Long–Half-Life ⁸⁹Zr-Labeled Radiotracers Can Guide Percutaneous Biopsy Within the PET/CT Suite Without Reinjection of Radiotracer

Patients

All patients were enrolled in an Institutional Review Board–approved protocol. This protocol was compliant with the Health Insurance Portability and Accountability Act. The prospective protocols for molecular imaging were performed under an investigational-new-drug process (9–11).

From 2013 to 2016, 12 patients (mean age, 61 y; range, 40–75 y) with positive findings on PET/CT imaging with ⁸⁹Zr-labeled anti-PSMA (J591 antibody or minibody, 7 men) or trastuzumab (5 women) were referred to interventional radiology for biopsy to confirm metastasis and obtain optimal molecular profiling of the tumor. The 7 men had a history of prostate cancer and presented with a rising level of prostatic-specific antigen despite treatment with testosterone-lowering hormonal therapy. The 5 women had confirmed HER2-negative primary breast cancer and underwent biopsy to assess ⁸⁹Zr-trastuzumab foci suggestive of HER2-positive disease.

The exclusion criteria included a previous anaphylactic reaction to PET imaging or radiotracers, treatment with any new anticancer therapy (gonadotropin-releasing hormone analog allowed) while on the study, abnormal hepatic laboratory values (bilirubin > 1.5 times the upper limit of normal [ULN], aspartate aminotransferase/alanine aminotransferase > 2.5 ULN, albumin < 2 g/dL, γ-glutamyl transferase > 2.5 ULN if alkaline phosphatase > 2.5 ULN), abnormal renal laboratory values (creatinine > 1.5 ULN), or any other severe acute or chronic medical condition that might increase the risk associated with study participation or investigational product administration. The patient characteristics are summarized in Table 1.

Preprocedural Imaging

Patients received radiolabeled antibody with a mean administered activity of 180 MBq (range, 126–190 MBq). A single dose of 10 mg of anti-PSMA antibody (J591) (11) or miniature antibody (df-IAB2M) (9) or 50 mg of HER2-targeted PET tracer (trastuzumab) (10) labeled with 185 MBq of ⁸⁹Zr was administrated intravenously over 5–10 min.

All imaging was performed on the same PET/CT scanner (Discovery DSTE; GE Healthcare). A CT protocol designed for attenuation correction with iterative reconstruction was used for anatomic localization of PET abnormalities. Thus, each patient underwent a single 80-mA CT scan followed by a 10-mA CT scan on each of the remaining days of imaging.

Molecular Imaging–Guided Interventional Procedures

Targeted lesions were determined on the basis of ⁸⁹Zr-labeled radiotracer PET/CT positivity and accessibility (target location, target size, needle path, and skin-to-target distance) by consensus at a multidisciplinary conference comprising oncologists, interventional radiologists, and nuclear medicine physicians.

The procedures were performed in an interventional radiology suite equipped with a PET/CT scanner (Discovery 690; GE Healthcare) without radiotracer reinjection. The patients had limited PET/CT imaging (1–2 bed positions) over the biopsy region of interest. A CT scan for attenuation correction and anatomic coregistration was obtained without oral or intravenous contrast material in every case (imaging parameters: 120 kVp, 115 mA, 1.25-mm collimation, 3.75-mm reconstructed slice thickness, and 512 × 512 matrix). Immediately after CT, PET was performed in 3-dimensional mode (128 × 128 matrix and 4.24 × 4.25 × 3.27 mm voxels) at 7 min per field of view. Biopsy needles were inserted under local anesthesia and conventional CT or CT–fluoroscopy guidance, but the CT images were intermittently fused with the PET dataset.

A coaxial 11-gauge system (Madison; Laurane Medical) was used for biopsy of bone, whereas other types of biopsy used needle diameters ranging from 18- to 20-gauge (Temno Evolution; Carefusion). Following an institutional protocol, 2 tissue samples were requested in bone biopsies and 3 in soft-tissue biopsies, but additional samples could be obtained. Pathologic evaluation of the tissue samples was performed at the time of biopsy.

Procedure-related complications were noted and classified on the basis of the Society of Interventional Radiology’s proposed criteria and the National Cancer Institute’s Common Terminology Criteria for Adverse Events (version 4.0) (12).

Statistical Analysis

Diagnostic accuracy was reported in terms of sensitivity and positive predictive value. The positive predictive value was defined as the proportion of malignant lesions and was calculated with 95% confidence intervals using the Wilson method.