br Material and methods br Results br Discussion In
Material and methods
Discussion In our series, fracture progression was noted in 53% of the lesions and 5 patients presented with new fractures after RT. Previous studies reported on the rate of pathologic fractures after single or multifraction RT; however, they did not stratify between spine and other locations in the skeleton [2,4–7]. Neither the impact of vertebral fractures upon treatment response nor the risk of fracture in different radiation regimens is assessed properly and need to be examined. More pathological fractures seemingly occurred after single fraction RT than after multifraction therapy, but the absolute percentage was low [2,6,7]. In general, dose prescription and fractionation should be adjusted to the therapeutic goal and patient prognosis. Patients included in this study had a relatively long expected survival. Consequently, local disease stabilization and prevention of neurological deficits were the main therapeutic goals, and all patients benefited from the fractionated regimen . Vertebral fractures at the initiation of RT were present in 69% of the patients in our series. This percentage is also higher than in previous reports that included patients with various cancer diagnoses [9,10], and this difference could reflect a higher incidence of vertebral body fractures in patients with breast cancer  and tumor biology with a tendency toward osteolytic metastases . The presence of significant bone destruction has been implicated as an indicator of poor prognosis for treatment outcomes ; however, the results of previous studies are inconsistent [9–11]. Zelefsky et al. showed that patients with retinoic acid receptor fractures with greater than 50% of vertebral body height loss were less likely to show favorable clinical and radiological responses to RT , whereas Maranzano and Latini showed that neither the presence of vertebral body collapse nor the number of spinal compression sites influenced survival or the response to RT . The study by Mitera et al. implied that the pain response after RT did not differ depending on the presence of a pathological fracture or any other imaging features related to the degree of tumor involvement . Our results are to some extent consistent with these reports. Patients with widespread bony metastases (diffuse infiltration of bone marrow or large metastases) and patients with spinal cord compression prior to RT frequently present with more aggressive disease and, according to our data, tend to show poorer responses to RT, not statistically significant. The pain response rate to RT was similar in patients with vertebral fractures, fracture progression or other recorded MRI findings. Importantly, the epidural tumor volume was reduced in all patients, and all but 3 patients showed an increase in the cross-sectional area of the spinal canal despite fracture progression. Additionally, there was excellent control of bone-only metastases; only 6% of the patients showed disease progression within the RT field, compared with 60% of the patients with progression of SM outside the RT field. The standard treatment protocol in patients included in this study involved a single posterior–anterior (PA) field. Using single PA beam treatment is common in the palliative irradiation of SM. However, dose coverage and heterogeneity may affect the treatment outcome, since distribution decreases in the anterior half of the vertebral body and anterior to the vertebral column . This may partly explain the progression of bone lesions in 1 of 2 patients with progressive disease within the RT field. The major limitation of this study remains restricted number of patients. Hence, the results should be verified in larger studies. Consequently, precisely predicting treatment response and identifying statistically significant groups is not feasible in small samples. Additional limitations include relatively broad time variations in the post-treatment MRI examinations – as a consequence of repeated MRIs not being part of the prospective study design .