Precursor lesions for prostate cancer

High-grade prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (PIN) is now accepted as the most likely preinvasive stage of adenocarcinoma, almost two decades after its first formal description. PIN has a high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent invasive carcinoma. The only method of detection is biopsy; PIN does not significantly elevate serum prostate-specific antigen (PSA) concentration or its derivatives and cannot be detected by current imaging techniques, including ultrasound. Most patients with PIN will develop carcinoma within 10 years. PIN is associated with progressive abnormalities of phenotype and genotype, which are similar to cancer rather than normal prostatic epithelium, indicating impairment of cell differentiation with advancing stages of prostatic carcinogenesis. Androgen deprivation therapy decreases the prevalence and extent of PIN, suggesting that this form of treatment may play a role in chemoprevention.

Contemporary pathology of prostate cancer

In less than 20 years since the introduction of serum PSA and the spring-loaded 18-gauge prostatic biopsy needle, pathologists have adjusted to the limited tissue requirements of narrow needle specimens to apply criteria for diagnosis and grading of prostate cancer, borrowing from lessons learned from radical prostatectomies. Substantial gains have been made during this period in the understanding of precancerous lesions, mimics of malignancy, the criteria for minimal cancer, variants of cancer, and treatment-induced changes. The light microscopic findings remain the criterion standard for diagnosis against which all new techniques should be measured. Numerous findings have proven to be of value, including simple quantitation of histopathologic features, cancer volume, perineural invasion, and others.

Diagnosis of localized prostate cancer: 10 years of progress

Advances in the diagnosis of early stage disease, and particularly the introduction of prostate-specific antigen (PSA) testing, have had a dramatic effect on the presentation and clinical management of prostate cancer during the past ten years. As a result, there have been significant epidemiological changes in countries where early diagnosis is recommended. The importance of PSA testing for the diagnosis of localized prostate cancer has become well established in clinical practice and this is reflected by improved outcomes from definitive treatment. The contribution of PSA-related parameters and molecular forms of PSA both to cancer detection and prediction of pathological stage continue to be explored. Concerns about the reliability of the standard sextant biopsy technique for cancer detection relate to the need for re-biopsy in a growing number of patients with negative biopsies and an increasing proportion of patients with low volume, multifocal disease. In men with cancer, additional prognostic information can be derived from biopsy findings, with important therapeutic implications. This relates also to the need for reliable markers indicating pathological stage and risk of progression. The opportunities for the prevention of prostate cancer have grown with improved understanding of its biology and the genetic basis of the early steps associated with malignant transformation. In the future, the need for therapeutic intervention is likely to be most influenced by successful prevention strategies.

Prevention of prostate-related cancers in Lobund-Wistar rats

BACKGROUND

Since prostate cancer (PC) development involves a combination of genetic predisposition and promotional mechanisms, especially the metabolic conversion of testosterone to 5alpha dihydrotestosterone (DHT) by 5alpha reductase, how do mechanisms in man relate to prostate-seminal vesicle (P-SV) tumor development in Lobund-Wistar (L-W) rats? The disease in man and in L-W rats shares developmental mechanisms and characteristics to the extent that prevention of P-SV tumors in L-W rats could be predictive of similar results in man. The epidemiology of PC in man and P-SV tumors in L-W rats indicates that both are hormone-related diseases based on genetic predisposition, high production of androgens (which are activated to DHT by 5alpha reductase), and early development of androgen-dependent and metastasizing late androgen-independent stages of adenocarcinomas, all after long latency periods.

METHODS

L-W rats at risk of developing spontaneous or induced P-SV tumors were subjected to putative antitumor agents or procedures. These included dietary restriction, testosterone ablation, soybean-derived isoflavones, antiangiogenic linomide, tamoxifen, and a vitamin D analogue.

RESULTS

L-W rats subjected to 1) early onset of dietary restriction manifested suppression of spontaneous and induced development of P-SV tumors; 2) testosterone-ablation by nonesterified DHT (NE-DHT) suppressed early onset of induced P-SV tumors and to a lesser extent late onset of spontaneous tumors; 3) diets containing soy protein isolate (high isoflavones) manifested marginal suppressive effects against induced P-SV tumors, but in 12-month-old rats, the development of spontaneous tumors was reduced in incidence; 4) early administrations of antiangiogenic linomide suppressed development of induced P-SV tumors and of transplanted prostate adenocarcinoma III (PA-III) tumors, but linomide had little antitumor effect against large advanced stage tumors; and 5) tamoxifen and vitamin D analogue suppressed development of P-SV tumors. Results in conditions 1-3 were negative when tested against PA-III tumors.

CONCLUSIONS

Developing stages of P-SV tumors were prevented in L-W rats with autochthonous spontaneous and induced tumors, but most of the agents tested were of no therapeutic benefit against advanced-stage and transplanted PA-III tumors. However, early administrations of antiangiogenic linomide suppressed early growth of induced and transplanted PA-III tumors.

Does screening for prostate cancer identify clinically important disease?

In this study the combination of digital rectal examination (DRE) and serum prostate-specific antigen (PSA) is shown to be effective for detecting early prostate cancer in a urological out-patient setting. PSA provides the means to detect cancer in men with normal DRE that may otherwise present as so-called incidental cancer at transurethral resection of the prostate (TURP) for apparently benign disease or later in the course of its natural history as locally advanced or metastatic disease. PSA progression in men with incidental cancer has been previously demonstrated to be predicted more reliably by residual cancer on needle biopsy after TURP than by tumour in the resected specimen and, therefore re-staging such patients is worthwhile when further treatment would be considered. Among men selected for radical prostatectomy, non-palpable tumours detected with PSA more predictable in pathological extent than incidental cancer and their particular pathological characteristics suggest they include clinically significant tumours that would progress if untreated to palpable and eventually metastatic disease. In view of this progressive behaviour, cancer detected by PSA should be considered clinically significant particularly in men with a life expectancy of at least 10 years. Therefore screening should be offered for such individuals, to detect and treat tumours at a curable stage and thereby eliminate the high mortality and often protracted morbidity commonly associated with metastatic disease.