The validation of advanced-stage Hodgkin lymphoma international prognostic index (A-HIPI) in Turkish patients with classical Hodgkin lymphoma

In advanced-stage classical Hodgkin lymphoma (cHL), the prognosis has improved due to combination chemotherapy and PET/CT-guided treatment modification, resulting in a decreased prognostic capacity of IPS models. A novel model, A-HIPI, was found to be superior to IPS in predicting prognosis. In this study, we aimed to validate the A-HIPI model among Turkish cHL patients and compare its performance with other clinical prediction models. We retrospectively evaluated patients diagnosed with advanced-stage cHL between 2005 and 2018 at Istanbul University-Cerrahpaşa. We used IPS-7, IPS-3, and A-HIPI scores to calculate the C-index (Harrell's Concordance Index) for discrimination; calibration intercept, and calibration slope for calibration. The models were compared using Akaike's Information Criterion (AIC). Two hundred and seven patients were enrolled with a median follow-up of 75 months, 37 patients (17.9%) died. The 5-year PFS and OS were 66.6% and 84.9%, respectively. All three models were found to be prognostic for PFS and OS. The A-HIPI model was well-calibrated for PFS and OS in patients aged ≤65 years, but not calibrated for patients aged > 65 years. With A-HIPI, the respective C-index for PFS and OS was 0.605 and 0.740; whereas, for IPS-7 it was 0.598 and 0.684, and for IPS-3 it was 0.624 and 0.705. The lowest AIC value for OS was observed with the A-HIPI. The lowest AIC value for PFS was observed with IPS-3. This study validated the A-HIPI model in a homogeneous patient group for treatment protocol, with all follow-ups performed at a single center after the early 2000s in Turkey. The A-HIPI model demonstrated better performance than other models, except for patients aged > 65 years. A new clinical prediction model is needed for patients > 65 years, as IPS models are out of date and A-HIPI has not been validated for this group.