Quantitative assessment of residual tumor is a strong and independent predictor of survival in methylated glioblastoma following radiochemotherapy with lomustine/temozolomide.

BACKGROUND

Maximum tumor resection improves overall survival (OS) in patients with glioblastoma. The extent of resection (EOR) is historically dichotomized. The response assessment in neuro-oncology (RANO) resects group recently proposed criteria for volumetry-based EOR assessment in patients that were treated according to Stupp´s protocol. The purpose of this study was (1) to investigate the prognostic value of EOR in patients receiving combined chemotherapy with lomustine (CCNU)/temozolomide (TMZ), and (2) to analyze the prognostic performance of binary EOR assessment compared to volumetric assessment.

METHODS

Seventy-eight patients with newly diagnosed MGMT-methylated GBM undergoing tumor resection followed by radiochemotherapy with CCNU/TMZ were included in this study. Residual contrast-enhancing (CE) tumor volume after the first resection was measured and its influence on OS and progression-free survival was analyzed using uni- and multivariable Cox regression analysis as well as two-sided log-rank test. Patients were divided into residual tumor volume (RTV) ≤1 cm³, >1-≤5 cm³, and >5 cm³ following the proposed criteria of the RANO resect group.

RESULTS

Prolonged OS was associated with age <60 years, low RTV, and gross total resection. RTV had a superior prognostic value compared to binary EOR assessment. Patients with total or near total resection of CE tumor (≤ 1 cm³ RTV) showed prolonged OS (median 54.4 months, 95% CI: 46.94-not reached), with a 5-year survival rate of 49%.

CONCLUSIONS

Low RTV is associated with increased survival in glioblastoma patients undergoing radiochemotherapy with CCNU/TMZ. This study demonstrates the applicability of the recently proposed RANO resect criteria in this subgroup of patients.