The Benefits of PET in Staging of Rectal Cancer
Background: A 52 year old male with rectal cancer was treated with surgery and chemoradiotherapy which was completed in February 2006. A follow up colonoscopy and CT scans demonstrated remission. In August 2007 he presented with a rising carcinoembryonic antigen and a CT scan revealed a new 15mm solitary pulmonary metastasis in the left lower lobe. Further investigation of this nodule was required and an FDG PET/CT scan was ordered.
Method: In September, 368MBq 18F-FDG was administered intravenously and images were acquired an hour later from the upper neck to upper thighs. The GE Discovery VH hybrid gamma/PET/CT system was used and low dose CT was acquired for the purpose of attenuation correction and anatomical localization.
Results: The images revealed that the nodule in the left lung was FDG avid and consistent with metastasis. In addition, an incidental focal intense uptake was seen in the inferior pole of the right thyroid lobe. A fine needle aspiration biopsy was performed under ultrasound and showed malignant cells, however, the origin of the tumour could not be identified. Therefore, thyroid surgery was undertaken to remove the nodule and determine the cell type. In October 2007, the patient underwent a right hemithyroidectomy and very unusually, the pathology results showed a papillary thyroid tumour but also a metastasis from his rectal cancer within this primary tumour.
Conclusion: The FDG PET/CT scan impacted on this patient's management firstly by identifying that the lung nodule was a metastatic deposit and secondly by discovering the incidental thyroid cancer. This guided the excision biopsy of the thyroid nodule and the very unique findings changed the patient's therapy from aggressive to palliative.