Vaccines against SARS-CoV-2 have shown high efficacy, but immunocompromised participants were excluded from controlled clinical trials. We compared immune responses to the Pfizer/BioNTech mRNA vaccine in solid tumor patients (n=53) on active cytotoxic anti-cancer therapy to a control cohort (n=50) as an observational study. Using live SARS-CoV-2 assays, neutralizing antibodies were detected in 67% and 80% of cancer patients after the first and second immunizations, respectively, with a 3-fold increase in median titers after the booster. Similar trends were observed in serum antibodies against the receptor-binding domain (RBD) and S2 regions of Spike protein, and in IFNγ+ Spike-specific T cells. Yet the magnitude of each of these responses was diminished relative to the control cohort. We therefore quantified RBD- and Spike S1-specific memory B cell subsets as predictors of anamnestic responses to additional immunizations. After the second vaccination, Spike-specific plasma cell-biased memory B cells were observed in most cancer patients at levels similar to those of the control cohort after the first immunization. We initiated an interventional phase 1 trial of a third booster shot (NCT04936997); primary outcomes were immune responses with a secondary outcome of safety. After a third immunization, the 20 participants demonstrated an increase in antibody responses, with a median 3-fold increase in virus-neutralizing titers. Yet no improvement was observed in T cell responses at 1 week after the booster immunization. There were mild adverse events, primarily injection site myalgia, with no serious adverse events after a month of follow-up. These results suggest that a third vaccination improves humoral immunity against COVID-19 in cancer patients on active chemotherapy with no severe adverse events.

Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have shown high efficacy, but immunocompromised participants were excluded from controlled clinical trials. In this study, we compared immune responses to the BNT162b2 mRNA Coronavirus Disease 2019 vaccine in patients with solid tumors (n = 53) who were on active cytotoxic anti-cancer therapy to a control cohort of participants without cancer (n = 50). Neutralizing antibodies were detected in 67% of patients with cancer after the first immunization, followed by a threefold increase in median titers after the second dose. Similar patterns were observed for spike protein-specific serum antibodies and T cells, but the magnitude of each of these responses was diminished relative to the control cohort. In most patients with cancer, we detected spike receptor-binding domain and other S1-specific memory B cell subsets as potential predictors of anamnestic responses to additional immunizations. We therefore initiated a phase 1 trial for 20 cancer cohort participants of a third vaccine dose of BNT162b2 ( NCT04936997 ); primary outcomes were immune responses, with a secondary outcome of safety. At 1 week after a third immunization, 16 participants demonstrated a median threefold increase in neutralizing antibody responses, but no improvement was observed in T cell responses. Adverse events were mild. These results suggest that a third dose of BNT162b2 is safe, improves humoral immunity against SARS-CoV-2 and could be immunologically beneficial for patients with cancer on active chemotherapy.

e15546 Background: Pancreatic cancer (PC) is a high mortality malignancy typically found when curative surgery is not an option. Liquid biopsies are a minimally invasive option that may allow earlier detection of PC. Using a bioinformatic analysis of TCGA and GEO we identified a novel set of blood-based biomarkers to detect PC with high sensitivity and specificity (AUROC = 0.999) (Vrba et al, Epigenetics 2019). Here we tested the ability of this DNA methylation signature (MS) to distinguish metastatic PC from pancreatic cysts (Cy) and healthy controls (HC) through quantitative DNA methylation analysis of cell free DNA (cfDNA). Methods: A 10 gene DNA methylation marker set that identifies PC was used to evaluate the cfDNA component of the plasma of PC patients, Cy patients and HC. The ROC analysis and AUC calculations were performed using the R library pROC (Robin et al, BMC Bioinformatics 2011). Plasma samples were collected in cfDNA collection tubes from patients with benign Cy, PC, and HC. Clinical information was collected including age, gender, smoking history, CA 19-9 level, cyst size, presence of liver metastases, and survival status. After processing and cfDNA extraction, qRT-PCR methylation analysis was performed on these prospectively collected samples. The difference in median DNA MS per marker of the full 10-gene marker set between the above groups was analyzed by Wilcoxon rank sum test and ROC analysis. A Cox proportional hazard regression model was used to test the association between MS and survival. Results: A total of 66 samples were collected (PC = 10, Cy = 12, HC = 44). Clinical information was collected on all patients included in the analysis. Using liquid biopsies for cfDNA analysis and a novel set of DNA methylation biomarkers, MS was substantially stronger in PC (median, 13.2) patients than Cy (median, 3.5) patients (p = 0.0001). Importantly, while there was no clear association between MS and age, gender, smoking status, CA 19-9 levels, or presence of liver metastases, higher methylation levels were non-significantly associated with worse overall survival in PC patients (HR, 1.29; 95% CI, 0.97–1.72; p = 0.082). Conclusions: While this is a small sample size, early findings suggest that a DNA MS may reliably distinguish PC from benign Cy. The strength of signal may be a prognostic marker that could play a role in determining treatment approaches. Given its utility in predicting PC, future directions include testing this tool as a blood-based early detection mechanism as well as a predictor for recurrence or response to PC treatment.

Purpose An accurate clinical and radiological staging is the pyramid of treatment decisions in locally advanced rectal cancer (LARC). Guidelines recommended neoadjuvant chemoradiation therapy (CRT) followed by surgical resection for fit patients with LARC. Determining the aggressiveness of intervention while avoiding needless morbidity according to patient risk remains an unmet pre-operative decision-making need. With newer magnetic resonance imaging (MRI) techniques and image acquisition available at our Cancer Center, we seek to retrospectively review the correlation between pre- and post-CRT MRI response to the surgical pathological stage in order to aide multidisciplinary team decision making. Methods Our Cancer Center Rectal Cancer Registry between 2011 and 2015 included 57 patients with LARC, 20 completed standard CRT with surgery, and of those 10 had repeated MRI after CRT. Results Our retrospective case series revealed that 90% of the patients had a downstage tumor response on surgical specimen compared to radiological evaluation after CRT, and furthermore, all patients who were re-staged with MRI prior to surgery correlated with the gold standard pathological stage (p = 0.02). Conclusions Post-CRT MRI could potentially aide decision making to further avoid 20% of patients with a complete pathological response from a morbid surgery, whereas 10% of patients with an upstaged disease state may require a more aggressive neoadjuvant or planned surgical intervention. We concluded that future multidisciplinary oncology care treatment decision making would benefit from a repeat MRI after neoadjuvant CRT of LARC.

Purpose:We determine if monomethyl fumarate (MMF) can protect the retina in mice subjected to light-induced retinopathy (LIR).Methods:Albino BALB/c mice were intraperitoneally injected with 50 to 100 mg/kg MMF before or after exposure to bright white light (10,000 lux) for 1 hour. Seven days after light exposure, retinal structure and function were evaluated by optical coherence tomography (OCT) and electroretinography (ERG), respectively. Retinal histology also was performed to evaluate photoreceptor loss. Expression levels of Hcar2 and markers of microglia activation were measured by quantitative PCR (qPCR) in the neural retina with and without microglia depletion. At 24 hours after light exposure, retinal sections and whole mount retinas were stained with Iba1 to evaluate microglia status. The effect of MMF on the nuclear factor kB subunit 1 (NF-kB) and Nrf2 pathways was measured by qPCR and Western blot.Results:MMF administered before light exposure mediated dose-dependent neuroprotection in a mouse model of LIR. A single dose of 100 mg/kg MMF fully protected retinal structure and function without side effects. Expression of the Hcar2 receptor and the microglia marker Cd14 were upregulated by LIR, but suppressed by MMF. Depleting microglia reduced Hcar2 expression and its upregulation by LIR. Microglial activation, upregulation of proinflammatory genes (Nlrp3, Caspase1, Il-1β, Tnf-α), and upregulation of antioxidative stress genes (Hmox1) associated with LIR were mitigated by MMF treatment.Conclusions:MMF can completely protect the retina from LIR in BALB/c mice. Expression of Hcar2, the receptor of MMF, is microglia-dependent in the neural retina. MMF-mediated neuroprotection was associated with attenuation of microglia activation, inflammation and oxidative stress in the retina.