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5094 Background: In prior studies, basal vs. luminal differentiation portends differential response to a) androgen suppression (AS) duration for high-risk prostate cancer (PCa) (NRG-GU-TS006) and b) docetaxel chemotherapy (CT) and AS for metastatic hormone-sensitive disease (CHAARTED). In NRG-GU-TS006, basal tumors appeared to benefit the most from longer duration of AS while those with luminal subtype did not whereas, in CHAARTED, luminal subtype had greater benefit from addition of CT. Herein, we examined basal-luminal subtyping to predict differential response to the addition of CT in the setting of high-risk PCa treated with AS and definitive radiotherapy (AS + RT) in NRG/RTOG 0521. Methods: Per pre-specified and approved NCI analysis plan (Navigator #1061), we obtained available NRG biobank biopsy specimens from patients enrolled on the NRG/RTOG 0521 phase III trial, which randomized patients to AS + RT +/- CT. The highest-grade tumors were profiled on clinical-grade whole-transcriptome arrays (Veracyte, San Diego, CA). Basal-luminal subtypes were generated using a 215-gene PCa subtyping classifier (PSC), a second generation PAM50 basal-luminal model. Treatment effects in Luminal Proliferating (LP) and non-LP subtypes were examined with Cox (for overall survival, OS, and metastasis-free survival, MFS) and Fine & Gray (for distant metastasis, DM) multivariable (MVA) models adjusted for age and trial risk stratification, as well as with restricted mean survival times (RMST). Results: Of 183 samples available for analysis (91 from control and 92 from the CT arm), 52 (28%) were classified as LP subtype. Median follow-up for OS was 9.9 years. No significant differences in clinical or pathological variables were observed between LP and non-LP subtypes. In MVA, we did not detect any significant LP subtype-by-CT treatment interaction but observed evidence of non-proportional hazards (Grambsch-Therneau test, p<0.05). In unselected patients, 5- and 10-year RMST difference between the arms was 0.9 (95% CI [-1.5, 3.4], p=0.46) and 5.7 (95% CI [-2.5, 13.9], p=0.17) months of OS. Stratifying by tumor subtype, at 5 years the RMST difference in months was 3.8 (95% CI [0.3, 7.2], p=0.03) for LP and -0.2 ([-3.4, 2.9], p=0.89) for non-LP. The RMST difference in months at 10-years was 13.7 (95% CI [-0.2, 27.5], p=0.053) for LP and 2.5 ([-7.6, 12.5], p=0.63) for non-LP. Conclusions: In pre-treatment biopsy samples from a Phase 3 trial cohort of localized high-risk men, luminal-basal subtyping of tumors demonstrated differential response to docetaxel CT. Similar to results from the CHAARTED trial of metastatic disease, LP tumors may derive greater benefit from addition of CT. Validation of these findings may enable effective earlier use of CT in men with PCa.

5071 Background: Best treatment of mCSPC involves doublet therapy (ADT + novel hormonal agent) or triplet therapy (ADT + novel hormone + docetaxel); however, opportunity remains for further improvement. Studies show that homologous recombination repair (HRR) gene mutations are enriched in metastatic prostate cancer, and may portend resistance to docetaxel. CASCARA tested quadruplet therapy (ADT + cabazitaxel/carboplatin + abiraterone) in high-volume mCSPC, aiming to enhance PSA responses and decrease progression at 1 year. Methods: This phase 2 study enrolled 61 mCSPC patients with high-volume disease who received ADT plus cabazitaxel (20 mg/m2 q21d x 6) and carboplatin (AUC=4 q21d x 6) followed by abiraterone (1000 mg, plus prednisone 5 mg). Primary endpoint was freedom from PSA/radiographic progression at 1 year. Other endpoints included PSA50 response, freedom from PSA progression, and safety. Archival biopsies were retrospectively evaluated for HRR ( BRCA1/2, ATM, CHEK2, CDK12, BRIP1, RAD51B) mutations at a CLIA-certified lab. A sample size of 61 was determined using a Simon two-stage design (stage 1: 32 men, stage 2: 29 men) with a null hypothesis of a 1-year PSA/radiographic progression-free rate of 0.80 against a one-sided alternative of 0.92. Results: From 11/2019 to 06/2022, 61 men enrolled at 7 sites. Median age was 64 (range, 45–76) years; 21% were African American. Median baseline PSA was 8.9 (range, 0.1–1021) ng/mL. 44% of men had ECOG=1. 91% had Gleason sum 8–10. Prevalence of DNA alterations (50 evaluable pts) was 18% for HRR mutations, 38% for TP53 muts, 22% for ERG fusions, 10% for SPOP muts. Freedom from PSA/radiographic progression at 1 year was 77% (95% CI, 63–87%), and freedom from PSA progression at 1 year was 81% (95% CI, 67–90%). The PSA50 rate response was 97%. PSA ≤0.2 ng/mL at month-7, a surrogate for survival in other mCSPC studies, was 61%; PSA ≤4 ng/mL at month-7 was 82%. Outcomes according to mutation status are shown. AEs included 7% grade (Gr)-3/4 myelosuppression, 8% Gr-3/4 infections, 10% Gr-3 GI disorders, and 3% Gr-3 fatigue. There were 4 treatment-related discontinuations. Conclusions: Quadruplet therapy with ADT + cabazitaxel/carboplatin + abiraterone was well tolerated. At 1 year, 77% of pts were progression-free. PSA ≤0.2 ng/mL at month-7 was 61%, exceeding the historical month-7 PSA ≤0.2 ng/mL rate of 45% in CHAARTED–docetaxel arm. Further exploration of this quadruplet strategy in randomized phase III studies is warranted. Clinical trial information: NCT03934840 . [Table: see text]

4006 Background: Liposomal irinotecan + 5-fluorouracil/leucovorin (5-FU/LV) is approved in the USA and Europe for mPDAC following progression with gemcitabine-based therapy. A phase 1/2 study (NCT02551991) demonstrated promising anti-tumor activity in patients with mPDAC who received first-line liposomal irinotecan 50 mg/m2 + 5-FU 2400 mg/m2 + LV 400 mg/m2 + oxaliplatin 60 mg/m2 (NALIRIFOX). Here, we present results from NAPOLI 3 (NCT04083235), a randomized, open-label, phase 3 study investigating the efficacy and safety of NALIRIFOX compared with nab-paclitaxel 125 mg/m2 + gemcitabine 1000 mg/m2 (Gem+NabP) as first-line therapy in patients with mPDAC. Methods: Eligible patients with histopathologically/cytologically confirmed untreated mPDAC were randomized (1:1; stratified by Eastern Cooperative Oncology Group [ECOG] performance status, geographic region and presence/absence of liver metastases) to receive NALIRIFOX on days 1 and 15 of a 28-day cycle or Gem+NabP on days 1, 8 and 15 of a 28-day cycle. The primary endpoint was overall survival (OS); secondary endpoints were progression-free survival (PFS), overall response rate (ORR) and safety. OS was evaluated when at least 543 events were observed using a stratified log-rank test with an overall one-sided significance level of 0.025. Results: Overall, 770 patients (NALIRIFOX, n = 383; Gem+NabP, n = 387) were included. Baseline characteristics were balanced between arms. At a median follow-up of 16.1 months, 544 events had occurred. Median OS was 11.1 months in the NALIRIFOX group versus 9.2 months in the Gem+NabP group; median PFS was 7.4 months versus 5.6 months. Median (95% CI) duration of response was 7.3 (5.8–7.6) and 5.0 (3.8–5.6) months in patients who received NALIRIFOX and Gem+NabP, respectively. Grade 3/4 treatment-emergent adverse events occurring in at least 10% of patients receiving NALIRIFOX versus Gem+NabP included diarrhea (20.3% vs 4.5%), nausea (11.9% vs 2.6%), hypokalemia (15.1% vs 4.0%), anemia (10.5% vs 17.4%) and neutropenia (14.1% vs 24.5%). Conclusions: First-line NALIRIFOX demonstrated clinically meaningful and statistically significant improvement in OS and PFS compared with Gem+NabP in patients with mPDAC. The NALIRIFOX safety profile was consistent with the profiles of the regimen components and generally manageable. Clinical trial information: NCT04083235 . [Table: see text]

Abstract Objectives We aimed to explore current practice and interregional differences in the treatment of idiopathic inflammatory myopathies (IIMs). We triangulated these observations considering countries' gross national income (GNI), disease subtypes, and symptoms using patient-reported information. Methods A cross-sectional ancillary analysis of the ‘COVID-19 vaccination in auto-immune disease’ (COVAD) e-survey containing demographic characteristics, IIM subtypes (DM, PM, IBM, anti-synthetase syndrome [ASSD], immune-mediated necrotizing myopathy [IMNM], overlap myopathies [OM]), current symptoms (surrogate for organ involvement) and treatments (corticosteroids [CS], immunomodulators [IM], i.e. antimalarials, immunosuppressants [IS], IVIG, biologic treatments and targeted-synthetic small molecules). Treatments were presented descriptively according to continents, GNI, IIM and organ involvement, and associated factors were analysed using multivariable binary logistic regressions. Results Of 18 851 respondents from 94 countries, 1418 with IIM were analysed (age 61 years, 62.5% females). DM (32.4%), IBM (24.5%) and OM (15.8%) were the most common subtypes. Treatment categories included IS (49.4%), CS (38.5%), IM (13.8%) and IVIG (9.4%). Notably, treatments varied across regions, GNI categories (IS mostly used in higher-middle income, IM in lower-middle income, IVIG and biologics largely limited to high-income countries), IIM subtypes (IS and CS associated with ASSD, IM with OM and DM, IVIG with IMNM, and biologic treatments with OM and ASSD) and disease manifestations (IS and CS with dyspnoea). Most inter-regional treatment disparities persisted after multivariable analysis. Conclusion We identified marked regional treatment disparities in a global cohort of IIM. These observations highlight the need for international consensus-driven management guidelines considering patient-centred care and available resources.

Summary Circulating tumor DNA (ctDNA) is measurable in the majority of metastatic castration-resistant prostate cancer patients. Data indicate that ctDNA present at baseline can serve as a prognostic biomarker and changes in the ctDNA posttreatment can rapidly predict both time to progression and survival. See related article by Tolmeijer et al., p. 2835

In Radiation Therapy Oncology Group 90-05, the maximum tolerated dose of single-fraction radiosurgery (SRS) for brain metastases of 21–30 mm was 18 Gy (biologically effective dose (BED) 45 Gy12). Since the patients in this study received prior brain irradiation, tolerable BED may be >45 Gy12 for de novo lesions. We investigated SRS and fractionated stereotactic radiotherapy (FSRT) with a higher BED for radiotherapy-naive lesions. Patients receiving SRS (19–20 Gy) and patients treated with FSRT (30–48 Gy in 3–12 fractions) with BED > 49 Gy12 for up to 4 brain metastases were compared for grade ≥ 2 radiation necrosis (RN). In the entire cohort (169 patients with 218 lesions), 1-year and 2-year RN rates were 8% after SRS vs. 2% and 13% after FSRT (p = 0.73) in per-patient analyses, and 7% after SRS vs. 7% and 10% after FSRT (p = 0.59) in per-lesion analyses. For lesions ≤ 20 mm (137 patients with 185 lesions), the RN rates were 4% (SRS) vs. 0% and 15%, respectively, (FSRT) (p = 0.60) in per-patient analyses, and 3% (SRS) vs. 0% and 11%, respectively, (FSRT) (p = 0.80) in per-lesion analyses. For lesions > 20 mm (32 patients with 33 lesions), the RN rates were 50% (SRS) vs. 9% (FSRT) (p = 0.012) in both per-patient and per-lesion analyses. In the SRS group, a lesion size > 20 mm was significantly associated with RN; in the FSRT group, lesion size had no impact on RN. Given the limitations of this study, FSRT with BED > 49 Gy12 was associated with low RN risk and may be safer than SRS for brain metastases > 20 mm.

Abstract Background/Aims Flares following COVID-19 vaccination are an emerging concern among patients with rare rheumatic disease like idiopathic inflammatory myositis (IIMs), whereas data and understanding of this is rather limited. We aimed to study the prevalence, characteristics and determinants of IIM flares following COVID-19 vaccination. Methods CoVAD (COVID-19 Vaccination In Autoimmune Diseases) surveys are global patient self-reported e-surveys from 109 countries conducted in 2021 and 2022. Flares of IIM were defined by 4 definitions; a. patient self-reported, b. physician and immunosuppression (IS) denoted, c. sign directed (new erythematous rash, or worsening myositis or arthritis), d. MCID worsening of PROMISPF10a score between the patients who had taken both surveys. Descriptive statistics and multivariate regression were used to describe the predictors of flare. Cox-regression analysis was used to differentiate flares by IIM subtypes. Results Among the 1,278 IIM patients, aged 63 (50-71) years, 276 (21.5%) were dermatomyositis, 237 (18.5%) IBM, 899 (70.3%) were female and most were Caucasian (80.8%). Flares of IIM were seen in 123/1278 (9.6%), 163/1278 (12.7%), 112/1278 (8.7%), and 16/96 (19.6%) by definitions a-d respectively with median time to flare being 71.5 (10.7-235) days. Muscle weakness (69.1%), and fatigue (56.9%) were the most common symptoms of flare. The predictors of self-reported flare were: inactive/disease in remission prior to first dose of vaccine (OR = 4.3, 95%CI=2.4-7.6), and anxiety disorder (OR = 2.2, 95%CI=1.1-4.7). Rituximab use (OR = 0.3, 95%CI=0.1-0.7) and IBM (OR = 0.3, 95%CI=0.1-0.7) were protective. Physician defined flares were seen more often in females, mixed ethnicity, and those with asthma, ILD, and anxiety disorder (OR ranging 1.6-7.0, all p &lt; 0.05). Notably, overlap myositis (OM) had higher HR for flare compared to polymyositis (HR = 2.3, 95%CI=1.2-4.4, p = 0.010). Conclusion Nearly one in ten individuals with IIM develop flares after vaccination, more so among women, those with overlap myositis, and inactive disease prior to vaccination. Formal definition of flares in IIM is needed. Disclosure L. Gupta: None. N. R: None. Z. Griger: None. V. Agarwal: None. P. Sen: None. M. Joshi: None. S. Saha: None. K. Jagtap: None. O. Distler: Honoraria; Abbvie, Acceleron, Alcimed, Amgen, AnaMar, Arxx, Baecon, Blade, Bayer, Boehringer Ingelheim, ChemomAb, Corbus, CSL Behring, Galapagos, Glenmark, GSK, Horizon (Curzion), Inventiva, iQvia, Kymera, Lupin, Medac, Medscape, Mitsubishi Tanabe, Novartis, Roche, Roivant, Sanofi, Serodapharm, Topadur and UCB. E. Nikiphorou: Honoraria; Celltrion, Pfizer, Sanofi, Gilead, Galapagos, AbbVie, and Lilly. Grants/research support; Pfizer and Lilly. A. Tan: Honoraria; Abbvie, Gilead, Janssen, Lilly, Novartis, Pfizer, and UCB. S. Shinjo: None. N. Ziade: Honoraria; Pfizer, Roche, Abbvie, Eli Lilly, NewBridge, Sanofi-Aventis, Boehringer Ingelheim, Janssen, and Pierre Fabre. M. Milchert: None. I. Parodis: Honoraria; Amgen, AstraZeneca, Aurinia Pharmaceuticals, Elli Lilly and Company, Gilead Sciences, GlaxoSmithKline, Janssen Pharmaceuticals, Novartis and F. Hoffmann-La Roche AG. M. Kuwana: None. A. Makol: None. J. Pauling: None. C. Wincup: None. J. Lilleker: Honoraria; Sanofi Genzyme, Roche, and Biogen. A. Nune: None. J. Day: Grants/research support; CSL Limited. H. Chinoy: Consultancies; Novartis, Eli Lilly, Orphazyme, Astra Zeneca. Honoraria; UCB, and Biogen. Grants/research support; Eli Lilly and UCB. V. Agarwal: None. R. Aggarwal: Consultancies; Bristol Myers-Squibb, Pfizer, Genentech, Octapharma, CSL Behring, Mallinckrodt, AstraZeneca, Corbus, Kezar, Abbvie, Janssen, Alexion, Argenx, Q32, EMD-Serono, Boehringer Ingelheim, and Roivant.

Abstract Background/Aims Post COVID-19 syndrome (PCS) is an emerging cause of morbidity and poor quality of life in COVID-19 survivors. We aimed to assess the prevalence, risk factors, outcomes, and association with disease flares of PCS in patients with autoimmune rheumatic diseases (AIRDs) and non-rheumatic autoimmune diseases (nrAIDs), both vulnerable groups understudied in the current literature using data from the 2nd COVID-19 Vaccination in Autoimmune Diseases (COVAD) global multicentre patient self-reported e-survey. Methods The survey was circulated from February to July 2022 by the international COVAD Study Group (157 collaborators from 106 countries), and demographics, comorbidities, AIRD/nrAID status, COVID-19 history, vaccination details, and PROMIS physical and mental function were recorded. PCS was defined as symptom resolution time &gt;90 days following acute COVID-19. Predictors of PCS were analysed using regression models for the different groups. Results 7666 total respondents completed the survey. Of these, 2650 respondents with complete responses had positive COVID-19 infection, and 1677 (45.0% AIRDs, 12.5% nrAIDs, 42.5% HCs) completed the survey &gt;90 days post acute COVID-19. Of these, 136 (8.1%) had PCS. Prevalence of PCS was higher in AIRDs (10.8%) than healthy controls HCs (5.3%) (OR: 2.1; 95%CI: 1.4-3.1, p = 0.002). Across the entire cohort, a higher risk of PCS was seen in women (OR: 2.9; 95%CI: 1.1-7.7, p = 0.037), patients with long duration of AIRDs/nrAIDs (OR 1.01; 95%CI: 1.0-1.02, p = 0.016), those with comorbidities (OR: 2.8; 95%CI: 1.4-5.7, p = 0.005), and patients requiring oxygen supplementation for severe acute COVID-19 (OR: 3.8; 95%CI: 1.1-13.6, p = 0.039). Among patients with AIRDs, comorbidities (OR 2.0; 95%CI: 1.08-3.6, p = 0.026), and advanced treatment (OR: 1.9; 95%CI: 1.08-3.3, p = 0.024), or intensive care (OR: 3.8; 95%CI: 1.01-14.4, p = 0.047) for severe COVID-19 were risk factors for PCS. Notably, patients who developed PCS had poorer PROMIS global physical [15 (12-17) vs 12 (9-15)] and mental health [14 (11-16) vs 11 (8-14)] scores than those without PCS. Conclusion Individuals with AIRDs have a greater risk of PCS than HCs. Associated comorbid conditions, and advanced treatment or intensive care unit admission for severe COVID-19 confer a higher risk of PCS. It is imperative to identify risk factors for PCS for immediate multidisciplinary management in anticipation of poor physical and mental health. Disclosure L. Gupta: None. P. Sen: None. N. R: None. M. Joshi: None. S. Saha: None. K. Jagtap: None. V. Agarwal: None. O. Distler: Consultancies; Abbvie, Acceleron, Alcimed, Amgen, AnaMar, Arxx, Baecon, Blade, Bayer, Boehringer Ingelheim, ChemomAb, Corbus, CSL Behring, Galapagos, Glenmark, GSK, Horizon (Curzion), Inventiva, iQvia, Kymera, Lupin, Medac, Medscape, Mitsubishi Tanabe, Novartis, Roche, Roivant, Sanofi, Serodapharm, Topadur and UCB. E. Nikiphorou: Honoraria; Celltrion, Pfizer, Sanofi, Gilead, Galapagos, AbbVie, and Lilly. Grants/research support; Pfizer and Lilly. A. Tan: Honoraria; Abbvie, Gilead, Janssen, Lilly, Novartis, Pfizer, and UCB. S. Shinjo: None. N. Ziade: Honoraria; Pfizer, Roche, Abbvie, Eli Lilly, NewBridge, Sanofi-Aventis, Boehringer Ingelheim, Janssen, and Pierre Fabre. M. Milchert: None. I. Parodis: Honoraria; Amgen, AstraZeneca, Aurinia Pharmaceuticals, Elli Lilly and Company, Gilead Sciences, GlaxoSmithKline, Janssen Pharmaceuticals, Novartis and F. Hoffmann-La Roche AG. M. Kuwana: None. A. Makol: None. J.D. Pauling: None. C. Wincup: None. J. Lilleker: Honoraria; Sanofi Genzyme, Roche, and Biogen. A. Nune: None. J. Day: Grants/research support; CSL Limited. H. Chinoy: Consultancies; Novartis, Eli Lilly, Orphazyme, Astra Zeneca. Honoraria; UCB, and Biogen. Grants/research support; Eli Lilly and UCB. V. Agarwal: None. R. Aggarwal: Consultancies; Bristol Myers-Squibb, Pfizer, Genentech, Octapharma, CSL Behring, Mallinckrodt, AstraZeneca, Corbus, Kezar, Abbvie, Janssen, Alexion, Argenx, Q32, EMD-Serono, Boehringer Ingelheim, and Roivant.