P1075: ADVANCED-STAGE CHL INTERNATIONAL PROGNOSTICATION INDEX: EXTERNAL VALIDATION IN A SINGLE-CENTER RETROSPECTIVE PATIENT DATASET AND COMPARISON TO THE HASENCLEVER IPS

Topic: 17. Hodgkin lymphoma - Clinical Background: The International Prognostic Score (IPS) for advanced-stage Hodgkin’s Lymphoma (aHL) was first published in 1998 [Hasenclever, NEJM 1998]. Thereafter, the advent of a PET-guided therapeutic approach and the introduction of novel agents in earlier lines of therapy have radically impacted on HL’s natural history, downgrading the prognostic impact of IPS score. Recently, the Advanced-Stage cHL International Prognostication Index (A-HIPI) a novel prognostic score was proposed, which was built on a large cohort of patients (n=4022) treated within clinical trials and subsequently validated on a group of patients (n=1431) extracted from major cancer registries, aimed at better defining overall and progression-free survival based on baseline characteristics [Rodday et al, JCO 2022]. Aims: This study was aimed at performing an external validation analysis of A-HIPI, comparing its performance to the IPS in a single-center retrospective cohort. Methods: We included HL patients diagnosed at the University Hospital of Padova between 2005 and 2022 treated with PET/CT guided ABVD. The number of cycles and the addition of radiotherapy were performed as dictated by stage and local policy. Both A-HIPI and IPS were calculated. Discrimination was assessed by the means of Harrel’s c-index of concordance. Prognostic model comparison was done using the Akaike’s Information Criterion (AIC). Results: One-hundred and fifty-seven patients were included in the analysis, with 38 (24%) and 55 (34%) having stage III and stage IV disease, respectively. Median age at diagnosis was 32 years, 83 (53%) patients were female and 67 (43%) had bulky disease. Mean hemoglobin was 11.9 g/dL (±1.7), mean albumin was 3.5 g/dL (±0.5) and mean lymphocyte count was 1.4 ×103/μL (±0.7). When stratified by IPS score, 7 (4%) patients had 0 risk factors, 34 (22%) had 1, 41 (26%) had 2, 37 (24%) had 3, 28 (18%) had 4 and 10 (6%) had ≥5. After a median follow up of 57 months, 9 (6%) patients died and 46 (29%) experienced a PFS-related event. The 5-year overall survival (OS) and progression-free survival (PFS) were 93.7% (95CI 87.0-97.0) and 66.5% (95CI57.8-73.8), respectively. After the application of the A-HIPI model in our cohort of patients, c-statistics were 0.644 (95CI 0-56-0.73) for 5-year PFS and 0.78 for 5-year OS (95CI 0.63-0.92). Calculated 5-year OS and PFS ranged from 0.57 to 0.98 and from 0.52 to 0.88, respectively (Figure 1). When evaluating the performance of the IPS, c-statistics were 0.65 (95CI 0.56-0.73) and 0.77 (95CI 0.61-0.92) for 5-year OS. The two models were then compared with the AIC, with the A-HIPI yielding lower values for OS (ΔAIC 1.99), but higher values for PFS (ΔAIC 2.77). Summary/Conclusion: In this study we validated the ability of the A-HIPI to predict 5-year OS and PFS in aHL, obtaining discrimination statistics similar to the ones reported by the authors in both the development and the validation dataset.Keywords: Hodgkin’s disease, Prognosis