malignancy.

Chloride inputs to the North Saskatchewan River watershed: the role of road salts as a potential driver of salinization downstream of North America's northern most major city (Edmonton, Canada)

Multiple anthropogenic activities are driving the salinization of freshwater environments threatening water resources worldwide. Accordingly, this research will first examine the spatial and temporal variability of major ions (i.e. Ca²⁺, Mg²⁺, Na⁺, K⁺, SO₄^2-, CO₃^2-, and HCO₃^-) upstream and downstream of the northernmost major city in North America (Edmonton, Canada). Second, this research will estimate the relative contributions of the major sources of chloride (Cl), the main constituent of road deicers, to the sub-basin around Edmonton. Monthly water quality data was for three sites on the North Saskatchewan River (NSR): Rocky Mountain House (RMH - downstream of the Rocky Mountain headwaters), Devon Bridge (upstream of Edmonton) and Pakan Bridge (downstream of Edmonton). Change ratios investigate the downstream alterations of major ions at Pakan and Devon, relative to RMH. Seasonal Kendall tests examine temporal trends (1987-2017). A mass-balance approach then quantifies the major sources of Cl in the sub-basin of the NSR between Devon and Pakan. Progressing from the Rocky Mountain headwaters (at RMH) to downstream of Edmonton (at Pakan), Cl^- increased by >5.5 times, Na⁺ by 4.8 times and K by 2.7 times. No significant temporal trends for Cl^-, Na⁺ and K⁺ were evident at Devon (upstream of Edmonton), whereas all three significantly increased at Pakan (downstream of Edmonton). Deicers (54%), agriculture (20%), along with waste water treatment plant and industrial effluent (15%) were the largest Cl sources in the NSR Devon-Pakan sub-basin. In total, 77 Gg yr^-1 of Cl (or 6 t km² yr^-1) is added to the Devon-Pakan sub-basin, of which, 43 Gg yr^-1 is retained. Understanding and managing the major drivers of freshwater salinization will be of increasing importance in the 21^st century owing to the potential salinization of freshwater resources in the context of a changing climate.