Comparison of whole-body FDG-PET and bone scintigraphy in the evaluation of skeletal metastases in patients with breast cancer

An established standard imaging modality for detecting bone metastases in patients with breast cancer is through the use of 99mTc-hydroxymethylene diphosphonate (99mTc-IIDP) bone scintigraphy. It is clearly documented that sensitivity is generally high while specificity is often lower because of tracer uptake in non-malignant processes. The aim of this study is to evaluate the diagnostic performance of whole body 2-deoxy-2-[18F]-D- glucose positron emission tomography (18 F-FDG PET) and bone scintigraphy in the detection of bone metastasis in patients with breast cancer.METHODS: There were 232 consecutive patients who underwent FDG PET for breast cancer staging/restaging at our center during the study period. We included those who only had a bone scintigraphy within a month before or after the PET scan. The results of each image interpretation were compared retrospectively by an experienced nuclear medicine physician. Per-patient and per-lesion detection rates were collected. Bone metastasis slams was established on the basis of multimodality imaging and/or clinical follow-up for at least 6 months Weighted kappa was also calculated to determine agreement between the two modalities.RESULTS: Forty-seven patients were included in the study with ages ranging from 28-86 years. For the patient-based data, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 90%, 92.6%, 90%, 92.6%, and 91.5%, respectively, for FDG PET, and 95%, 44.4%, 55.9%, 92.3% and 66%, respectively,for bone scintigraphy. For the lesion-based data, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 66.4%, 90%, 94.7%, 50%, and 72.8%, respectively, for FDG PET, and 74.5%, 27%, 752%, 26.3% and 62.6%, respectively, for bone scintigraphy Agreement between the two modalities was slight.CONCLUSIONS: Overall, FDG PET shows to be as sensitive as bone scintigraphy in picking up bone metastases Furthermore, on both per patient and per lesion bases; PET was shown to be more confirmatory and more accurate with evidence of statistical significance. FDG PET and bone scintigraphy should play complementary roles in the detection of skeletal metastases.

Incidental finding of colon adenocarcinoma on I-131 whole body scan in a patient with recurrent papillary thyroid carcinoma

?Iodine-131 (I-131) whole body scan is a procedure routinely done after radioactive iodine therapy. It helps detect presence of functioning thyroid tissue remnants in the neck, as well as distant metastases. However, not all that take up I-131 are of thyroidal origin. Our patient is a 74-year-old woman with recurrent papillary thyroid carcinoma, who underwent a repeat radioactive iodine therapy (RAIT). Her post-RAIT whole body scan showed an unusual iodine-avid focus in the transverse colon which was later confirmed to be another primary malignancy of colonic origin through colonoscopy with biopsy, as well as post-surgical histopathology. This case report distinctively demonstrates uptake of I-131 in extra-thyroidal malignancy. It also emphasizes the importance of evaluating carefully any irregular-looking focal iodine uptake in areas with seemingly physiologic activity on a routine I-131 whole body-scan.

Papillary thyroid carcinoma identified on bone scan with SPECT/CT in a patient presenting with multiple bone metastases

This is a case report of a 65-year-old female with lumbar vertebral lesions secondary to an unknown primary malignancy. 99mTc-methylene diphosphonate bone scintigraphy showed multiple bone metastases as well as focal extraosseous uptake in the area above the right supraclavicular area. Further imaging with SPECT/CT localized the calcified extraosseous uptake to the right thyroid bed. These findings narrowed down the primary malignancy to a thyroidal origin, which was eventually proven as such through immunohistologic studies of the lumbar lesions. Different pathophysiologic mechanisms of extraosseous uptake in bone scintigraphy and how SPECT/CT can increase the diagnostic value of a standard nuclear medicine procedure are highlighted in this paper.