Value of second-opinion review of outside institution PET-CT examinations

Abstract

Objective: This study aimed to determine whether second-opinion reviews of PET/CT examinations by subspecialists alter reporting of malignant findings.

Materials and methods: This IRB-approved study compared 240 fluorine-18 fluorodeoxyglucose PET/CT consecutively dictated reports by two nuclear medicine subspecialists against the original outside institution reports. Subspecialist reviews documented whether malignant findings on the outside report were malignant and noted additional malignant findings not described on the outside report. The final diagnosis of malignancy or benignity was determined by pathology when available, otherwise by imaging follow-up.

Results: A total of 22 findings (in 20 reports) called suspicious/malignant on the outside reports were deemed benign by subspecialist review. A final diagnosis was available for 20 of 22 findings by pathology (n=3) or follow-up imaging (n=17). The subspecialist review was accurate in 20 (100%) of 20 cases where a final diagnosis was available. The subspecialist review called 11 findings (in 11 reports) suspicious/malignant that were not described or deemed benign on the outside reports. Definitive diagnosis was available for 10 of 11 findings by pathology (n=7) or follow-up imaging (n=3). The second-opinion report was accurate in seven (70%) of 10 cases where a final diagnosis was available.

Conclusion: In 31 (13%) of 240 fluorine-18 fluorodeoxyglucose PET/CT examinations performed at an outside institution, subspecialist review resulted in at least one discordant opinion of malignancy. For 28 discrepant cases where a final diagnosis was available, the subspecialist review defined malignancy or benignity correctly in 25 (89%) of 28 cases. This provides evidence for the cost and effort invested in performing second-opinion reviews of PET/CT studies.

Figure 1

48-year-old woman with invasive ductal breast cancer. FDG PET/CT was ordered for systemic staging. (A) FDG PET MIP demonstrates multiple FDG-avid foci in the medial thorax (arrows). (B) Axial FDG PET, (C) axial non-contrast CT, and (D) axial FDG PET/CT demonstrate the FDG-avid foci localize symmetrically to the mediastinum and bilateral hila (arrows), without corresponding masses on CT. These findings were called nodal metastases on the initial report. Second opinion report called these findings likely benign, noting that bilateral hilar and mediastinal nodal metastases without axillary or internal mammary nodal metastases would be highly unlikely. A mediastinal biopsy was performed, yielding a diagnosis of sarcoidosis.

Figure 2

73-year-old woman with ovarian cancer. FDG PET/CT was ordered for staging. (A) Axial CT and (B) axial fused PET/CT demonstrate an FDG-avid focus in the inferior pelvis, without corresponding mass on CT. This was called malignant on the initial report. Second opinion report called this finding benign, noting the FDG-avid focus localized to the distal rectum and represented the rectal sphincter. Follow-up FDG PET/CT with (C) axial CT and (D) axial fused PET/CT demonstrated resolution of the FDG-avid focus, consistent with benign rectal sphincter avidity.

Figure 3

55-year-old woman with invasive ductal breast cancer. FDG PET/CT was ordered for systemic staging. (A) Axial FDG PET, (B) axial non-contrast CT, and (C) axial FDG PET/CT demonstrate the FDG-avid locally advanced left breast cancer (long arrows). The CT on lung windows demonstrated multiple small rounded nodules, without corresponding FDG avidity on PET. The nodules were called probably benign on the original report, noting lack of FDG avidity. Second opinion report called the lung nodules probably malignant. Biopsy demonstrated metastatic breast cancer, which increased the patient’s tumor stage to IV.