Introduction: Our goal is to investigate the external validity of two previously developed prognostic models for overall survival (OS) and progression free survival (PFS) using a scoring system counting unfavorable risk factors (age, performans status, bone marrow involvement, gamma globulin level and fibrinogen level) in elderly patients with a classical Hodgkin lymphoma (cHL)
Methods: The performance of the prediction models was evaluated on a retrospective cohort of patients ≥ 59 years with newly diagnosed cHL treated in eight hospitals in France. Model discrimination was evaluated by computing hazard ratio (HR) across risk groups. A comparison with the International Prognostic Score (IPS) was performed using ROC curves.
Results: 288 patients were included (November 1990 –June 2015): median age at diagnosis was 70 years (range, 59-93), 55% were male, 53% presented with B symptoms, 25% had a PS>2, 61% had Ann Harbor stage III/IV, 26% had at least one comorbidity scored 3 or 4 on CIRS.
Median follow up is 64 months (0-232). 25% of patients have progressed or relapsed and 103 patients died, 40% within the first year of treatment.
OS and PFS at 36 months were 72.1% [95% CI: 66.2%; 77.1%] and 63.5% [57.5%; 68.9%], respectively.
On 188 evaluable patients, HR for PFS were 8.2, 7.9, and 9.6 for the presence of 1, 2, and 3/4 factors respectively (reference=absence of factor).
On 215 evaluable patients, HR for OS were 1.3, 2.2 and 4.0 for the presence of 1, 2 and 3 factors respectively. Patients with 0, 1, 2 and 3 factors had a 3 years OS of 82.3, 77.3, 69.5 and 38.1% respectively (p=0.001). The areas under the curve were not significantly different (p=0.9754) for OS between our score and IPS.
Conclusion: These results provide evidence of a satisfactory discrimination ability of the prediction model for OS, with a predictive power similar to IPS. A larger evaluable cohort is required to have a better prognostic model for PFS. This study is a first step in establishing the external validity of these models before use in clinical practice, together with geriatric assessment, in order to offer adequate treatment to patients.