Seminal vesicle invasion combined with extraprostatic extension is associated with higher frequency of biochemical recurrence and lymph node metastasis than seminal vesicle invasion alone: Proposal for further pT3 prostate cancer subclassification

The 8th edition of the American Joint Committee on Cancer (AJCC) TNM staging system subdivides prostatic pT3 tumors into pT3a, which includes cases with extraprostatic extension (EPE) and pT3b, which is defined by the presence of seminal vesicle invasion (SVI) with or without EPE. Yet, it is not established whether combined SVI and EPE impart a worse prognosis compared to SVI alone. We studied a cohort of 69 prostatectomy patients with SVI with or without EPE. Patient age at the time of radical prostatectomy was documented and Gleason score and presence or absence of EPE and/or SVI were determined. Biochemical recurrence (BCR) was defined as a PSA rise >0.2 ng/mL. The frequency of BCR was 33.9% in cases with combined EPE and SVI versus 12.5% in cases with SVI alone (relative risk = 2.71). An additional cohort of 88 patients also showed a higher frequency of lymph node metastasis of 29% in patients with combined SVI and EPE at the time of radical prostatectomy versus a 10% frequency of lymph node metastasis in patients with SVI alone (relative risk = 2.9). Based on our data, we propose further subdividing pT3 prostate cancers into three groups: EPE alone (pT3a), SVI alone (pT3b), and combined EPE and SVI (pT3c). This classification system would more accurately identify patients with pT3 prostate cancer who are more likely to experience worse outcomes and provide clinicians with additional information to aid in follow-up and postoperative treatment decisions.