AO Spine identifies patient variables associated with post-operative clinical outcomes for spinal metastatic disease

AO Spine Knowledge Forum Tumor—a group of international spine oncology experts—has published a scoping review in Lancet Oncology on the Systemic Considerations for the Surgical Treatment of Spinal Metastatic Disease. The purpose of the work was to identify the pre-operative systemic variables that influence post-operative clinical outcomes among adult patients surgically treated for spinal metastatic disease (SMD).

Corresponding author Michael H. Weber explains, “Patients with spine metastasis are becoming a bigger and bigger part of our population, because of our success in managing this pathology with chemotherapy, immune therapies, and radiotherapy.” An estimated 10% of cancer patients develop spinal metastatic disease. Approximately 5–10% of those patients require spine surgery to improve pain, neurological function, health-related quality of life (HRQoL), and survival. To complicate the situation, many patients with SMD are elderly and have multiple comorbidities. The concept of “frailty” is important here, even though it has not been clearly defined in this patient group.

According to first author Mark A. MacLean, “It remains challenging to accurately assess patient's systemic condition and the ability to tolerate palliative surgery. This is in part due to the complex interaction of many systemic variables that can be weighed during the decision-making process. Our review is the first to concisely summarize these variables and their impact on clinical outcomes. The findings are relevant to medical, radiation, and surgical oncologists. These factors might inform shared decision-making with patients and their families.”

The findings

For this comprehensive scoping review, the AO Spine group first identified all potentially relevant, peer-reviewed articles published in English from January 2000 through July 2021. These initial searches yielded 4,295 unique articles, which were further screened based on pre-defined criteria. Studies had to involve at least 30 patients who were at least 18 years old and undergoing a first surgery for spinal metastasis. The intervention could involve any spinal surgical procedure or minimally invasive surgery (MIS) for the purpose of treating intractable pain, spinal instability, progressive neurological deficit, or for general oncological resection. When multiple studies used the same patient cohort, only one representative study was considered for inclusion. A total of 61 articles satisfied all criteria, representing a combined total of 22,335 patients. This patient population was 63% male, with the mean age at the time of surgery being 60.4 years.

Contributing author Miltiadis Georgiopoulos explains, “The identified systemic variables included demographics (e.g., older age, black race, male gender, abnormal body mass index, smoking status), deconditioning and ambulatory status, performance status, health-related quality of life, medical comorbidities, biochemical and hematological abnormalities, and cancer systemic disease burden. These variables were found to negatively impact surgical outcomes including survival and complications in most studies, but also postoperative deconditioning and ambulatory status, performance status, HRQoL, length of hospital stay, non-home discharge, re-operation, and re-admission.”

Georgiopoulos adds, “The mind-boggling number of preoperative variables may render this subject difficult to digest, but our review summarized the evidence in a simpler, yet comprehensive way.” Similar results from different studies were grouped together to allow for concise summarization in a handful of tables. For example, 40 of the 61 studies examined survival as an outcome, while only one study examined health-related quality of life as an outcome. In the exploration of pre-operative variables, older age was associated with a decrease in overall survival (OS) in 8 studies after univariate analysis, and in 3 studies after multivariate analysis. Low BMI or weight loss at pre-op was associated with a poor outcome at the 90-day follow-up in 2 studies after univariate analysis and multivariate analysis.

According to Weber, “We were able to identify a bunch of variables that were showing up again and again as being predictive of patients that do well, and patients that are a little more vulnerable and probably not good surgical candidates.” Weber believes the results will give surgeons an opportunity to ask, “Where does my patient line up on this continuum? Do they have some of these variables or not? Sometimes surgery isn’t in a patient’s best interest, or maybe a smaller procedure—a more palliative, minimalistic procedure—would make sense.”

Next steps

MacLean explains, “The great thing about a scoping review is the ability to identify knowledge gaps for future study. We know that preserving quality of life—as opposed to just length—is important to patients. Despite this, few studies examined quality of life.” Dr. Georgiopoulos adds, “We were taken aback to find that only 2 studies investigated the impact of preoperative HRQoL on surgical outcomes. This review represents a first step toward the development of a more accurate and evidence-based tool for prognosticating spinal metastatic disease-related surgical outcomes on the basis of patients’ systemic condition.”

Weber describes the ongoing work of AO Spine Knowledge Forum Tumor, “We spent the winter elaborating on the variables we’ve identified and created a survey that was distributed through AO International. We received responses from some 300 or so spine surgeons from around the world and are writing a paper on the survey results—on what surgeons from around the world consider to be important.” The plan is then to create a definitive scoring system that can be widely accepted for predicting surgical outcomes and post-operative HRQoL, based on systemic condition in patients with SMD. Finally, the Knowledge Forum “will take this new classification system and actually ask the AO patient registry—the AO Spine Metastatic Tumor Research and Outcomes Network (MTRON) registry—how these variables impact patient outcomes.”