Evidence & Methods
Although a number of studies support the benefits of en-bloc surgical resection for survival in the setting of benign-aggressive and malignant spinal tumors, information is limited regarding long-term outcomes. Furthermore, most data are derived from small retrospective series and case reports. To address this shortcoming, the authors endeavored to present results for a series of 103 consecutive patients treated with en-bloc vertebral resection over a 20-year period.
At mean follow-up of 100 months, 69 patients treated with en-bloc resection showed no evidence of disease recurrence. The success rate of en-bloc resection in achieving adequate margins was determined to be approximately 82%. Postoperative complications occurred in over 40% of patients and post-surgical mortality approached 2%.
This study makes a valuable contribution to the literature in terms of its capacity to provide long-term follow-up data on a large series of patients treated with en-bloc vertebral resection. Given the rarity of these tumors, as well as the ethical implications associated with treatment, it is difficult to envision that research providing a higher level of evidence is possible. Nonetheless, in spite of the methods used by the authors to collect their data, this series is uncontrolled and subject to substantial confounding by indication. While clearly demonstrating the complication-profile and potential benefit the en-bloc technique has for select individuals, the evidence presented cannot be considered anything above level IV. In addition, as the authors themselves emphasize, the results achieved by a surgical center with vast experience in treating these types of complex spinal tumors are not necessarily translatable to other hospitals or health care systems.
—The Editors
Primary bone tumors of the spine are extremely rare. They represent 11% [1] of all primary tumors of the musculoskeletal system, 4.2% [2] of all spinal tumors, and approximately 0.4% [3] of all malignancies.
En bloc resection of primary tumors refers to the surgical removal of the whole tumor in a single piece, fully encased by a layer of healthy tissue. This procedure was first proposed by Enneking et al. [4] for bone and soft-tissue limb tumors, possibly in combination with adjuvant chemotherapy within the so-called “limb salvage surgery.” The new procedure dramatically reduced the rate of amputations without the negative impact and sometimes even improving the local and systemic disease control.
The application of this philosophy to spinal bone tumors is debatable because of anatomic constraints and to the proximity of unresectable structures. Stener [5] was the first pioneer of en bloc resections in the spine, followed later on by Roy-Camille et al. [6], and finally by Tomita et al. [7]. According to histologic diagnosis and oncological staging system [4], en bloc resection in the spine is indicated for aggressive benign tumors (Stage 3) and malignant primary tumors. Adjuvant treatments should also be considered for high-grade malignancies. The Weinstein-Boriani-Biagini (WBB) surgical staging system [8] was created for planning en bloc resection to achieve the appropriate histologic margins, and it has been validated both clinically [9] and by a reliability assessment [10].
En bloc resection, however, is mostly a very demanding surgery, associated with high morbidity. Functionally relevant structures are often contiguous with the tumor or invaded by it. The sacrifice of these structures, such as nerve roots, is sometimes required to achieve an appropriate margin.
Discussion is open regarding balancing surgical aggressiveness planned on Enneking criteria, possibly provoking severe functional damages versus intentional transgression to these principles to save function [9], combined with adjuvant therapies.
The decision-making process, therefore, should include not only oncological criteria but also a risk/benefit discussion considering the sacrifices required to achieve the appropriate margins.
The results obtained from the previous publication support the use of en bloc resection in the surgical management of primary tumors of the spine, despite the low quality of evidence of the literature because of the rarity of these tumors [9], [11], [12], [13], [14], [15], [16], [17], [18]. In addition, the use of different terminology reduces the level of reliability [11], [19], [20], [21].
The authors collected the data from 103 consecutive patients submitted to en bloc resection during 20 years of experience in a single institution. Data were analyzed according to a careful methodology [22] in a prospective cohort study to validate the application of en bloc resection to the aggressive benign and primary malignant spinal tumors.
To assess the effectiveness and the safety of this procedure, we formulated two research questions. First, we sought to examine whether surgical margins obtained during en bloc resection (among other surgical and clinical parameters) predicted recurrence or mortality. As secondary goals, we sought to describe the effect of the diagnostic workup on the results and the morbidity and mortality of these procedures.