Page 45 - Predicting survival in patients with spinal bone metastasesL

Even though the results of the Van der Linden classification improved after modification, accuracy is still lacking, as is the case for the Tokuhashi and Bauer classifications. An explanation for this finding may be the relatively long survival of patients with lung cancer in this study (median survival 6.9 months). Bias might have been introduced by selection of only those lung cancer patients with preoperative estimated long survival. Whereas in the Tomita classification this primary is mixed with other fast growing tumors such as melanoma (median survival 3.4 months) and colon cancer (median survival 1.7 months), the other classifications use this primary as a separate entity. This underlines another advantage of the Tomita tumor classification: its adaptability. We believe it is impossible to present a globally valid tumor classification, considering the differences in incidences and ever-changing treatment options. By creating categories based on contemporary regional survival data, results will be more accurate than when adhering to semi-rigid classifications as presented in other classifications.
As a marker for progression of disease, the presence of visceral metastases does not directly influence survival. In their models, Tomita and Tokuhashi make use of a third category, namely operability. Tokuhashi initially based this category on a single patient out of the 64 studied4 and Tomita on 7 out of 67 patients6. As is shown in the results, operable visceral metastases have a similar median survival when compared to no visceral metastases. Unfortunately, the treatable visceral metastases group only consisted of 6 patients. These results are most likely due to patient selection. If a patient is considered fit enough to undergo metastasectomy, survival will most likely be prolonged based on their general condition and not the removal of the visceral metastasis. A recent retrospective study of 504 breast cancer patients irradiated for metastatic spinal cord compression by Rades et al.13 also found a strong negative effect on survival if visceral metastases were present, similar to Wibmer et al., Yamashita et al. and Crnalic et al.12,14,15
Performance status is generally accepted as a strong prognostic factor for survival in metastatic disease16, but in case of spinal metastases it remains controversial. Even though both the Tokuhashi and the Van der Linden models make use of the KPS, evidence is still limited. In his article, Tokuhashi writes: “(...) the standard deviation was too great for the values to be sufficiently meaningful.4”
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