Comment on Kasai et al.: Clinical profile of long-term survivors of breast or thyroid cancer with metastatic spinal tumours
Dear Editor, We thank Dr. Abdel-Wanis and colleagues for their interest in our paper . We do not mean at all to deny the value of Tokuhashi’s score  and Tomita’s score  as scoring systems to predict a prognosis of patients with metastatic spinal tumours. Our unpublished data showed a significant correlation between each score and survival period in 89 patients with breast cancer, thyroid cancer, and other cancers with metastatic spinal tumours. In our study of metastatic spinal tumours, the number of patients analysed was small. There were 25 patients, including 13 with breast cancer and 12 with thyroid cancer, and we compared survival periods only between a long-term survival group (5 years survival or more) and a non-long-term survival group (less than 5 years survival). To estimate survival period of patients stratified by the score as Dr. Abdel-Wanis did, we need to increase the number of patients analysed. This is the key issue of our future study. Meanwhile, we believe that Tokuhashi’s and Tomita’s scoring systems have negative aspects in that they are cross-sectional assessments at a certain point without a longitudinal view over time, and do not include the progression rate of cancer in an individual. Our study containing the viewpoint of longitudinal assessment showed that patients with breast cancer or thyroid cancer as a primary cancer could be expected to have longer postoperative survival when spinal surgery was carried out more than 5 years after diagnosis of their primary cancers. Such a longitudinal assessment for prediction of prognosis is rarely performed. Thus, we believe that this type of study should be done avidly in the future. Once again, we appreciate the comments on our study made by Dr. Abdel-Wanis and the editor.