Predictive Scores Underestimate Survival of Patients With Metastatic Spine Disease

A Retrospective Study of 315 Patients in Sweden

Christian Carrwik, MD; Claes Olerud, MD, PhD; Yohan Robinson, MD, PhD, MBA

Disclosures

Spine. 2020;45(6):414-419. 

In This Article

Materials and Methods

Study Design

This is a retrospective cohort study in consecutively treated patients with spinal metastatic disease. It is reported according to the RECORD statement[9] and was approved by the Regional Ethical Review Board in Uppsala (no. 2012/133).

Setting

This study is performed in Sweden, which has a national healthcare system. In Sweden, a national registry for spine surgery (Swespine) is maintained to follow surgical results and to maintain quality of spinal surgery. Swespine started 1993 and today has a coverage of 49 of 50 clinics performing spine surgery in Sweden. A metastatic spinal disease module was added to Swespine in 2006.[10]

Participants

All patients undergoing spinal surgery due to metastatic spinal disease at Uppsala University Hospital between January 1, 2006 and December 31, 2012 were included in the study. These patients were identified from the spinal metastatic disease module of Swespine.

For every included patient individual patient history was obtained from medical records in the hospital information system at Uppsala University Hospital. The patient record includes a date of death, obtained from the Swedish Population Register.

Variables

Baseline Values. In Swespine, all patients are asked to self-report background data regarding quality of life preoperatively. The module for spinal metastatic disease in Swespine contains domains including indication for surgery, type of primary tumor, Frankel classification, type of surgery, and spinal levels of surgery. This part is surgeon reported.

Data on skeletal metastasis status were derived from the medical records. In cases of missing data, the patient's magnetic resonance imaging of the spine before surgery was analyzed by one of the authors (C.C.) and if more than one vertebra was involved the number of skeletal metastasis was considered to be higher than one. If only one vertebral metastatic lesion was found on the magnetic resonance imaging, the radiology reports from other scans (pelvis, chest, abdomen, extremities) were retrieved. If any of those included skeletal metastasis, the total was considered to be higher than one. The same radiology reports were used to evaluate the presence of visceral metastasis.

The mean body mass index for the included patients was 26.0 (range 15–55), with data missing for 58 patients (18%). Regarding smoking status, 20 out of 182 (6%) were reported by the surgeon to be smokers, whereas data are missing for 202 patients (64%).

Tokuhashi Score. The Tokuhashi Score involves patient-specific data from six domains. Points are given for performance status, number of extraspinal metastases, number of vertebral body metastases to major internal organs, primary tumor, and spinal cord palsy. In every domain, 0 to 2 points are awarded and the sum will range from 0 to 12 points. Higher total score suggests a longer estimated survival. If the total score is 5 or lower, survival is expected to be less than 3 months. A score of 9 and higher suggests survival over 12 months and "excisional operation" is recommended.

Revised Tokuhashi Score. The revised Tokuhashi score differentiates more between types of primary tumors. The primary tumor domain now awards a score 0 to 5, making the maximum score with the other domains added 15. A score greater than 9 suggests survival over 6 months, whereas 12 to 15 suggests survival over 12 months. The most dismal prognosis with a score 0 to 8 is now adjusted to 6 months or lower expected survival.

Tomita Score. The Tomita score consists of three domains, where the patient gets 1, 2, or 4 points in each. Points are given for the type of primary tumor, the presence of visceral metastasis and the presence of bony metastasis. This scoring system gives more weight to the type of primary tumor but does not consider the patient's performance status or presence of neurological impairment due to the metastases. The sum is converted to prognosis of survival where the highest score (8–10 points) predicts survival less than 3 months and the lowest score (2–4) means a predicted survival of more than 2 years. Based on the total estimated survival, four levels of recommendations are given where three are surgery of various extent and one is supportive care.

Bauer Score. The Bauer score included the presence of a pathologic fracture in the decision making. A simplification suggested by Leithner et al[11] removed pathologic fracture as a predictor and the Modified Bauer Score generates points in four domains, where all are questions that can be answered with yes or no. Points are given for the presence of positive prognostic factors which are no visceral metastasis, no lung cancer, a primary tumor from a selected group (breast, kidney, lymphoma, multiple myeloma), and if there is only one solitary skeletal metastasis. The patient's performance status or neurological deficit does not affect the score. Total points can be 0 to 4 where 0 to 1 suggests dismal prognosis and no surgery recommended, and 3 to 4 points suggest more extensive surgery. The survival prognosis is not estimated in time but rather in the level of treatment recommended.

Karnofsky Performance Status. The patient's performance according to Karnofsky Performance Status (KPS) is a part of the Tokuhashi and Revised Tokuhashi Scores. The original KPS score was introduced by Karnofsky in 1949 and awards a score 0 to 100 where 0 means death and 100 is no sign of disease.[12] In our material, the KPS score is rarely used in the medical records but has been calculated retrospectively. For the purpose of this study, the important levels are "poor" (10–40), "moderate" (50–70), and "good" (80–100) as the thresholds are used in the Tokuhashi and Revised Tokuhashi scores. The KPS level was determined by the information in the medical records. If a patient was reported to be ambulatory without or with some effort, the KPS was determined to be "good" for the sake of the scoring. If the patient needed some assistance but was able to care for most needs, the KPS was estimated to be "moderate." Patients completely unable to ambulate or take care of themselves were entered in to the "poor" group. There were no cases of missing data regarding the patient's performance when using these definitions.

Surgical Treatment Data. The possible indications for surgery as reported by the surgeon to Swespine are neurologic deficit, pain, progressive deformity, or any combination of these. The type of surgery reported by the surgeon to Swespine can be posterior decompression, anterior decompression, and/or fusion. Any implants used are coded according to the type and manufacturer.

Survival. Survival data were acquired from the Swedish Population Register, which also includes date of death. All patients defined as alive in this study were alive as of November 27th, 2018, according to the register.

Analysis. We defined a scoring to underestimate survival if a patient was scored in the group with the shortest estimated survival but lived longer than 6 months after surgery. If a patient was scored in the group with the longest expected survival but died within 3 months after surgery, we defined that scoring to overestimate survival.

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