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 veebrae in x-ray. The spread of this cancer to the above veebrae was through -

Prostatic cancer spreads to the bones through blood vessels; first into Batson's periprostatic venous plexus and then into the internal veebral plexus of veins. This metastasis is possible because of valveless communication between the periprostatic and veebral plexus of veins. Ref : S. Das Textbook of Surgery, 3/e p1247