Detection of a second malignancy in prostate cancer patients by using [(18)F]Choline PET/CT: a case series.

Background: The role of radiolabeled choline (Cho) in patients with biochemical recurrence after radical treatment for prostate cancer (PCa) is well established. Its widespread clinical use has prompted the depiction of incidentalomas, unusual sites of metastatic lesions, as well as false positive and negative cases. We reported a series of patients affected by biochemical recurrence of PCa imaged by [(18)F]Cho positron emission tomography/computed tomography (PET/CT) which resulted suspected for a second malignancy.

Case Presentation: [(18)F]Cho PET/CT was performed in patients with biochemical PCa recurrence. From an internal clinical database we identified patients in which PET/CT resulted suspected for a second malignancy. A second malignancy was suspected in presence of "unusual" site of [(18)F]Cho uptake not consistent with clinical-instrumental history. Histology was used as reference standard for final diagnosis. Seven PCa patients (76 years, 71-84 years) with the suspicion of a second tumor based on [(18)F]Cho PET/CT findings were identified. Mean value of PSA at the time of [(18)F]Cho PET/CT was 2,37 ng/mL. The median time between PCa diagnosis and PET/CT was 6 years (range 0-14 years). In two cases history of a second malignancy (lung cancer and cutaneous basocellular carcinoma) was known (diagnosed 12 and 6 years after PCa, respectively). PET/CT identified 13 sites of [(18)F]Cho uptake (lung = 5, lymph node = 7, bone = 1). Final diagnosis was consistent with lung cancer in 5/7 cases (first diagnosis = 4/5, recurrence = 1/5), colorectal cancer and nodal metastases from melanoma in 1 case each.

Conclusions: Although the clinical usefulness of Cho PET/CT for detecting cancer lesions other than prostate origin is known, for those patients who undergo this examination according to indication, the diagnosis of a second tumor has a significant impact on their therapeutic management.