Lymphopenia and outcomes of bendamustine-based therapy in follicular lymphoma.

e19540 Background: Bendamustine plus rituximab (BR) is the preferred first-line immunochemotherapy for follicular lymphoma (FL) due to its efficacy and generally favorable adverse effect profile. However, it often causes prolonged lymphopenia, and impaired lymphocyte recovery after BR therapy has been recognized as a risk factor for opportunistic infections. On the other hand, little is known about the impact of profound lymphopenia on the overall treatment outcomes of BR. We examined the relationship between lymphopenia and treatment response in patients with FL who received BR at our institution. Methods: We retrospectively identified patients who received BR as first-line therapy for FL at the Lifespan Cancer Institute between October 2008 and November 2020. We used log-transformed absolute lymphocyte count (ALC) as the potential prognostic variable, integrated as the area under curve based on all available laboratory tests over the typical duration of BR (6 months). Outcomes included complete response to BR determined by post-treatment positron emission tomography or computed tomography, survival, and occurrence of hospitalization or herpes zoster on therapy. The association between ALC and survival or binary endpoints was examined using Cox or logistic models, respectively, adjusting for age, sex, cumulative bendamustine dose, and baseline ECOG performance status (PS). Results: We included 53 patients followed for a median of 69 months from start of BR. At treatment initiation, most patients had a PS of 0-1, stage III or IV disease, and high-risk lymphoma as defined by the Follicular Lymphoma International Prognostic Index (FLIPI) (Table). We observed an association between higher ALC during treatment and increased rates of CR (adjusted odds ratio, 2.50, 95% CI 1.04 – 6.00; p = 0.040), longer progression free survival (PFS) (adjusted hazard ratio [HR], 0.53, 95% CI 0.31 – 0.92, p = 0.023), and overall survival (OS) (HR, 0.45, 95% CI 0.23 – 0.87, p = 0.018). Higher ALC values during treatment and 1 month after treatment initiation were also associated with lower probability of hospitalization (p = 0.048 and p = 0.028, respectively). We did not find a statistically significant association between ALC and rates of zoster infection, but the number of observed events was low (n = 6). Conclusions: Our results suggest an association between higher ALC values during bendamustine therapy and improved treatment outcomes. Improvement in PFS, OS, and hospitalization rates with higher ALC values may be due relative preservation of nutritional balance and immune reserve. The association with survival should be confirmed in larger datasets and its potential mechanism elucidated.[Table: see text]