The treatment for patients with MSCC should be planned by taking into account independent prognostic factors, which allow estimating the patient’s prognosis. Prognostic factors that indicate the effect of radiotherapy on functional outcome are important to identify patients who appear adequately treated with radiotherapy alone, i.e. patients who have a high probability to maintain or regain the ability to walk after irradiation. Such prognostic factors can also identify patients who do not achieve a satisfying functional outcome with radiotherapy alone and, therefore, could benefit from upfront decompressive surgery in addition to radiotherapy. In randomized study of 101 highly selected patients that compared decompressive surgery followed by radiotherapy to radiotherapy alone, significantly more patients were able to walk after treatment in the surgery plus radiotherapy group (84% vs. 57%, p = 0.001) .
To be able to predict the patient’s survival prognosis is also very important for the selection of the appropriate treatment regimen. Patients with a more favorable prognosis are likely to benefit from longer-course radiotherapy programs supplemented by bisphosphonate treatment rather than from short-course radiotherapy. This is because short-course radiotherapy results in worse local control of MSCC, which becomes more of an issue in patients surviving 6 months or longer following treatment [4, 5]. Prognostic factors that allow predict survival are important also for identifying patients with a very poor survival prognosis, for whom a short-course radiotherapy would be a better option in order to avoid unnecessary distress for these often debilitated patients.
This study aimed to identify prognostic factors for both functional outcome and survival, because both endpoints are important in order to choose the most appropriate treatment regimen for the individual patient with MSCC from cancer of unknown primary. The multivariate analysis of functional outcome revealed that patients who had visceral metastases at the time of radiotherapy and experienced a rapid development of motor deficits prior to radiotherapy had an unfavorable functional outcome. These findings agree with our previous report on MSCC from cancer of unknown primary published five years ago . The finding that a rapid development of motor deficits was associated with a worse functional outcome could be explained by the fact that a rapid decline in motor function was caused by disruption of the arterial blood flow resulting in spinal cord infarction [7, 8]. In contrast, a slower decline in motor function was most likely a result of venous congestion, which was reversible in many cases. In our present study, 21% of the patients showed a deterioration of motor function after radiotherapy alone, and 12% did not improve after complete paraplegia. In a recent retrospective study of 51 patients who received surgical management of MSCC from CUP, deterioration was observed only in 6% of patients . Therefore, it appears that a considerable proportion of patients with MSCC from cancer of unknown primary may be considered for decompressive surgery, in particular those patients with a rapid development of motor deficits or visceral metastases who do not have an extraordinarily poor survival prognosis.
Prognostic factors predicting the patient’s survival prognosis are important in two ways. They can help identify patients who may not be candidates for decompressive surgery because they have a very poor survival prognosis, although functional outcome following radiotherapy alone is not expected to be satisfying. Furthermore, the estimated survival time has an impact on the selection of the radiotherapy regimen. In the present study, survival was negatively associated with four prognostic factors indicating an advanced and rapidly progressing disease: poor performance status, being not ambulatory prior to radiotherapy, presence of visceral metastases, and rapid development of motor deficits prior to radiotherapy. Patients with these negative predictors may receive short-course radiotherapy to avoid that these patients have to spend a considerable part of their remaining life time with treatment. In the group of patients (n = 28) with all four negative prognostic factors, the 6-month survival rate was only 4%. These patients may be candidates for single-fraction radiotherapy or best supportive care.
The prognostic value of the ECOG-PS has not been observed in our previous study published five years ago and can, therefore, be considered a new prognostic factor for patients with MSCC from cancer of unknown primary . Potential prognostic factors for local control of MSCC have not yet been investigated in patients with MSCC from cancer of unknown primary at all. Therefore, the present study provides new and important results in addition to our previous report. However, the retrospective nature of this study must be taken into account during the interpretation of the results. Retrospective studies always bear the risk of hidden selection biases. However, a prospective study will be difficult to perform in patients with MSCC from cancer of unknown primary, as it will take several years to include a sufficiently large number of such patients.