Main Session
Sep
28
PQA 04 - Breast Cancer, Patient Reported Outcomes/QoL/Survivorship, Functional Radiation Medicine, Hematologic Malignancies, Palliative Care, and International/Global Oncology
2756 - A Comparative Study of Proton vs. Photon Volumetric Modulated Arc Therapy Craniospinal Irradiation for Hematologic Leptomeningeal Disease
Presenter(s)
Gene Lamanilao, MD - University of California San Diego, La Jolla, CA
B. Hostler1, G. G. Lamanilao2, T. Le3, A. R. Jeong4, C. Costello4, H. G. Jona2, P. Sanghvi2, and K. R. Tringale2; 1Department of Psychology, San Diego State University, San Diego, CA, 2Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA, 3School of Medicine, University of California San Diego, La Jolla, CA, 4Department of Medical Oncology, University of California San Diego, La Jolla, CA
Purpose/Objective(s):
Craniospinal irradiation (CSI) is an effective treatment for hematologic leptomeningeal disease (LMD). Comparative outcome data for proton CSI (“pCSI”) vs photon-based volumetric modulated arc therapy (VMAT, “xCSI”) are yet to be described specifically for hematologic malignancies, which comprise a particularly vulnerable patient population given their often-limited bone marrow reserve. We compared outcomes between xCSI and pCSI, hypothesizing higher toxicity with xCSI but similar survival.Materials/Methods:
Hematologic patients who received CSI between 2020–2025 were identified. Hematologic and non-hematologic toxicities were graded with CTCAE v.5.0 at baseline, during treatment, and 1- and 3-months post-CSI. Overall survival (OS) was evaluated from CSI start and analyzed with Cox proportional hazards models adjusted for ECOG. Progression-free survival (PFS) and CNS progression-free survival (CNS-PFS) were also evaluated.Results:
34 patients received CSI: 26 (76%) xCSI, 8 (24%) pCSI. Radiation dose ranged from 7.2 Gy-30.6 Gy in 4-17 fractions. Baseline characteristics were similar between groups: acute lymphoblastic leukemia (59%) and non-Hodgkin lymphoma (18%) were the most common histologies (p=.51) and most were ECOG 1 (p=.80). Non-hematologic toxicities were largely grade 1-2, with fatigue, nausea, and pain most frequently reported, with no significant differences between modalities. Grade =3 lymphopenia was more common during xCSI compared with pCSI (87.5% vs 50.0%; p=.047) but this difference was not observed at 1 month (36.4% vs 66.7%; p=.35). Median OS was 28.3 months with no significant difference for xCSI vs pCSI (24.1m vs NR, respectively; p=.23), including after ECOG adjustment (HR 0.16; 95% CI 0.02–1.45; p=.10). PFS (8.6m vs 27.9m; p=.30) and CNS-PFS (18.6m vs NR; p=.20) were numerically higher after pCSI but did not significantly differ by modality. CNS-PFS differed significantly by treatment indication (bridging vs definitive treatment vs consolidation; 18.6m vs 8.6m vs NR, respectively; p=.02). OS demonstrated a similar pattern by treatment indication (24.1m vs 28.3m vs NR; p=.06).Conclusion:
pCSI and xCSI showed comparable toxicity in patients with hematologic malignancies, supporting the safety of VMAT xCSI. However, higher rates of severe lymphopenia during xCSI warrant attention in this vulnerable population and may support pCSI when available in high-risk patients. In addition, outcomes differed by treatment indication, with poorer survival and CNS control in patients treated definitively with CSI. This is an important first step toward optimizing neuraxial radiotherapeutic management in hematologic LMD.