Introduction Radiotherapy (RT) is the single most effective modality to achieve local control
of Hodgkin lymphoma (HL) [1]. However, large treatment fields of the past are associated with an increased morbidity
and mortality in long-term survivors [2]. In the management of pediatric patients with HL (pHL), recent treatment protocols
use a response-based approach to achieve omission of consolidating RT following combination
chemotherapy due to the risk of late toxicity. Event-free survival rates decrease
with up to 10% when RT is omitted, but salvage treatment is effective and overall
survival rates are similar so far [3]
[4]. However, intensive salvage treatment is also associated with significant late effects.
It is recognized that most relapses occur within the initially involved sites if RT
is not used [5]. Here, we analyze the relapse-localization relative to the initially involved site,
and if irradiated, to the irradiated site in pHL.
Methods The Danish Childhood Cancer Registry was used to identify children diagnosed with
HL and those who relapsed from 1990–2018 at two institutions. Patient characteristics,
treatment details (including RT plans), and diagnostic imaging were collected. We
merged scans from the time of diagnosis and the time of relapse using the Eclipse
treatment planning system (Varian Medical Systems) and visually assessed the relapse-localization
relative to the initially involved site and, if irradiated, the irradiated site.
Results A total of 130 children were diagnosed with HL and 18 relapses were registered. Out
of 18 patients 3 had refractory disease resulting in 15 relapses and a crude relapse-rate
of 11.5%. The patients’ median age at time of diagnosis was 13 years (range 5–17)
and the median time to relapse was 6 months (range 2–59). Out of 15 patients 14 relapsed
within the initially involved site. Six patients had received RT and 5 relapsed within
both the initially involved and irradiated site (3 single site, 2 multiple sites).
One patient relapsed outside of both the initially involved site and the irradiated
site. Out of 5 patients with initially bulky disease, 2 relapsed within (no RT) and
3 relapsed outside (2 irradiated, 1 not) the site of bulky disease.
Conclusion It is reasonable to conclude that most relapses occur within the initially involved
sites, and that RT improves local control. However, the number of relapses is small,
and it is difficult to draw conclusions regarding the relapse pattern. Relapses-localization
in pHL from all of Denmark will be analyzed.
