Identification of prostate cancer risk categories according to surgical margins status, pathological stage and Gleason score

Molecular margin status after radical prostatectomy using glutathione S-transferase P1 (GSTP1) promoter hypermethylation

OBJECTIVE

To assess the potential for molecular staging in biopsies of the prostatic fossa after radical prostatectomy (RP) by searching for occult tumour cells through analysis of glutathione S-transferase P1 (GSTP1) methylation status.

PATIENTS AND METHODS

We analysed 2446 biopsies: 2286 biopsies from a group of 254 patients with clinically organ-confined prostate cancer who underwent RP and 160 biopsies from a control group of 32 patients. After prostate gland excision, biopsies were obtained from defined areas of the prostatic fossa and bisected for histopathological and molecular genetics analyses. Results were related to clinicopathological data including tumour stage, lymph node status, resection status, tumour grading, initial PSA level, and biochemical recurrence.

RESULTS

In total, 34 patients (13.4%) had at least one core positive for the GSTP1 promoter hypermethylation, six of whom (17.6%) were characterised as having a clinically localised tumour stage (pT2, pN0) and 28 (82.4%) as an advanced tumour stage (≥pT3 and/or pN1). GSTP1 promoter hypermethylation significantly correlated with tumour stage (P < 0.001), International Society of Urological Pathology grading (P = 0.001), lymph node status (P < 0.001), surgical margin status (P < 0.001), and biochemical recurrence (P = 0.001). Furthermore, in 46 patients (18.1%) further analysis led to a down- or upgrading of conventional surgical margin status. Classical R-status (margins of the specimen) is significantly superior to histological sampling from the fossa (P = 0.006) but not to GSTP1 analysis from the fossa (P = 0.227).

CONCLUSION

For the detection of residual tumour in the fossa after RP in order to better predict recurrence, molecular GSTP1 promoter hypermethylation has some value; however, the classical R-status (margins of the specimen) is simpler and more widely applicable with similar results.

Risk prediction models for biochemical recurrence after radical prostatectomy using prostate-specific antigen and Gleason score

Many computer models for predicting the risk of prostate cancer have been developed including for prediction of biochemical recurrence (BCR). However, models for individual BCR free probability at individual time-points after a BCR free period are rare. Follow-up data from 1656 patients who underwent laparoscopic radical prostatectomy (LRP) were used to develop an artificial neural network (ANN) to predict BCR and to compare it with a logistic regression (LR) model using clinical and pathologic parameters, prostate-specific antigen (PSA), margin status (R0/1), pathological stage (pT), and Gleason Score (GS). For individual BCR prediction at any given time after operation, additional ANN, and LR models were calculated every 6 months for up to 7.5 years of follow-up. The areas under the receiver operating characteristic (ROC) curve (AUC) for the ANN (0.754) and LR models (0.755) calculated immediately following LRP, were larger than that for GS (AUC: 0.715; P = 0.0015 and 0.001), pT or PSA (AUC: 0.619; P always <0.0001) alone. The GS predicted the BCR better than PSA (P = 0.0001), but there was no difference between the ANN and LR models (P = 0.39). Our ANN and LR models predicted individual BCR risk from radical prostatectomy for up to 10 years postoperative. ANN and LR models equally and significantly improved the prediction of BCR compared with PSA and GS alone. When the GS and ANN output values are combined, a more accurate BCR prediction is possible, especially in high-risk patients with GS ≥7.

Endothelial Caveolin-1 regulates the radiation response of epithelial prostate tumors

The membrane protein caveolin-1 (Cav1) recently emerged as a novel oncogene involved in prostate cancer progression with opposed regulation in epithelial tumor cells and the tumor stroma. Here we examined the role of stromal Cav1 for growth and radiation response of MPR31-4 prostate cancer xenograft tumors using Cav1-deficient C57Bl/6 mice. Syngeneic MPR31-4 tumors grew faster when implanted into Cav1-deficient mice. Increased tumor growth on Cav1-deficient mice was linked to decreased integration of smooth muscle cells into the wall of newly formed blood vessels and thus with a less stabilized vessel phenotype compared with tumors from Cav1 wild-type animals. However, tumor growth delay of MPR31-4 tumors grown on Cav1 knockout mice to a single high-dose irradiation with 20 Gray was more pronounced compared with tumors grown on wild-type mice. Increased radiation-induced tumor growth delay in Cav1-deficient mice was associated with an increased endothelial cell apoptosis. In vitro studies using cultured endothelial cells (ECs) confirmed that the loss of Cav1 expression increases sensitivity of ECs to radiation-induced apoptosis and reduces their clonogenic survival after irradiation. Immunohistochemical analysis of human tissue specimen further revealed that although Cav1 expression is mostly reduced in the tumor stroma of advanced and metastatic prostate cancer, the vascular compartment still expresses high levels of Cav1. In conclusion, the radiation response of MPR31-4 prostate tumors is critically regulated by Cav1 expression in the tumor vasculature. Thus, Cav1 might be a promising therapeutic target for combinatorial therapies to counteract radiation resistance of prostate cancer at the level of the tumor vasculature.

Extraprostatic extension into periprostatic fat is a more important determinant of prostate cancer recurrence than an invasive phenotype

PURPOSE

Although micrometastasis development correlates closely with the depth of invasion of many tumor types, it is unclear whether invasion into but not through the prostatic pseudocapsule has a negative impact on prognosis, similar to extraprostatic extension. We defined the impact of pseudocapsular invasion on the risk of post-prostatectomy biochemical recurrence.

MATERIALS AND METHODS

Patients with pT2-3a prostate cancer were identified from a prospectively recorded database. Those with pT2 disease were categorized according to pseudocapsular invasion presence or absence. The impact of pseudocapsular invasion on biochemical recurrence was determined by univariable and multivariable Cox regression analysis.

RESULTS

In a cohort of 1,338 patients we identified 595 with organ confined cancer positive for pseudocapsular invasion. Compared to tumors without evidence of invasion, pseudocapsular invasion was positively associated with higher Gleason grade and tumor volume (1.2 vs 1.9 cc, each p<0.001). On univariable analysis there was no difference in biochemical recurrence-free survival between patients with vs without pseudocapsular invasion, although those with extraprostatic extension had significantly lower biochemical recurrence-free survival (p<0.001). This was confirmed on multivariable analysis, which revealed that extraprostatic extension was a significant independent predictor of biochemical recurrence (HR 1.53, p=0.018). The presence of pseudocapsular invasion had no effect (HR 0.81, p=0.33).

CONCLUSIONS

Pseudocapsular invasion is not a pathological feature associated with an adverse outcome after prostatectomy. Thus, the depth of tumor invasion is not a continuum of risk and access to periprostatic adipose tissue is a more important determinant of disease behavior than an invasive phenotype.