19 patients (11 DLBCL, 5 MZL, 3 MCL) were identified with 21 courses of splenic RT. Median age was 75 (42–94); median KPS was 80 (50–90). Most patients (68%) had splenic only disease. Median splenic height pre-RT was 13.6 cm (6.4–26.6); 12 patients (57%) had baseline splenomegaly. Median splenic volume was 682cc (104–3355). 9 patients (43%) were symptomatic pre-RT (most frequently with pain: n=7, dyspnea: n=4, or nausea: n=4). 90% had any cytopenia before RT with median baseline WBC 5 (2–60), ANC 3 (0–11), Lymph 17 (3–76), Hgb 10 (7–13), and Plt 113 (22–208). RT was performed with definitive (n=7), palliative (n=7), or consolidative (n=4) intent, or as bridging to CAR T cells (n=3). Median dose was 30Gy for DLBCL (10.8–45), and 4Gy for MCL/MZL (0.6–20); 10 patients received ≥20Gy.
RT was well tolerated with 38% of courses without AEs and 57% with G1-2 AEs. AEs with frequency >10% were G1 fatigue (n=6), G1 anorexia (n=5), G1 nausea (n=5), G1 diarrhea (n=3), and G2 fatigue (n=3). There were no G3-4 AEs. One patient died from respiratory failure secondary to fungal pneumonia in the setting of lymphopenia following splenic RT. Cytopenias were evaluated in the 10 cases for which no chemo was given within 30d of RT. Median nadirs: WBC 3 (1–5), ANC 2 (1–4), Lymph 4 (1–17), Hgb 12 (6–13), Plt 78 (9–182) with 9, 9, 9, 6, and 11 median days from RT start to nadir, respectively. Lymph and Plt were disproportionately affected with Hgb preserved (Fig1; median reduction: WBC 38%, ANC 54%, Lymph 72%, Hgb 2%, Plt 84%; p<0.003). A greater absolute reduction in platelets was seen with ≥20Gy (median 107 vs. 68; p=0.02). In 3 patients (14%) cytopenias completely normalized post-RT. 4/11 symptomatic patients (36%) experienced complete relief. Median reduction in splenic volume was 34% (0–90; Fig2). ORR by PET was 80%: 37% CR, 43% PR, 10% SD, 5% PD. With a median follow up of 12mo, median duration of radiographic response was 8mo (0.5–103) with more durable response at ≥20Gy (median 35 vs. 5mo, p=0.01).