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.

Predictors of Low Anterior Resection Syndrome after Long-Course Chemoradiation for Locally Advanced Rectal Cancer

PURPOSE/OBJECTIVE(S)

Low anterior resection syndrome (LARS) describes disordered bowel function including tenesmus, frequent, clustered, incomplete, urgent or incontinent bowel movements. The impact of clinical and radiation dosimetric factors on LARS score is unknown. We aimed to evaluate the radiation plans for patients who received long course chemoradiation (LC-CRT) to identify potential dosimetric predictors of LARS.

MATERIALS/METHODS

We identified patients with rectal cancer treated with LC-CRT (50.4Gy in 28 fractions) at our institution from 2016-2020 who were alive and without disease. As a part of a larger patient-reported outcome survey, we obtained the Low Anterior Resection Syndrome Score (LARS) for patients without an ostomy at the time of the survey. We utilized clinical and dosimetric variables in a multivariate analysis including age at LC-CRT, body mass index, sex, distance of the tumor from the anal verge (AV), threatened mesorectal fascia (MRF) on staging imaging, T-stage, N-stage, receipt of surgery (vs non-operative management (NOM), radiation technique (3DCRT vs VMAT), mean dose and D0.03ccs for the anal canal (defined as 4cm from the anal verge) and D0.03cc, V30Gy and V45Gy for the small bowel loops. We then created a multiple linear regression model to predict LARS using P>.20 on univariate testing.

RESULTS

Of 110 patients treated with preoperative LC-CRT and who did not have an ostomy, 57 responded (51.8%). The median [interquartile range (IQR)] interval from completion of LC-CRT to survey completion was 38.4 months [26.3-48.9]. Thirty-four patients (60%) were men, the median [IQR] BMI was 28 [24-31.9], the median [IQR] distance of the tumor to the anal verge was 7cm [5-10], 40 (70%) had T3 tumors, 7 (12%) had T4 tumors, 45 (79%) were N+. Forty-one patients (72%) had surgery following LC-CRT, and 16 (28%) had non-operative management. 3D conformal technique was used for 47 (82%) and VMAT used for 10 patients (18%). The median [IQR] LARS score was 32 [24-38] with 35 patients (61%) classified as Major LARS (LARS score = 30-42). On multiple linear regression modeling (Table), only receipt of surgery significantly predicted for higher (worse) LARS score.

CONCLUSION

In our cohort, patients who received surgery after LC-CRT had a significantly higher LARS score. Of the dosimetric parameters tested, D0.03ccs was the best predictor and could potentially be significant with a larger number of patients. Further work is needed to improve bowel function and quality of life for patients treated with LC-CRT for rectal adenocarcinoma.

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.

Patient Education Practices and Preferences of Interprofessional Radiation Oncology Providers

PURPOSE/OBJECTIVE(S)

Patient understanding of radiotherapy (RT) processes and data regarding optimal approaches to patient education (PE) within radiation oncology (RO) are limited. Our objective was to evaluate PE practices and preferences of interprofessional RO providers to inform recommendations for delivering inclusive, accessible, and patient-centered education.

MATERIALS/METHODS

An anonymous 17-item online survey, approved by an ethics review board, was administered to all members of the Radiation Oncology Education Collaborative Study Group (ROECSG) between 10/5/22 to 11/23/22. Respondent demographics, provider practices/preferences, and institutional practices were collected. Qualitative items explored key strategies, challenges, and desired resources for PE. Descriptive statistics summarized survey responses. Fisher's exact test compared PE practices by provider role and PE timing. Thematic analysis was used for qualitative responses.

RESULTS

A total of 123 ROECSG members, including RO attendings (64%), RO trainees (21%), medical physicists (7%), physician assistants/nurses (2%), and radiation therapists (2%), completed the survey (31% response rate). Most practiced in an academic setting (86%) in North America (82%). The most common PE resources used were custom created institution-specific (61%) and electronic health system generated materials (38%). PE was delivered primarily by one-on-one teaching (72%), paper handouts (69%), and organizational websites (21%) (e.g., RTanswers.org). Almost half (41%) reported that PE practices differed based on type of clinical encounter, for example paper handouts for in-person visits and multimedia for virtual visits. The majority (86%) stated that their institution has disease site-specific PE materials, with nearly all having breast cancer materials (91%). Only 58% reported access to non-English PE materials. RO attendings/trainees were more likely than other team members to deliver PE at consultation (98% vs 71%, p = 0.03). PE practices amongst radiation oncologists differed according to the timing along the RT care path (consultation vs simulation vs first fraction, respectively): one-on-one teaching: 89% vs 49% vs 56%, p<0.01 and paper handouts: 69% vs 28% vs 16%, p<0.01. Key PE strategies included incorporating multimedia resources, personalizing delivery, and repetition at multiple timepoints by the interprofessional team. Limited time, inadequate administrative support, and lack of customized resources were identified as challenges in PE delivery.

CONCLUSION

Interprofessional RO providers engage in PE, with most utilizing institution-specific materials. PE practices differ according to the type of clinical encounter and timing in the RT care path. Increased adoption of multimedia materials and partnerships with patients to tailor PE resources based on language, learning styles, and cultural preferences are needed to foster high-quality, patient-centered PE delivery.