A real-world study of combined modality therapy for early-stage Hodgkin lymphoma: too little treatment impacts outcome

Multiple clinical trials have assessed de-escalation strategies from combined modality therapy (CMT) to chemotherapy-alone for the treatment of early-stage classical Hodgkin lymphoma (cHL), confirming similar outcomes. The application of these data to the real-world is limited, however. We conducted a retrospective, multicenter cohort study comparing CMT vs chemotherapy-alone in patients with early-stage cHL (stage IA-IIB) treated between January 2010 and December 2020. Positron emission tomography (PET) scans after chemotherapy cycle 2 (PET2) were independently reviewed by a nuclear radiologist (Deauville score >= 4, positive; <= 3, negative). Patient outcomes were compared by using an intention-to-treat analysis. Among 125 patients (CMT, n = 63; chemotherapy-alone, n = 62) with a median follow-up of 59.8 months (95% CI, 48.6-71.0), no differences in overall survival were observed (5-year overall survival, CMT 98.0% vs chemotherapy-alone 95.1%; log-rank test, P = .38). However, there was reduced progression-free survival (PFS) with chemotherapy-alone among all patients (2-year PFS, CMT 95.1% vs chemotherapy-alone 75.3%; log-rank test, P = .005) and in those with bulky (n = 43; log-rank test, P < .001), unfavorable (n = 81; log-rank test, P = .002), or PET2-positive (n = 15; log-rank test, P = .02) disease. No significant differences in PFS were seen for patients with non-bulky (log-rank test, P = .35), favorable (log-rank test, P = .62), or PET2-negative (log-rank test, P = .19) disease. Based on our real-world experience, CMT seems beneficial for patients with early-stage cHL, especially those with PET2-positive and unfavorable disease. Chemotherapy-alone regimens can lead to comparable outcomes for patients with favorable, non-bulky, or PET2-negative disease. We conclude that although results seen in clinical trials are replicated in certain patient subgroups, other subgroups not fitting trial criteria do poorly when radiotherapy is excluded.