Artikel
HOT-SPOTS in dynamic 18FET PET are associated with unfavorable outcome in patients with suspected WHO grade II Glioma
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Veröffentlicht: | 4. Juni 2012 |
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Objective: Three different uptake patterns of O-(2-[(18)F]fluoroethyl)-l-tyrosine (18FET) have been shown to occur in patients with suspected WHO II glioma after dynamic PET evaluation: 1) a constantly increasing uptake throughout the entire tumor volume indicative for a grade II glioma. 2) an early peak of uptake with following decline throughout the entire tumor volume indicative for a malignant glioma. 3) a heterogeneous uptake exhibiting both low- and high-grade characteristics (HOT SPOT) at different sites of the tumor. The prognostic impact of these findings remains unclear so far. For clarification the following prospective study (2006–2010) was conducted.
Methods: Adult patients with a magnetic resonance imaging based suspicion of a so far untreated grade II glioma were considered eligible. Date of last follow-up was October 2011. Informed consent was available for all patients. Dynamic FET PET evaluation was performed according to the protocol of Poepperl et al (2007). All patients underwent PET-guided stereotactic biopsy. Progression free survival (PFS) was estimated with the Kaplan Meier method.
Results: Ninety-eight patients (f/m 56/42, median age 45 years) were included. Median follow-up was 16 months. Histological evaluation revealed 53 grade II and 45 high-grade gliomas. Tumor progression was noted in 31 patients. The diagnostic sensitivity and specificity of FET PET was 89% and 87%. Homogeneous low-grade, homogeneous high-grade, and heterogeneous kinetics were seen in 52, 27 and 19 patients, respectively. The size of the HOT SPOT in the heterogeneous group ranged from 2% to 90% of the entire tumor volume. One-year PFS for patients exhibiting homogeneous low-grade, homogeneous high-grade, and heterogeneous kinetics was 86%, 63%, and 87%, however, two-year PFS was 78%, 35%, and 26%, respectively (p=0.002). Patients exhibiting heterogeneous kinetics did no better than those with homogeneous malignant kinetics (p>0.05). The size of the HOT SPOT did not gain prognostic relevance.
Conclusions: Consideration of HOT SPOT volumes within suspected grade II glioma is essential for histological and prognostic evaluation. Failure to detect these sometimes small malignant foci either by microsurgery or biopsy could easily lead to both undergrading and undertreatment.