Adult low-grade glioma: 19-year experience at a single institution.
OBJECTIVE
To determine prognostic factors and optimal timing of postoperative radiation therapy (RT) in adult low-grade gliomas.


METHODS
Records from 554 adults diagnosed with nonpilocytic low-grade gliomas at Mayo Clinic between 1992 and 2011 were retrospectively reviewed.


RESULTS
Median follow-up was 5.2 years. Histology revealed astrocytoma in 22%, oligoastrocytoma in 34%, and oligodendroglioma in 45%. Initial surgery achieved gross total resection in 31%, radical subtotal resection in 10%, subtotal resection (STR) in 21%, and biopsy only in 39%. Median overall survival (OS) and progression-free survival (PFS) were 11.4 and 4.1 years, respectively. On multivariate analysis, factors associated with lower OS included astrocytomas and use of postoperative RT. Adverse prognostic factors for PFS on multivariate analysis included tumor size, astrocytomas, STR/biopsy only and not receiving RT. Patients undergoing gross total resection/radical subtotal resection had the best OS and PFS. Comparing survival with the log-rank test demonstrated no association between RT and PFS (P=0.24), but RT was associated with lower OS (P<0.0001). In patients undergoing STR/biopsy only, RT was associated with improved PFS (P<0.0001) but lower OS (P=0.03). Postoperative RT was associated with adverse prognostic factors including age > 40 years, deep tumors, size≥5 cm, astrocytomas and STR/biopsy only. Patients delaying RT until recurrence experienced 10-year OS (71%) similar to patients never needing RT (74%; P=0.34).


CONCLUSIONS
This study supports the association between aggressive surgical resection and better OS and PFS, and between postoperative RT and improved PFS in patients receiving STR/biopsy only. In addition, our findings suggest that delaying RT until progression is safe in patients who are eligible.
*College of Medicine Departments of ‡Pathology §Neurosurgery ∥Neurology ¶Radiation Oncology, Mayo Clinic, Rochester, MN †Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX.
Ryan S
RS
Youland
Paul D
PD
Brown
Caterina
C
Giannini
Ian F
IF
Parney
Joon H
JH
Uhm
Nadia N
NN
Laack
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001254:Astrocytoma / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D001932:Brain Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery*; D005260:Female; D005910:Glioma / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009364:Neoplasm Recurrence, Local; D009837:Oligodendroglioma / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D011184:Postoperative Period; D011379:Prognosis; D011829:Radiation Dosage; D012189:Retrospective Studies; D015996:Survival Rate; D016896:Treatment Outcome; D055815:Young Adult