Patterns of Progression

The pattern of CaP progression has been well defined. The likelihood of local extension outside the prostate (extracapsular extension) or seminal vesicle invasion and distant metastases increases with increasing tumor volume and more poorly differentiated cancers. Small and well-differentiated cancers (grades 1 and 2) are usually confined to the prostate, whereas large-volume (> 4 cm³) or poorly differentiated (grades 4 and 5) cancers are more often locally extensive or metastatic to regional lymph nodes or bone. Penetration of the prostatic capsule by cancer is a common event and often occurs along perineural spaces. Seminal vesicle invasion is associated with a high likelihood of regional or distant disease. Locally advanced CaP may invade the bladder trigone, resulting in ureteral obstruction. Of note, rectal involvement is rare as Denonvilliers’ fascia represents a strong barrier.

Lymphatic metastases are most often identified in the obturator lymph node chain. Other sites of nodal involvement include the common iliac, presacral, and periaortic lymph nodes. The axial skeleton is the most usual site of distant metastases, with the lumbar spine being most frequently implicated. The next most common sites in decreasing order are proximal femur, pelvis, thoracic spine, ribs, sternum, skull, and humerus. The bone lesions of metastatic CaP are typically osteoblastic. Involvement of long bones can lead to pathologic fractures. Vertebral body involvement with significant tumor masses extending into the epidural space can result in cord compression. Visceral metastases most commonly involve the lung, liver, and adrenal gland. Central nervous system involvement is usually a result of direct extension from skull metastasis.