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better than in the current database. However, as a nearly identical c-score shows, the presented model is still capable of stratification based on the identified risk factors.
As has been established in literature, primary tumor type – in this study represented by clinical profile – is shown to be the factor of greatest influence on survival in patients with symptomatic SBM21. This means that an accurate and up-to-date tumor classification is essential for prognostication. The positive effect of new treatments such as anti-VEGF therapy will mean that in the near future survival with symptomatic SBM may increase considerably for certain tumors22. Also, it is unclear whether there is a difference in survival for patients with SBM from different subtypes of the same primary cancer, as is the case in breast cancer with estrogen, progesterone and HER2 interactions23. These topics should be the subject of further SBM-specific studies.
A poor performance status nearly doubles the risk of death in all three clinical profiles and is the second most important variable to assess in patients with SBM. Even though the Karnofsky score is a subjective score and highly susceptible to changes in neurological functioning, it remains an effective tool to quickly assess a patient’s general condition. The use of a performance related score as risk factor when estimating survival is also superior when compared to age, as age only gives an indirect measure of a patients’ functional status. Contrary to the Tokuhashi and Van der Linden models, the KPS was divided into two categories instead of three in order to facilitate clinical decision-making.
To the authors’ best knowledge, this is the first study to describe that the effect of visceral and brain metastases differs per primary tumor category. Overall, there was no influence of brain metastases and the effect of visceral metastases was only marginal. However, after stratification for the clinical profile, a statistically significant effect on survival for visceral and brain metastases was found in the favorable category only. The presence of brain or visceral metastases were not associated with survival of patients in both the moderate and unfavorable profiles, obviating the need for additional radiologic examinations in these groups when estimating survival. Most likely, this is due to the fact that survival in these two categories already is very short based on the primary tumor and the effect of visceral or brain metastases therefore becomes negligible.
IV
PREDICTIVE MODEL
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