Date: 18 Sep 2009

Potential impact of 68Ga-DOTATOC PET/CT on stereotactic radiotherapy planning of meningiomas

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Abstract

Purpose

Since meningiomas show a high expression of somatostatin receptor subtype 2, PET with 68Ga-DOTATOC was proposed as an additional imaging modality beside CT and MRI for planning radiotherapy. We investigated the input of 68Ga-DOTATOC-PET/CT on the definition of the “gross tumour volume” (GTV) in meningiomas, in order to assess the potential value of this method.

Methods

Prior to radiotherapy, 42 patients with meningiomas (26 f, 16 m, mean age 55) underwent MRI and 68Ga-DOTATOC-PET/CT examinations. History: operated n = 24, radiotherapy n = 1, operation and radiotherapy n = 8, no treatment n = 9. PET/CT and MRI data were co-registered using a BrainLAB workstation. For comparison, the GTV was defined first under consideration of CT and MRI data, then using PET data.

Results

3/42 patients were excluded from the analysis (two with negative PET results, one with an extensive tumour, not precisely delineable by MRI or PET/CT). The average GTVCT/MRI was 22(±19)cm³; GTVPET was 23(±20)cm³. Additional GTV, obtained as a result of PET was 9(±10)cm³ and was observed in patients with osseous infiltration. In some pre-treated patients there were intratumoural areas (as identified in CT/MRI) without SR-expression (7(±11)cm³). Common GTV as obtained by both CT/MRI and PET was 15(±14)cm³. The mean bi-directional difference between the GTVCT/MRI and GTVPET accounted to 16(±15)cm³ (93%, p < 0.001). In a subgroup of seven patients with multiple meningiomas, PET showed a total of 19 lesions; nine of them were not recognizable by CT or MRI.

Conclusion

68Ga-DOTATOC-PET enables delineation of SR-positive meningiomas and delivers additional information to both CT and MRI regarding the planning of stereotactic radiotherapy. The acquisition on a PET/CT scanner helps to estimate the relation of PET findings to anatomical structures and is especially useful for detection of osseous infiltration. 68Ga-DOTATOC-PET also allows detection of additional lesions in patients with multiple meningiomas.

Fonyuy Nyuyki and Michail Plotkin contributed equally to this work.