Practice Patterns Pre-CART for Aggressive B-Cell Lymphomas: Patient Selection and Real World Salvage and Bridging Practices

Introduction

The treatment of aggressive B-cell NHL has evolved rapidly over the last 5 years, owing to the FDA approval of 3 CD19 CAR T-cell constructs (CARTs) along with other novel targeted therapies. Real world practice data suggest that CARTs have been successfully administered in populations typically excluded from clinical trials. However, data on how to best utilize novel targeted agents as a pathway to CARTs and feasibility of CARTs in rare histologies remains limited. This retrospective multicenter study describes patient (pt) selection and practice patterns in pts treated with CD19 CARTs and provides insight on feasibility of CARTs in special populations.

Methods

Adult pts with R/R aggressive B-cell NHL treated with CD19 CARTs between 2015- 2020 across 12 US academic centers were identified. Data on demographic and clinical characteristics, disease and toxicity outcomes were collected. Univariate analyses (UVA) were performed to determine impact of demographic/clinical variables on survival. Survival curves were calculated using Kaplan-Meier method. Subgroup analysis was performed for pts with secondary central nervous system lymphoma (sCNSL).

Results

Clinical and demographic features were recorded from 400 pts (Table 1). Median age was 59 years (range 18-84). Of 271 pts with immunohistochemistry data, 79 (29%) had double-expressor lymphoma. Of 178 pts with FISH data captured, 62 (35%) had double/triple-hit lymphoma. Most common histological subtypes included 271 (68%) pts with de novo DLBCL, 81 (20%) with transformed FL, 13 (3%) with Richter's syndrome, and 8 (2%) with PMBCL. Rare histologies included 7 (2%) with transformed MZL, 5 (1%) with PTLD and 2 (0.5%) with grey zone lymphoma. 24 (6%) pts had sCNSL at time of CART apheresis. Two (0.5%) pts were HIV-positive.

Median number of lines of therapy prior to CART was 2 (range 1-8); 182 (46%) pts received ≥ 3 lines. 114 (28%) pts previously had an autologous stem cell transplant. Targeted therapies used as salvage regimens at any point prior to CART are listed in Table 2: commonly used salvage targeted therapies included lenalidomide based therapy (imids, n=37, 9%), BTK inhibitors (BTKis, n=30, 8%), checkpoint inhibitors (CBIs, n=17, 4%) and polatuzumab-containing regimens (n=10, 3%). 2 (1%) pts received loncastuximab, and no pts received tafasitamab.

Six (1.5%) pts proceeded to CART despite complete response to most recent pre-CART therapy. 191 (48%) pts received bridging between apheresis and CART infusion, choice of bridging noted in Table 2: the majority received chemotherapy (n=103, 54%); 28 (15%) received radiation (XRT); 25 (13%), 24 (13%) and 18 (9%) pts received imids, polatuzumab-containing regimens, or BTKis, respectively.

With median follow-up of 22.4 months (mo) for the overall group, median (m) PFS was 11 mo (n=363); mOS, was 27 mo (n=397; Fig 1). Pts with sCNSL had a mPFS and mOS of 2 and 4 mo, respectively (Fig 1). On UVA, factors predicting poorer PFS and OS in the overall group included ≥3 pre-CART lines (p </= 0.004), use of bridging (p </=0.001), IPI 4-5 at apheresis (p=0.014), LDH elevation at apheresis (p=/<0.001), and sCNSL (p </= 0.013).

For outcomes according to bridging regimens: mPFS after CART for most commonly used systemic bridging therapies was 86 days (d) for platinum-based chemotherapy, 77 d for imids, 90 d for BTKis, 98 d for polatuzumab-bendamustine/rituximab, and 274 d for XRT. Median PFS for XRT bridging (274 d) was statistically better when compared to mPFS for listed systemic therapies combined (p <0.05) (Fig 2).

Conclusion

Survival outcomes with CARTs in our data set are consistent with those reported in clinical trial settings. CARTs are utilized in real world practice in rare subsets of aggressive R/R B-cell NHL not routinely included in clinical trials. Despite early data suggesting pts with sCNSL benefit from CART, our data suggest outcomes with CART are dismal in this group. Targeted therapies including imids, polatuzumab, BTKis and CBIs are feasible choices for salvage and/or bridging as a pathway to CARTs. Bridging with XRT resulted in improved mPFS post CART as compared to bridging with systemic therapies and suggests differences in pt selection for each with systemic therapies likely favored in those with more widespread disease burden. Minimal use of CD19-targeted agents pre-CART is attributed to later approval of these agents and concern for potential loss of CD19 antigen leading to CART resistance.

Figure 1

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Figure 1

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