Abstract
Background: The spine is not only the most frequent site of skeletal metastasis of a known carcinoma but it is also the most frequent site of bone metastasis of unknown primary tumor origin, however, most of the existing reports that analyzed the clinical features of patients who presented with skeletal metastasis of unknown origin have included cases of bone metastasis at any location. Objective: This study was conducted to analyze the clinical features, survival, and specific diagnostic implications in patients presented with spinal metastasis of unknown primary malignant tumor. Method: In this prospective study, 40 patients presented with spinal metastasis of unknown primary tumor origin to Mosul Oncology Hospital were followed up. Result: The primary malignant tumor was identified in (97.5%) of cases, lung cancer was the most frequently identified primary tumor (35%) followed by carcinoma of the breast (30%) and prostatic cancer (12.5%). We found that Computed tomography scan of the chest, abdomen, and pelvis were the most useful diagnostic modality to identify the primary malignant tumor and there was a significant difference in the overall survival of patients with different primary tumor sites, shorter survival time was observed for aggressive tumor like lung cancer compared to patients having less aggressive primary tumor like breast and prostatic cancer. Conclusion: Spinal metastasis of unknown primary carries a diagnostic challenge to the clinician, it is possible to detect the primary site in the majority of patients if we follow optimal diagnostic strategies. Detection of primary tumor site could help the clinician to provide the best therapeutic strategies.
Highlights
3.5 Overall survival: The mean survival duration for all 40 patients was 13.6 months ranging from 430 months, shorter survival duration was reported for patient with hepatocellular carcinoma (4 months), the mean survival duration for patients with lung cancer was 6.6 months ranging from (5-9 months) and it is significantly shorter comparing with the survival duration for patients with breast and prostatic cancers (P value =0.000), This study showed that the mean survival duration for patients with breast cancer was 18.7 months ranging from 10-23 months, while for the prostatic cancer patients, the mean survival duration was 18.8 months ranging from 15-26 months, as shown in figure 1
Prostatic cancer with its high probability for bone metastasis 29 was the 3rd most frequently identified malignancy in this study, which is consistent with the results of most previous studies, 19,21,26 but we did not identified any gynecological primary malignancy, most of previous studies showed that gynecological malignancy was rarely found to be the primary tumor. 19,22,27 We found that CT scan of the chest was helpful diagnostic tool for the detection of 10 (71.4%) out of 14 patients with lung cancer, a similar detection rate was reported by other study
36 Regarding the location of spinal metastasis, we found that lumber spine was the most frequent site of spinal metastasis of unknown primary, followed by thoracic spine, this result is different from the result of Sagban et al which included 5 cases with spinal metastasis of unknown primary and showed that dorsal metastasis is more frequent followed by lumber metastasis
Summary
The bone is the third most frequent distal site of metastatic cancer after liver and lung, it could be the first manifestation of malignant tumor in about 25-30% of cancer patients.[1,2] Any malignant tumor may metastasize to the skeleton, cancer that originate from epithelium is characterized by a particular propensity for bone metastasis,[3,4,5,6] all literatures data reported that lung cancer is the most common identified cancer that metastasize to the bone.[4,5,6,7,8] Other most frequent primary tumor that metastasize to bone are prostatic cancer, breast cancer, renal cell carcinoma and gastrointestinal tumors.[4,5,6,7,8] The spine was reported to be the most frequent site of skeletal metastasis followed by pelvic bone and bones of extremities,[6] and the majority of cases have multiple bone lesions, while solitary bone lesion occurred only in about 32.5%. 9,10. Diagnostic work up for those patients presented with bone metastasis of unknown primary tumor is overlapping with overall cancer of unknown primary workup. It includes medical history, physical examination, bone metabolism biochemical test, and Computed Tomography (C.T scan) of chest, abdomen and pelvis .12,13. It has been reported that the spine is the most frequent site of skeletal metastasis of a known carcinoma and it is the most frequent site of skeletal metastasis of unknown primary tumor origin,[15,16] most of the published reports on the skeletal metastasis of unknown primaries had included cases of bone metastasis at any location, we conducted this study to analyze the clinical features and specific diagnostic and therapeutic implications in patients presented with spinal metastasis of unknown primary tumor origin.
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