Objectives: To characterize the anatomical extension pattern of prostate cancer arising in the peripheral zone (PZ) in radical prostatectomy (RP) specimens and to evaluate its prognostic significance.
Patients and methods: Of 174 consecutive patients undergoing RP, 128 diagnosed as having PZ cancer (PZC) were enrolled. The maximum tumour area (MTA) and maximum tumour volume (MTV) in RP specimens were measured using digital planimetry. A circle with an area equal to the MTA, in which the central point was the intersection of the longest line of the MTA and the line perpendicularly bisecting the first line, was defined as a hypothetical extension area, regardless of anatomical structure. The area within this circle that did not overlap the MTA was defined as DeltaTA.
Results: There was a significant correlation between the MTV and DeltaTA/MTA, introduced as a variable representing the degree of PZC extension along the anatomical shape of the PZ. The DeltaTA/MTA in patients with a MTV of >5 mL was significantly greater than that in those with a MTV of < or = 5 mL. Furthermore, DeltaTA/MTA was significantly associated with several prognostic indicators, including extracapsular extension, surgical margin status and perineural invasion. Multivariate analysis identified DeltaTA/MTA in addition to preoperative serum prostate-specific antigen level, extracapsular extension and surgical margin status as independent predictors of biochemical recurrence after RP.
Conclusions: PZC tends to extend along the anatomical shape of the PZ during progression, resulting in higher DeltaTA/MTA value in advanced PZC than that in early PZC.