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Sexual function before and after various treatments for symptomatic benign prostatic hyperplasia.

OBJECTIVE: To determine the effect of various treatments for benign prostatic hyperplasia (BPH) on sexual function. PATIENTS AND METHODS: In a longitudinal multicentre study carried out in the Netherlands, 670 consecutive patients with BPH (aged > or = 50 years) were examined at baseline and 9 months after inclusion. All patients completed a questionnaire about symptomatology, bothersomeness and sexual function before and after treatment. Other diagnostic information was retrieved from the medical records. RESULTS: At baseline, 49-59% of the population (mean age 66 years) reported normal potency and 69% a normal libido. Outcomes at 9 months were stratified by type of treatment, i.e. surgery in 207, alpha-blockers in 43, finasteride in 47 and watchful waiting in 234 men. Patients with multiple or other treatments (131) or recent surgery (eight) were excluded from the analyses. For the four sexual items included, 84% of the patients reported no changes. All treatments showed both improvement and deterioration in 3-14% and 0-16% of the patients, respectively. CONCLUSION: For sexual function, most patients remained stable after treatment for BPH, while positive and negative changes occurred in equal proportions for all treatments. These results question the previously reported high incidence of sexual adverse events, particularly after surgical intervention.

Aged↗

Unique synergism or antagonism of combinations of chemotherapeutic and hormonal agents in human prostate cancer cell lines.

OBJECTIVE: To evaluate combinations of anti-tumour agents in tissue cultures using three established cell lines derived from patients with prostate cancer to obtain potential candidates for therapeutic testing in patients with prostate cancer. MATERIALS AND METHODS: Seventeen anti-tumour agents were tested for synergism or antagonism in combination studies in DU 145, PC 3 and LnCaP cell lines. After determining the dose required for 50% inhibition of growth in each, combinations were screened using the median-effect plot and combination-index isobolograms. RESULTS: Estramustine (the primary product of dephosphorylation of estramustine phosphate) showed strong synergism in all three cell lines with hydroxyflutamide, the non-immunosuppressive cyclosporin analogue PSC 833, and Liarozole. In the hormone-sensitive cell line LnCaP alone, synergism was also observed with vinblastine, paclitaxel, docetaxel, bicalutamide, ketoconazole and all-trans-retinoic acid. Other synergistic combinations of two agents were: Liarozole plus docetaxel in LnCaP, PSC 833 plus bicalutamide in DU 145 and PC 3, dexamethasone plus docetaxel in LnCaP, and finasteride plus hydroxyflutamide. Synergistic combinations of three agents were: estramustine plus PSC 833 and Liarozole and schedule-dependent combinations of estramustine, PSC 833, and all-trans-retinoic acid. CONCLUSION: Some of the synergistic combinations have shown clinical effects in patients with hormone-refractory prostate cancer. Based on these findings, new combinations, e.g. estramustine with either PSC 833 or Liarozole, need to be clinically evaluated.

Antineoplastic Agents, Hormonal↗

Increased expression of the neuropeptide Y receptor Y(1) gene in the medial amygdala of transgenic mice induced by long-term treatment with progesterone or allopregnanolone.

The neurosteroid allopregnanolone, a reduced metabolite of progesterone, induces anxiolytic effects by enhancing GABA(A) receptor function. Neuropeptide Y (NPY) and GABA are thought to interact functionally in the amygdala, and this interaction may be important in the regulation of anxiety. By using Y(1)R/LacZ transgenic mice, which harbour a fusion construct comprising the promoter of the mouse gene for the Y(1) receptor for NPY linked to the lacZ gene, we previously showed that long-term treatment with benzodiazepine receptor ligands modulates Y(1) receptor gene expression in the medial amygdala. We have now investigated the effects of prolonged treatment with progesterone or allopregnanolone on Y(1)R/LacZ transgene expression, as determined by quantitative histochemical analysis of beta-galactosidase activity. Progesterone increased both the cerebrocortical concentration of allopregnanolone and beta-galactosidase expression in the medial amygdala. Finasteride, a 5alpha-reductase inhibitor, prevented both of these effects. Long-term administration of allopregnanolone also increased both the cortical concentration of this neurosteroid and transgene expression in the medial amygdala. Treatment with neither progesterone nor allopregnanolone affected beta-galactosidase activity in the medial habenula. These data suggest that allopregnanolone regulates Y(1) receptor gene expression through modulation of GABA(A) receptor function, and they provide further support for a functional interaction between GABA and neuropeptide Y in the amygdala.

Amygdala↗

Genetic analysis of male pattern baldness and the 5alpha-reductase genes.

Genetic predisposition and androgen dependence are important characteristics of the common patterned loss of scalp hair known as male pattern baldness. The involvement of the 5alpha-reductase enzyme in male pattern baldness has been postulated due to its role in the metabolism of testosterone to dihydrotestosterone. There are two known isozymes of 5alpha-reductase. Type I has been predominantly localized to the skin and scalp. Type II, also present on the scalp, is the target of finasteride, a promising treatment for male pattern baldness. We conducted genetic association studies of the 5alpha-reductase enzyme genes (SRD5A1 on chromosome 5 and SRD5A2 on chromosome 2) using dimorphic intragenic restriction fragment length polymorphisms. From a population survey of 828 healthy families comprising 3000 individuals, we identified 58 young bald men (aged 18-30 y) and 114 older nonbald men (aged 50-70 y) for a case control comparison. No significant differences were found between cases and controls in allele, genotype, or haplotype frequencies for restriction fragment length polymorphisms of either gene. These findings suggest that the genes encoding the two 5alpha-reductase isoenzymes are not associated with male pattern baldness. Finally, no clear inheritance pattern of male pattern baldness was observed. The relatively strong concordance for baldness between fathers and sons in this study was not consistent with a simple Mendelian autosomal dominant inheritance. A polygenic etiology should be considered.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

Diagnosis and treatment of benign prostatic hyperplasia. Practice patterns of primary care physicians.

OBJECTIVE: To define primary care physicians' (PCPs) practices in managing patients with benign prostatic hyperplasia [BPH], and to compare these practices to portions of the Agency for Health Care Policy and Research BPH guideline and urologists' practices. DESIGN: Mail survey. PARTICIPANTS: Nationwide random sample of PCPs and urologists, selected from the American Medical Association Registry. METHODS: Initial mailing, postcard reminder, second mailing, telephone reminder, final mailing. MAIN RESULTS: Primary care physicians (n = 444, response = 51%) reported seeing a median of 35 patients with BPH over the preceding year, in contrast to 240 for urologists (n = 394, response = 68%). Regarding tests recommended by the guideline, two thirds of PCPs reported rarely or never using the American Urological Association (AUA) symptom index, nearly all reported routinely performing digital rectal examinations, and many (66%) reported routinely ordering tests to determine the serum creatinine level. Although considered "optional" by the guideline, more than 90% of PCPs reported routinely ordering a prostate-specific antigen test, while infrequently using other optional tests. Regarding "not recommended" studies, a substantial minority reported selectively or routinely ordering intravenous pyelography (34%) and renal ultrasound (33%), while two thirds reported rarely or never ordering these tests. Eighty-six percent of PCPs reported prescribing medications for BPH over the preceding year; alpha blockers to a median of 12 patients, and finasteride to a median of 2. Variation in urology referral thresholds was suggested in responses to two patient scenarios. CONCLUSIONS: Primary care physicians are actively managing patients with BPH. Some of their diagnostic evaluations vary from the recommendations of a national guideline and urologists' practices. Referral thresholds appear to vary considerably.

Adult↗

Enhanced anticonvulsant activity of neuroactive steroids in a rat model of catamenial epilepsy.

PURPOSE: Perimenstrual catamenial epilepsy may in part be due to withdrawal of the endogenous progesterone-derived neurosteroid allopregnanolone that potentiates gamma-aminobutyric acidA (GABA(A)) receptor-mediated inhibition. Here we sought to determine whether the anticonvulsant potencies of neuroactive steroids, benzodiazepines, phenobarbital (PB), and valproate (VPA) are altered during the heightened seizure susceptibility accompanying neurosteroid withdrawal in a rat model of perimenstrual catamenial epilepsy. METHODS: Test drugs were evaluated for their ability to alter the convulsant activity of pentylenetetrazol (PTZ) in young adult female rats, in pseudopregnant rats with prolonged exposure to high levels of progesterone (and its neurosteroid metabolites), and in pseudopregnant rats 24 h after acute withdrawal of neurosteroids by treatment with the 5alpha-reductase inhibitor finasteride. Test drugs were administered at doses equivalent to twice their ED50 values for protection against PTZ-induced clonic seizures in naive young adult female rats. RESULTS: The anticonvulsant activity of allopregnanolone (5 mg/kg, s.c.), pregnanolone (5 mg/kg, s.c.), allotetrahydrodeoxycorticosterone (15 mg/kg, s.c.), and tetrahydrodeoxycorticosterone (10 mg/kg, s.c.) were enhanced by 34-127% after neurosteroid withdrawal. The anticonvulsant activity of PB (65 mg/kg, i.p.) was also enhanced by 24% in neurosteroid-withdrawn animals. In contrast, the anticonvulsant activity of diazepam (4 mg/kg, i.p.), bretazenil (0.106 mg/kg, i.p.), and VPA (560 mg/kg, i.p.) were reduced or unchanged in neurosteroid-withdrawn animals. CONCLUSIONS: The anticonvulsant activity of neuroactive steroids is potentiated after neurosteroid withdrawal, supporting the use of such agents in the treatment of perimenstrual catamenial epilepsy.

Allosteric Regulation↗

Pharmacological profile of 9,11-dehydrocortexolone 17alpha-butyrate (CB-03-04), a new androgen antagonist with antigonadotropic activity.

A series of new cortexolone-related derivatives has been synthesized and investigated for potential anti-androgenic activity. Among the steroids evaluated, 9,11-dehydrocortexolone 17alpha-butyrate (CB-03-04) was the most promising one. The compound displayed a strong local antiandrogenic activity in hamster's flank organ test, and it was also found to be effective in the rat after subcutaneous injection. When compared to other well known androgen antagonists, the rank order of topical anti-androgenic activity in that test was: cyproterone acetate (CAS 427-51-0) > or = CB-03-04 > finasteride (CAS 98319-26-7) > flutamide (CAS 13311-84-7). In addition, the steroid had selective antigonadotropic activity, when injected into parabiotic rats, and was about as active as progesterone. The activity of CB-03-04 was ascribed mainly to its ability to compete with the stimulating effects of testosterone and dihydrotestosterone and, concurrently, to inhibit the gonadotropins hypersecretion. This bimodal mechanism of action could be predictive for the clinical usefulness of the steroid in the treatment of prostate cancer and benign prostate hypertrophy.

Anabolic Agents↗

Biological profile of cortexolone 17alpha-propionate (CB-03-01), a new topical and peripherally selective androgen antagonist.

The aim of this study was to investigate the antiandrogenic activity of a new monoester of cortexolone, cortexolone 17alpha-propionate (CAS 19608-29-8, CB-03-01). Although the compound displayed a strong local antiandrogenic activity in hamster's flank organ test, it did not exhibit antiandrogenic activity in rats after subcutaneous injection, nor did it affect gonadotropins hypersecretion when injected to parabiotic rats. As topical antiandrogen, the steroid resulted about 4 times more active than progesterone (CAS 57-83-0) and, when compared to known antiandrogen standards, it was about 3 times more potent than flutamide (CAS 13311-84-7), about 2 times more effective than finasteride (CAS 98319-26-7) and approximately as active as cyproterone acetate (CAS 427-51-0). Its pharmacological activity seemed to be primarily related to its ability to antagonistically compete at androgen receptor level; nevertheless its primary pharmacological target needs to be further investigated. Its topical activity, along with the apparent absence of systemic effects, anticipates this compound to have the potential of representing a novel and safe therapeutic approach for androgen-dependent skin disorders.

Administration, Topical↗

[Drug therapy for benign prostatic syndrome (BPS)].

Alpha1-receptor blockers (alfuzosin, doxazosin, tamsulosin and terazosin), 5alpha-reductase inhibitors (dutasteride and finasteride) and combinations thereof are used in the drug treatment of benign prostatic syndrome. As before, there is still no evidence supporting the use of plant extracts, the use of anticholinergic substances alone or in combination with other BPS drugs is currently under investigation and should not be attempted outside of clinical trials. For all drugs the placebo effect is considerable. Accordingly, deviations from the recommended doses are rapidly associated with an activity loss over that of placebo. alpha1-Receptor blockers show a rapid onset of action and are slightly superior to 5alpha-reductase inhibitors with regard to the relief of symptoms. All alpha1-receptor blockers are similarly effective at adequate doses, however, quantitative differences are seen in the side effect profiles. 5alpha-reductase inhibitors also provide relief from BPS-associated symptoms with the relief being volume-dependent. Prostate volume-dependent complications of BPS (operation risk and risk of acute urine retention) can be reduced by 5alpha-reductase inhibitors. Long-term drug studies have demonstrated the superiority of combination therapies over monotherapies with alpha1-receptor blockers and 5alpha-reductase inhibitors in patients with a high risk for progression. This superiority is accompanied by a combination of the respective side-effect profiles and their absolute increase. Besides poorer tolerability, combination therapies also result in higher costs. Thus, it is important to decide at an early stage which patients are to be treated with drugs and which by surgery.

5-alpha Reductase Inhibitors↗

Possible mechanisms of miniaturization during androgenetic alopecia or pattern hair loss.

In androgenetic alopecia, or pattern hair loss, follicles undergo miniaturization, shrinking from terminal to vellus-like hairs. Traditionally, this process is thought to progress gradually over a number of follicular cycles. However, it is unlikely that miniaturization can be explained only by a series of progressively shorter anagen cycles. Simple calculations show that this process would take too long for significant miniaturization to occur secondary to shorter anagen cycles alone, especially in view of the latent lag period seen in pattern hair loss that occurs between the loss of a telogen hair and the appearance of an anagen hair. Evidence is presented to support a new concept that miniaturization is an abrupt, large-step process that also can be reversed in 1 hair cycle, as has been shown clinically, with confirmatory histologic evidence, in patients with pattern hair loss responding to finasteride treatment. It is hypothesized that the miniaturization seen with pattern hair loss may be the direct result of reduction in the cell number and, hence, size of the dermal papilla.

Alopecia↗

Variations in the diagnostic process among urologists in one region recorded using an interactive computer program.

To analyse how male cases suffering from lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH) are handled within a well-defined health-care region in Scandinavia, an interactive computer program containing 20 cases suffering from LUTS due to BPH was used for recording the diagnostic process and the treatment decisions; 37 out of a total of 50 urologists practicing within a small health region participated. The diagnostic process varied considerably due to a varying choice of diagnostic tests and the large differences in interpreting the qualities described by the tests. The probability that a patient would be offered a treatment within the region was analysed. For many patients the probability that a treatment was chosen was in the vicinity of 50%. No treatment probability was correlated to the symptom score of the patients. While the probability that a transurethral prostatic resection would be offered to the patients within the region was correlated significantly to urodynamic variables, residual urine and to cystoscopy findings, the probability that transurethral microwave or finasteride therapy would be offered was not correlated to any of the described qualities. The costs of the diagnostic process in all the patients incurred by each of the urologists varied by up to 500%. It was estimated that approximately 40% of the costs involved diagnostic tests that did not influence the decision to offer or not to offer treatment. In conclusion, the enormous variations in the handling of the cases recorded in the study stress the need that a management formula should be used in the handling of patients with LUTS.

Decision Making, Computer-Assisted↗

Evidence for independent modulation of human 11-HSD and 5 alpha/5 beta reductase activities.

The increased ratio of 5 alpha to 5 beta reduced steroids associated with apparent mineralocorticoid excess (AME) may be a necessary consequence of altered 11 beta-hydroxysteroid dehydrogenase (11-HSD) activity. In order to test this hypothesis we have compared changes in 11-HSD activity and 5 alpha/5 beta reduction in a variety of clinical and experimental conditions. The ratio of 11-oxo/11 beta-hydroxy metabolites of cortisol (11-oxo/11-OH FM) was used as an index of 11-HSD activity and the ratio of allotetrahydrocortisol/ tetrahydrocortisol (allo THF/THF) was used as an index of 5 alpha/5 beta reduction. Ratios were derived from 24 hour urinary steroid profiles measured by high resolution gas chromatography. The clinical conditions studied were Cushing's Syndrome, Major Depression and hirsutism. In each study, the patient group were compared with age-matched healthy controls. For the experimental conditions, subjects treated with either hydrocortisone, dexamethasone, metyrapone or finasteride acted as their own controls. No consistent relationship was found between changes in the ratios of 11-oxo/11-OH FM and allo THF/THF. We conclude that there is no evidence of consistent metabolic interaction between 11-HSD and 5 alpha/5 beta reductase activities under a wide range of conditions. Furthermore, the patterns of metabolic changes seen in these conditions are no less characteristic, although more subtle, than the well-documented metabolic changes seen in inborn errors of steroid metabolism.

11-beta-Hydroxysteroid Dehydrogenases↗

Expanding horizons in breast and prostate cancer prevention and early detection. The 1992 Samuel C. Harvey Lecture.

Breast cancer and prostate cancer, the most common cancers in American women and men, respectively, are major public health concerns. Investigations into the prevention and early detection of breast and prostate cancer include research on the potential impact of diet, particularly dietary fat, on breast cancer risk; the chemoprevention of breast cancer using tamoxifen and N-(4-hydroxyphenyl)retinamide(4-HPR); the importance of mammography in early detection of breast cancer; the potential of finasteride in preventing or retarding the progression of early-stage prostate cancer; and improved detection of prostate cancer by combining various screening modalities. The importance of transferring information gained though such research to the health care community cannot be overemphasized. Further, it is critical that cancer prevention and detection education be built into the curricula of leading medical and biomedical institutions. Education is key to developing a strong and vigorous cancer prevention and early detection research program.

Antineoplastic Agents↗

Preventing diseases of the prostate in the elderly using hormones and nutriceuticals.

The prostate has only one function, namely to secrete fluid containing substances that are needed for reproduction. This requires an extremely high concentration of androgens in the tissues. Benign prostatic hypertrophy (BPH) seems to be related to the long-term exposure of the prostate to the strong androgen 5alpha-dihydrotestosterone (DHT) and, possibly, to estrogens. The relation between prostate cancer and androgens is suggested to be U-shaped, with both extremes of androgen concentrations being associated with increased risk of invasive cancer. In the treatment of patients with BPH, the lipidic liposterolic extracts of Serenoa repens were as effective as the pharmaceutical inhibitors of the 5alpha-reductase enzyme or alpha1-adrenergic blockers in relieving urinary symptoms. In addition to moderately inhibiting the 5alpha-reductase activity, Serenoa seems to exert anti-inflammatory and complementary cellular actions with beneficial effects on the prostate. Unlike the pharmaceutical 5alpha-reductase inhibitors, finasteride and dutasteride, Serenoa does not suppress serum PSA, facilitating the follow-up and the early detection of prostate cancer. We suggest a strategy to prevent prostate cancer that aims at providing men with partial androgen deficiency correct testosterone substitution with a sustained release buccal bio-adhesive tablet. In addition, food supplementation with extracts of Serenoa repens and a combination of the antioxidants selenium, (cis)-lycopene and natural vitamin E, together with fish oil rich in long-chain polyunsaturated essential fatty acids of the omega-3 group seems warranted. Clearly, a holistic approach including careful clinical and biological monitoring of the aging man and his prostate remains mandatory.

Aged↗

New aromatic esters of progesterone as antiandrogens.

The in vivo and in vitro antiandrogenic activity of four new progesterone derivatives: 4-bromo-17alpha-(p-fluorobenzoyloxy)-4-pregnene-3,20-dione 1,4-bromo-17alpha-(pchlorobenzoyloxy)-4-pregnene-3,20-dione 2, 4-bromo-17alpha-(p-bromobenzoyloxy)-4-pregnene-3,20-dione 3 and 4-bromo-17alpha-(p-toluoyloxy)-4-pregnene-3, 20-dione 4 was determined. These compounds were evaluated as antiandrogens on gonadectomized hamster prostate and reduced the weight of the prostate glands in gonadectomized hamsters treated with testosterone 5 (T) or dihydrotestosterone 6 (DHT) in a similar manner to that of commercially available finasteride, thus indicating a potent in vivo effect. The in vitro studies showed that steroids 1-4 have a weak inhibitory activity on 5alpha-reductase with IC50 values of: 280 (1), 2.6 (2), 1.6 (3) and 114 microM (4). The presence of Cl and Br atoms in the C-17 benzoyloxy group tends to increase the inhibitory potency of the compounds. The binding efficiency of the synthesized steroids 1-4 to the androgen receptor of the prostate gland is also evaluated. All compounds form a complex with the receptor and this explains the weight reduction of the seminal vesicles in the animals treated with DHT plus steroids 1-4.

5-alpha Reductase Inhibitors↗

Hair transplantation: new concepts in 2005.

This article will provide a brief review of the current concepts in hair transplantation. Currently, hair transplantation creates natural appearing transplanted hair for men and women. Patient consultation is an essential component of a successful procedure. During the consultation realistic expectations are essential and are based on the patient's donor density, caliber of hair follicle, and rate of hair loss. Alternative and adjunctive therapies such as finasteride and minoxidil should be a basic component of any consultation. The only limit to the procedure is the amount of donor hair each patient has available. For the vast majority of patients, elliptical donor harvesting provides the most efficient technique for harvesting hair. Follicular unit extraction can be a useful technique for a minority of patients.

Alopecia↗

Vapor resection: a good alternative to standard loop resection in the management of prostates >40 cc.

BACKGROUND AND PURPOSES: The morbidity of transurethral vesection of the prostate (TURP) necessitates constant attempts at modifications to the standard equipment and technique. Patients with larger prostates (>40 cc) need a longer time for the procedure, and the blood loss, requirement for irrigation fluid, and incidence of postoperative complications tend to be greater. We report on the safety and efficacy of TURP with the thick vapor resection loop compared with the standard wire loop in comparable groups of patients with prostates >40 cc. PATIENTS AND METHODS: We randomized 100 patients with benign prostatic hyperplasia (BPH) into two groups of 50 each which were similar in age. The inclusion criteria included an indication for prostatectomy and prostate size >40 cc. Patients who were on finasteride preoperatively (six) and those who had histopathologic adenocarcinoma of the prostate (three) were excluded. Preoperative evaluation included assessment of International Prostate Symptom Score (IPSS), prostate volume by abdominal ultrasonography, maximum flow rate (Q(max)), and residual urine volume. The two groups were similar in the signs and symptoms of BPH. Patients in Group 1 underwent transurethral vapor resection of the prostate (TUVRP) using the vapor resection loop (Wing trade mark; Richard Wolf, Germany), while patients in Group 2 underwent TURP using a standard wire loop. All procedures were performed by consultant urologists with equivalent experience. We used a Martin ME 401 (Gebruder Martin, Tuttlingen, Germany) electrosurgical generator with settings of 120 to 150 Watts and 50 to 70 W for cutting and coagulating, respectively, for the thick loop and 70 to 80 W and 40 to 50 W for the standard loop. Operating time, resected tissue weight, duration of catheterization, nursing contact time, hospital stay, hemoglobin change, serum sodium concentrations, and any complications were noted and analyzed using the Kruskal-Wallis paired variables test, and P values were calculated. P value <0.04 was considered significant. The IPSS, Q(max), and residual urine volume were reevaluated at 6 months and 1 year after the procedure and compared for the two groups. RESULTS: The median prostate volume was 63 cc and 54 cc in Groups 1 and 2, respectively, and the median resected weight was 20 and 19 g, respectively (P = NS). The differences in operating time (median 45 v 60 minutes; P < 0.0001), intraoperative irrigant use (15 v 21 L; P < 0.0001), and intraoperative blood loss (median 52.5 v 150 mL; P < 0.0001) in the two groups were statistically significant. Peroperative blood loss was estimated by the indicator dilution method of Freedman et al in three 5-mL samples of the irrigant fluid and arriving at the average of the three values and adjusted for the volume of irrigant fluid used. The differences in postoperative irrigant (P < 0.01) and catheter duration (P = 0.04) were also significant. Two patients received blood transfusion in Group 2 and none in Group 1. The difference in the change in hemoglobin and serum sodium postoperatively in the two groups was not statistically significant. The complications were dysuria in six patients lasting for a month and one capsular perforation in Group and incontinence lasting for 6 months in two patients and stricture in one patient in Group 2. The efficacy, assessed with IPSS, Q(max), and residual urine volume, was comparable at 6 months and at 1 year. CONCLUSION: The use of a thick vapor resection loop for TURP coupled with higher generator settings as recommended for them, especially for prostates >40 cc, is beneficial, as it significantly reduces operating time, blood loss, irrigant requirement, nursing contact time, and duration of catheterization, besides providing clear vision during surgery and ease of resection. There was no reduction in efficacy or increase in complications.

Aged↗

The population dynamics of cancer: a Darwinian perspective.

Carcinogenesis, at least for some types of cancer, can be interpreted as the consequence of selection of mutated cells similar to what, in the theory of evolution, occurs at the population level. Instead of considering a population of organisms, we can refer to a population of cells belonging to multicellular organisms. Many carcinogens are mutagens, and the observed geographic distribution of cancer is, at least in part, attributable to environmental mutagens. However, the rapid change in risk for some cancers after migration suggests that carcinogenesis involves--in addition to mutations--some late event that most probably consists of the selection of cells already carrying mutations. We review a few examples of such selective pressures: finasteride in prostate cancer, vitamin supplementation in smokers, acquired resistance to chemotherapy, peripheral resistance to insulin, and sunlight and mutations in melanoma. A disease model for such a hypothesis is represented by Paroxysmal Nocturnal Hemoglobinuria (PNH). Mutations can be present at birth, as in the case of PNH, and can have a frequency much higher than the occurrence of the corresponding disease (PNH or lymphocytic leukaemia in children). However, PNH does not require a mutator phenotype, only a mutant phenotype followed by selection. A characteristic feature of cancer, instead, is likely to be the development of the mutator phenotype. We propose a 'Darwinian' model of carcinogenesis. If the model is correct, it suggests that prevention is more complex than avoiding exposure to mutagens. Mutations and genetic instability can be already present at birth. Mutations can be selected in the course of life if they increase survival advantage of the cell under certain environmental circumstances. In addition, gene-environment interactions cannot be interpreted according to a simplified linear model (based on the 'analysis of variance' concept); experimental work suggests that a more comprehensive non-linear interpretation based on the idea of 'norm of reaction' is needed.

Cell Transformation, Neoplastic↗