Intraoperative and postoperative gamma detection of somatostatin receptors in bone-invasive en plaque meningiomas

Abstract

Objective: Scintigraphy with a radiolabeled somatostatin analog ((111)In-diethylenetriaminepenta-acetic acid octreotide) detects the somatostatin receptors that are found in vitro in all meningiomas. Previous studies have proved the benefit of radioimmunoguided surgery, with a hand-held gamma probe, for the assessment and removal of neuroendocrine tumors. We conducted a study to determine whether intraoperative radiodetection of somatostatin receptors is feasible and could increase the probability of complete meningioma resection, especially for bone-invasive en plaque meningiomas, which are difficult to control surgically.

Methods: Eighteen patients with en plaque sphenoid wing and cranial convexity meningiomas were studied by preoperative and postoperative somatostatin receptor scintigraphy. In 10 of them, intraoperative radiodetection with a hand-held gamma probe was performed 24 hours after the intravenous administration of (111)In-diethylenetriaminepenta-acetic acid octreotide. This procedure was combined with a computer-aided navigation system.

Results: All preoperative scintigrams were positive. Intraoperative gamma probe detection was achieved for the invaded bone, dura, and periorbit of sphenoid wing meningiomas. The average tumor/nontumor count ratio was 2:1, with a maximum of 12:1, thus allowing precise detection capable of defining the tumor margins. In three cases of sphenoid wing meningiomas, postoperative scintigrams were helpful for the determination of recurrences that magnetic resonance imaging failed to detect.

Conclusion: These preliminary data show that intraoperative radiodetection of somatostatin receptors with a hand-held gamma probe is feasible and may be helpful to guide the surgical removal of bone-invasive en plaque meningiomas. Preoperative and postoperative scintigraphy may be useful for the management and follow-up of patients with these tumors.

Figure 1

Picture of the gamma probe (Tec probe 2000) used for the intraoperative detection of somatostatin receptors of bone invasive meningiomas. The probe has a diameter of 10 mm, and a length of 15mm. The electronic unit provides both visual and audible indication of the counting rate (cps).

Figure 2

Diagram of the maximal uptake (in counts per second) of somatostatin receptors determined during the surgical removal of the invaded bone of 10 “en plaque” invasive meningiomas. This was measured using an intraoperative handheld gamma probe on the invaded skull before its removal (Tumoral bone: measurements in the center of the tumor) and after the tumor resection, on the margins of the resection (Post resection). These were compared with the data obtained at distant normal skull bone (Non tumoral bone). Mean values are indicated with a bar. Statistical analysis of the different data are calculated (Mann Whitney, non parametric double sided). (Cps: counts per second)

Figure 3

This 66 years old woman complained of exophthalmus and visual loss. A large “en plaque” sphenoid wing meningioma associated with a second frontal meningioma was discovered. The uptake of the tumors on pre-operative somatostatin receptors scintigraphy was high (A). Three months after an extensive resection the scintigraphy (B) confirmed the complete removal demonstrated on MRI. One year later, the exophthalmus recurred with no clear evidence of recurrence on conventional images, but the scintigraphy was demonstrative (C). After radiation therapy, the somatostatin receptor uptake decreased (D). (E: preoperative MR image; F: one year post-operative MRI. The arrow head points out a possible remnant or recurrence at the orbital apex.)

Figure 3

This 66 years old woman complained of exophthalmus and visual loss. A large “en plaque” sphenoid wing meningioma associated with a second frontal meningioma was discovered. The uptake of the tumors on pre-operative somatostatin receptors scintigraphy was high (A). Three months after an extensive resection the scintigraphy (B) confirmed the complete removal demonstrated on MRI. One year later, the exophthalmus recurred with no clear evidence of recurrence on conventional images, but the scintigraphy was demonstrative (C). After radiation therapy, the somatostatin receptor uptake decreased (D). (E: preoperative MR image; F: one year post-operative MRI. The arrow head points out a possible remnant or recurrence at the orbital apex.)

Figure 3

This 66 years old woman complained of exophthalmus and visual loss. A large “en plaque” sphenoid wing meningioma associated with a second frontal meningioma was discovered. The uptake of the tumors on pre-operative somatostatin receptors scintigraphy was high (A). Three months after an extensive resection the scintigraphy (B) confirmed the complete removal demonstrated on MRI. One year later, the exophthalmus recurred with no clear evidence of recurrence on conventional images, but the scintigraphy was demonstrative (C). After radiation therapy, the somatostatin receptor uptake decreased (D). (E: preoperative MR image; F: one year post-operative MRI. The arrow head points out a possible remnant or recurrence at the orbital apex.)

Figure 3

This 66 years old woman complained of exophthalmus and visual loss. A large “en plaque” sphenoid wing meningioma associated with a second frontal meningioma was discovered. The uptake of the tumors on pre-operative somatostatin receptors scintigraphy was high (A). Three months after an extensive resection the scintigraphy (B) confirmed the complete removal demonstrated on MRI. One year later, the exophthalmus recurred with no clear evidence of recurrence on conventional images, but the scintigraphy was demonstrative (C). After radiation therapy, the somatostatin receptor uptake decreased (D). (E: preoperative MR image; F: one year post-operative MRI. The arrow head points out a possible remnant or recurrence at the orbital apex.)

Figure 3

This 66 years old woman complained of exophthalmus and visual loss. A large “en plaque” sphenoid wing meningioma associated with a second frontal meningioma was discovered. The uptake of the tumors on pre-operative somatostatin receptors scintigraphy was high (A). Three months after an extensive resection the scintigraphy (B) confirmed the complete removal demonstrated on MRI. One year later, the exophthalmus recurred with no clear evidence of recurrence on conventional images, but the scintigraphy was demonstrative (C). After radiation therapy, the somatostatin receptor uptake decreased (D). (E: preoperative MR image; F: one year post-operative MRI. The arrow head points out a possible remnant or recurrence at the orbital apex.)

Figure 3

This 66 years old woman complained of exophthalmus and visual loss. A large “en plaque” sphenoid wing meningioma associated with a second frontal meningioma was discovered. The uptake of the tumors on pre-operative somatostatin receptors scintigraphy was high (A). Three months after an extensive resection the scintigraphy (B) confirmed the complete removal demonstrated on MRI. One year later, the exophthalmus recurred with no clear evidence of recurrence on conventional images, but the scintigraphy was demonstrative (C). After radiation therapy, the somatostatin receptor uptake decreased (D). (E: preoperative MR image; F: one year post-operative MRI. The arrow head points out a possible remnant or recurrence at the orbital apex.)