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Abstract Background Multisystem inflammatory syndrome in children (MIS-C), linked to antecedent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, is associated with considerable morbidity. Prevention of SARS-CoV-2 infection or coronavirus disease 2019 (COVID-19) by vaccination might also decrease MIS-C likelihood. Methods In a multicenter, case-control, public health investigation of children ages 5–18 years hospitalized from 1 July 2021 to 7 April 2022, we compared the odds of being fully vaccinated (2 doses of BNT162b2 vaccine ≥28 days before hospital admission) between MIS-C case-patients and hospital-based controls who tested negative for SARS-CoV-2. These associations were examined by age group, timing of vaccination, and periods of Delta and Omicron variant predominance using multivariable logistic regression. Results We compared 304 MIS-C case-patients (280 [92%] unvaccinated) with 502 controls (346 [69%] unvaccinated). MIS-C was associated with decreased likelihood of vaccination (adjusted OR [aOR]: .16; 95% CI: .10–.26), including among children ages 5–11 years (aOR: .22; 95% CI: .10–.52), ages 12–18 years (aOR: .10; 95% CI: .05–.19), and during the Delta (aOR: .06; 95% CI: .02–.15) and Omicron (aOR: .22; 95% CI: .11–.42) variant-predominant periods. This association persisted beyond 120 days after the second dose (aOR: .08; 95% CI: .03–.22) in 12–18-year-olds. Among all MIS-C case-patients, 187 (62%) required intensive care unit admission and 280 (92%) vaccine-eligible case-patients were unvaccinated. Conclusions Vaccination with 2 doses of BNT162b2 is associated with reduced likelihood of MIS-C in children ages 5–18 years. Most vaccine-eligible hospitalized patients with MIS-C were unvaccinated.

OBJECTIVES To evaluate risk factors for postdischarge sequelae in children and adolescents hospitalized for acute coronavirus disease 2019 (COVID-19) or multisystem inflammatory syndrome in children (MIS-C). METHODS Multicenter prospective cohort study conducted in 25 United States pediatric hospitals. Patients <21-years-old, hospitalized May 2020 to May 2021 for acute COVID-19 or MIS-C with follow-up 2 to 4 months after admission. We assessed readmissions, persistent symptoms or activity impairment, and new morbidities. Multivariable regression was used to calculate adjusted risk ratios (aRR) and 95% confidence intervals (CI). RESULTS Of 358 eligible patients, 2 to 4 month survey data were available for 119 of 155 (76.8%) with acute COVID-19 and 160 of 203 (78.8%) with MIS-C. Thirteen (11%) patients with acute COVID-19 and 12 (8%) with MIS-C had a readmission. Thirty-two (26.9%) patients with acute COVID-19 had persistent symptoms (22.7%) or activity impairment (14.3%) and 48 (30.0%) with MIS-C had persistent symptoms (20.0%) or activity impairment (21.3%). For patients with acute COVID-19, persistent symptoms (aRR, 1.29 [95% CI, 1.04–1.59]) and activity impairment (aRR, 1.37 [95% CI, 1.06–1.78]) were associated with more organ systems involved. Patients with MIS-C and pre-existing respiratory conditions more frequently had persistent symptoms (aRR, 3.09 [95% CI, 1.55–6.14]) and those with obesity more frequently had activity impairment (aRR, 2.52 [95% CI, 1.35–4.69]). New morbidities were infrequent (9% COVID-19, 1% MIS-C). CONCLUSIONS Over 1 in 4 children hospitalized with acute COVID-19 or MIS-C experienced persistent symptoms or activity impairment for at least 2 months. Patients with MIS-C and respiratory conditions or obesity are at higher risk of prolonged recovery.

Abstract E1496 is a phase III trial designed to evaluate the ability of 2 years (yr) of maintenance rituximab (MR) to prolong progression-free survival (PFS) after CVP (cyclophosphamide 1 G/m2 day [d] 1, vincristine 1.4 mg/m2 [max = 2 mg] d 1, prednisone 100 mg/m2 d 1–5) chemotherapy in stage III–IV follicular grade 1 and 2 and small lymphocytic lymphoma. After CVP treatment to maximum response, (6–8 cycles), stable and responding patients (pt) were randomized to MR (375 mg/m2 weekly x 4) every 6 months x 4 or observation (OBS). Stratification factors included histology, response and residual disease after CVP. With 3-yr median follow-up, survivals (from time of randomization, one-sided logrank p values) for all pt (n=304) favored MR for PFS (p = 3 x 10–8; hazard rate {HR} = 0.38 [0.28;0.54, 95% confidence intervals]) and OS (p = 0.09; HR = 0.66 [0.36–1.22]). Because the large majority of pt have FL and because rituximab efficacy is notably greater in FL, we focused in this report on the 237 FL pt. Median age was 58 yr, 65% were stage IV, 64% had marrow disease, 64% had high tumor burden and 37% had high-risk disease by the follicular lymphoma prognostic index. PFS after randomization was significantly longer for MR vs OBS (p = 3 x 10-7; HR = 0.39 [0.27;0.57]). The estimated PFS at 4 yr (~4.5 yr after start of treatment) was 56% for MR vs 33% for OBS. Differences in PFS were significant within the predefined strata and the differences were most significant in favor of MR for pt with high initial tumor burden and minimal residual disease after CVP. Overall survival was superior for MR (p = 0.03; HR = 0.51 [0.25;1.04]. Estimated OS at 4 yr (~4.5 years after start of treatment) was 88% for MR vs 72% for OBS. Of 33 deaths, 21 occurred on the OBS arm. These data demonstrate that maintenance rituximab not only significantly delays disease progression in FL compared with OBS but that a substantial proportion of patients treated with MR remain disease-free at 4 years after the completion of CVP. These are the first data to strongly suggest a survival benefit with a therapy that includes rituximab and CVP and the first to strongly suggest a survival benefit with maintenance rituximab in FL.

8011 Background: Maintenance therapy is generally not used in treatment of DLBCL. However, older pts are a unique group in which to study this approach, due to poorer outcome. Methods: As part of intergroup trial E4494/C9793, 415 pts >= 60 years (yr) of age with DLBCL who responded to induction therapy with CHOP or R-CHOP were randomized to MR (rituximab, 375 mg/m2 weekly {wk} X 4 every 6 months for 2 yr) starting 4 wk after the last chemotherapy (n=207) or observation (OBS, n=208) in a prospective 2 × 2 randomized trial design (J Clin Oncol 2006;24:3121). Impact of MR on failure-free survival (FFS) was the primary objective, and impact on time to failure (TTF) and overall survival (OS) were secondary objectives. All p-values are two-sided. Results: Results are presented for 352 centrally reviewed evaluable pts, with a median follow-up after maintenance randomization of 5.5 yr. All results were similar for the intent-to-treat population. Baseline characteristics and response to induction therapy are balanced among the CHOP/R-CHOP pts. At 6 yr, FFS was 46% for those pt who received MR and 36% for the OBS cohort (p=0.005, hazard rate {HR} 0.64); 6-yr OS was 62% for MR and 64% for OBS (p=0.83, HR 0.96). Outcome was also examined in the four treatment subgroups. The 6-yr FFS were: CHOP+MR 44%, CHOP+OBS 35%, R-CHOP+MR 47%, and R- CHOP+OBS 40%. No differences in 6-yr OS were observed according to maintenance randomization following CHOP (57% MR vs 55% OBS) or R-CHOP (67% MR and 72% OBS). Median TTF after maintenance randomization following CHOP+MR was 5.2 yr vs 1.6 yr for CHOP-OBS (p=0.0004), and following R-CHOP+MR was 5.6 yr vs 5.4 yr with R-CHOP-OBS (p=0.50). Proportionately more of the treatment failures occurred within 2 yr after CHOP+OBS (85%) compared to CHOP+MR (61%), p=0.01. In contrast, the proportion of failures within 2 yr was similar for R- CHOP+OBS (47%) and R-CHOP+MR (53%), p=NS. Conclusions: MR after CHOP, but not after R-CHOP, significantly prolongs TTF, but fails to prolong OS, possibly due to a delayed pattern of relapse and/or the efficacy of rituximab in the salvage setting. As 6-yr FFS declined to <50% among R-CHOP responders, with or without MR, there is a need for more effective treatment strategies in older DLBCL pts. No significant financial relationships to disclose.

8004 Background: To determine optimal induction and the role of maintenance, the E1496 study randomized patients (pts) to induction CVP (cyclophosphamide, vincristine, prednisone) versus CF (cyclophosphamide 1 G/m2 d1, fludarabine 20 mg/m2 d1–5 every 28 d) for 2 cycles beyond best response (maximum 8). Responding and stable pts were secondarily randomized to MR (375 mg/m2 weekly × 4 every 6 months for 2 years [yr]) or observation (OBS). Methods: Due to early deaths the CF arm was closed to accrual with 115 pts randomized to CF and 119 pts to CVP (thereafter all pts were assigned to CVP prior to maintenance randomization). The results presented here compare the outcome of CF patients with the subset of E1496 pts randomized to CVP (CVPR). Results: Median follow-up on pts randomized to induction is 6.5 yr. Toxic deaths occurred in 8 (7%) CF pts during induction and 4 additional deaths (1 OBS, 3 MR) occurred among the 69 (6%) CF pts randomized to MR or OBS. Causes of death were infection (9), liver failure (2), CNS gliosis (1). CF pts received a median of 5 cycles compared to 7 cycles for CVPR. The CR rate was 51% vs 22% (p=0.00001) and the PR rate was 35% vs 55% for CF vs. CVPR, respectively. Four-yr PFS for CF vs. CVPR was 49% vs 45% (p=0.19) and OS was 66% vs. 81% (p=0.12), respectively. Of 45 CF deaths, 23 (51%) occurred without lymphoma progression compared to 5 (13%) of 38 CVPR deaths (p=0.0004). More than 90% of CF patients randomized to maintenance achieved protocol-defined minimal residual disease compared with 64% CVPR pts. Maintenance therapy had no impact on 2 yr PFS for the 67 evaluable randomized CF pts, which was 74% for MR vs. 73% for OBS (p=0.19). In contrast, 2 yr PFS was 73% for MR and 42% for OBS in randomized CVPR pts (p=0.004). Survival at 2 yr for MR vs OBS was: CF 79% vs 91% (p=0.19) compared with CVP 98% vs 93% (p=0.21). Conclusions: Induction with CF results in higher CR and miminal residual disease rates than CVP. However, gains in remission quality with CF (in the dose and schedule used here) were offset by early and late deaths in the absence of progressive lymphoma. In E1496, the benefit of MR was influenced by the induction chemotherapy. [Table: see text]

Abstract Background We have previously reported and validated that the E-IPI, provided better discrimination of overall survival (OS) than the IPI for DLBCL patients > 60 years of age treated with R-CHOP (Advani et al., BJH 2010 and 12-ICML 2013 Abstract 222). Recent reports suggest that males > 60 years treated with R-CHOP have worse outcomes likely related to differences in rituximab clearance (Muller et al., Blood 2012). In this study, we explored if the addition of male sex to the E-IPI further improved risk stratification. Methods DLBCL patients > 60 years treated with R-CHOP on the E4494, RICOVER-60 and GELA 98-5 trials were included. A multivariate analysis was performed to assess whether male sex is an independent prognostic factor for OS in addition to the five E-IPI risk factors, E-IPI score, and E-IPI risk group. Male sex (S) was added as an additional risk factor to the E-IPI (S-EIPI, 0-6) and patients regrouped according to the number of risk factors: low (L)=0-1, low intermediate (LI)=2, high intermediate (HI)=3 and high (H)=4-6 based on the observed OS using Kaplan-Meier curves. C-statistic was used to compare the discrimination ability. The 5 year OS was estimated using the Kaplan-Meier method. Results 1079 patients (E4494, n=267; RICOVER-60, n=610; GELA 98-5, n=202) with a median follow-up of 8.9 years were included. In multivariate analyses, male sex was a significant independent predictor for OS adjusting for all five E-IPI factors, (HR 1.5, p < 0.0001), E-IPI score (HR 1.42, p < 0.001), and E-IPI risk group (HR 1.42, p < 0.001) (Table 1). C-statistic was 0.66 for S-EIPI and 0.64 for EIPI. Incorporation of sex into the E-IPI shifted 35% patients to higher risk groups, including 110 patients into the highest risk group (Table 2). The estimated 5 year OS for the S-EIPI L, LI, HI, and H risk groups was 87%, 70%, 58%, and 40%, respectively (Table 3). Compared to E-IPI, the 95% C.I. did not overlap among S-EIPI risk groups. Conclusion For DLBCL patients >60 years treated with R-CHOP, our results suggest the addition of male sex to the E-IPI may improve categorization of patients into well-defined clinically relevant risk groups. Patients with low risk S-EIPI have an excellent outcome (5 year OS 87%). Patients with high risk S-EIPI have a 5 year OS of only 40% and therapies beyond standard R-CHOP need to be explored. Disclosures: Horning: Genentech: Employment; Roche: Equity Ownership.

Preclinical and clinical evidence suggest a potential advantage for infusional therapy in lymphoma. Sixty-two analyzable patients with predominantly intermediate-grade non-Hodgkin lymphoma received cyclophosphamide (200 mg/m2 per day), doxorubicin (12.5 mg/m2 per day), and etoposide (60 mg/m2per day) (CDE) by continuous intravenous infusion for 4 days (96 hours) every 3 weeks for a maximum of 8 cycles. By the age-adjusted International Prognostic Index (IPI), 42% were at high risk and 58% were at high-intermediate risk. Complete response (CR) occurred in 30 (48%) patients (95% confidence interval [CI], 35%, 64%), and partial response occurred in 16 (26%) patients, yielding an overall response rate of 74% (95% CI, 62%, 84%). Failure-free survival (FFS) rates at 1 and 2 years were 55% (95% CI, 43%, 67%) and 50% (95% CI, 38%, 62%), respectively. When comparing the outcome for 62 patients receiving infusional CDE with historical data derived from 927 IPI-matched lymphoma patients using a Cox proportional hazards model, there was a nonsignificant trend favoring CDE in FFS (P = .12) and overall survival (P = .09). Severe or life-threatening toxicity included neutropenia (68%), anemia (57%), thrombocytopenia (44%), and infection (24%). Two patients (3%) died of treatment-related infectious complications. The primary end point of improving 1-year FFS from 55% to 70% was not achieved with infusional CDE given as initial therapy in patients with poor-risk intermediate-grade lymphoma. It is unlikely that infusional therapy as used in this study produces a 25% or greater relative improvement in FFS compared with standard therapy.

We showed in a phase I trial that the maximum tolerated dose of the ProMACE-CytaBOM regimen in patients with aggressive lymphoma was 200% (Gordon et al, J Clin Oncol 14:1275, 1996). Based on these observations, we initiated a phase II trial designed to determine response, toxicity, and dose intensity using this regimen. We analyzed 74 patients with advanced-stage (III or IV) or bulky stage II aggressive lymphoma. The overall complete response rate was 69% (72% in evaluable patients). With a median follow-up of 4.5 years, the median survival has not yet been reached. The 4-year survival rate is 73% (95% confidence interval [CI] 62, 83%) and no difference was observed among International Prognostic Index (IPI) groups. The 4-year disease-free survival was 71% (95% CI 58, 84%) with no statistical difference between patients with IPI 0 to 1 versus 2 to 4. The toxicity was acceptable, though the grade 4 hematologic toxicity rate for this regimen was 100%. Grade 4 nonhematologic toxicity was 36%. Three cases of either myelodysplastic syndrome or acute leukemia occurred at 7 months, 3.4 years, and 4.2 years after registration. Cytogenic analysis was available in two cases, showing inv(16) without French American British classification (FAB) M4 EO histology in one patient and a 5q-syndrome in the other. These data suggest that 200% ProMACE-CytaBOM with either granulocyte-macrophage colony-stimulating factor (GM-CSF) or G-CSF results in a high complete remission rate and a disease-free survival comparable to any prior risk-based analysis in aggressive lymphoma. Before using this regimen in general practice, phase III clinical trials should be conducted.

Abstract Abstract 3705 Improved outcomes were reported in USA studies in DLBCL (Habermann et al. J Clin Oncol 2006) in a two-staged randomized study of R-CHOP (rituximab, cyclophosphamide, Adriamycin, vincristine, and prednisone) versus CHOP with a second randomization assignment to maintenance rituximab (MR) or observation (OBS) (E4494) and in follicular lymphoma (FL) in patients in a trial with CVP (cyclophosphamide, vincristine, and prednisone) followed by randomization to MR versus OBS in advanced-stage indolent lymphoma (E1496) (Hochster et al. J Clin Oncol 2009). The details of the treatment regimens have been previously described. The German High Grade Lymphoma Study Group has reported differences between men and women in outcomes in DLBCL with improved outcomes in women treated with rituximab (Müller et al. Blood 2012). Methods: Survival outcomes by sex were analyzed using a stratified weighted cox regression, removing the effect of maintenance rituximab in DLBCL (E4494), and a log-rank test in patients with follicular histology (E1496). A Cox regression model was used to evaluate the differences between males and females together with weight (below or above the median). Wilcoxon test and Fisher's exact test were used to compare medians and proportions, respectively. Results: In DLBCL, there were 273 eligible males and 273 females. The median age was 69 in males and 70 in females. There were no differences in baseline patient characteristics among the male and female populations. 138 males and 129 females were treated with R-CHOP. There was no difference in treatment received, with 83% females and 75.3% males receiving 6 cycles or more of R-CHOP treatment (p=0.14). The complete remission (CR) and partial remission (PR) rates after RCHOP were higher in females (82.6%) versus males (71.5%) (P = 0.04). With a median follow-up of 9.45 years, the failure free survival (FFS) and overall survival (OS) were improved in females (P = 0.02, 0.002; HR=0.63, 0.54) compared with males in the R-CHOP group. The outcomes were not different in the CHOP group for FFS (P = 0.81) or OS (P= 0.57) between males and females. Within the R-CHOP group, the failure free survival (FFS) was significantly different between women and men (P = 0.002) and body weight (P = 0.03), but only female sex (P = 0.001) was significant and not weight (P = 0.26) for OS. Of 282 evaluable patients with advanced-stage follicular lymphoma who received initial treatment with CVP, 115 patients were randomly assigned to MR and 113 to OBS. 120 patients were male, and 108 were female. The median age was 58 years in the MR arm and 54 years in the OBS arm. At a median follow-up of 8.04 years, MR markedly improved the PFS (P=0.003) compared with OBS. There were no differences in PFS (P= 0.17) between males and females treated with MR or OS (P = 0.27). In conclusion, in induction therapy with rituximab in DLBCL there is a sex dependent effect with rituximab with males benefiting less than females. In contrast, in patients with follicular lymphoma treated with chemotherapy followed by maintenance rituximab, there were no differences. The differences in outcomes in patients of different sex with DLBCL treated with immunochemotherapy and FL treated with maintenance rituximab will require further analysis of multiple clinical and biologic variables. Disclosures: Fisher: Roche: Advisory Board Other. Cheson:Genentech: Consultancy. Kahl:Genentech, Roche: Consultancy, Research Funding. Horning:Genetech, Roche: Employment, stock (Roche) Other.