(en) Tumour bulk is an established prognostic factor in Hodgkin lymphoma (HL) but most patients with limited-stage (LS) HL do not have 'bulk' by standard binary definitions. In the RAPID trial, maximum tumor diameter (MTD) was associated with risk of relapse for LS-HL patients achieving PET-negativity after ABVD chemotherapy. We aimed to externally validate these findings in the H10 trial. Patients with stage I/IIA HL, without mediastinal bulk, who achieved PET-negativity with ABVD were included. 'PET-negative' patients received 3x ABVD plus radiotherapy (n=208) or 3x ABVD alone (n=211) in RAPID, and 3-4x ABVD plus radiotherapy (n=556) or 4-6x ABVD alone (n=303) in H10. Baseline MTD was measured by CT. MTD was strongly associated with event-free survival (relapse or HL-related death) in H10 (HR=1.22, 95%CI:1.07-1.38, p=0.003), a similar effect to the RAPID trial (HR=1.19, 95%CI:1.02-1.39, p=0.02), giving an estimated 21% increase in HL-risk per centimetre MTD (HRpooled=1.21, 95%CI:1.09-1.33, p<0.001). Findings were consistent when adjusting for baseline risk stratification and chemotherapy cycles. The effect sizes were similar for patients treated with chemotherapy alone (HRpooled=1.19, 95%CI:1.01-1.35, p=0.005) and combined modality treatment (ABVD plus radiotherapy; HRpooled=1.24, 95%CI:1.05-1.46, p=0.009) with no evidence of a differential effect (pinteraction=0.97). Treatment modality and MTD were independent risk factors; patients with higher MTD receiving chemotherapy alone had the greatest risk of relapse. This international validation study confirms that MTD is strongly associated with the risk of relapse for LS-HL patients achieving PET-negativity. These findings refine assessment of risk in LS-HL and can inform clinical discussions for risk-adapted application of radiotherapy. NCT00943423 and NCT00433433.
Phillips, E. H., Counsell, N., Illidge, T. M., André, M., Aurer, I., Fiaccadori, V., Fortpied, C., Neven, A., Federico, M., Barrington, S. F., Raemaekers, J. M., & Radford, J. (2025). Maximum Tumor Diameter is Associated with Relapse Risk in Limited-Stage Hodgkin Lymphoma: An International Study. Blood Advances, 9(9), 2266-2274. https://doi.org/10.1182/bloodadvances.2024015140 (Original work published 2025)