Outcomes with Bridging Radiation Therapy Prior to CAR-T Cell Therapy in Pts with Aggressive B Cell Lymphomas

PURPOSE/OBJECTIVE(S)

Select patient (pts) with relapsed/refractory aggressive B cell lymphoma may benefit from bridging radiation (bRT) prior to anti-CD19-directed chimeric antigen receptor T cell therapy (CART). Here, we examined pt and treatment factors associated with outcome after bRT and CART.

MATERIALS/METHODS

We retrospectively reviewed adults with DLBCL who received bRT prior to axicabtagene ciloleucel 11/2017-12/2022. Clinical/treatment characteristics, response, and toxicity were extracted. Progression free survival (PFS), disease specific survival (DSS) and overall survival (OS) were modeled using Kaplan-Meier for events distributed over time, or binary logistic regression for disease response. Fisher's Exact Test or Mann-Whitney U methods were used.

RESULTS

Among 40 pts, 11 (28%) had limited stage disease at apheresis, and 14 (35%) received bRT in addition to bridging systemic therapy. Thirty-two (80%) pts received bRT post-leukapheresis. bRT was delivered with a median dose of 30 Gy (range: 4-46) in 10 fractions (range: 2-23). Eighteen (45%) pts received <30 Gy. Twenty-two pts (55%) received bRT comprehensively to all sites of disease, including 9 pts who had limited stage. Eleven pts had bulky disease (≥ 10 cm) at the time of bRT. After CART, 4 pts (10%) experienced Grade ≥3 cytokine release syndrome (CRS), 16 (40%) had Grade ≥2 CRS, and 16 (38%) had Grade ≥3 neurotoxicity. Twenty-three pts (57.5%) had CR at 30 days post-CART infusion. Nine had PR (22.5%), of whom 2 pts eventually developed CR at three months and 1 at nine months. Eight pts (20%) had either PD or SD. Of 23 pts who experienced CR, 11 relapsed-6 at three months and 5 at six months. At a median follow up of 9.6 months (95% CI: 6.6-16.2), 22 pts relapsed: 6 (27.3%) in-field, 10 (5.5%) out-of-field, 4 (18.2%) both, and 2 (9.1%) unknown. The median PFS was 8.87 months and median OS was 22 months. PFS at 1 year was 70% (53-82) and at 2 years was 42% (27-57). OS at 1 and 2 years was 72.5% (56-84) and 51% (34-65), respectively. Seventeen pts (42.5%) remain alive at last follow-up, 13 (76.5%) of whom have no evidence of disease (NED). On univariate analysis, OS and PFS at 1 year were 67% (43-83) and 49% (27-68) for those who received RT comprehensively (n = 22), and 41.9% (19-64) and 33.3% (14-54) for those who did not (n = 18; both p≤0.03). Disease bulk (≥10 cm) was associated with significant decrement in DSS (p = 0.03), but not PFS (p = 0.16) or OS (p = 0.24). Among pts treated comprehensively with bRT (n = 22), there was no association of tumor bulk with OS, PFS, or DSS (p>0.2). IPI ≥3 was associated with worse DSS (p = 0.045) and trended towards worse PFS (p = 0.054), but not OS (p = 0.23). There was no difference in PFS, OS, or DSS between pts who received bRT or chemoRT (p>0.3).

CONCLUSION

bRT and CART is a good treatment strategy for select pts with aggressive B cell lymphoma. When feasible, and with a caveat that other variables influence patient disposition, bRT for CART is associated with improved outcomes after comprehensive RT to all sites of disease.

Dorsal Column Myelopathy Following Intrathecal Chemotherapy for Leukemia

PURPOSE/OBJECTIVE(S)

Intrathecal (IT) methotrexate (Mtx) and/or cytarabine (AraC) improve CNS disease control in patients (pts) with hematologic malignancies. There are increasing number of case reports of irreversible, primarily dorsal column myelopathy in pts treated with IT chemotherapy. By describing the largest case series of myelopathy following IT chemotherapy, we aim to raise awareness about this devastating albeit rare complication.

MATERIALS/METHODS

We retrospectively reviewed 25 pts with leukemia who developed paraplegia following IT chemotherapy between 2/2006 and 9/2021. Clinical/treatment characteristics, response, and toxicity were extracted from the medical records.

RESULTS

Seventeen pts (68%) were male, 16 had B-cell ALL (64%), 4 had AML (16%), 2 had CML (8%), 2 had T-ALL (8%), and 1 had BPDCN (4%). The median age at diagnosis was 38 years (IQR 30-59). All pts required systemic salvage treatment after induction chemotherapy with a median number of 3 regimens received (IQR 2-5.5). In total, the median number of IT treatments was 19 per pt (IQR 14-27). Most pts (84%, n = 21) received single agent IT Mtx alternating with single agent AraC. Fifteen pts (60%) received triple IT therapy with a median of 3 treatments (IQR 0-8). Prior to the onset of myelopathy, 10 pts (40%) received allogeneic SCT and 9 pts (36%) were treated with radiation therapy. Median follow-up from diagnosis was 1.9 yrs (IQR 1.3-4.1). Myelopathy was progressive and irreversible in all pts (n = 25); 84% (n = 21) experienced sensory loss, and all pts had extremity weakness. Symptoms were ascending in 11 pts (44%) and descending in 4 pts (16%). Irreversible bowel/bladder incontinence developed in 12 pts (48%). CSF analysis at the time of symptom onset was negative for leukemia cells in most pts (n = 21, 84%) and showed malignant cells in 4 pts (16%). CSF studies showed elevated protein in 21 pts (84%). Myelin basic protein was elevated in all 13 assessed pts. On T2 weighted spinal MRI, all pts had enhancement of the dorsal columns, including 80% of pts with this dorsal column abnormality reported at the time of the study and 20% of pts (n = 5) with the dorsal enhancement noted retrospectively. Due to concern for occult disease, 20 pts (80%) received additional CNS-directed therapy after symptom onset. Twenty-two pts (88%) died at last follow-up. The time between neurological symptom onset and death was a median 3.5 months (IQR 2.6 and 5). Three pts (12%) are alive with paraplegia at a median of 4.4 years from symptom onset.

CONCLUSION

Dorsal column myelopathy is a rare but devastating condition that can occur after IT chemotherapy in heavily pre-treated leukemia pts. T2 weighted spinal MRI can be helpful in the evaluation of pts that present with unexplained weakness and sensory changes. We recommend delaying additional CNS-directed therapy until work-up to rule out alternative etiologies is complete. Future strategies are desperately needed to address this irreversible treatment complication.

Outcomes and Toxicities in Patients with Diffuse Large B-Cell Lymphoma of the Gastrointestinal Tract

PURPOSE/OBJECTIVE(S)

Diffuse large B-cell lymphoma (DLBCL) involving the gastrointestinal (GI) tract is rare and long-term outcomes are not well defined. Combined modality therapy (CMT) with radiotherapy (RT) in addition to systemic therapy in this setting is not commonly pursued. We aim to characterize outcomes in patients with GI DLBCL treated with systemic therapy, with or without RT.

MATERIALS/METHODS

Patients diagnosed with DLBCL of the GI tract (with or without mesenteric involvement) treated at a single institution from 1988-2022 were retrospectively reviewed on an IRB-approved protocol. Clinical and treatment data were collected including adverse events (AE; acute vs late defined as before or 4 weeks after therapy end). Kaplan-Meier and Cox regression models were used to estimate survival.

RESULTS

Of 207 patients, 62% were male and median age at diagnosis was 63 (IQR 52-73). Gastric involvement was most common (n = 130, 63%), followed by small intestines (n = 48, 23%) and colon/rectum (n = 24, 12%). Most presented with early-stage disease (n = 124, 60%), with a median IPI score of 1. All patients received chemotherapy. Of 182 treated with CHOP/EPOCH, 36 (20%) were treated in the pre-rituximab era while 146 (80%) received rituximab. 66 patients (32%) were treated with RT, 89% as part of first line CMT. 50 cases (76%) received consolidative RT, while 10 (15%) targeted residual gross disease and 4 (6%) targeted distant sites. Median dose and fractionation were 36Gy (IQR 30.6-39.6) in 18 fractions (IQR 17-22). Over half (n = 132, 64%) developed grade 3+ acute chemotherapy AEs, and the most common were anemia (n = 64), febrile neutropenia (n = 40), and neutropenia (n = 20). Grade 3+ late chemotherapy AEs occurred in 14 patients (7%). Acute grade 3+ radiation AEs were uncommon (n = 2, 3%; colitis, emesis). No grade 3+ late radiation AEs were noted. Median follow-up was 46 months (IQR 16-97). 169 (81.6%) had a complete response (CR), with 154 (91%) after first line chemotherapy, 9 (5%) after second line, and 6 (4%) after RT. CR was defined by PET (62%), endoscopy (22%), CT (9%), or other methods (7%). The 5-year progression-free survival for those treated with one line of chemotherapy with or without RT was 95%. Median overall survival (OS) was not reached. Improved OS was associated with early-stage disease (p = 0.003), low IPI (p = 0.001), fewer chemotherapy lines (p<0.001), and CR (p<0.001). OS did not differ by gender, age, immunophenotype, GI site, SUVmax, or RT. Patients with early stage DLBCL treated with RT in the post-rituximab era received fewer chemotherapy cycles compared to those treated without RT (p = 0.02; median of 4 (IQR 3-6) vs 6 cycles (IQR 4-6)), with no OS difference.

CONCLUSION

GI DLBCL patients have favorable outcomes after CMT with minimal late toxicity. CMT with RT to the GI tract is well tolerated with no OS difference compared to chemotherapy alone, and may mitigate risks from additional chemotherapy cycles for selected early-stage patients.

Ultra Low-Dose Radiation for Extranodal Marginal Zone Lymphoma of the Lung

PURPOSE/OBJECTIVE(S)

Definitive radiation treatment (RT) for extranodal marginal zone lymphoma (ENMZL) of mucosal associated lymphoid tissue historically involves treatment to 24-30 Gy. There is increasing data supporting the use of ultra-low dose RT as part of a response-adapted approach in the treatment of orbital and gastric ENMZL. With this approach, patients receive initial treatment with 4 Gy, and additional RT is considered for those with persistent or locally progressive disease. However limited data to date assesses the efficacy of 4 Gy in the management of ENMZL of the lung.

MATERIALS/METHODS

We performed an IRB-approved retrospective review of 17 patients with ENMZL of the lung treated with 4 Gy between 7/2015 and 12/2022 with response assessed after RT. Clinical/treatment characteristics, response, and toxicity were extracted from medical records. Statistics were performed using Mann-Whitney U and Fisher's Exact Test.

RESULTS

Eight patients (47%) were female, 15 (88%) white, and 1 (6%) Hispanic. Median age at RT was 66 (interquartile range (IQR) 59-77). All had disease limited to the lung at diagnosis and 15 had stage IE disease. Four patients (24%) were diagnosed incidentally on screening/surveillance imaging in the absence of symptoms. Sixteen patients received 4 Gy in 2 fractions, while one patient received a single fraction of 4 Gy. Median SUVmax prior to RT was 4.5 (IQR 3.2-7.2). Median planning target volume (PTV) was 74 cc (IQR 47-130cc). Six patients (35%) had respiratory symptoms prior to RT, which improved or resolved in 3 (50%). A larger PTV was associated with improvement in symptoms following RT with a median PTV of 266 cc (IQR 171-402) in those who experienced improvement vs. 64 cc (IQR 42-100) in those who did not (p = 0.032). One patient experienced toxicity following RT with pleuritic chest pain, which resolved with corticosteroids. At a median follow-up of 15 months following RT (IQR 7-43 months), the overall response rate (ORR) was 100% (CR, n = 15; PR, n = 2). Fourteen patients had follow-up PET/CT, of whom 13 had a complete metabolic response (CMR) at a median of 3 months following RT (IQR 3-5 months). Two additional patients had a complete response (CR) on CT while one had a partial response on CT. Achieving a CR was not associated with SUV prior to RT (p = 0.50) or PTV size (p = 0.62). In patients with stage IE disease, the ORR rate was 100% and there have been no distant failures to date. Fifteen of 17 patients were alive at last follow-up; two passed away of unrelated causes (one from Alzheimer's disease and one from recurrent squamous cell carcinoma).

CONCLUSION

Ultra-low dose radiation of 4 Gy is associated with excellent local control in the management of ENMZL of the lung and is very well tolerated. Four Gy was effective for local control and symptom palliation even for larger tumors and is an effective initial therapy as part of a response-adapted approach even in limited stage patients.

Characterization of Lymphopenia during Bridging Radiation Therapy Prior to CAR-T Cell Therapy in Patients with Aggressive B Cell Lymphomas

PURPOSE/OBJECTIVE(S)

Bridging RT (bRT) may be used as a strategy for disease control in patients with relapsed/refractory aggressive B cell lymphoma treated with anti-CD19-directed chimeric antigen receptor T-cell therapy (CART). The correlation of treatment-related lymphopenia with adverse outcomes in patients has been widely documented in several malignancies. Here, we assessed lymphocyte kinetics during bRT and impact on clinical outcome.

MATERIALS/METHODS

After IRB-approval, records were retrospectively reviewed for adults with DLBCL who received bRT for axicabtagene ciloleucel 11/2017-12/2022. Clinical/treatment characteristics, lab values, and outcomes were extracted. ALC Δ RT was computed by subtracting pre-RT ALC from post-RT ALC count. Survival was modeled using Kaplan-Meier for events distributed over time, or binary logistic regression for disease response. Fisher's Exact Test or Mann-Whitney U methods were used.

RESULTS

Forty patients met inclusion criteria. Fourteen (35%) received bRT with systemic therapy. Thirty-two (80%) patients received bRT that started post-leukapheresis. bRT was delivered with a median dose of 30 Gy (range: 4-46) in 10 fractions (range: 2-23). Twenty-three patients (57.5%) had CR at 30 days post-CART infusion. Nine had PR (22.5%), and 8 patients (20%) had PD or SD. Median PFS was 8.9 months and median OS was 22 months. The pre-RT ALC mean ± SD was 0.74 ± 0.49 K/µL, and post-RT was 0.43 ± 0.35 K/µL. The absolute ALC Δ RT was 0.31 ± 0.43 K/µL, and ratio post-RT/pre-RT was 0.74 ± 0.64. Stratifying by receipt of bRT alone or with systemic therapy, there was no statistically significant difference in ALC count post-RT (chemoRT: 0.33 ± 0.23 vs. RT: 0.48 ± 0.4, p = 0.2), but there was a lower ALC count pre-RT in the chemoRT group (0.5 ± 0.3 vs. 0.87 ± 0.52 for RT alone, p = 0.02). Post-RT ALC was not significantly associated with CR/PR vs. PD/SD, or with DSS, PFS, or OS. A greater drop in ALC Δ RT trended towards association with improved 90-day response (p = 0.066), without correlation with DSS, OS, or response at 30 days. Median dose per fraction was lower among patients that got pre-leukapheresis RT (2.25 vs. 2.5, p = 0.04), but total dose of bRT or number of fractions was not significantly different. Otherwise, the groups were similar in terms of stage, disease bulk, or comprehensive vs. focal bRT. The average decrease in ALC post-RT for patients who received bRT prior to apheresis was 0.215 K/µL, compared to 0.268 K/µL for patients who received bRT post-apheresis (p = 0.75). Treatment with pre-leukapheresis bRT or ALC Δ RT among these patients were not associated with worse DFS, PFS, or OS (p>0.15).

CONCLUSION

Post-bRT ALC and reduction in ALC during bRT is not associated with worse treatment response or survival outcomes after CAR-T cell treatment in aggressive B cell lymphoma. Pre-leukapheresis bRT did not appear to substantially impact ALC, and ALC Δ RT among these patients were not associated with worse outcomes.