system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 49-year-old man suffering from carcinoma of the prostate was x -rayed. He showed areas of sclerosis and collapse of T10 and T11 vertebrae in x-ray. The spread of this cancer to the above vertebrae was through -
assistant
The correct answer is  Prostatic cancer spreads to the bones through blood vessels; first into Batson's periprostatic venous plexus and then into the internal vertebral plexus of veins.
This metastasis is possible because of valveless communication between the periprostatic and vertebral plexus of veins.