Advanced stage Hodgkin lymphoma international prognostic index (A-HIPI) in classic Hodgkin lymphoma and its comparison with other clinical prediction models

Aim: The prognosis of advanced-stage classical Hodgkin lymphoma (cHL), has improved with doxorubicin-based combination chemotherapy and PET/CT-guided treatment modification. Thus, the prognostic capacity of IPS models has decreased. Advanced Stage Hodgkin Lymphoma International Prognostic Index (A-HIPI) was found to be superior to IPS models for the population in which it was developed. This study aimed to validate A-HIPI in our population, compare it with other clinical prediction models, and determine the appropriate model for advanced-stage cHL. Material and Method: Patients who were diagnosed with advanced-stage cHL between 2005–2018 were retrospectively evaluated. By calculating IPS-7, IPS-3, and A-HIPI scores, in the entire sample, patients aged ≤65 years and >65 years; C-index (Harrell's Concordance Index) was used for discrimination, calibration curves, calibration intercepts (CI) and calibration slope (CS) were used for calibration. Models were compared with Akaike's Information Criteria (AIC). Results: Two hundred and seven patients were enrolled and the age range of these patients was 18–82 years (median: 37 years) with 19 patients (9.2%) aged >65 years. Herein, 28%, 37.2%, and 34.8% patients had disease stages 2B, 3, and 4, respectively. With a median follow-up of 75 months, 37 patients (17.9%) died. The 5-year PFS and OS were 67% and 84.9%, respectively. All three models were found to be prognostic for PFS and OS in the regression analyses. The A-HIPI model appeared to be well calibrated for PFS and OS, excluding the patient group aged >65 years. With A-HIPI, the respective C-index for PFS and OS was 0.591 and 0.726; whereas, with IPS-7 it was 0.600 and 0.684, and with IPS-3 it was 0.619 and 0.705, respectively. The lowest AIC value for OS was with A-HIPI (A-HIPI, IPS-7 ΔAIC: 12.8; A-HIPI, IPS-3 ΔAIC: 9.7). The lowest AIC value for PFS was with IPS-3 (IPS-3, A-HIPI ΔAIC: 1.3). Conclusion: 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 early 2000's in Turkey. The A-HIPI model was observed to have 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65 years, as IPS models are out of date and A-HIPI has not been validated for this group. Keywords: Clinical Prediction Models, IPS, A-HIPI, Prognostic score, Prognosis