Outcomes Following Intolerance to Tacrolimus/Sirolimus Graft-versus-Host Disease Prophylaxis for Allogeneic Hematopoietic Cell Transplantation.

Although tacrolimus and sirolimus (TAC/SIR) is an accepted graft-versus-host disease (GVHD) prophylaxis regimen following allogeneic hematopoietic cell transplantation (HCT), toxicity from this regimen can lead to premature discontinuation of immunosuppression. There are limited studies reporting outcomes and subsequent treatment of patients with TAC/SIR intolerance. This study was conducted to assess the outcomes of patients with TAC/SIR intolerance and guide their subsequent management. We retrospectively analyzed transplantation outcomes of consecutive adult patients at Moffitt Cancer Center who underwent allogeneic HCT with TAC/SIR as GVHD prophylaxis between 2009 and 2018. TAC/SIR intolerance was defined as discontinuation of either TAC or SIR due to toxicity before post-transplantation day +100. A total of 777 patients met the inclusion criteria. The median duration of follow-up was 22 months (range, 0.2 to 125 months). Intolerance occurred in 13% (n = 104) of the patients at a median of 30 days (range, 5 to 90 days). The most common causes of intolerance were acute kidney injury (n = 53; 51%), thrombotic microangiopathy (n = 31; 28%), and veno-occlusive disease (n = 23; 22%). The cumulative incidence of grade II-IV acute GVHD at 100 days was 50% (95% CI, 39% to 64%) in the TAC/SIR-intolerant patients and 25% (95% CI, 22% to 29%) in patients tolerant to this regimen (P < .0001). In multivariate analyses, the incidence of grade II-IV 4 acute GVHD was significantly higher in the TAC/SIR-intolerant patients (hazard ratio [HR], 2.40; 95% CI, 1.59 to 3.61; P < .0001). Similarly, in multivariate analyses, the TAC/SIR-intolerant patients had a higher incidence of chronic GVHD (HR, 1.48; 95% CI, 1.03 to 2.12; P = .03). The nonrelapse mortality (NRM) at 1 year was 47% (95% CI, 38% to 59%) in the TAC/SIR-intolerant patients and 12% (95% CI, 10% to 15%) in those tolerant to the regimen (P < .0001). The 2-year relapse-free survival was 35% (95% CI, 25% to 44%) in the TAC/SIR-intolerant patients and 60% (95% CI, 57% to 65%) in the TAC/SIR-tolerant patients (HR, 2.30; 95% CI, 1.61 to 3.28; P < .0001). Intolerance stratified by early (≤30 days) versus late (31 to 100 days) significantly affected the cumulative incidence of acute GVHD at 75% (early; 95% CI, 59% to 94%) versus 33% (late; 95% CI, 21% to 50%) (P = .001), as well as the cumulative incidence of NRM at 61% (early; 95% CI, 48% to 77%) versus 35% (late; 95% CI, 24% to 51%) (P = .006). Most patients who developed TAC/SIR intolerance were switched to an alternative 2-drug regimen (71 of 104; 68%), most commonly mycophenolate mofetil in addition to continuing TAC or SIR (68 of 71; 96%). Overall, TAC/SIR intolerance was associated with poorer outcomes. Early intolerance contributed to a higher risk of acute GVHD, increased NRM, and inferior survival. Patients with early intolerance were often switched to an alternative agent, and patients with late intolerance tended to be continued on single-drug therapy without substitution. The use of single-drug versus 2-drug regimens after intolerance did not appear to affect outcomes. Management strategies to mitigate the risks of intolerance are warranted.