Feasibility Evaluation of Radioimmunoguided Surgery of Breast Cancer

Breast-conserving surgery involves completely excising the tumour while limiting the amount of normal tissue removed, which is technically challenging to achieve, especially given the limited intraoperative guidance available to the surgeon. This study evaluates the feasibility of radioimmunoguided surgery (RIGS) to guide the detection and delineation of tumours intraoperatively. The 3D point-response function of a commercial gamma-ray-detecting probe (GDP) was determined as a function of radionuclide (131I, 111In, 99mTc), energy-window threshold, and collimator length (0.0–3.0-cm). This function was used to calculate the minimum detectable tumour volumes (MDTVs) and the minimum tumour-to-background activity concentration ratio (T:B) for effective delineation of a breast tumour model. The GDP had larger MDTVs and a higher minimum required T:B for tumour delineation with 131I than with 111In or 99mTc. It was shown that for 111In there was a benefit to using a collimator length of 0.5-cm. For the model used, the minimum required T:B required for effective tumour delineation was 5.2 ± 0.4. RIGS has the potential to significantly improve the accuracy of breast-conserving surgery; however, before these benefits can be realized, novel radiopharmaceuticals need to be developed that have a higher specificity for cancerous tissue in vivo than what is currently available.

Intraoperative and Postoperative Gamma Detection of Somatostatin Receptors in Bone-invasive en Plaque Meningiomas

OBJECTIVE: Scintigraphy with a radiolabeled somatostatin analog (111In-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 111In-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.