Primary malignant sarcomas of the spine are extremely rare. It has been estimated that they account for 5% to 10% of all primary bone neoplasms. 5,10 Primary sarcomas of the spinal column are difficult to classify as a clinical entity. The complex neuromusculoskeletal development of the spine may account for a spectrum of malignant tumors with distinct biologic behaviors. 4 Because of biologic heterogeneity, these tumors have variable sensitivity to radiation and chemotherapy. 4 Characterization of the tumor type is essential for devising an appropriate therapeutic strategy.
Adequate local control through complete tumor removal is an important therapeutic goal. However, aggressive resection of tumors in the spinal column must be coupled with restoration of spinal column stability and minimization of neural deficits. 2 The balance of these factors makes treatment of primary sarcomas of the spine challenging, and dictates an individual approach to treatment.
There is evidence that entering a sarcoma during its surgical resection has a detrimental effect with respect to local recurrence and survival. 1,3,21,22 Advances in surgical approach, instrumentation, and stabilization techniques have allowed surgeons to attempt resection and reconstruction of extensive tumors. Although wide excision is the surgical mainstay of oncologic resection in the mobile spine, it is limited by proximity to neurologic and vascular structures. Furthermore, reconstruction of large multisegmental defects of the spine creates challenges for stabilization and long-term fusion. As these techniques evolved, resection of multiple vertebral segments with clinically acceptable morbidity has become possible. Surgical treatment is aimed at cure rather than palliation whenever possible. 11
The purpose of the current study was to review the treatment of primary sarcomas of the mobile spine, with particular attention to the relationship of resection technique and surgical margins to local recurrence, and surgical factors that contribute to overall patient outcome.
MATERIAL AND METHODS
The study population consisted of 30 consecutive patients (20 men and 10 women) with primary sarcomas of the mobile spine that were operated on at the authors’ institution from January 1, 1970 through December 31, 2000. Only patients were included whose entire surgical care occurred at the authors’ institution. Details on demographics, distribution of tumors by spinal column level, and histologic type are shown in Tables 1 and 2. The age distribution is shown in Figure 1.
Data for the current study were reviewed retrospectively from medical records maintained in the tumor registry at the authors’ institution. The tumor registry is an electronic database system that contains detailed information on treatment and followup of each patient with cancer who was treated at the authors’ institution. These data included patient age, histologic type of the tumor, tumor localization, extent of spinal column resection, type of tumor removal as documented by the surgeon in the operative note, intraoperative neurologic complications, resection margins achieved as documented by the pathologist, local recurrence, and overall survival.
All patients enrolled in the study had surgical excision of the lesion. In 12 patients (40%), surgeons documented that en bloc resection was accomplished. In the remaining 18 patients (60%), the surgeon documented that the tumor was resected in a piecemeal fashion. The surgical margins were classified as wide in seven patients (23.3%), marginal in three patients (10%), and intralesional in 20 patients (66.7%). In 11 patients (36.7%), the extent of resection was limited to one vertebral level. In the remaining 19 patients, four patients (13.3%), six patients (20%), seven patients (23.3%), and two patients (6.7%) had resection of two, three, four, and five vertebral levels, respectively. Of the 12 patients who had en bloc resection, seven (58.3%) had one-level resection, four (33.3%) had a two-level resection, seven (58.3%) had one-level resection, four (33.3%) had a two-level resection, and one (8.3%) had a three-level resection. Pathologic evaluation revealed that resection margins of 12 specimens (40%) were free of tumor. In the remaining 18 specimens (60%), nine (30%) had microscopic involvement of the resection margins with tumor and nine (30%) margins contained macroscopically evident tumor tissue at the resection. One patient died of cardiac arrest on postoperative Day 14 after en bloc resection of a primary sarcoma of the spine. Overall, 12 of 30 patients (40%) experienced local recurrences of their tumors after primary surgical resection.
Analysis of Local Recurrences
Status of Margin
Of the 30 patients in the study, 12 patients had margins free of tumor (negative margins) at the time of surgery. Of these 12 patients, two had a local recurrence of tumor. One patient had a myofibroblastic sarcoma and the other patient had a chondrosarcoma. The local recurrence rate for patients with a negative margin was 16.7% (two of 12). The remaining 10 patients, who had negative margins, had no local recurrence.
Eighteen patients had residual tumor after surgery (positive margins). Of these 18 patients, 10 had a local recurrence. Five patients had microscopic involvement and five patients had macroscopic involvement. Therefore, the rate of recurrence for patients with positive margins is 55.6% (10 of 18). There were equal numbers of local recurrences in patients who had microscopically positive or macroscopically positive resection margins.
Type of Resection: En Bloc Versus Piecemeal Resection
The method of tumor removal may have an important effect on local recurrence rates. When the tumor was removed en bloc, and had negative margins, only one of nine patients (11.1%) had a local recurrence. When the tumor was removed piecemeal, and had negative margins, one of three patients had a local recurrence (33%). As noted previously, if the margins were positive, high rates of local recurrence were observed irrespective of resection method. For en bloc resections with positive margins, the recurrence rate was 67% (two of three). For piecemeal resections with microscopically or macroscopically positive margins, the recurrence rates were 50% and 57%, respectively.
Patients with local recurrence did poorly. Local recurrence resulted in disease progression and the patients’ death in 11 of 12 patients (92%). The average time of death was 16.6 months after diagnosis of the local recurrence. The remaining patient had secondary surgical resection and still is alive without evidence of disease. The median survival in this series was 56 months. For patients who had en bloc resection, the median survival was 62 months. The median survival of the patients who had piecemeal resection was 37 months.
Surgical treatment of primary sarcomas of the mobile spine is challenging. The goal of complete tumor removal must be weighed against the ability to preserve neural function and restore spinal stability. As with any surgical procedure, the first measure of quality is safety. Specifically, can the resection of the malignant lesion of the spine be done with acceptable rates of mortality and morbidity? In agreement with currently available reports, 11,19,20 the current data show that resection of malignant lesions of the mobile spine can be completed safely in the majority of the patients. In the current series, resections of the tumor of as many as five vertebral levels were accomplished successfully at locations from C3-L5. The technique requires a portion of the vertebral canal ring to be free of tumor to allow a path through which the specimen can be separated from the thecal sac. Unilateral nerve root transection may be required for tumors that involve the pedicle, neural foramen, or extraforaminal paravertebral tissues. No significant intraoperative neurologic complications were observed in the current study.
Another important parameter for success is the local recurrence rate, because local recurrence correlates highly with poor clinical outcome. The current data show that local recurrence is dependent on the condition of the resection margin. The likelihood of recurrence is five times higher if the surgical margin contains tumor cells, whether it is evident microscopically or macroscopically.
The method of tumor resection also may be important. The current data showed that piecemeal resection, even though negative margins are achieved, led to a relatively high recurrence rate (33%). In contrast, en bloc resection with tumor free margins had a low rate of recurrence (11%). There are only a small number of patients in the current study; therefore, statistical significance is limited. Earlier reports showed that violation of the tumor capsule, the tumor, or both resulted in a two -to eightfold increased risk of local recurrence. 6,9,12,14–17 Fidler 7,8 reported that piecemeal resection can produce acceptable results. He reported good results using intralesional excision combined with extralesional resection of the entire pseudocapsule and meticulous removal of any tumor spill. The question of whether approach combined with radiation therapy can provide comparable local tumor control to complete en bloc resection remains to be answered.
The current study also showed a relationship between local control and overall survival. Most of the deaths in the current series were attributable to complications from local recurrences. More than 90% of the patients with local recurrence died at an average of 16.6 months after diagnosis of local recurrence. Other authors observed similar trends. 13,18,22,23
Despite the unavoidable limitations of this study, which include small sample size, histologic heterogeneity of the tumors, and varying nonoperative treatment strategies, improved clinical results tend to be achieved with en bloc, complete tumor resection. In the current study, residual tumor at the surgical margin, and resection in a piecemeal fashion, resulted in higher recurrence rates that were associated with early mortality. Therefore, the surgeon should attempt complete en bloc tumor resection whenever possible.
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Mark T. Scarborough, MD; B. Hudson Berry, MD; W.F. Enneking, MD; Albert Aboulafia, MD; and Eugene Mindell, MD, Guest Editors