Page 44 - Predicting survival in patients with spinal bone metastasesL

CHAPTER III DISCUSSION
In this study on 106 patients operated for symptomatic SEM, primary tumor type, presence of visceral metastases and functional status were found to be significant predictors of survival. Other risk factors as gender, presence of other bone metastases, number and location of spinal metastases, age and neurologic status did not have an effect on survival.
For the purpose of accurately evaluating the individual risk factors, modifications to two items were made. We agree with Wibmer et al. that the primary tumor classifications are not up to date12. However, based on survival data in this study, the conclusion that patients suffering from kidney cancer have a prognosis comparable to those with breast cancer cannot be followed. Median survival in patients with prostate cancer was compatible with the ‘moderate growth’ category in the Tomita model and therefore it was decided to remove it from the ‘slow growth’ category. In 2004, Van der Linden et al. studied 342 patients with spinal metastases who were conservatively treated for pain by means of external beam radiation therapy7. Since patients with renal cell carcinoma were excluded and patients with thyroid cancer were underrepresented, these primary tumors are not mentioned separately in the model. Scoring these tumors in the ‘other’ category is incorrect and adjustments are needed: kidney cancer was added to the ‘prostate group’ and thyroid cancer was added to the ‘breast group’.
The preoperative assessment of the Karnofsky performance score was standardized. In a patient population notoriously at risk for acute neurologic decline, we believe it is wrong to take such a measurement just prior to surgery because of the acute distorting effect of neurologic impairment on functional impairment. Therefore, it was decided by the authors that functional status had to be evaluated before the onset of acute neurologic decline.
When assessing primary tumor type, the Tomita classification was found to be the most practical and – after modification – also the most accurate of the four classifications. The difference in survival between slow and moderate growth tumors is not significant on both univariate (p=0.073) and multivariate analysis (HR 1.7, 95%CI 0.9-3.3, p=0.099), but the difference between slow and fast growth (p<0.001) and moderate and fast growth (p=0.007) is strongly significant.
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