A validated preoperative score predicting survival and functional outcome in lung cancer patients operated with posterior decompression and stabilization for metastatic spinal cord compression

Approximately 28 % of the patients with lung cancer are estimated to develop metastatic spinal cord compression (MSCC) during their disease course [1]. The most appropriate treatment for MSCC is still debated. A phase III trial (N = 101) strongly suggested that direct decompressive surgery following postoperative radiotherapy was superior to treatment with radiotherapy alone for MSCC in 2005 [2]. Rades et al. [3] proposed the opposite result in 2010, the outcome of radiotherapy alone was not significantly inferior to those of surgery plus radiotherapy. Maranzano et al. [4] stated that the choice of radiotherapy alone or surgery in MSCC depended on accurate patient selection. Recently, only a few studies specifically addressed surgical treatment of MSCC in lung cancer [5‐7]. Generally speaking, good surgical results are obtained from lung cancer patients with MSCC, while who may benefit from decompressive surgery remains unclear. Selection of the optimal treatment for the individual patient should take into account patient’s estimated survival time, as well as functional outcome after therapies.

Several scoring systems have been proposed to assess survival prognosis for spinal metastasis after surgery or radiotherapy alone [8‐11]. However, (1) the number of patients with lung cancer in those studies is very low, making it difficult to draw conclusions on this specific tumor type; (2) postoperative function outcome is not considered in all of those studies; (3) some old and commonly used scoring systems have underestimated the life expectancy of patients with spinal metastases of lung cancer due to the increased survival time for those patients in recent years [12, 13]. (4) Furthermore, those scores were designed for patients with spinal metastasis in general, not particularly for patients with motor impairment due to MSCC. A score for each tumor entity is really needed, since each tumor entity leading to spinal metastasis and consequent MSCC has its own biological behavior and metastatic patterns, only if specific scores are available for each of these entities can optimal treatment personalization be realized. Therefore, our present study is designed to develop and validate a survival score and analyze functional outcome particularly for patients with MSCC from lung cancer after decompressive surgery.

Personalization of cancer therapy has penetrated into the sphere of oncology in recent decades. Individual strategies are particularly important for patients with MSCC, and patients with very short survival time and poor functional outcome should not be the candidates for decompressive surgery. They appear to be best treated with radiotherapy, even best supportive cares, which means less discomfort for these debilitated and enervated patients. In contrast, patient with a more favorable survival prognosis and functional outcome may benefit from decompressive surgery, which facilitates better local control of MSCC. Individual treatment approaches are often based on the patient’s survival and functional prognosis which can be estimated with the help of significant prognostic factors and scoring systems.

Several prognostic factors have been identified to have statistically significant associations with survival. Better postoperative ambulatory status, improvement in neurologic status after surgery, and postoperative radiotherapy were significantly associated with longer survival which have been shown in some studies [5, 6]. However, those significant factors were in postoperative level, making it nonsense to determine whether surgical treatment is appropriate for patients before surgery.

In the present study, we analyzed 10 preoperative characteristics. Preoperative ambulatory status, ECOG-PS, number of involved vertebrae, visceral metastases, and time developing motor deficit had significant impact on survival on univariate analysis. According to the Cox proportional hazards model, three of above five significant factors, preoperative ambulatory status, visceral metastases, and time developing motor deficits, maintained significant impact on survival, which was in accordance with other studies [1, 5, 9, 10, 15]. The three preoperative factors and corresponding points are very easy to remember and obtained from patients before surgery. Ambulatory status and time developing motor deficits can be obtained from patient’s sign and history, an emergency B ultrasonic can be used to determine whether liver, renal, and adrenal gland, the most common organs that lung cancer tends to metastasise to, are involved, and an X-ray can be used to make sure whether patients have primary lung cancer when patients present MSCC as the first manifestation.

Various scoring systems have been proposed for patient with spinal metastasis on the basis of retrospective data from relatively small total number of patients treated with surgery or radiotherapy alone. In 1990, Tokuhashi et al. [8] presented a score which was mostly used based on the data of 64 patients with a metastatic spine tumor who underwent spinal surgery, and only 6 patients had lung cancer. In 1995, Sioutos et al. [9] developed a score that comprised 109 patients, including 45 lung cancer patients. 10 years later, Tokuhashi has revised their score in a series of 246 patient, rarely 26 patients with lung cancer. Notably, 33.3 % (82/246) of participants were not treated with surgery in Tokuhashi’s study [10]. The revised Tokuhashi score was found to be useful to predict survival for patients with spinal metastases from breast cancer alone [16] or other solid cancers [17, 18]. Unfortunately, there was no difference in neurological outcome between the three groups: the revised Tokuhashi score 0–8, 9–11 and 12–15 [17], and the data that the revised Tokuhashi score seem to be a suboptimal tool for the prediction of an individual prognosis in the group of lung cancer patients has been shown in Hessler et al. study in 2011 [12]. In their study, 67 patients with spinal metastasis from lung cancer, all of the patients underwent surgical treatment. Hessler et al. [12] concluded that the Tokuhashi scoring system underestimated the life expectancy of patients with lung cancer due to the increased survival time for this patient group. In 2013, Morgen et al. [13] also found a statistically significant increase in survival over the years for lung cancer patients with MSCC (n = 2321, 499 patients with lung cancer, 103 lung cancer patients were received surgical treatment). For patients with lung cancer who underwent surgery for MSCC, survival increased from 9 % in year 2005 up to 30 % in year 2010 (P = 0.047). In our study, overall 1-year survival is 23 % in the test group. More recent studies have reported improvements among patients with advanced lung cancer because of the new treatment options [19, 20]. With the increasing survival time of patients with lung cancer during recent years, the Tokuhashi scoring system and other scores may be no longer suitable for patents with lung cancer. Furthermore, these scores were designed for patients with spinal metastasis in general, not particularly for patients with motor impairment due to MSCC. Rades et al. [11] developed and validated a scoring system for survival of patients (n = 356, all patients with lung cancer) with MSCC from non-small cell lung cancer who had been treated with radiotherapy alone. Except the Rades score, the above scoring systems included relatively small number of patients with spinal metastasis from various primary tumors. In fact, participants in Rades score were received radiotherapy alone, and functional outcome was not considered in their study.

In our study, a score was developed based on the data derived from 73 patients with lung cancer who underwent decompressive and stabilized surgery for MSCC. The indication for surgery is neurological deficits. Therefore, the patient’s individual situation is taken more into account in the present scoring system. In order to validate our score, the risk group A and B of the test group were compared to the corresponding group A and B of the validation group. The 6-month survival rates and median survival times of the two risk groups in the validation group proved to be similar to the corresponding 6-month survival rates and median survival times of the two risk groups in the test group. Thus, this new score for MSCC from lung cancer appears valid and reproducible. Functional outcome was also considered in our study, in our scoring system, the patients group with shorter median survival (group A) also had worse neurological outcome. Functional outcome was acceptable in the entire cohort of 73 patients, 68.5 % (50 of 73) of the patients were able to walk 4 weeks after decompression; 51.5 % (17/33) of nonambulatory patients before operation regained the ability to walk. 74–84 % of patients were able to walk after surgery [2, 5] and 22–68 % of nonambulatory patients became ambulatory again in other studies [5, 7].

However, there is always patient’s hope for an intervention that might preserve ambulation and drastically improve quality of life, despite poor prognosis predicted by some clinical scores. So the decision about treatment of patients with MSCC is complex and should not only rely on clinical scores. Moreover, the present scoring system is based on retrospective data, and the statistical analysis not included a relatively larger number of patients. Therefore, despite good predictive value in our scoring system, the score still warrants a prospective study to be confirmed.

In conclusion, since the survival rates and median survival of the validation group were similar to those of the test group, this score seems to be reproducible. The scoring system can help select the individual treatment for patients with metastatic spinal cord compression from lung cancer to avoid excessive and inadequate treatments. Patients with scores of 0–2 points have short survival time (Life expectancy less than 3 months) and poor functional outcome after surgery. Surgery may be no longer took into consideration in most of patient in this group, and radiotherapy alone or best supportive care can be considered. Patients with scores of 3–6 points should be surgical candidates, because survival prognosis (Life expectancy more than 10 months) and functional outcome were favorable after surgery. This scoring system appears to be valid, while a larger prospective confirmation is still needed.