ORLANDO – Rituximab conferred a significant progression-free survival benefit in reduced intensity conditioning regimens for patients with B-cell non-Hodgkin lymphoma who underwent allogeneic hematopoietic cell transplantation, based on data from the Center for International Blood & Marrow Transplant Research.

Further, higher cumulative rituximab doses appeared to confer a benefit in overall survival.

Rituximab is frequently a component of reduced intensity conditioning (RIC) regimens in allogeneic hematopoietic cell transplantation (HCT), but there has been a “paucity of comparative data” for rituximab-containing (R-RIC) versus non–R-RIC conditioning regimens for allogeneic transplant patients, Narendranath Epperla, MD, of the Medical College of Wisconsin, Milwaukee, said during the combined annual meetings of the Center for International Blood & Marrow Transplant Research and the American Society of Blood and Marrow Transplantation.

Using data from the Center for International Blood & Marrow Transplant Research, Dr. Epperla and his colleagues identified 1,022 patients who received rituximab and 379 patients who did not with diffuse large B-cell lymphoma, follicular lymphoma, mantle cell lymphoma, and marginal zone lymphoma. The patients received their first RIC or non-myeloablative allogeneic HCT between 2008 and 2014. The donors were matched, and either related or 8x8 allele-matched unrelated; the graft source could be bone marrow or peripheral blood. Graft versus host disease (GVHD) suppression was calcineurin inhibitor based.

Patients who had received myeloablative conditioning, or who had received radioimmunotherapy or alemtuzumab were excluded, as were those who received alternative donor allografts.

Dr. Epperla and his colleagues factored in patient and disease characteristics, as well as differences in transplant regimen, in determining the adjusted cumulative incidence of relapse or progression, as well as the incidence of nonrelapse mortality.

In the multivariable analysis, overall survival did not differ between the R-RIC and the non–R-RIC cohorts (relative risk [RR] of all-cause mortality, R-RIC = 0.83, 95% CI 0.67-1.03, P = .09).

Based on the cumulative dose of rituximab that patients had received, though, “we noted that patients who got higher doses of rituximab had lower risk of nonrelapse mortality,” Dr. Epperla said. “Higher cumulative doses of rituximab seem to confer overall survival benefit.” This was true even though the higher rituximab doses had no significant effect on the risk of therapy failure, nonrelapse mortality, or the risk of progression/relapse.

When the cumulative rituximab dose was 2,000 to 3,375 mg/m², the hazard ratio for all-cause mortality fell to 0.43 compared to a cumulative rituximab dose of less than 1,000 mg/m² (95% confidence interval [CI] 0.21-0.90, P = .02).

Among the R-RIC group, there was a nonsignificant trend toward reduced risk of progression or relapse (relative risk of progression/relapse, R-RIC = 0.79, 95% CI 0.63-1.01, P = .055). However, the R-RIC group fared significantly better in terms of progression-free survival (RR of PFS, R-RIC = 0.76, 95% CI 0.62-0.92, P = .006).

After transplant, patients in the R-RIC group were no more likely than those in the non–R-RIC group to experience chronic GVHD (RR of GVHD, R-RIC = 1.15, 95% CI 0.96-1.39, P = .13). There was no difference in the adjusted curves of nonrelapse mortality between the groups (RR of nonrelapse mortality, R-RIC = 0.90, 95% CI 0.67-1.22, P = .51).

Also, there were no fatal cytopenias in the R-RIC arm, although the literature warrants some concern for increased risk of infection with rituximab, Dr. Epperla said.

At baseline, there were no significant differences in demographic characteristics between the nonrituximab and rituximab arms of the study population. More than 90% of patients were white, and 65% were male; the median age was 57 years (range, 18-74).

Patients had been diagnosed about 3 years before receiving HCT; about 60% of patients had a baseline Karnofsky performance score greater than 90, and the HCT comorbidity index was 2. About 86% of patients were chemosensitive, and patients in both study arms had received a median of three prior lines of therapy.

There were some differences in conditioning regimens between the two groups. “There were a significantly higher number of patients in the nonrituximab group who received fludarabine/busulfan, while there were a significantly high number in the rituximab group who received a fludarabine/cyclophosphamide-based conditioning regimen,” Dr. Epperla said. Follicular lymphomas were more common in the R-RIC arm, while diffuse large B-cell lymphomas were seen more in the non–R-RIC arm.

Given the survival benefit and similar rates of chronic GVHD seen in the retrospective analysis, a prospective, randomized head-to-head trial of R-RIC versus non–R-RIC is warranted, Dr. Epperla concluded.

During the postpresentation discussion, Dr. Epperla acknowledged the variability of the lymphomas in the study, but that there was no significant statistical effect of specific histologies on the findings in a subgroup analysis. Dr. Epperla added that the chemosensitivity status at transplant was checked to account for patient exposure to rituximab before RIC, and that there was no effect of prior rituximab exposure on the outcomes examined.

Dr. Epperla reported no conflicts of interest.

koakes@frontlinemedcom.com

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Adding rituximab to reduced intensity conditioning boosts PFS