ASH 2024 | Follow-up from the RAPID trial: involved-field radiotherapy versus no further treatment in HL

The abstract that I presented was giving the long-term follow-up data on the RAPID trial in stages 1A or 2A Hodgkin lymphoma. And just to remind colleagues, what we did back in 2003 is set up a trial in limited-stage Hodgkin lymphoma, seeing if we could use PET scanning to identify a group of individuals with a very good prognosis for whom consolidation radiotherapy was not required. And so in that UK-wide trial, we recruited 602 patients. They all had three cycles of standard ABVD chemotherapy, and they then had a PET scan. And those that were PET negative following central review, and this was 75% of the patients, they were randomized between no further treatment and involved-field radiotherapy. And so 420 patients who were PET negative were randomized and we looked at the results and these were published back in 2015 in the New England Journal of Medicine and that showed that the survival between the two arms was identical although the progression-free survival was a little better in those that had received radiotherapy but of course for that improvement we had to irradiate everybody to get to that point. An editorial at the time showed that or indicated that overall survival was the key metric here and that five years of follow-up, which is what we had at the time, was simply too short to be able to make any definitive conclusions. And so this work was about providing much longer follow-up for the same cohort of patients. Of course, at this length of time, many of the patients have been discharged from hospital back to primary care and individual trial sites that don’t have the resources to follow these patients up. So what we decided was to obtain these data by linking the RAPID cohort with the National Cancer Registry so that we could find out who had died and who was alive and what the cause of death was. And so by working with the various national bodies, we’ve been able to match 76% of the RAPID patients in England and Wales to the cancer registry. And that allowed us to look at survival in that group. And also we took into account all the follow-up that we already had for those patients that were not matched. So as a result of that, we had a median follow-up of 16 years, which is much longer than many clinical trials have access to. And in that, once again, we found that there was no difference. There was no evidence of difference in survival between those that had received radiotherapy and those who did not. In terms of the deaths, there were 11 in the involved-field radiotherapy group, 15 in the no further treatment group, no evidence of any difference. The top four causes of death were respiratory causes, non-Hodgkin lymphoma, cardiac causes, and carcinoma. Interestingly enough, in the randomized group, there was only one death from Hodgkin lymphoma, and that was in the involved-field radiotherapy group. If we look at the PET positive patients, those that were not randomized, there were seven deaths from Hodgkin lymphoma, indicating that a positive PET scan is associated with a poor prognosis. So the conclusion from this is that after prolonged follow-up, we can find no evidence of benefit or disbenefit from giving radiotherapy to PET-negative patients, that the survival curves are overlapping, and that we can use this novel way of matching data with nationally available data sets to obtain this prolonged follow-up. And the final thing we can say is that as a result of these data, involved-field radiotherapy really only needs to be considered in early-stage Hodgkin lymphoma in those patients who are deemed at high risk of recurrent disease. The rest do very well with chemotherapy alone if they become PET negative. And what we’re planning to do now is not only look at the fatalities, but also the incidence of second cancers that have been non-fatal so far and also the incidence of cardiovascular disease so that we can get an overall picture of the benefits, disbenefits between radiotherapy and no further treatment in this cohort of patients.

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