Characterization of the anatomical extension pattern of localized prostate cancer arising in the peripheral zone

Study Type – Diagnostic (non-consecutive series) Level of Evidence 3b 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 ΔTA. RESULTS There was a significant correlation between the MTV and ΔTA/MTA, introduced as a variable representing the degree of PZC extension along the anatomical shape of the PZ. The ΔTA/MTA in patients with a MTV of >5 mL was significantly greater than that in those with a MTV of ≤5 mL. Furthermore, ΔTA/MTA was significantly associated with several prognostic indicators, including extracapsular extension, surgical margin status and perineural invasion. Multivariate analysis identified ΔTA/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 ΔTA/MTA value in advanced PZC than that in early PZC.