Evaluation of 18-F-fluoro-2-deoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) as a staging and monitoring tool for dogs with stage-2 splenic hemangiosarcoma - A pilot study

Abstract

Positron Emission Tomography-Computed Tomography (PET-CT) is routinely used for staging and monitoring of human cancer patients and is becoming increasingly available in veterinary medicine. In this study, 18-fluorodeoxyglucose (18FDG)-PET-CT was used in dogs with naturally occurring splenic hemangiosarcoma (HSA) to assess its utility as a staging and monitoring modality as compared to standard radiography and ultrasonography. Nine dogs with stage-2 HSA underwent 18FDG-PET-CT following splenectomy and prior to commencement of chemotherapy. Routine staging (thoracic radiography and abdominal ultrasonography) was performed prior to 18FDG-PET-CT in all dogs. When abnormalities not identified on routine tests were noted on 18FDG-PET-CT, owners were given the option to repeat a PET-CT following treatment with eBAT. A PET-CT scan was repeated on Day 21 in three dogs. Abnormalities not observed on conventional staging tools, and most consistent with malignant disease based on location, appearance, and outcome, were detected in two dogs and included a right atrial mass and a hepatic nodule, respectively. These lesions were larger and had higher metabolic activity on the second scans. 18FDG-PET-CT has potential to provide important prognostic information and influence treatment recommendations for dogs with stage-2 HSA. Additional studies will be needed to precisely define the value of this imaging tool for staging and therapy monitoring in dogs with this and other cancers.

Fig 1. PET-CT scan #1 from dog 2.

The images from left to right are transverse (A, B, and C), sagittal (D), and dorsal plane (E), all acquired 1 hour following ¹⁸FGD injection. A and B represent the CT and PET transverse images, respectively, whereas C is the fused PET-CT transverse image. D represents the whole body ¹⁸FDG PET-CT scan, and E is the dorsal reconstruction whole body image. Fused and dorsal reconstruction images show increased metabolic activity at the right auricular appendage compared to background tissue. The focal area of uptake at the right auricular appendage is highlighted by the arrow.

Fig 2. PET-CT scan #2 from dog 2.

The images from left to right are transverse (A, B, and C), sagittal (D), and dorsal plane (E), all acquired 1 hour following ¹⁸FGD injection. A and B represent the CT and PET transverse images, respectively, whereas C is the fused PET-CT transverse image. D represents the whole body ¹⁸FDG PET-CT scan, and E is the dorsal reconstruction whole body image. Fused and dorsal reconstruction images show further increase in metabolic activity at the right auricular appendage compared to background tissue and growth of the right auricular mass compared to images obtained from PET-CT scan #1. The focal area of uptake at the right auricular appendage is highlighted by the arrow.

Fig 3. PET-CT scan #1 from dog 6.

The images from left to right are transverse (A, B, and C), sagittal (D), and dorsal plane (E), all acquired 1 hour following ¹⁸FGD injection. A and B represent the CT and PET transverse images, respectively, whereas C is the fused PET-CT transverse image. D represents the whole body ¹⁸FDG PET-CT scan, and E is the dorsal reconstruction whole body image. There was a focal area of uptake in the liver in proximity of the apex of the gall bladder highlighted by the arrow.

Fig 4. PET-CT scan #2 from dog 6.

The images from left to right are transverse (A, B, and C), sagittal (D), and dorsal plane (E), all acquired 1 hour following ¹⁸FGD injection. A and B represent the CT and PET transverse images, respectively, whereas C is the fused PET-CT transverse image. D represents the whole body ¹⁸FDG PET-CT scan, and E is the dorsal reconstruction whole body image. The focal area of uptake in the liver in proximity of the apex of the gall bladder is larger and exhibits further increase in metabolic activity compared to PET-CT #1.