METHODS
Between 2006 and 2007, 32 consecutive patients with glioblastoma were treated with AHRT and TMZ.
The total dose of 66 Gy was administered in 33 fractions within 6 weeks. In phase I, PTV1 received 40
Gy (2 Gy per fraction, five times per week). In phase II, 26 Gy was delivered to PTV2 by adding a second
daily fraction at intervals of 8 hours once every 3 days. All patients received chemotherapy according to
the Stupp protocol. Toxicities were evaluated based on the CTCAE v3.0.
RESULTS
The median follow-up period was 18 months. A total of 28 patients completed the planned radiotherapy
schedule, and 20 patients received six cycles of adjuvant TMZ. Median overall survival (OS) and
progression-free survival (PFS) were 17 and 10 months, respectively. In univariate analysis, age, performance
status, and RPA classes III-IV were found significant for OS. Multivariate analysis showed that
six cycles of TMZ administration affected both OS and PFS. Late grade-4 central nervous system (CNS)
toxicities were observed in five patients.
CONCLUSION
It was observed that it is both feasible and effective to administer AHRT with TMZ in a selected group of
patients. It provides better short-term survival advantage than the standard treatment regimen.
Keywords: Accelerated hyperfractionation; glioblastoma; radiotherapy; temozolomide
The standard treatment for patients with newly
diagnosed GB is wide surgical resection followed
by postoperative RT and concurrent plus adjuvant
chemotherapy. Despite the advancements in treatment
modalities, the prognosis is still poor, and the five-year
survival rate is below 10%.[
In this study, the late radiation results in patients
with newly diagnosed GB who were treated with accelerated
hyperfractionated RT and concurrent plus
adjuvant TMZ were evaluated.
Patient Selection
Between 2006 and 2007, 32 patients with newly diagnosed
GB were enrolled in the study. Inclusion criteria
for the patients were as follows: (a) histologically confirmed
GB (WHO grade IV); (b) age between 18 and
70 years; (c) total or subtotal resection; (d) Karnofsky
performance status (KPS) score ≥70%; and (e) normal
hematologic, renal, and hepatic parameters. Patients who
had received prior RT to the brain and with recurrent
disease or concurrent other malignancy were excluded.
Treatment Characteristics
All of the patients underwent surgery; 29 of them had
(90.6%) gross total resection, and 3 (9.4%) of them
had subtotal resection. RT started within 6 weeks after
the surgical resection in 81% of the patients. During
simulation and treatment, patient immobilization was provided with an individualized thermoplastic mask.
The computed tomography simulation was made in the
supine position with a 0.5-cm thick slice. Initial clinical
target volume 1 (CTV1) included the contrast-enhancing
lesion and surrounding edema on the preoperative
MRI with a 15-mm margin. Then the field was reduced,
and the volume of boost (CTV2) was defined as the
area of contrast-enhancing lesion plus a 15-mm margin.
Planning target volumes were created by adding 5-mm
margins to CTVs. Treatment plans were planned using
the Three-Dimensional Conformal Radiotherapy Technique
(3-D CRT). According to tumor location, radiation
was delivered from three or four fields with 6-18
MV linear accelerators. The total dose of 66 Gy was administered
in 33 fractions over 6 weeks. In the first phase
of treatment, PTV1 received 40 Gy (2 Gy per fraction a
day, five times a week). In phase II, the total dose was
increased to 26 Gy by adding a second daily fraction at
intervals of 8 hours once every 3 days.
All patients received concurrent TMZ 75 mg/m2 daily during RT. One month after completion of RT, according to the Stupp protocol, adjuvant TMZ was administered 150-200 mg/m2 daily for 5 days every 28 days.
Follow-Up
During chemoradiotherapy, patients were followed up
for weekly blood count, and they were evaluated for
acute toxicities. In addition, during adjuvant TMZ period,
monthly follow-ups with blood tests and serum
chemistries were conducted. A neurologic examination
was also performed at each visit. Later on, follow-ups
were conducted every 3 months for the first 2 years and
every 6 months thereafter. A contrast-enhanced cranial
MRI was performed 1 month after the end of RT and
every 3 months thereafter. If radiation necrosis was suspected
in patients, perfusion MRI or MR spectroscopy
was performed. Disease progression is defined radiologically
(a 25% or greater increase in the largest vertical diameter
of a contrast-enhancing tumor on MRI, or a new
lesion). In case of progression, each patient was re-evaluated
for second-line treatment options such as surgery,
RT, or chemotherapy. Treatment-related toxicities were
graded according to the Common Terminology Criteria
for Negative Events (CTCAE) 3.0.[21]
Statistical Analysis
Overall survival (OS) time was calculated from the
date of diagnosis (biopsy or surgical resection) to the
date of death from any cause. Progression-free survival
(PFS) time was calculated from the date of diagnosis
to the date of progression of the disease or to the time at which new lesions appeared. Survival analyses were
performed according to the intention-to-treat principle.
The Kaplan-Meier method was used to calculate
the OS and PFS rates. In univariate analysis, the logrank
test was used to compare survival according to
different prognostic factors. A multivariate Cox regression
analysis was used to determine prognostic factors
affecting OS and PFS. For the statistical analysis, SPSS
version 20 for Windows (IBM Corp., Armonk, NY)
was used. The p-value <0.05 was accepted to be significant.
Of the 32 patients, 28 (87.5%) completed the planned 66 Gy of RT dose. TMZ at 75 mg/m2/day was started concomitant with RT in all patients, but treatment was discontinued due to toxicities in two patients. Six cycles of adjuvant TMZ was completed in 20 patients (62.5%). Six patients did not receive the adjuvant chemotherapy. One patient refused the treatment, one patient discontinued treatment due to grade IV pancytopenia, one patient died of pneumonia during RT, and three patients died due to disease progression at the end of RT.
Survival Outcomes and Prognostic Factors
The median follow-up period was 18 months (range:
2-98 months). At the time of the analysis, all of the
patients who participated in the study were dead.
Only two patients lived longer than 5 years (96 and 98
months). The median OS time was 17 months. The OS
rates from 1 to 5 years were 75%, 28.1%, 12.5%, 9.4%,
and 6.3%, respectively (Fig.
Distant metastasis or leptomeningeal disease was
not observed in any patient. However, a local failure
developed in all patients during follow-up. Salvage
chemotherapy was given to 12 patients. Nine of them
received TMZ, and the remaining three had fotemustine.
Ten patients had best supportive care, five patients
underwent re-operation, and one patient re-irradiated
with stereotactic radiosurgery. The median PFS time
was 10 months. The PFS rates at 1 and 2 year were
35.5% and 6.5%, respectively (Fig.
In univariate analyses, the age (≤50 years) (p=0.011),
RPA classes III-IV (p=0.011), KPS ≥90 (p=0.013), and use
of six cycles of adjuvant TMZ (p<0.0001) were
found as significant prognostic factors for OS. The
PFS rate was significantly higher in patients who received
six cycles of adjuvant TMZ compared to that
in patients who received less than six cycles (11 vs. 4
months, p<0.001) (Table
In multivariate analysis, only the use of adjuvant
six cycles of TMZ was found to be the most important prognostic factor for both the OS (p=0.003) and PFS
(p=0.005) (Table
Acute and Late Toxicity
The most commonly developed acute side effect during
chemoradiotherapy was hematologic toxicity. Grade-4
toxicity was observed in eight patients. Six patients had
grade-4 lymphopenia, one patient had grade-4 leukopenia,
and one patient had grade-4 thrombocytopenia.
Furthermore, fatigue was observed as the most common
non-hematologic toxicity (Table
As a late toxicity, radiation necrosis was detected
in 12 (42.8%) patients after median 12.5 months from
RT. Radiation necrosis was diagnosed with radiological
imaging in ten patients and with biopsy in two patients.
However, most of the patients were asymptomatic, only
one patient had grade-3 necrosis, and the other had
grade-4 necrosis. In addition, other late grade 3-4 central
nervous system (CNS) toxicities included visual
loss in two patients, somnolence in one patient, cognitive
disturbance in one patient, and memory impairment in one patient (Table
GB is a highly radio-resistant tumor. In the preclinical
studies, it has been reported that high doses (≥80
Gy) are required to eliminate malignant glial cells.[
The current standard dose used in GB treatment
is 60 Gy. However, in follow-ups, the most common
problem is still a local failure, and most of the recurrences
develop within the high-dose area.[
Increasing the treatment dose by altered fractionation
has been used for a long time in rapidly growing
tumors. The aim is to exploit radiobiological advantages.
In this way, the total radiation dose is increased
without prolonging the duration of the treatment and
without excessive late toxicity. Thus, repopulation is
prevented. For this reason, hyperfractionation was frequently
used in the early dose-escalation trials. However,
most of these studies have failed, and no survival
advantage has been demonstrated compared to standard
conventional fractionation.[
Most of the above-mentioned studies have been
performed before the TMZ period. In 2005, Stupp et
al. showed a remarkable improvement in survival with
the addition of TMZ in GB treatment, and they opened
a new era.[
Kaul et al. compared 64 patients who underwent
accelerated hyperfractionated RT with 67 patients
who underwent conventional RT, and they found no
significant difference between the two groups.[
In this study, the total radiation dose was increased
to 66 Gy with accelerated hyperfractionation. The
1-year and 2-year OS rates were found as 75% and
28.1%, respectively. In addition, the median OS time
was 17 months, and the median PFS time was 10
months. Whereas, in the Stupp's trial, the 1-year and
2-year OS rates were reported as 61.1% and 26.5%, respectively. There was a median 2.5-month survival advantage
according to this trial. But the 5-year survival
rates are similar.
In this study, it was observed that patients with
good performance status and younger age (≤50 years)
have a higher survival rate. These findings are consistent
with the prognostic factors mentioned in previous
trials. Also, the RPA model, which was defined as a
prognostic factor by Curran et al., showed well correlation
with survival rates in our study.[
In several AHRT trials, it has been reported that
the duration of treatment can be safely shortened with
acceptable acute and late toxicities.[
On the other hand, radio-necrosis is regarded
as a favorable event in terms of survival by some researchers.
A correlation between radio-necrosis and
improved outcomes has been shown in some series.
[
There are some limitations in this study. First, the
number of patients investigated was small, and they
were retrospectively assessed. Secondly, since the study
was conducted about 10 years ago, the MGMT methylation
status of the patients was unknown. Thirdly, while
dose-intensification studies of today are conducted
with modern RT techniques such as IMRT, 3-D CRT
was used in our study at that time. However, the positive
aspect of the study is that all patients were followed
up to death, and long-term results were presented.
Peer-review: Externally peer-reviewed.
Conflict of Interest: No conflict of interest was declared by
the authors.
Ethics Committee Approval: This study was approved by
the Ethics Committee of İstanbul University, İstanbul Medical
Faculty.
Financial Support: None declared.
Authorship contributions: Concept - R.M., M.A., Ş.A.E.;
Design - R.M., Ş.A.E., M.A.; Supervision - R.M., M.A.; Materials
- Ş.A.E., R.M., M.A.; Data collection &/or processing
- Ş.A.E.; Analysis and/or interpretation - Ş.A.E., R.M.;
Literature search - Ş.A.E.; Writing - Ş.A.E., R.M.; Critical
review - R.M., M.A.