Utilizing 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) to define suspected nonenhancing tumor for radiation therapy planning of glioblastoma

Aim

The authors sought to evaluate the impact of 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) on radiation therapy planning for patients diagnosed with glioblastoma (GBM) and the presence of suspected nonenhancing tumors compared with standard magnetic resonance imaging (MRI).

Evaluation of MR markers that predict survival in patients with newly diagnosed GBM prior to adjuvant therapy

Purpose Glioblastoma Multiforme (GBM) is the most common and lethal primary brain tumor in adults. The goal of this study was to test the predictive value of MR parameters in relation to the survival of patients with newly diagnosed GBM who were scanned prior to receiving adjuvant radiation and chemotherapy. Methods The study population comprised 68 patients who had surgical resection and were to be treated with fractionated external beam radiation therapy and chemotherapy. Imaging scans included anatomical MRI, diffusion and perfusion weighted imaging and (1)H MRSI. The MR data were acquired 3-5 weeks after surgery and approximately 1 week before treatment with radiation therapy. The diffusion, perfusion and spectroscopic parameter values were quantified and subjected to proportional hazards analysis that was adjusted for age and scanner field strength. Results The patients with larger lesion burden based upon volumes of anatomic lesions, volume of CNI2 (number of voxels within the T2 lesion having choline to NAA index >2), volume of CBV3 (number of pixels within the T2 lesion having relative cerebral blood volume >3), and volume of nADC1.5 (number of pixels within the T2 lesion having normalized apparent diffusion coefficient <1.5) had a higher risk for poor outcome. High intensities of combined measures of lactate and lipid in the T2 and CNI2 regions were also associated with poor survival. Conclusions Our study indicated that several pre-treatment anatomic, physiological and metabolic MR parameters are predictive of survival. This information may be important for stratifying patients to specific treatment protocols and for planning focal therapy.     

Concurrent boost radiotherapy as preoperative treatment for locally advanced rectal carcinoma: a new beam arrangement

PURPOSE: To describe a new beam arrangement for preoperative concurrent boost radiotherapy in locally advanced rectal carcinoma. MATERIAL AND METHODS: Three different volumes, ie posterior pelvis, total mesorectal space, and gross tumor volume plus 2 cm, are selected to receive radiation doses of 47 Gy, 51 Gy, and 54 Gy, respectively, in 24 fractions. There are two prerequisites for the use of such a radiotherapy schedule: complete displacement of the small bowel outside the boost volume, and horizontal positioning of the rectal long axis. Both conditions can be attained by patient positioning on a new device, the "Up-Down Table" (UDT). The dose gradient between the three volumes is realized with two daily arc rotation fields with an isocenter that is different from the three additional multileaf collimator pelvic fields (postero-anterior + 2 laterolateral). RESULTS: The treatment data are reported according to the ICRU 62 criteria. A comparison was made between concurrent arc rotation and concomitant static boost techniques. CONCLUSION: The new beam arrangement, with the use of the UDT, allows to administer different radiation doses to three volumes with different tumor cell density in order to obtain the same probability of local response in all target volumes without increasing the toxicity.     

Phase II preradiation R115777 (tipifarnib) in newly diagnosed GBM with residual enhancing disease

Glioblastoma multiforme (GBM) is a lethal primary malignant brain tumor in adults. R115777 (tipifarnib) is an oral agent with antiproliferative effects, being a potent and selective inhibitor of farnesyltransferase. This multicenter, open-label phase II study was designed to evaluate the efficacy and safety of R115777 given after surgery and prior to radiation in patients with newly diagnosed and residual enhancing GBM. Following surgery, an MRI confirmed the presence of residual enhancing tumor. Patients on enzyme-inducing antiseizure drugs (EIASDs) received 600 mg twice per day, and those not on EIASDs received 300 mg twice per day. One to three monthly cycles of R115777 were administered, and radiation was initiated with progression or after three cycles. A cycle consisted of 3 weeks of continuous R115777 followed by a 1-week rest. MRI was done monthly. The primary end point was overall survival; secondary end points were tumor response rate and toxicity. A total of 28 confirmed GBM patients entered the study; 15 patients (54%) were on EIASDs. The overall median time of survival was 7.7 months. There were no tumor responses. Eight patients (29%) had stable disease as the best response. The study was stopped early due to progression of the disease in 12 patients (48%). A total of 24 patients (85%) were off study before the planned treatment schedule for radiation therapy. R115777 administered prior to radiation therapy in patients with newly diagnosed GBM and residual enhancing disease did not result in any measurable responses or improvement in survival. R115777 administered prior to radiation therapy is not recommended for patients with newly diagnosed GBM.     

Results of phase I study of a multi-modality treatment for newly diagnosed glioblastoma multiforme using local implantation of concurrent BCNU wafers and permanent I-125 seeds followed by fractionated radiation and temozolomide chemotherapy

Previously we demonstrated median survival of 69 weeks after combination therapy of permanent, low-activity I-125 seeds and BCNU wafers for recurrent glioblastoma multiforme (GBM). We designed this prospective phase I trial to assess efficacy of this combination treatment for newly diagnosed GBM. Patients with newly diagnosed GBMs deemed amenable to gross total resection were included. This dose-escalation study of I-125 seeds included three 6-patient cohorts, receiving increasing doses of 3000, 6000, and 9000 cGy, and a maximal number of BCNU wafers placed surgically. Postoperatively patients underwent standard fractionated radiation to 5,940 cGy followed by temozolomide chemotherapy. During enrollment of the first 6-patient cohort, the trial was stopped when 3 of 5 patients developed radiation toxicity. Five patients (median age 55 years, range 46-64 years) completed postoperative radiation; Karnofsky Performance Status ranged from 70 to 90. This lowest-dose cohort received I-125 seeds at 3,000 cGy and maximal BCNU wafer placement, and reached endpoint (median 26 weeks follow-up). Two patients developed local disease progression (median 34.4 weeks). The 3 patients who developed radiation toxicity, which was documented on follow-up MRI and confirmed by MRI spectroscopy (median 20 weeks), underwent treatment with steroids and bevacizumab. Our phase I study was closed during enrollment of the first 6-patient cohort because of the high incidence (60 %) of early radiation toxicity. We do not recommend the seed-wafer therapy for newly diagnosed GBM patients but rather reserve this as salvage therapy for select patients with recurrent GBM.     

MR-spectroscopy guided target delineation for high-grade gliomas.

PURPOSE: Functional/metabolic information provided by MR-spectroscopy (MRSI) suggests MRI may not be a reliable indicator of active and microscopic disease in malignant brain tumors. We assessed the impact MRSI might have on the target volumes used for radiation therapy treatment planning for high-grade gliomas. METHODS AND MATERIALS: Thirty-four patients (22 Grade III; 12 Grade IV astrocytomas) were evaluated; each had undergone MRI and MRSI studies before surgery. MRI data sets were contoured for T1 region of contrast enhancement (T1), region of necrosis, and T2 region of hyperintensity (T2). The three-dimensional MRSI peak parameters for choline (Cho) and N-acetylaspartate (NAA), acquired by a multivoxel technique, were categorized based on an abnormality index (AI), a quantitative assessment of tissue metabolite levels. The AI data were aligned to the MRI and displayed as three-dimensional contours. AI vs. T conjoint and disjoint volumes were compared. RESULTS: For both grades, although T2 estimated the region at risk of microscopic disease as being as much as 50% greater than by MRSI, metabolically active tumor still extended outside the T2 region in 88% of patients by as many as 28 mm. In addition, T1 suggested a lesser volume and different location of active disease compared to MRSI. CONCLUSION: The use of MRSI to define target volumes for RT treatment planning would increase, and change the location of, the volume receiving a boost dose as well as reduce the volume receiving a standard dose. Incorporation of MRSI into the treatment-planning process may have the potential to improve control while reducing complications.     

Metastatic Seeding of the Stereotactic Biopsy Tract in Glioblastoma Multiforme: Case Report and Review of the Literature

Objective and importance. The first case was recently reported of tumor seeding by glioblastoma multiforme (GBM) after stereotactic biopsy. This occurred despite radiosurgical treatment of the lesion post-biopsy. We report the first case of metastatic seeding along the needle biopsy tract of a GBM in which the tract was within the treatment field of subsequent fractionated radiation therapy. Clinical presentation. A 56-year-old man presented with left-sided focal motor seizures. An MRI showed an enhancing right cingulate gyrus lesion. Intervention. A stereotactic biopsy of the lesion disclosed GBM. Radiation therapy was begun 25 days after biopsy and was completed 39 days thereafter. The biopsy tract received a minimum of 60Gy. Subsequent magnetic resonance scanning showed the lesion to have doubled in size and evidence of enhancement along the biopsy tract. At surgery, specimens obtained from the biopsy tract, as determined using surgical navigation, revealed GBM. Conclusion. Seeding of the biopsy tract, radioresistance and the time interval until radiotherapy are the most likely explanations for tumor growth along the biopsy tract in this case. Consideration should be given for an early start to radiotherapy among those who undergo stereotactic biopsy for GBM. Further research will allow one to determine the radiosensitivity of these tumors and determine which patients may benefit from a radiosurgical or fractionated radiotherapy boost to the biopsy tract.     

Improving the consistency in cervical esophageal target volume definition by special training

PURPOSE: Three-dimensional conformal radiation therapy requires the precise definition of the target volume. Its potential benefits could be offset by the inconsistency in target definition by radiation oncologists. In a previous survey of radiation oncologists, a large degree of variation in target volume definition of cervical esophageal cancer was noted for the boost phase of radiotherapy. The present study evaluated whether special training could improve the consistency in target volume definitions. METHODS AND MATERIALS: A pre-training survey was performed to establish baseline values. This was followed by a special one-on-one training session on treatment planning based on the RTOG 94-05 protocol to 12 radiation oncologists. Target volumes were redrawn immediately and at 1-2 months later. Post-training vs. pre-training target volumes were compared. RESULTS: There was less variability in the longitudinal positions of the target volumes post-training compared to pre-training (p < 0.05 in 5 of 6 comparisons). One case had more variability due to the lack of a visible gross tumor on CT scans. Transverse contours of target volumes did not show any significant difference pre- or post-training. CONCLUSION: For cervical esophageal cancer, this study suggests that special training on protocol guidelines may improve consistency in target volume definition. Explicit protocol directions are required for situations where the gross tumor is not easily visible on CT scans. This may be particularly important for multicenter clinical trials, to reduce the occurrences of protocol violations.     

Transcranial sonography: integration into target volume definition for glioblastoma multiforme

PURPOSE: Recent studies indicate that transcranial sonography (TCS) reliably displays the extension of malignant brain tumors. The effect of integrating TCS into radiotherapy planning for glioblastoma multiforme (GBM) was investigated herein. METHODS AND MATERIALS: Thirteen patients subtotally resected for GBM underwent TCS during radiotherapy planning and were conventionally treated (54 to 60 Gy). Gross tumor volumes (GTVs) and stereotactic boost planning target volumes (PTVs, 3-mm margin) were created, based on contrast enhancement on computed tomography (CT) only (PTV(CT)) or the combined CT and TCS information (PTV(CT+TCS)). Noncoplonar conformal treatment plans for both PTVs were compared. Tumor progression patterns and preoperative magnetic resonance imaging (MRI) were related to both PTVs. RESULTS: A sufficient temporal bone window for TCS was present in 11 of 13 patients. GTVs as defined by TCS were considerably larger than the respective CT volumes: Of the composite GTV(CT+TCS) (median volume 42 ml), 23%, 13%, and 66% (medians) were covered by the overlap of both methods, CT only and TCS only, respectively. Median sizes of PTV(CT) and PTV(CT+TCS) were 34 and 74 ml, respectively. Addition of TCS to CT information led to a median increase of the volume irradiated within the 80% isodose by 32 ml (median factor 1.51). PTV(CT+TCS) volume was at median 24% of a "conventional" MRI(T2)-based PTV. Of eight progressions analyzed, three and six occurred inside the 80% isodose of the plans for PTV(CT) and for PTV(CT+TCS), respectively. CONCLUSION: Addition of TCS tumor volume to the contrast-enhancing CT volume in postoperative radiotherapy planning for GBM increases the treated volume by a median factor of 1.5. Since a high frequency of marginal recurrences is reported from dose-escalation trials of this disease, TCS may complement established methods in PTV definition.     

A phase II trial of accelerated radiotherapy using weekly stereotactic conformal boost for supratentorial glioblastoma multiforme: RTOG 0023

PURPOSE: This phase II trial was performed to assess the feasibility, toxicity, and efficacy of dose-intense accelerated radiation therapy using weekly fractionated stereotactic radiotherapy (FSRT) boost for patients with glioblastoma multiforme (GBM). METHODS AND MATERIALS: Patients with histologically confirmed GBM with postoperative enhancing tumor plus tumor cavity diameter <60 mm were enrolled. A 50-Gy dose of standard radiation therapy (RT) was given in daily 2-Gy fractions. In addition, patients received four FSRT treatments, once weekly, during Weeks 3 to 6. FSRT dosing of either 5 Gy or 7 Gy per fraction was given for a cumulative dose of 70 or 78 Gy in 29 (25 standard RT + 4 FSRT) treatments over 6 weeks. After the RT course, carmustine (BCNU) at 80 mg/m(2) was given for 3 days, every 8 weeks, for 6 cycles. RESULTS: A total of 76 patients were analyzed. Toxicity included: 3 Grade 4 chemotherapy, 3 acute Grade 4 radiotherapy, and 1 Grade 3 late. The median survival time was 12.5 months. No survival difference is seen when compared with the RTOG historical database. Patients with gross total resection (41%) had a median survival time of 16.6 months vs. 12.0 months for historic controls with gross total resection (p = 0.14). CONCLUSION: This first, multi-institutional FSRT boost trial for GBM was feasible and well tolerated. There is no significant survival benefit using this dose-intense RT regimen. Subset analysis revealed a trend toward improved outcome for GTR patients suggesting that patients with minimal disease burden may benefit from this form of accelerated RT.     

Longitudinal MRI evidence for decreased survival among periventricular glioblastoma

While the prognosis of patients with glioblastoma (GBM) remains poor despite recent therapeutic advances, variable survival times suggest wide variation in tumor biology and an opportunity for stratified intervention. We used volumetric analysis and morphometrics to measure the spatial relationship between subventricular zone (SVZ) proximity and survival in a cohort of 39 newly diagnosed GBM patients. We collected T2-weighted and gadolinium-enhanced T1-weighted magnetic resonance images (MRI) at pre-operative, post-operative, pre-radiation therapy, and post-radiation therapy time points, measured tumor volumes and distances to the SVZ, and collected clinical data. Univariate and multivariate Cox regression showed that tumors involving the SVZ and tumor growth rate during radiation therapy were independent predictors of shorter progression-free and overall survival. These results suggest that GBMs in close proximity to the ependymal surface of the ventricles convey a worse prognosis-an observation that may be useful for stratifying treatment.     

Standardization and Quality Assurance of Radiation Therapy Volumes for Adults With High-Grade Gliomas

Standard treatment for Glioblastoma Multiforme (GBM) consists of a combination of chemotherapy and radiation therapy followed by adjuvant chemotherapy. While the optimal dose of radiation therapy has been established, significant variability in volume of tissue irradiated exists. In this article we review the current guidelines, patterns of care, patterns of failure, imaging advances and toxicity related to radiation therapy volumes in the treatment of GBM.     

胶质母细胞瘤放射治疗靶区设计现状与思考

The use of adjuvant external-beam RT is well established in the postoperative treatment of glioblastoma multiforme (GBM). It is consensus that target volume should be determined based on the fusion images of MRI and CT, but the inclusion of peritumoural edematous is controversial. The vast majority of recurrences occur within 2 cm of the original tumor site or “in radiation field”. There is no inevitable relation between the degree of peritumoral edema and recurrence model. The clinical and pathological characteristics may be as predictive and prognostic factors for the treatment of GBM. Target volume delineation for GBM tend to individual, which can maintain known outcomes and reduce treatment toxicity.     

Positron emission tomography-guided conformal fast neutron therapy for glioblastoma multiforme

Glioblastoma multiforme (GBM) continues to be a difficult therapeutic challenge. Our study was conducted to determine whether improved survival and tumor control could be achieved with modern delivery of fast neutron radiation using three-dimensional treatment planning. Ten patients were enrolled. Eligibility criteria included pathologic diagnosis of GBM, age >or=18 years, and KPS >or=60. Patients underwent MRI and (18)F-fluorodeoxyglucose PET (FDG PET) as part of initial three-dimensional treatment planning. Sequential targets were treated with noncoplanar fields to a total dose of 18 Gy in 16 fractions over 4 weeks. Median and 1-year overall survival were 55 weeks and 60%, respectively. One patient remains alive at last follow-up 255 weeks after diagnosis. Median progression-free survival was 16 weeks, and all patients had tumor progression by 39 weeks. Treatment was clinically well tolerated, but evidence of mild to moderate gliosis and microvascular sclerosis consistent with radiation injury was observed at autopsy in specimens taken from regions of contralateral brain that received approximately 6-10 Gy. Fast neutron radiation using modern imaging, treatment planning, and beam delivery was feasible to a total dose of 18 Gy, but tumor control probability was poor in comparison to that predicted from a dose-response model based on older studies. Steep dose-response curves for both tumor control and neurotoxicity continue to present a challenge to establishing a therapeutic window for fast neutron radiation in GBM, even with modern techniques.     

Simultaneous integrated boost for breast cancer using IMRT: a radiobiological and treatment planning study

PURPOSE: The purpose of this work is to explore the possibility of using intensity-modulated radiation therapy (IMRT) to deliver the boost dose to the tumor bed simultaneously with the whole-breast IMRT to reduce the radiation treatment time by 1-2 weeks. METHODS AND MATERIALS: The biologically effective dose (BED) for different treatments was calculated using the linear-quadratic (LQ) model with parameters previously derived for breast cancer from clinical data (alpha/beta = 10Gy, alpha = 0.3Gy(-1)). A potential doubling time of 15 days (from in vitro measurements) for breast cancer and a generic alpha/beta ratio of 3 Gy for normal tissues were used. A series of regimens that use IMRT as initial treatment and an IMRT simultaneous integrated boost (SIB) were derived using biologic equivalence to conventional schedules. Possible treatment plans with IMRT SIB to the tumor bed were generated for 2 selected breast patients, 1 with a shallow tumor and 1 with a deep-seated tumor. Plans with a simultaneous integrated electron boost were also generated for comparison. Dosimetric merits of these plans were evaluated based on dose volume histograms. RESULTS: A commonly used conventional treatment of 45 Gy (1.8 Gy x 25) to the whole breast and then a boost of 20 Gy (2 Gy x 10) is biologically equivalent to an alternative plan of 1.8 Gy x 25 to the whole breast with a 2.4 Gy x 25 SIB to the tumor bed. The new regime reduces treatment time from 7 to 5 weeks. For the patient with a deep-seated tumor, the IMRT plans reduce the volume of the breast that receives high doses (compared with the conventional photon boost plan) and provides good coverage of the target volumes. CONCLUSION: It is biologically and dosimetrically feasible to reduce the overall treatment time for breast radiotherapy by using an IMRT simultaneous integrated boost. For selected patient groups, IMRT plans with a new regimen can be equal to or better than conventional plans.     

The promise of dynamic contrast-enhanced imaging in radiation therapy

Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and computed tomography (CT) scanning are emerging as valuable tools to quantitatively map the spatial distribution of vascular parameters, such as perfusion, vascular permeability, blood volume, and mean transit time in tumors and normal organs. DCE MRI/CT have shown prognostic and predictive value for response of certain cancers to chemotherapy and radiation therapy. DCE MRI/CT offer the promise of early assessment of tumor response to radiation therapy, opening a window for adaptively optimizing radiation therapy based upon functional alterations that occur earlier than morphologic changes. DCE MRI/CT has also shown the potential of mapping dose responses in normal organs and tissue for evaluation of individual sensitivity to radiation, providing additional opportunities to minimize risks of radiation injury. The evidence for potentially applying DCE MRI and CT for selection and delineation of radiation boost targets is growing. The clinical use of DCE MRI and CT scanning as a biomarker or even a surrogate endpoint for radiation therapy assessment of tumor and normal organs must consider technical validation issues, including standardization, reproducibility, accuracy and robustness, and clinical validation of the sensitivity and specificity for each specific problem of interest. Although holding great promise, to date, DCE MRI and CT scanning have not been qualified as a surrogate endpoint for radiation therapy assessment or for treatment modification in any prospective phase III clinical trial for any tumor site.     

Radiation therapy target volume reduction in pediatric rhabdomyosarcoma

BACKGROUND:

The use of radiation therapy (RT) “cone‐down” boost to reduce high‐dose treatment volumes according to tumor response to induction chemotherapy in patients with pediatric rhabdomyosarcoma (RMS) may reduce treatment morbidity, yet the impact on tumor control is unknown.

METHODS:

Fifty‐five children, including 18 (33%) with parameningeal (PM) RMS and 37 (67%) with non‐PM RMS, who received definitive treatment with chemotherapy and RT from April 2000 through January 2010 were retrospectively reviewed.

RESULTS:

In total, 28 patients (51%) received a cone‐down boost. The high‐dose boost volume was reduced by a median of 56% of the initial target volume (range, 5%‐91%). The median time to initiating RT was 3 weeks for patients with PM RMS and 16 weeks for patients with non‐PM RMS (P < .001). After a median follow‐up of 41 months, local failure occurred in 5 patients (9%), including 2 patients who received a cone‐down boost, and there were no marginal failures. Twelve patients (67%) with PM RMS had intracranial tumor extension. In this subgroup, 4 patients (30%) who received a cone‐down boost and had ≥ 3 weeks between chemotherapy and RT initiation experienced leptomeningeal failure as their first site of disease progression, and a delayed time to RT initiation was associated with decreased survival (P = .055)

CONCLUSIONS:

A cone‐down boost allowed for significant reductions in high‐dose RT treatment volume while maintaining excellent tumor control in most patients. However, in the subset of patients with PM RMS and intracranial tumor extension, early RT initiation and wider margin RT to cover adjacent areas at high risk for meningeal extension may be more important for adequate disease control. Cancer 2013. © 2012 American Cancer Society.     

Irradiation of paranasal sinus tumors, a delineation and dose comparison study.

PURPOSE: To determine the influence of observer variation and treatment planner variation on the dose delivered to the target and normal structures when irradiating paranasal sinus carcinomas. PATIENTS AND METHODS: Nine patients with paranasal sinus tumors underwent debulking surgery and subsequent radiation therapy. Two observers from two different institutions delineated the clinical target volumes (CTVs) for the elective and the boost volumes. These volumes were expanded in three dimensions with a 5-mm margin. At both institutions, a three-dimensional conformal treatment plan of 46 Gy to the elective volumes, plus 20 Gy to the boost target volumes, was designed. The delineated volumes and treatment plans were compared. RESULTS: The mean volume ratio between institutions of the elective CTVs was 0.9 (standard error = 0.05). The differences were located mainly at the bottom of the nasal cavity and at the frontal border of the target areas. The differences in boost CTVs were large; the mean volume ratio was 2.6 (standard error = 0.58). After expansion of the CTV, the mean distance between the planning target volume (PTV) and the chiasm differed by 0.5 cm between the two institutions. Cases with smaller distances between the PTV and the chiasm had more underdosage to the PTV. This effect was less pronounced for institution A (1 vol.%/cm) than for institution B (10 vol.%/cm) treatment plans, which were less conformal. When the treatment plan was designed for the PTV of institution B, 23 volume % of the PTV of institution A received <95% of the prescribed dose. If the treatment plan was designed for the (on average larger) PTV of institution A, the underdosed volume of PTV at institution B was 17%. The relative underdosage to the "other" PTV was larger when the original treatment plan was more conformal. CONCLUSION: In the irradiation of paranasal sinus cancer, both the treatment planner and the observer have a significant influence on the dose to the target and organs at risk. Both effects are similar in magnitude. The observer effect increases with more conformal treatment plans. Minimizing the observer variation is important for adequate irradiation of paranasal sinus cancer.     

Prognostic impact of postoperative, pre-irradiation F-fluoroethyl-l-tyrosine uptake in glioblastoma patients treated with radiochemotherapy

Background and purpose

Resection is considered as essential for the efficacy of modern adjuvant treatment of glioblastoma multiforme (GBM). Previous studies have indicated that amino acid PET is more specific than contrast enhancement on MRI for detecting residual tumor tissue after surgery. In a prospective study we investigated the prognostic impact of postoperative tumor volume and tumor/brain ratios (TBR) in PET using O-(2-[¹⁸F]fluoroethyl)-l-tyrosine (FET) in comparison with MRI.

Materials and methods

Forty-four patients with GBM were investigated by FET PET and MRI after surgery. Tumor volume in FET PET with a tumor/brain ratio (TBR) > 1.6 and a TBR > 2, mean and maximum TBR and gadolinium contrast-enhancement on MRI (Gd-volume) were determined. Thereafter patients received a fractionated radiotherapy with concomitant temozolomide (RCX). The median follow-up was 15.4 (3-35) months. The prognostic value of postoperative residual tumor volume in FET PET, TBR_mean, TBR_max and Gd-volume was evaluated using Kaplan-Maier estimates for disease-free survival (DFS) and overall survival (OS).

Results

Postoperative tumor volume in FET PET had a significant independent influence on OS and DFS (OS 20.0 vs. 6.9 months; DFS 9.6 vs. 5.1 months, p < 0.001; cut-off 25 ml). Similar results were observed when a TBR ? 2 (cut-off 10 ml) was used to define the tumor volume in ¹⁸F-FET PET. The TBR_mean and TBR_max of FET uptake had a significant influence on DFS (p < 0.05). Gd-volume in MRI had significant effect on OS and DFS in the univariate analysis. No independent significant influence in OS or DFS could be observed for Gd-volume in MRI.

Conclusions

Our data indicate that the tumor volume in FET PET after surgery of GBM has a strong prognostic impact for these patients. FET PET appears to be helpful to determine the residual tumor volume after surgery of GBM and may serve as a valuable tool for optimal planning of radiation treatment.