Mesorectal nodal metastasis with seminal vesicle invasion in biochemically recurrent prostate cancer

Abstract

ObjectivesTo determine the prevalence and predictors of mesorectal lymph node (MLN) metastases on prostate‐specific membrane antigen (PSMA)‐based positron emission tomography/computed tomography (PET/CT) in patients with biochemically recurrent prostate cancer (PCa) following radical therapy.Materials and MethodsThis was a cross‐sectional analysis of all PCa patients with biochemical failure following radical prostatectomy or radiotherapy who underwent an 18F‐DCFPyL‐PSMA‐PET/CT at the Princess Margaret Cancer Centre between December 2018 and February 2021. Lesions with PSMA scores ≥2 were considered positive for PCa involvement (PROMISE classification). Predictors of MLN metastasis were evaluated using univariable and multivariable logistic regression analyses.ResultsOur cohort consisted of 686 patients. The primary treatment method was radical prostatectomy and radiotherapy in 528 (77.0%) and 158 patients (23.0%), respectively. The median serum PSA level was 1.15 ng/mL. Overall, 384 patients (56.0%) had a positive scan. Seventy‐eight patients (11.3%) had MLN metastasis, with 48/78 (61.5%) having MLN involvement as the only site of metastasis. On multivariable analysis, presence of pT3b disease (odds ratio 4.31, 95% confidence interval 1.44–14.2; P = 0.011) was significantly associated with increased odds of MLN metastasis, whereas surgical factors (radical prostatectomy vs radiotherapy; performance/extent of pelvic nodal dissection), surgical margin positivity, and Gleason Grade were not.ConclusionsIn this study, 11.3% of PCa patients with biochemical failure had MLN metastasis on 18F‐DCFPyL‐PET/CT. pT3b disease was associated with 4.31‐fold significantly increased odds of MLN metastasis. These findings suggest alternate drainage routes for PCa cells, either via alternate lymphatic drainage from the seminal vesicles themselves or secondary to direct extension from posteriorly located tumours invading the seminal vesicles.

A case of rectal metastasis of prostate cancer mimicking extramural growth-type rectal tumor

“…The most likely mode of rectal metastasis in this case was lymphatic, as microscopic metastasis of prostate cancer was also observed in the resected mesorectal lymph node. Studies show that prostate cancer with seminal vesicle invasion has a high rate of metastasis to mesorectal lymph nodes [ 2 ], and we hypothesized that prostate cancer metastasized to the mesorectal lymph nodes near the rectum, invaded the surrounding area, and became close to the muscularis propria of the rectum, mimicking an extramural growing rectal tumor. Data on the utility of FDG PET-CT in prostate cancer are lacking, but the sensitivity in untreated primary prostate cancer is 33% [ 3 ], and the FDG accumulation rate is generally low [ 4–6 ].…”