Patterns of Relapse After Salvage Autologous Stem Cell Transplant for Hodgkin's Lymphoma: Should Sites of Relapse Relative to Initially Involved Sites Be Used to Guide Indications for Peri-Transplant Radiation Therapy

Purpose: We aimed to assess patterns of relapse in patients undergoing salvage autologous stem cell transplant (ASCT) for relapsed Hodgkin lymphoma in the modern era with the hypothesis that patients who suffer a relapse at initially involved sites are at increased risks of relapse post-ASCT that may help guide the application of peri-transplant radiation therapy.

Methods and materials: A retrospective review was conducted of 38 patients undergoing ASCT between 2002 and 2017 for relapsed or refractory Hodgkin lymphoma. The site of relapse at the time of ASCT and subsequent relapses were compared with sites of the initial involvement at the time of diagnosis using follow-up imaging (most commonly positron emission computed tomography). Relapse and overall survival rates were calculated from the date of ASCT using the Kaplan-Meier method with a multivariate analysis, completed using a Cox multivariate analysis.

Results: The median follow-up time was 38 months (interquartile range, 18-66 months). Twenty-two patients (58%) suffered a relapse after ASCT at a median time to relapse of 9.1 months (interquartile range, 2.9-12.3 months) with a 5-year risk of relapse of 58% (95% confidence interval [CI], 41%-75%). On univariate analysis, relapse at an initially involved site was significant for higher rates of relapse at 71% at 5-years (95% CI, 52%-90%) compared with relapse at initially uninvolved sites at 30% (95% CI, 2%-58%; P = .05). The relapse rate was also significantly higher in patients age <30 years at the time of diagnosis at 80% (95% CI, 59%-100%) compared with 40% (95% CI, 18%-62%) at 5 years in patients aged >30 years (P < .01). On multivariate analysis, relapse at initially involved sites was significant for higher rates of relapse (hazard ratio: 8.3; 95% CI, 1.2-57.4; P = .03).

Conclusions: Relapses at initially involved sites may potentially increase the risk of relapse after ASCT. Additional studies are needed to clarify whether this should be used as an additional factor to guide recommendations for peri-transplant radiation therapy.