Validation of Combs prognostic scoring system in Indian recurrent glioma patients treated with re-radiation

Abstract

Purpose: Retrospective audit of recurrent glioma patients treated by different fractionation schedules and to validate the modified Combs prognostic score in Indian patient cohort.Material and Methods: Between Jan 2009 and June 2022, 66 recurrent gliomas patients treated with standard adjuvant treatment—radiation (RT) ± temozolomide (chemotherapy)—and re-treated with RT (±chemotherapy) were categorized as per modified Combs prognostic criteria and outcomes were compared.Results: Sixty-six patients with recurrent gliomas who received reirradiation (re-RT) were audited—53% males; 61% Karnofsky performance status (KPS) ≥80 at time of re-RT; median age 41.5 years (range, 6 to 70 years); 67% <50 years; primary histology low-grade glioma in 33% ; grade III 27%, grade IV 40%; initial median dose of 60 Gy equivalent dose in 2 Gy fractions EQD2; maximum safe resection at recurrence 41%; mean and median follow-up 78 ± 51 months and 66 months. Mean time interval between RT was 46.4 ± 39 months. Mean planning target volume (PTV) volume in conventional RT (Conv-RT), hypofractionated RT (Hypo-RT), and ultra-hypofractionated RT (UF-RT) was 226.1 ± 140.7 mL, 162.8 ± 123.3 mL, and 143.3 ± 145.8 mL. Mean dose for Conv-RT, Hypo-RT, and UF-RT was 50 Gy (range, 40 to 60), 31 Gy (range, 20 to 40), and 20 Gy (range, 10 to 30). Mean overall survival (OS) in Conv-RT, Hypo-RT, and UF-RT cohort was 18.8 months (range, 2.4 to 76.8); 6.6 months (range, 2 to 17.4), and 13.9 months (range, 3 to 131.9). Median OS as per Combs criteria were 16.6 months (Group a), 24.6 months (Group b), 4.6 months (Group c), and 3 months (Group d). Significant survival benefit was with good KPS score (KPS >80 vs. <80; 20.46 vs. 5.25 months; p < 0.001), patients receiving salvage chemotherapy (20.46 vs. 6.96 months; p = 0.001), and patients received re-RT biological equivalent dose BED3 >80 Gy (16.62 vs. 5.48 months; p = 0.03). Median OS in our patient cohort and Combs cohort in Group a was 16.6 and 19.5 months; Group b was 24.6 and 11.3 months; Group c was 4.7 and 8.1 months, and Group d was 2 and 5.5 months, respectively. Six months survival in our patient cohort and Combs cohort in Groups a, b, c, d were 100%, 92%, 34%, 17% and 94%, 79%, 70%, 41%, respectively. Twelve months survival in our patient cohort and Combs cohort in Groups a, b, c, d were 88%, 74%, 22%, 0% and 88%, 47%, 22%, 7%, respectively.Conclusion: Modified Combs prognostic factors predicts OS and is applicable in Indian subcontinent patient population.