ESTRO 2024 - Abstract Book

S832

Clinical - CNS

ESTRO 2024

dosage increment and timing of chemotherapy regimen. Response to treatment was assessed using the Response Assessment in Neuro-Oncology (RANO) criteria. Univariate analyses were performed using Kaplan-Meier method and the log-rank test. Differences between groups were analyzed using Chi- square, Fisher’s test or T -test as appropriate. Values of p<0.05 were considered significant. All statistical analyses were performed in IBM SPSS Statistics version 26.

Results:

Accordingly to the described material/methods, from 139 patients with glioblastoma treated at our institution: 63.3% were male (n=88), with a mean age of 62.46 ± 11.36 years, 57.6% had ECOG score of 1 (n=80), the mean interval between surgery and radiotherapy was 41.22 ± 14.44 days, 84.2% were submitted to surgical resection (n=117), 5.8% (n=8) had imagiologic complete resection, MGMT+ was present in 10.8% of the patients (n=15). 71.9% underwent CF (n=100) and 69.8% received concurrent chemotherapy (n=97). Grade 3 and 4 toxicities were present in 23.7% (n=33) of patients and 24.5% (n=34) required corticosteroid dosage increment during treatment. The mean overall survival (OS) was 17.54 months (95% CI=15.23-19.85) with a 12-month survival rate of 55%, 2-year survival rate of 30% - Fig 1(A). The mean progression-free survival (PFS) was 9.72 months (95% CI=7.78-11.65). The patients that required corticosteroids dosage increment, presented mean OS of 11.83 months (95% CI=8.88-14.78), which was significantly lower than those who didn’t, with mean OS of 18.56 months (95% CI=16.01 -21.12) (p=0.031) - Fig. 1(B). In our population, there weren’t any significantly differences in OS or PFS between populations regarding interval between surgery and start of radiotherapy >30 days, GTR or STR, MGMT+, IDH- (p>0.05). Within these 139 patients, we compared the two fractionation schemes, the 27.1% (n=39) of patients that were submitted to HF were significantly older, with a mean age of 66.0 ± 13.86 years when compared to those treated with CF, with 61.1 ± 9.96 years (p<0.05). However, the mean OS between these two fractionations was not significantly different, CF OS mean was 17.95 months (95% CI=15.29-20.60) and HF OS mean 16.57 months (95% CI=12.0- 21.15) (p=0.48). There weren’t any significant differences between mean PFS with CF, 9.13 months (95% CI=7.12-11.13) and HF, 11.16 months (95% CI=7.31-14.99) (p=0.242). The proportion of grade 3 and grade 4 between the two groups of fractionation were not significantly different (p=0.221 and p=0.487 respectively) nor the necessity of corticosteroid dosage increment (p=0.265). In those 39 patients submitted to hypofractionation, mean OS was significantly different between the three chemotherapy timing schemes, being the concurrent regimen the most favorable one with mean OS of 26.06 months (95% CI=17.17-34.93), sequential chemotherapy was associated with mean OS of 13.37 months (95% CI=8.17-18.59) and patients that did not undergo any chemotherapy had a mean OS of 10.49 months (95% CI =6.48 14.49) (p=0.02) - Fig. 2(C). Also, younger patients (<70 years) that underwent HF were benefited with mean OS of 22.19 (95% CI=16.09- 28.2) compared to older patients (≥70 years) with mean OS of 8.04 (95% CI=5.5 -10.57) (p=0.00)- Fig. 2 (D). Mean PFS in CF was 9.13 months (95% CI= 7.12- 11.13), which wasn’t significantly lower than mean PFS in HF with 11.16 months (95% CI=7.31-14.99) (p=0.242).