ESTRO 2021 Abstract Book

S905

ESTRO 2021

rate (ORR), symptoms control, treatment related toxicity according to CTCAE v5.0 and survival outcomes (PFS- OM and OS) were analyzed. Dosimetric data are reported as well.

Results From May 2012 to January 2020, 35 treatments were performed, baseline characteristics are highlighted in Table 1. In pts treated with CK, mean prescribed dose was 2000cGy (range 1800-2400) for a mean of 3.75 fractions (range 2-5), prescribed at a mean isodose line (IDL) of 77.7% (range 71.5-80.9). In pts treated with VMAT-HFRT, a 3000cGy in 10 fractions was adopted, prescribed at the 95% IDL. Median follow-up after HFRT treatment was 19 months (IQR 5-26.7), overall response rate was 48.6%, with 13 and 4 pts presenting a partial and complete response, respectively. Mean time to the best measured response was 14.9 months (range 1-70). 7 patients were still alive, with a LC rate of 100%. We reported 2 local progression, with a mean LC rate of 13 months. Retreatment with CK after local progression was performed in 1 case. Thirty pts had symptomatic OM- BC at diagnosis: 19, 9 and 2 pts had reduced visual field, impaired visual acuity and ocular pain, respectively. Ocular motility at OM-BC diagnosis was compromised in 18 pts (51.4%). Overall, 7 pts reported improvement of symptoms after treatment. Seven pts presented acute toxicity (<3 months) after HFRT (2 diplopia G2, 2 xerophthalmia G2, 2 eyelid edema G1 and 1 floaters G1). Median PFS OM-BC was 16 months (IQR 4.2-25.7) and mean OS was 715.3 months (range 400-924). In CK cases there are 5 GTV prescriptions with a median GTV dose coverage of 96.3% (IQR 90.5-97.5), while the remaining 23 pts presented a median PTV dose coverage of 97% (IQR 94.1-98.2). In VMAT-HFRT cases median PTV dose coverage was 97% (IQR 95.2-99.7). Mean maximum dose (Dmax) to the eye globe was 2145.7 cGy[b1] (range 467-3345). Median maximum dose (Dmax) to optic nerve, optic chiasm and lens was 1791cGy (IQR 1516.7-2400.5), 335cGy (IQR 195.7-1006.5) and 286cGy (IQR 133.5- 714.0), respectively.