ESTRO 2024 - Abstract Book

S1151

Clinical - Haematology

ESTRO 2024

of RT. Acute skin AEs were estimated within 3 months by the end of RT and scored with CTCAE 5.0 classification. Secondary endpoints were local control (LC) and progression-free survival (PFS). Time to event endpoints were calculated from the starting date of RT with the Kaplan-Meier method, and were compared among subgroups using the log-rank test. Univariate and Multivariable (MVA) Cox proportional hazards were calculated to estimate the effect of covariates on patients’ outcome. Logistic regression models were used to investigate the correlation between RT-related factors and clinical toxicity events.

Results:

125 patients were included: 79 (63%) were male and median age at treatment was 69 (range 22-94) years. The median number of previous treatment lines was 1 (range 0-11). Indolent B-cell, diffuse large B-cell and T-cell histology were detected in 24%, 22% and 42% of the patients respectively. Before treatment, 45% of the patients had local skin symptoms such as itching, pain or ulceration in the treated site. RT was delivered with HT in 74% and with LINAC in 26% of patients. Median prescribed dose was 30 Gy (range 4-50 Gy), delivered in daily fractions of 2 Gy (range 1.6-8 Gy) to a median PTV volume of 488 cc (range 7-7871 cc). ORR at 1 month was 97% (61% CR and 36% PR). Acute skin AEs of any grade (G>=1) were detected in 73%, G>=2 events in 22% and G3 events only in 3% of patients. No G4-5 events were observed (Table). Total RT dose >30 Gy was related with higher risk of developing any grade AE (85% vs 54%, p<0.001), while PTV volume >700 cc was related with higher risk of G>=2 AEs (34% vs 16%, p = 0.03). Daily RT dose had no impact on acute AEs. With a median follow-up of 15 months, 1-year LC and PFS were 84% and 60%, respectively (Figure). On MVA, PTV volume >700 cc had a negative impact on LC (HR=5.48; p=0.01). The presence of skin symptoms before RT (HR=2.90; p=0.003), T-cell histology (HR=1.59; p=0.04) and again PTV volume >700 cc (HR=2.90; p=0.003) negatively affected PFS. The prescribed RT dose did not affect neither LC nor PFS.