Combined modality treatment consisting of 4 cycles of chemotherapy (CT) followed by involved field radiotherapy (IF-RT) is the standard treatment for early unfavourable HL. In our prior trial for this group of patients (HD8), overall survival (OS) and freedom from treatment failure (FFTF) at 5 years were 91% and 83%, respectively. The HD11 trial thus addressed two major questions: (1) improving outcome by intensifying CT (4xABVD vs. 4xBEACOPPbaseline; Bbas) and (2) defining the best radiation dose (30Gy vs. 20Gy IF-RT).
Between May 1998 and January 2003, 1395 eligible patients aged 16–75 years with untreated early unfavourable stage HL (CS I, IIA with at least one of the risk factors large mediastinal mass (a), extranodal disease (b), elevated ESR (c) or ≥ 3 nodal areas (d); IIB with risk factors c and/or d) were randomized into one of the following 4 treatment arms: 4xABVD + 30Gy (A), 4xABVD + 20Gy (B), 4x Bbas + 30Gy (C) or 4x Bbas + 20Gy (D). Since there are strong indications for an interaction between CT- and RT-doses, a comparison of pooled treatment arms (A+B vs. C+D for comparison of 4×ABVD vs. 4× Bbas and A+C vs. B+D for comparison of 30Gy IF-RT vs. 20Gy IF-RT) would be misleading. Therefore all treatment arms were analysed separately.
Patient characteristics were well balanced between the 4 arms (median age 33 years, 49% male, 6% stage I, 29% B-symptoms). CT- and RT-related acute toxicity occurred significantly more often in the arms with the more intensive therapy (CT: 74.1% vs. 51.8%; RT: 12.3% vs. 5.5%). The complete remission rate 3 months after end of therapy was 94.1% for the whole group and did not differ significantly between the 4 arms. The 5-year estimate of FFTF (primary endpoint) is 85.0% (OS 94.5%, PFS 86.0%).
Bbas is more effective than ABVD if followed by 20Gy IF-RT (5y-FFTF difference 5.7%, 95%-CI [0.1%; 11.3%]). This effect does not exist in combination with 30Gy IF-RT (5y-FFTF difference 1.6% [-3.6%; 6.9%]). Similar results are observed for the RT-question: After 4 cycles of Bbas, 20Gy is not inferior to 30Gy (5y-FFTF difference -0.1%, 95%-CI [-5.1%; 4.9%]), whereas after 4xABVD, a relevant inferiority of 20Gy cannot be excluded (-4.0% [-9.5%; 1.4%]).
A reduction of RT dose from 30Gy to 20Gy IF-RT seems to be justified only in combination with Bbas, but not with a less effective chemotherapy such as 4xABVD. Patients will benefit from an intensified CT such as Bbas only in combination with 20Gy IF-RT but not with 30Gy IF-RT.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.