Evaluation of the International Prognostic Score (IPS-7) and a Simpler Prognostic Score (IPS-3) for advanced Hodgkin lymphoma in the modern era

Abstract

The International Prognostic Score (IPS-7) is the most commonly used risk stratification tool for advanced Hodgkin lymphoma (HL), however recent studies suggest the IPS-7 is less discriminating due to improved outcomes with contemporary therapy. We evaluated the seven variables for IPS-7 recorded at study entry for 854 patients enrolled on Eastern Cooperative Oncology Group 2496 trial. Univariate and multivariate Cox models were used to assess their prognostic ability for freedom from progression (FFP) and overall survival (OS). The IPS-7 remained prognostic however its prognostic range has narrowed. On multivariate analysis, two factors (age, stage) remained significant for FFP and three factors (age, stage, haemoglobin level) for OS. An alternative prognostic index, the IPS-3, was constructed using age, stage and haemoglobin level, which provided four distinct risk groups [FFP (P = 0·0001) and OS (P < 0·0001)]. IPS-3 outperformed the IPS-7 on risk prediction for both FFP and OS by model fit and discrimination criteria. Using reclassification calibration, 18% of IPS-7 low risk patients were re-classified as intermediate risk and 13% of IPS-7 intermediate risk patients as low risk. For patients with advanced HL, the IPS-3 may provide a simpler and more accurate framework for risk assessment in the modern era. Validation of these findings in other large data sets is planned.

Keywords: ABVD; Hodgkin lymphoma; International Prognostic Score; Stanford V; prognostic score.

Figure 1

Freedom from progression (FFP) and overall survival (OS) according to the International Prognostic Score (IPS) factors (a, b) and the simpler prognostic index IPS-3 (c,d)

Figure 2

Time weighted area under the receiver operator characteristics curves (AUC) for freedom-from progression (A) and overall survival (B) according to the International Prognostic Score factors IPS-7 and simpler prognostic index IPS-3.

Figure 3. Kaplan-Meier (KM) analysis of observed and predicted (by IPS-7 and IPS-3) FFP and OS for patients whose risk categories were reclassified by IPS-3

N=153 patients low risk by IPS-7 but intermediate risk by IPS-3 (a1, a2); n=54 patients intermediate risk by IPS-7 but low risk by IPS-3 (b1, b2); n=28 patients high risk by IPS-7 but intermediate risk by IPS-3 (c1,c2). The predicted survival rates were produced by univariate Cox models using IPS-3 and IPS-7 as covariates.