Extraprostatic Extension in Core Biopsies Epitomizes High-risk but Locally Treatable Prostate Cancer

Abstract

Background: Extraprostatic extension (EPE) is defined as local spread of prostate cancer (PC) beyond prostate boundaries. Although extensively evaluated in radical prostatectomy (RP) specimens, its significance in prostate biopsy (PB) specimens is understudied.

Objective: To analyze the clinicopathologic characteristics and treatment outcomes for patients with nonmetastatic PC with EPE on diagnostic PB.

Design, setting, and participants: We identified all patients at Princess Margaret Cancer Center with EPE on their diagnostic PB between 2005 and 2016. All patients underwent definitive curative-intent treatment with either RP or radiotherapy (RT) with or without androgen deprivation therapy (ADT).

Outcome measurements and statistical analyses: Clinicopathologic variables were compared using a χ² or Kruskal-Wallis test; log-rank analyses were applied for outcomes comparison. Primary and secondary endpoints were 5-yr biochemical recurrence (BCR) and the occurrence of metastasis or cancer-specific death, respectively.

Results and limitations: A total of 127 patients with reported EPE in their PB were identified. One-third of patients underwent RP (n=43) and two-thirds received RT (n=84). Baseline prognostic variables (prostate-specific antigen, clinical T stage, biopsy pathologic grade group, and proportion of cores involved with PC) were similar between the treatment groups. More than two-thirds of RT patients received concomitant ADT (median duration 36 mo, interquartile range 24-36), while 39.5% of RP patients received postoperative radiotherapy±ADT. Of the RP patients, 95.3% had ≥pT3a disease and 27.9% had pN1 disease. Median follow-up after RP and RT was similar (43.7 vs 45.8 mo; p=0.516). The 5-yr BCR and metastasis rates in the RP versus RT groups were 25.6% versus 11.9% (p=0.09) and 7% versus 11.9% (p=0.386), respectively. Only one patient died from metastatic PC (RT group). Limitations include the single-center and retrospective design with a moderate sample size and relatively short follow-up.

Conclusions: EPE on PB is an infrequent finding that is strongly associated with high-risk clinicopathologic prognostic features that accurately predict EPE in RP specimens. Despite entailing aggressive disease characteristics, EPE on PB should not preclude patients from receiving definitive radical local therapy.

Patient summary: Extraprostatic extension on prostate biopsies is an uncommon finding, but is strongly correlated to additional aggressive disease features. This finding accurately predicts the presence of extraprostatic extension on the final prostate specimen after surgery. Despite the associated high-risk features, finding extraprostatic extension in prostate biopsies should not preclude patients from undergoing curative-intent radical local therapy.

Keywords: Biochemical recurrence; Extraprostatic extension; Needle core biopsy; Prostate cancer.