Systemic therapy of prostate cancer. New concepts from prostate cancer tumor biology

Focal therapy for localized cancer: a patent review

INTRODUCTION

Conventional cancer treatments such as radical surgery and systemic therapy targeting the organ or organ system might have side effects because of damage to the surrounding tissue. For this reason, there is a need for new instruments that focally treat cancer.

AREAS COVERED

This review provides a comprehensive overview of the patent literature on minimally and noninvasive focal therapy instruments to treat localized cancer. The medical section of the Google Patents database was scanned, and 128 patents on focal therapy instruments published in the last two decades (2000-2021) were retrieved and classified. The classification is based on the treatment target (cancer cell or network of cancer cells), treatment purpose (destroy the cancerous structure or disable its function), and treatment means (energy, matter, or a combination of both).

EXPERT OPINION

We found patents describing instruments for all groups, except for the instruments that destroy a cancer cell network structure by applying matter (e.g. particles) to the network. The description of the different treatment types may serve as a source of inspiration for new focal therapy instruments to treat localized cancer.

Neoadjuvant hormonal therapy in carcinoma of the prostate

The rising incidence of and mortality from prostate cancer has generated great interest in improving the results of current methods of treatment. It is well-established that large tumour volumes and positive surgical margins are correlated with higher rates of local failure and distant metastasis. Significant decreases in both tumour volume and the rates of positive surgical margins are seen with NHT. Follow-up data from one randomized trial of hormonal therapy before RT have shown significantly improved disease-free survival, but so far there has been no benefit in overall survival. However, the addition of adjuvant hormonal therapy has been reported to improve survival. The results suggest that neoadjuvant and adjuvant hormonal therapy may be a viable option in men with locally advanced prostate cancer in whom cure is probably impossible, but disease progression can potentially be slowed. What remains to be determined is whether hormonal therapy alone can produce the same results. For younger men with clinically localized prostate cancer, radical prostatectomy is increasingly the treatment of choice. Prospective randomized trials of NHT have produced impressive statistics for decreasing the incidence of positive surgical margins, but the potential to down-stage tumours remains controversial. Follow-up serum PSA measurements have thus far shown no benefit from neoadjuvant therapy. The possibility that patients who fail biochemically, whether they are from the pretreated or control group, may simply represent a subgroup with aggressive tumours that may not respond to androgen withdrawal, has yet to be proved. As more follow-up data are analysed within the next several years, there must be a clear survival advantage if NHT is to be offered as a treatment option. Despite the potential of neoadjuvant therapy, the use of androgen withdrawal before definitive surgical treatment should be limited to clinical trials until a clearer picture emerges. Some may argue that although there is no evidence of a true advantage for NHT, neither is there evidence of harm. However, it must be recognized that androgen withdrawal therapy has side-effects and adds significantly to the overall cost of treatment. Furthermore, NHT delays definitive treatment; clearly, this can be a source of anxiety for the patient and the impact on survival is unknown. Currently, the rates of pathologically organ-confined disease are high in some subsets of patients (e.g. low-stage, low-grade and low PSA) so that NHT is unlikely to have great additional benefit. Although the influence of hormones on prostate growth has been known for many decades, we are only now elucidating the biological mechanisms of hormonal therapy. Although androgen ablation therapy has been used in men with metastatic prostate cancer for more than 50 years, further research at the cellular and molecular level is essential if we are to refine treatment modalities for both localized and advanced disease. Furthermore, until we have more follow-up data from randomized clinical trials of NHT, it cannot be considered part of the standard treatment for carcinoma of the prostate. There are still too many unknown factors; only time will tell if the initial promise of NHT will be fulfilled.

Effect of early treatment of prostate cancer with the 5alpha-reductase inhibitor turosteride in Dunning R3327 prostatic carcinoma in rats

BACKGROUND

Turosteride, a selective 5alpha-reductase inhibitor, was reported to be effective in inhibiting the growth of established tumors in the Dunning R3327 rat prostatic carcinoma model. We evaluated the preventive effect of turosteride when administered during the latency period in this prostatic tumor model.

METHODS

Turosteride was given orally, 6 days a week for 10-15 weeks, starting at different times: 1) 5 weeks after tumor implantation, when tumors were not yet palpable, or 2) 1 day after tumor implantation. In each experiment, one group of animals was castrated on the first treatment day.

RESULTS

When treatment started 5 weeks after tumor implantation, neither turosteride (at 50 and 200 mg/kg/day) nor castration reduced tumor incidence (91-100%). Tumor growth was reduced in groups treated with the highest dose of turosteride and in castrated rats. When treatment started 1 day after tumor implantation, castration resulted in a 62% tumor incidence compared to 100% in controls, while turosteride at 200 mg/kg/day was not effective in reducing tumor incidence. However, as in the previous experiment, the compound was highly effective in reducing tumor growth.

CONCLUSIONS

The antitumor activity profile of turosteride seems not to be related to the timing of treatment. Given either 5 weeks or 1 day after tumor implantation, the compound did not reduce tumor take, while it maintained effective tumor growth-inhibiting activity in both cases.

Effect of the dual 5alpha-reductase inhibitor PNU 157706 on the growth of dunning R3327 prostatic carcinoma in the rat

PNU 157706 [N-(1,1,1,3,3,3-hexafluorophenylpropyl)-3-oxo-4-aza-5alpha-androst-1-ene-17beta-carboxamide] is a novel, potent and selective dual 5alpha-reductase inhibitor. We have investigated its effect on tumor growth, endocrine organ weights and prostatic dihydrotestosterone (DHT) content in rats bearing the androgen dependent Dunning R3327 prostatic carcinoma. Animals with tumor diameters of about 1 cm were treated orally for 9 weeks with PNU 157706 (2 and 10 mg/kg/day, 6 days a week) or they were castrated, to check the hormone responsiveness of the tumor. PNU 157706 was effective at both doses tested in reducing tumor growth (53 and 51% inhibition at 2 and 10 mg/kg/day, respectively), while castration caused higher inhibition (82%) of tumor growth. A marked reduction of ventral prostate weight occurred in rats treated with both doses of PNU 157706 (75 and 78%) or castrated (91%). Seminal vesicle weight was also reduced by PNU 157706 administration (56 and 61% inhibition), whereas testes, adrenal, thymus and pituitary weights were not affected. Prostatic DHT content was markedly suppressed (85 and 91%) in PNU 157706 treated rats, compared to 95% suppression caused by castration. These data support a possible role of dual 5alpha-reductase inhibitors in the hormonal therapy of prostatic cancer.

The future of gene therapy in the treatment of urologic malignancies

Gene therapy as a field of academic inquiry and as a medical technology is perhaps the inevitable consequence of living in today's technologic age. At its essence, gene therapy is merely therapy using molecular information. The identification of the pivotal role of DNA in the information systems of life and the subsequent emergence of molecular biology and its technologies has led to routine use of the genetic code-like software to treat human disease in clinical trials.

Serum vascular endothelial growth factor is a candidate biomarker of metastatic tumor response to ex vivo gene therapy of renal cell cancer

We report the close correlation between changes in serum immunoreactive vascular endothelial growth factor 165 (iVEGF165) levels and metastatic tumor burden measured by computed tomography scan before treatment, during the antitumor response, and during early progression in a patient treated with ex vivo gene therapy for renal cell carcinoma. With the researcher blinded to outcome, iVEGF levels were measured in archived serum samples from a patient with metastatic renal cell carcinoma who demonstrated a 7-month partial remission to treatment with autologous, irradiated human GM-CSF gene transduced tumor vaccine. Although a spontaneous regression could not be formally excluded in this patient, the appearance of 20 new pulmonary metastases on computed tomography scan after nephrectomy and before vaccination indicates that if spontaneous regression occurred, it took place at the start of vaccine treatment.

Molecular carcinogenesis of prostate cancer: potential clinical relevance and nursing implications

OBJECTIVES

Describe the current state of knowledge on the molecular basis of prostate carcinogenesis, potential clinical relevance of findings, and nursing implications.

DATA SOURCES

Published research articles, clinical summaries, proceedings of conferences, and personal communication with investigators.

CONCLUSION

The understanding of the molecular basis of prostate cancer lags behind that of other common solid tumors. Until recently, much research was reliant on cell line and animal data. Epidemiologic studies, a recently recognized hereditary variant, and cytogenetic analysis of human prostate tissue have provided insight into prostate carcinogenesis. Like other cancers, prostate cancer results from combined somatic and genetic mutations, gene activations, and interplay of genetic and environmental factors. To date, the most consistent changes are those of allelic loss events with the majority of tumors examined showing loss of alleles from at least one chromosomal arm. No specific genes have yet been identified. Clinical applications of these findings are still in developmental stages or early stages of clinical trials.

IMPLICATIONS FOR NURSING PRACTICE

An understanding of the molecular basis of cancer is requisite to the provision of up-to-date patient education and to understanding newly developing diagnostic, treatment, and preventive strategies.

Effect of turosteride, a 5 alpha-reductase inhibitor, on the Dunning R3327 rat prostatic carcinoma

BACKGROUND

Turosteride (FCE 26073) is a new, potent, and selective 5 alpha-reductase inhibitor. We have investigated its effect on tumor growth, organ weight, and serum hormone levels in rats bearing the androgen sensitive Dunning R3327 prostatic carcinoma.

METHODS

Animals with tumor diameters of 0.5-1.5 cm were treated for 9 weeks with turosteride (50 and 200 mg/kg/day, 6 days a week, orally), flutamide (25 mg/kg/day, 6 days a week, orally), and leuprolide (300 micrograms/rat, every 3 weeks, subcutaneously) or they were castrated.

RESULTS

Turosteride was ineffective at the dose of 50 mg/kg/day, whereas at 200 mg/kg/ day it significantly decreased tumor growth by 45%. Flutamide and leuprolide were highly effective in reducing tumor growth (70 and 77%), although their effect was slightly lower than that of castration (85%). A significant reduction of ventral prostate weight occurred in rats treated with turosteride at 50 and 200 mg/kg/day (53% and 60%). In contrast to leuprolide and castration, the inhibitory effect of turosteride on tumor growth and prostate weight was not associated to any decrease in serum testosterone.

CONCLUSIONS

Turosteride has antitumor activity on Dunning prostatic tumor growth and its role in prostatic cancer treatment is worthy of further investigation.

Antisense RNA to the type I insulin-like growth factor receptor suppresses tumor growth and prevents invasion by rat prostate cancer cells in vivo

Prostate carcinoma is the second leading cause of death from malignancy in men in the United States. Prostate cancer cells express type I insulin-like growth factor receptor (IGF-IR) and prostate cancer selectively metastazises to bone, which is an environment rich in insulin-like growth factors (IGFs), thereby supporting a paracrine action for cancer cell proliferation. We asked whether the IGF-IR is coupled to tumorigenicity and invasion of prostate cancer. When rat prostate adenocarcinoma cells (PA-III) were stably transfected with an antisense IGF-IR expression construct containing the ZnSO4-inducible metallothionein-1 transcriptional promoter, the transfectants expressed high levels of IGF-IR antisense RNA after induction with ZnSO4, which resulted in dramatically reduced levels of endogenous IGF-IR mRNA. A significant reduction in expression both of tissue-type plasminogen activator and of urokinase-type plasminogen activator occurred in PA-III cells accompanying inhibition of IGF-IR. Subcutaneous injection of either nontransfected PA-III or PA-III cells transfected with vector minus the IGF-IR insert into nude mice resulted in large tumors after 4 weeks. However, mice injected with IGF-IR antisense-transfected PA-III cells either developed tumors 90% smaller than controls or remained tumor-free after 60 days of observation. When control-transfected PA-III cells were inoculated over the abraded calvaria of nude mice, large tumors formed with invasion of tumor cells into the brain parenchyma. In contrast, IGF-IR antisense transfectants formed significantly smaller tumors with no infiltration into brain. These results indicate an important role for the IGF/IGF-IR pathway in metastasis and provide a basis for targeting IGF-IR as a potential treatment for prostate cancer.

Role of laparoscopy in the diagnosis and treatment of prostate cancer

Laparoscopic surgical techniques were originally applied to the staging of prostate cancer in the form of laparoscopic pelvic lymph node dissection. The efficiency of laparoscopic pelvic lymph node dissection has proven to be comparable to open lymphadenectomy in tissue yield and also shows a considerable decrease in postoperative morbidity. Subsequently, laparoscopy has been used as an adjuvant to perineal prostatectomy for preliminary dissection of the seminal vesicles. Laparoscopic radical prostatectomy has been performed but the long-term efficacy of this treatment is unknown at this point. Future clinical applications of laparoscopic surgical techniques in the diagnosis and treatment of prostate cancer include harvesting of primary and metastatic prostatic tissue for adjuvant gene therapies for prostate cancer.

Selection of men at high risk for disease recurrence for experimental adjuvant therapy following radical prostatectomy

OBJECTIVES

Following surgery, men with recurrent prostate cancer have an isolated elevation in serum prostate-specific antigen (PSA) well in advance of measurable metastatic disease. Rational patient selection for new forms of adjuvant therapy, for example, gene therapy, is imperative.

METHODS

In a retrospective study of two cohorts, we used proportional hazards regression analysis to develop and validate a multifactor model for identifying men who are at high risk of cancer recurrence. The model cohort consisted of 216 men with clinical Stage T2b and T2c treated by 1 urologist. The validation cohort consisted of 214 men with Stage T2b and T2c disease.

RESULTS

A model for log relative risk, Rw, used serum PSA with a sigmoidal transformation (PSAST), radical prostatectomy Gleason score (GS), and pathologic stage (PS) as specimen confined or nonspecimen confined: Rw = (PSAST x 0.06) + (GS x 0.54) + (PS x 1.87). Recurrence risk categories were determined as low risk if Rw is less than 4.0, intermediate risk if it is 4.0 to less than 5.75, and high risk if Rw is more than 5.75. The observed Kaplan-Meier actuarial analysis of the three risk groups correlated well with the predictions determined for the model cohort. We then validated this model independently using a second cohort of 214 men with similar age, stage, and grade treated by 3 different urologists at two different institutions.

CONCLUSIONS

The recurrence rates for men in the high-risk group are similar to those for men with positive lymph nodes and justifies exploration of experimental adjuvant therapy within this group using this model of patient selection.

Interleukin-6: a candidate mediator of human prostate cancer morbidity

OBJECTIVES

Interleukin-6 (IL-6) is evaluated as a candidate mediator of morbidity in patients with metastatic adenocarcinoma of the prostate.

METHODS

IL-6 concentration is measured by enzyme-linked immunoadsorbent assay (ELISA) in the ejaculate plasma of healthy men, in primary culture of prostate epithelial cells, in human prostate cancer cell line cultures and SCID mouse xenografts, and in the plasma of 73 men with metastatic adenocarcinoma of the prostate.

RESULTS

High levels of IL-6 secretion are found in the normal human ejaculate, in prostate epithelial primary culture, and in three of four anaplastic, androgen-independent human prostate cancer cell lines tested. In contrast, the hormone-responsive and PSA-secreting cell lines and the hormone-independent line PPC-1 do not secrete detectable levels of IL-6 by ELISA: The acquisition of a p53 mutation in LNCaP-GW and PPC-1 is not sufficient to confer the phenotype of high IL-6 secretion. Seventy-three men with well-characterized, advanced, hormone refractory prostate cancer prior to suramin therapy are tested for incidence of abnormal circulating levels of IL-6. Plasma IL-6 levels have a bimodal distribution, with the upper quartile of patients having abnormal levels from 9 to 61 pg/mL. A direct comparison of the high and low serum IL-6 groups show that elevated IL-6 levels are strongly correlated with objective measures of morbidity: decreased hematocrit, hemoglobin, and serum cholesterol, and increased white blood cell count and serum lactate dehydrogenase levels all in the absence of clinical infection.

CONCLUSIONS

These data show that IL-6 is a prostate exocrine gene product, a candidate mediator of prostate cancer morbidity, and a candidate marker of disease activity for prospective clinical testing.