S. Rudoler et al., PATTERNS OF TUMOR PROGRESSION AFTER RADIOTHERAPY FOR LOW-GRADE GLIOMAS - ANALYSIS FROM THE COMPUTED-TOMOGRAPHY MAGNETIC-RESONANCE-IMAGING ERA, American journal of clinical oncology, 21(1), 1998, pp. 23-27
Postoperative radiotherapy for low-grade gliomas has been shown in ret
rospective series to improve survival, compared with surgery alone. To
determine the proper radiotherapy treatment volume and dose, an under
standing of the patterns of failure with current radiotherapy techniqu
es is necessary. We studied 30 consecutive patients who had a patholog
ic diagnosis of low-grade nonpilocytic glioma treated in our departmen
t between 1975 and 1994. Before radiotherapy, 5 patients underwent bio
psy, 22 had subtotal resection, and 3 had gross total excision. All ha
d pre-and posttreatment computed tomographic (CT) or magnetic resonanc
e imaging (MRI) scanning. Megavoltage radiotherapy was delivered to sh
rinking partial (22 patients) or whole-brain (8 patients) fields. Medi
an dose was 59.4 Gy (range, 46.4-64 Gy) in 1.8- to 2-Gy fractions. Med
ian follow-up was 44 months (3-215 months) for the cohort and 105 mont
hs for survivors. For the entire series, 5-year overall survival and r
elapse-free survival rates were 50% and 41%, respectively. Sixteen pat
ients (53%) progressed at a median of 30 months. At the time of failur
e, 71% (5 of 7) of pathologically evaluated tumors were of high grade.
Recurrence originated within the field in all patients. Higher 5-year
overall survival and relapse-free survival rates were associated (p <
0.001) with preradiotherapy functional status 1 versus functional sta
tus 2 through 4 (60% vs. 0% and 55% vs. 0%, respectively). Seizure as
initial presentation was favorable over other symptoms (5-year overall
survival, 64% versus 14%; p = 0.057). We conclude that 1) low-grade n
onpilocytic gliomas can transform to high-grade lesions after treatmen
t with conventional radiotherapy, 2) recurrence uniformly occurs withi
n the treatment volume, and 3) pretreatment functional status correlat
es prognostically with survival. The local pattern of failure suggests
that radiotherapy dose escalation within conformal fields could impro
ve results.