Clinical Efficacy of Bendamustine Plus Rituximab (BR) for B-cell Relevant Indolent Non-Hodgkin's Lymphoma and Role of β2-MG in Predicting the Efficacy of BR Regimen: A Real-World Retrospective Study in China

BACKGROUND: Domestic bendamustine has been approved for appearing on the market in China in the past two years. The report on bendamustine plus rituximab (BR) in the treatment of Chinese B-cell-associated indolent non-Hodgkin's lymphoma (iNHL) has not yet been published. This study probed into clinical efficacy of the BR regimen for B-cell-associated iNHL in China as well as the value of β2-microglobulin (β2-MG) as a prognostic factor. METHODS: We retrospectively analyzed clinical data of 73 B-cell-associated iNHL patients who received BR treatment in The First Affiliated Hospital, College of Medicine, Zhejiang University from January 2020 to January 2021, including clinical characteristics, therapies, therapeutic efficacy, and prognosis-related factors. Thirty-three patients (45.2%) did not receive any other treatment before the BR regimen, and other patients received CHOP, R-CHOP, and other regimens in the past. The cutoff date for follow-up was May 2021. Clinical characteristics of patients were analyzed. The clinical efficacy of the BR regimen was evaluated. Differences of β2-MG expression before and after treatment were analyzed between the CR+PR group and the SD+PD group. Main outcomes were progression-free survival (PFS) and overall survival (OS). A multivariate Cox regression model was taken to analyze prognostic factors relative to survival rate of patients, and adverse events (AEs) during treatment. RESULTS: The objective response rate (ORR) of B-cell-associated iNHL patients who received BR regimen as first-/multiline treatment was 79.5%, with complete response (CR) of 37.0%, partial response (PR) of 42.5%, median PFS of 12.1 months (95% confidence interval (CI): 10.9-13.2), and median OS of 15.5 months (95% CI: 14.8-16.1). Before treatment, there was no statistical significance in the β2-MG level between the CR+PR group and the SD+PD group (p > 0.05). After treatment, the β2-MG level in the CR group was noticeably lower than that in the SD+PD group (p < 0.05). The β2-MG level in the CR+PR group decreased conspicuously after treatment (p < 0.05). The β2-MG level in the SD+PD group after treatment was not notably different from that before treatment (p > 0.05). According to the median expression level of β2-MG before treatment, patients were divided into two groups. The average PFS of the low expression group was 12.69 ± 0.77 months, which was longer than the high expression group (10.13 ± 0.74 months), but the difference between the groups was not statistically significant (p > 0.05). Multivariate Cox regression analysis showed that B-cell-associated iNHL subtype was the independent prognostic marker most likely to affect PFS of patients (p = 0.051). Incidence of any grade of AEs in all patients was 32.9% (24/73). CONCLUSION: B-cell-associated iNHL patients who received BR regimen had favorable clinical efficacy and were tolerable to AEs. Though the β2-MG level in this study could not be used to predict clinical outcome, a lower level before treatment seemed to be implicated in better survival outcomes of patients. Our research also unraveled that B-cell-associated iNHL subtype may be a key factor to patient's prognosis. Overall, this study offers some important insights into clinical application of the BR regimen for Chinese B-cell-associated iNHL patients.