The role of [18F]fluoro-2-deoxyglucose-PET scanning in the diagnosis of paraneoplastic neurological disorders

Abstract

The detection of an occult tumour in a patient with a suspected paraneoplastic neurological disorder (PND) may be difficult because of the limitations of conventional imaging techniques. [(18)F]fluoro-2-deoxyglucose-PET (FDG-PET) can visualize a small tumour anywhere within the body. We retrospectively reviewed the case notes of 43 unselected patients with suspected PND referred for FDG-PET scanning to determine how useful this technique was when conventional imaging was negative. All patients had undergone standard radiological investigations and bronchoscopy (where appropriate) prior to PET scanning. There were discrete areas of hypermetabolism suggestive of malignancy (positive) in 16 patients (37%). A tissue diagnosis of cancer was subsequently made in seven patients (two at post-mortem), further radiological studies were suggestive of cancer in one patient, one patient subsequently presented with a metastatic deposit which was biopsied, and four patients died shortly afterwards without a post-mortem. In three patients, subsequent investigations were negative for cancer. Serum anti-neuronal antibodies were present in 43% and CSF oligoclonal bands were present in 46% of patients with positive PET scans compared with 16 and 26%, respectively, in PET-negative patients, but this was not significant. Only one patient with a negative scan has been diagnosed subsequently as having malignancy on prolonged follow-up. These findings confirm that FDG-PET scanning is a useful technique in the detection of small tumours in patients with suspected PND. False positives and false negatives do occur, but at a sufficiently low frequency to justify the clinical usefulness of this technique.

Managing Paraneoplastic Neurological Disorders

“…Often, the tumor is detected by high-resolution computed tomography (CT) of the chest, abdomen, and pelvis. If the CT scan remains negative, whole-body fluorodeoxyglucose positron emission tomography (FDG-PET) or PET/CT is recommended to detect an occult tumor or its metastases [20][21][22]. In addition, the type of antibody and PNS may suggest a specific underlying tumor and indicate further diagnostic tests, such as mammography (may be replaced by MRI) or ultrasound of the testes or pelvis (Table 2).…”

“…When anti-Hu antibodies are detected or when the patient is at risk for lung cancer (smoking, age >50 years), a careful and repeated search for underlying SCLC is warranted. When the CT scan is negative, a total-body FDG-PET scan or FDG-PET/CT scan may detect the neoplasm [20,21]. When a tumor other than SCLC is detected in a patient with anti-Hu antibodies, it may unexpectedly express the Hu antigen [2] or may be an unrelated secondary neoplasm [31].…”

Paraneoplastic neurological syndrome in a patient with gastric cancer

“…In this context, it has been reported that PNS is unresponsive to treatment when the defi cits are fully established and irreversible neurological damage has occurred [9][10][11]. In most instances, the tumor is revealed by computed tomography (CT) of the chest, abdomen, and pelvis, and whole-body fl uorodeoxyglucose positron emission tomography (PET) may also be useful for detecting the primary lesion [12,13]. However, if the primary lesion is in the gastrointestinal tract, the tumor may be missed using these approaches.…”

Autoimmune and Paraneoplastic Channelopathies

“…If initial computed tomography of the chest is unremarkable, close follow-up or additional imaging with metabolic positron emission tomography (PET) is important. 30 Successful treatment of SCLC often leads to improvement in the symptoms of LES.…”