br Conclusions In patients with only one
Conclusions: In patients with only one bone containing a metastasis but no visceral metastasis, bones near the primary were more likely to be first metastasized. This may be a valuable clue to primary tumor sites in patients with cancers of unknown primaries.
The skeleton is the most common site for distant metastases from malignant tumors, with the prevalence highest in breast and prostate cancers [1,2]. As many complications of bone metastasis, including severe bone pain, pathological fractures, spinal cord compression, and hypercalcemia, are threats to patients’ wellbeing and quality of life, early diagnosis of bone metastases is of great importance for patients
Bone metastasis of cancer can be a result from systemic blood spreading or vertebral venous plexus spreading . Metastases carried through the circulatory system may spread to any bone in the body, as this pathway is considered to be random . Although numerous stu-dies have been published about systemic circulatory bone metastases, few studies had addressed bone metastasis through the vertebral venous plexus [8–11], and the pattern of vertebral venous plexus related bone
E-mail addresses: [email protected] (Z. Luo), [email protected] (X. Hu). 1 These authors have contributed equally to this work.
metastasis had not been elucidated.
The vertebral venous plexus is generally described as a valveless network of veins that extends from cranium to pelvis . The ver-tebral venous plexus, consisting of an external and an internal series which are in free communication , anastomose with the vertebral, posterior intercostal and lumbar veins . The intercostal veins ana-stomose with the veins in the shoulder girdle , so tumor 546-06-5 can metastasize to the shoulder girdle through the vertebral venous plexus. Although vertebral venous plexus spread bone metastasis can aﬀect any bone in the torso, it rarely reaches the extremities. Therefore, our study excluded patients with only metastasis in their extremities, and the patterns of extremities metastasis were not included in our analysis.
Bone scan is a sensitive but not specific method . And in direct comparisons with conventional bone scans, positron emission tomo-graphy (PET) revealed more lesions , and a combined positron emission tomography/computed tomography (PET/CT) scanner fuses PET image and CT image to depict lesions in suﬃcient anatomic details . However, as PET/CT is not a full-body scan, but bone scanning is, we added the extra clinical data of bone scans to our analyses.
This study was undertaken to explore bone metastasis pattern in patients whose primary tumors had been well identified, in hope of providing clues to origins of primary tumors for patients with cancers of unknown primaries (CUP).
As visceral metastasis is mainly spread via the circulatory system, we excluded patients with visceral metastasis to preclude those with circulatory system-carried metastasis, and assumed that bone metas-tases of the remaining patients were through vertebral venous plexus, to ensure that our study was focused on debating about the vertebral venous plexus as an alternative metastatic route.
2. Patients and methods
Of 2559 consecutive cancer patients with bone metastases who were diagnosed by 18F-fluoro-2-deoxyglucose (FDG) PET/CT scans between January 1, 2015 and October 19, 2017 at Fudan University Shanghai Cancer Center, we filtered out those with visceral metastases (per pa-thology confirmation), multiple primary tumors, or with only bone metastases to the extremities (n = 8). Finally, we enrolled 290 patients. All patients involved in this study provided signed informed consent before their bone scan and PET/CT examination. Our study is in ac-cordance with the Code of Ethics of the World Medical Association.
2.2. PET/CT imaging and interpretation
All the patients fasted for 4–6 h before PET/CT and their blood glucose levels were under 10 mmol/L at the time of FDG injection. Examination was initiated 1 h after i.v. injection of FDG (7.4 MBq/kg). FDG PET/CT scanning was performed on Siemens biograph 16HR PET/ CT scanner (Knoxville, Tennessee, USA). First, unenhanced low-dose CT scans (120 kV automatic mA, modulation range of 130–370 mA) were acquired. Immediately after CT scans, three-dimensional PET scans were acquired (3–4 min per bed position). PET data were reconstructed iteratively by applying CT data for attenuation correction, and co-re-gistered images were displayed on a workstation.
Images were reviewed and manipulated in a multimodality com-puter platform (Syngo, Siemens, Knoxville, Tennessee, USA). Two ex-perienced nuclear medicine physicians, unaware of patients’ clinical information, evaluated the images independently. The reviewers reached a consensus in cases of discrepancy. FDG uptakes of lesions were measured as the maximum standardized uptake value (SUVmax).