The majority of spinal metastases involve multiple columns and have epidural disease with cord compression and spinal instability. The goal of surgery is often palliative, with circumferential decompression and reconstruction of the spine. This often requires staged anterior and posterior approaches, which carry a high morbidity. We achieved a high success rate in functional outcome and pain relief that improved the quality of life of our patients. Furthermore, this was achieved with an acceptable rate of perioperative morbidity and mortality. In surgical candidates, avoiding preoperative radiotherapy might decrease complications.
In early 1980, Stener and Roy-Camille were the first to describe en bloc spondylectomy via a posterior approach after complete resection of the dorsal vertebral structures, i.e., both laminae, spinous process and parts of the pedicles, resulting in an oncological adequate resection for primary bone tumor locations not extending beyond the vertebral body [23, 26]. Based on these reports, several authors have begun to develop further techniques for en bloc vertebrectomy encompassing variable indications, approaches, stabilization techniques and yielding promising results in view of local control and overall prognosis [6, 20, 27, 32, 38]. Tomita et al. reported a technique with dorsal en bloc resection after transpedicular osteotomy followed by ventral vertebrectomy [32]. Significant progress in decision making for surgical therapy of spinal malignancies was made by the surgical classification for tumors of the spine described by Boriani et al. [8]. Depending on the stage, localization and extension of the tumor within the affected vertebra, the approach and mode of resection can be deduced. In addition, applying the oncological principles of muskuloskeletal surgery of the extremities to the spine, Tomita et al. have modified the surgical staging system of Enneking et al. [13] and developed a surgical classification of vertebral tumors, considering tumors strictly located in the vertebral body, pedicle or laminae as intra-, and malignancies spreading beyond the vertebral cortex into the spinal canal (epidural space), paraspinal area or disk space as extracompartmental [32]. While wide resections for tumor not penetrating the cortex of the vertebra are definitely feasible, attainment of wide resection margins for extracompartmentally located spinal tumors is profoundly complicated and may require additional resection of adjacent tissue layers functioning as a biological border for invading tumor cells. Furthermore, as described by Krepler et al., extracompartmental tumor growth into the spinal canal with invasion of the dura can necessitate en bloc spondylectomy with dura resection and replacement, again underscoring the essential importance of wide margins in the surgical treatment of malignant spinal bone tumors [19]. However, extracompartmental tumor growth with circumferential dura invasion or anterior invasion around major vascular structures does not allow for wide resection, but verges on the limits of what is surgically feasible and oncologically useful.
Based upon these reports, the aim of the current study was to present our results of total en bloc spondylectomy (TES) for patients with solitary spinal metastasis and primary malignant vertebral tumors.
Tomita et al. were the first to extend the surgical oncological concept of en bloc spondylectomy also to the treatment strategy of solitary spinal metastases of selected patients with specific tumor entities [33-35]. According to these studies, there is general consensus that indication for en bloc spondylectomy requires careful patient selection for which the following criteria might be helpful: (1) no underlying tumor type, which is considered to be a systemic disease, (2) tumor types that are known to be biologically favorable and to have a prolonged course (e.g., renal cell or mamma carcinoma), (3) radical treatment of the original/primary tumor, (4) long period between treatment of primary tumor and diagnosis of solitary metastatic disease, and (5) verification of isolated/solitary metastatic disease in CT scans, bone scan and/or PET.
Tomita et al. have developed a prognostic scoring system for spinal metastases [33-35] by revealing a relationship between grades of malignancy and the extent of visceral and further bone metastases on the one hand and long-term local controls as well as disease-free survival on the other. Based on the prognostic score and expected survival periods, treatment goals could be defined and the appropriate oncological surgical strategy, ranging from simple spinal cord decompression to en bloc spondylectomy, can be selected. In this context, Sakaura et al. reported on the outcome of TES for solitary metastasis of the thoracolumbar spine with a local recurrence in two patients, 23 and 25 months after surgery, and dead of disease in 5 of 12 patients [24]. These reports are partly consistent with our results showing no local tumor relapse and dead of disease after a mean survival of 10 months in 2 of 12 patients. Based on the observation that local recurrence of solitary metastases occurred in cases of extracompartimental extension, Sakaura et al. proposed that TES should be limited to intracompartmental solitary lesions. Although in none of our patients with extracompartmental metastatic location local tumor relapse occurred, distant metastases developed in four patients (36%) with initially solitary metastatic lesions. Therefore, efforts must be undertaken to effectively improve postoperative control of distant disease.
Most studies analyzing the results by management with en bloc spondylectomy focus on the oncological outcome without assessing postoperative function and quality of life. As measured by Oswestry-low-back-pain-disability index and the SF-36 health survey, the present study shows that en bloc spondylectomy results in acceptable function as well as physical and mental health (Fig. 2). Results of the validated psychometric questionnaire SF-36 demonstrate that in relation to the normal population, the impact of en bloc spondylectomy on physical components (physical function, role physical, body pain) is more pronounced than on mental scales (vitality, social functioning, role emotional, mental health), which have been nearly comparable to normative values. This notion is underscored by the inverse correlation between the ODI and SF-36 score (Fig. 3) of the surviving patients, indicating the causal role of physical dysfunction (increased ODI) for decreased SF-36 (reduced quality of life) after en bloc resections when compared to the normal population.
Conclusion
This study agrees with previous investigations [2, 6, 18, 21, 24, 32, 34, 38] supporting en bloc spondylectomy for treatment of primary malignant vertebral bone tumors and solitary spinal metastasis of certain tumor entities. En bloc spondylectomy followed by dorsoventral reconstruction allowed radical resections with negative margins in all patients. The present results of a very low local recurrence rate in all patients should be interpreted with caution, as some patients have a follow-up period of less than 18 months and no conclusions can be drawn for these patients in terms of long-term tumor-free survival. However, despite a mean follow-up time of only 33 months, heterogeneity of histological diagnoses and a relatively small number of patients in the current study, long-term local relapse-free survival could be achieved. While en bloc spondylectomy is a technically demanding and risky operation, it allows in attaining wide to marginal resections for primary tumors and solitary metastatic lesions of the spine. However, exact preoperative diagnostic imaging and planning has to precede a realistic evaluation if wide to marginal resections can be achieved in order to justify the risk for the patient. Furthermore, careful selection of patients, consideration of underlying tumor type and extensive experience in spine surgery and reconstruction are essential preconditions for low complication rates, acceptable function and increased overall outcome. Finally, despite excellent local control rates, the limitation for long-term disease-free survival in our patients is distant metastases. Consequently, systemic therapies need to be developed aimed at targeting pathways involved in postoperative metastatic spread and to modify them to impair disseminated tumor growth.
In early 1980, Stener and Roy-Camille were the first to describe en bloc spondylectomy via a posterior approach after complete resection of the dorsal vertebral structures, i.e., both laminae, spinous process and parts of the pedicles, resulting in an oncological adequate resection for primary bone tumor locations not extending beyond the vertebral body [23, 26]. Based on these reports, several authors have begun to develop further techniques for en bloc vertebrectomy encompassing variable indications, approaches, stabilization techniques and yielding promising results in view of local control and overall prognosis [6, 20, 27, 32, 38]. Tomita et al. reported a technique with dorsal en bloc resection after transpedicular osteotomy followed by ventral vertebrectomy [32]. Significant progress in decision making for surgical therapy of spinal malignancies was made by the surgical classification for tumors of the spine described by Boriani et al. [8]. Depending on the stage, localization and extension of the tumor within the affected vertebra, the approach and mode of resection can be deduced. In addition, applying the oncological principles of muskuloskeletal surgery of the extremities to the spine, Tomita et al. have modified the surgical staging system of Enneking et al. [13] and developed a surgical classification of vertebral tumors, considering tumors strictly located in the vertebral body, pedicle or laminae as intra-, and malignancies spreading beyond the vertebral cortex into the spinal canal (epidural space), paraspinal area or disk space as extracompartmental [32]. While wide resections for tumor not penetrating the cortex of the vertebra are definitely feasible, attainment of wide resection margins for extracompartmentally located spinal tumors is profoundly complicated and may require additional resection of adjacent tissue layers functioning as a biological border for invading tumor cells. Furthermore, as described by Krepler et al., extracompartmental tumor growth into the spinal canal with invasion of the dura can necessitate en bloc spondylectomy with dura resection and replacement, again underscoring the essential importance of wide margins in the surgical treatment of malignant spinal bone tumors [19]. However, extracompartmental tumor growth with circumferential dura invasion or anterior invasion around major vascular structures does not allow for wide resection, but verges on the limits of what is surgically feasible and oncologically useful.
Based upon these reports, the aim of the current study was to present our results of total en bloc spondylectomy (TES) for patients with solitary spinal metastasis and primary malignant vertebral tumors.
Tomita et al. were the first to extend the surgical oncological concept of en bloc spondylectomy also to the treatment strategy of solitary spinal metastases of selected patients with specific tumor entities [33-35]. According to these studies, there is general consensus that indication for en bloc spondylectomy requires careful patient selection for which the following criteria might be helpful: (1) no underlying tumor type, which is considered to be a systemic disease, (2) tumor types that are known to be biologically favorable and to have a prolonged course (e.g., renal cell or mamma carcinoma), (3) radical treatment of the original/primary tumor, (4) long period between treatment of primary tumor and diagnosis of solitary metastatic disease, and (5) verification of isolated/solitary metastatic disease in CT scans, bone scan and/or PET.
Tomita et al. have developed a prognostic scoring system for spinal metastases [33-35] by revealing a relationship between grades of malignancy and the extent of visceral and further bone metastases on the one hand and long-term local controls as well as disease-free survival on the other. Based on the prognostic score and expected survival periods, treatment goals could be defined and the appropriate oncological surgical strategy, ranging from simple spinal cord decompression to en bloc spondylectomy, can be selected. In this context, Sakaura et al. reported on the outcome of TES for solitary metastasis of the thoracolumbar spine with a local recurrence in two patients, 23 and 25 months after surgery, and dead of disease in 5 of 12 patients [24]. These reports are partly consistent with our results showing no local tumor relapse and dead of disease after a mean survival of 10 months in 2 of 12 patients. Based on the observation that local recurrence of solitary metastases occurred in cases of extracompartimental extension, Sakaura et al. proposed that TES should be limited to intracompartmental solitary lesions. Although in none of our patients with extracompartmental metastatic location local tumor relapse occurred, distant metastases developed in four patients (36%) with initially solitary metastatic lesions. Therefore, efforts must be undertaken to effectively improve postoperative control of distant disease.
Most studies analyzing the results by management with en bloc spondylectomy focus on the oncological outcome without assessing postoperative function and quality of life. As measured by Oswestry-low-back-pain-disability index and the SF-36 health survey, the present study shows that en bloc spondylectomy results in acceptable function as well as physical and mental health (Fig. 2). Results of the validated psychometric questionnaire SF-36 demonstrate that in relation to the normal population, the impact of en bloc spondylectomy on physical components (physical function, role physical, body pain) is more pronounced than on mental scales (vitality, social functioning, role emotional, mental health), which have been nearly comparable to normative values. This notion is underscored by the inverse correlation between the ODI and SF-36 score (Fig. 3) of the surviving patients, indicating the causal role of physical dysfunction (increased ODI) for decreased SF-36 (reduced quality of life) after en bloc resections when compared to the normal population.
Conclusion
This study agrees with previous investigations [2, 6, 18, 21, 24, 32, 34, 38] supporting en bloc spondylectomy for treatment of primary malignant vertebral bone tumors and solitary spinal metastasis of certain tumor entities. En bloc spondylectomy followed by dorsoventral reconstruction allowed radical resections with negative margins in all patients. The present results of a very low local recurrence rate in all patients should be interpreted with caution, as some patients have a follow-up period of less than 18 months and no conclusions can be drawn for these patients in terms of long-term tumor-free survival. However, despite a mean follow-up time of only 33 months, heterogeneity of histological diagnoses and a relatively small number of patients in the current study, long-term local relapse-free survival could be achieved. While en bloc spondylectomy is a technically demanding and risky operation, it allows in attaining wide to marginal resections for primary tumors and solitary metastatic lesions of the spine. However, exact preoperative diagnostic imaging and planning has to precede a realistic evaluation if wide to marginal resections can be achieved in order to justify the risk for the patient. Furthermore, careful selection of patients, consideration of underlying tumor type and extensive experience in spine surgery and reconstruction are essential preconditions for low complication rates, acceptable function and increased overall outcome. Finally, despite excellent local control rates, the limitation for long-term disease-free survival in our patients is distant metastases. Consequently, systemic therapies need to be developed aimed at targeting pathways involved in postoperative metastatic spread and to modify them to impair disseminated tumor growth.
