Chemotherapy for advanced prostate cancer: Results of new clinical trials and future studies

Chemotherapy for the initial treatment of metastatic prostate adenocarcinoma and neuroendocrine carcinoma at diagnosis: real world application and impact in the SEER database (2004 -2018)

Background

Randomized controlled phase III trials have reported significant improvements in disease response and survival with the addition of chemotherapy to androgen deprivation therapy for men presenting with metastatic prostate cancer. We examined the implementation of such knowledge and its impact within the Surveillance, Epidemiology, and End Results (SEER) database.

Method

The administration of chemotherapy for men with an initial presentation of metastatic prostate cancer from 2004 to 2018 in the SEER database and its association with survival outcomes was examined. Kaplan-Meier estimates were applied to compare survival curves. Cox proportion hazard survival models were used to analyze the association of chemotherapy and other variables with both cancer- specific and overall survival.

Result

A total of 727,804 patients were identified with 99.9% presenting with adenocarcinoma and 0.1% with neuroendocrine histopathology. Chemotherapy as initial treatment for men with de novo distant metastatic adenocarcinoma increased from 5.8% during 2004-2013 to 21.4% during 2014-2018. Chemotherapy was associated with a poorer prognosis during 2004-2013 but was associated with improved cancer-specific (hazard ratio (HR) = 0.85, 95% confidence interval (CI): 0.78-0.93, p=0.0004) and overall survival (HR= 0.78, 95% CI: 0.71-0.85, p < 0.0001) during 2014-2018. The improved prognosis during 2014-2018 was observed in patients with visceral or bone metastasis and most impactful for patients aged 71-80 years. These findings were confirmed by subsequent propensity score matching analyses. Furthermore, chemotherapy was consistently provided to 54% of patients with neuroendocrine carcinoma at diagnosis from 2004 to 2018. Treatment was associated with improved cancer-specific survival (HR= 0.62, 95% CI: 0.45-0.87, p=0.0055) and overall survival (HR= 0.69, 95% CI: 0.51-0. 94, p=0.0176) during 2014-2018 but not significant in earlier years.

Conclusion

Chemotherapy at initial diagnosis was increasingly employed in men with metastatic adenocarcinoma after 2014 and consistent with the evolution of National Comprehensive Cancer Network (NCCN) guidelines. Benefits for chemotherapy are suggested after 2014 in the treatment of men with metastatic adenocarcinoma. The use of chemotherapy for neuroendocrine carcinoma at diagnosis has remained stable, and outcomes have improved in more recent years. Further development and optimization of chemotherapy continues to evolve for men with de novo diagnosis of metastatic prostate cancer.

Inhibition of prostate cancer growth by immunization with a GM-CSF-modified mouse prostate cancer RM-1 cell vaccine in a novel murine model

Advanced prostate cancer is difficult to treat owing to a lack of effective approaches for disrupting immune tolerance. C57BL/6 male and female mice implanted with viable RM-1 cells represent a novel murine model of advanced prostate cancer for studying antitumor effects following immunization with a granulocyte-macrophage colony-stimulating factor (GM-CSF)-modified RM-1 cell vaccine, which has been described previously. In vitro cytotoxic activity and cytokine secretion experiments were conducted to investigate the antitumor response. The cytotoxicity profile of splenocytes from female mice immunized against RM-1 cells primarily involved cytotoxic T lymphocyte (CTL) lysis and, to a lesser extent, natural killer (NK) cell lysis. NK cell lysis was also observed in males, which exhibited no evidence of CTL lysis. The secretion of interferon-γ in the GM-CSF-modified cell vaccine group was significantly increased compared with the other groups. The level of interleukin-4 was low. To investigate the antitumor immune response further, cluster of differentiation 4 (CD4) T cells and CD8 T cells were analyzed in the spleens and tumors of female mice receiving the GM-CSF-modified RM-1 cell vaccine. Unlike female mice, males exhibited the highest proportion of NK cells in the spleen. NK cells were not detected in the tumor tissue in any of the groups. The difference between the sexes may explain the specificity of the immune response, as females are intolerant to prostate antigens whereas males are. This model is clinically relevant as it translates to human immunology and offers an effective and convenient method for studying immunotherapy for prostate cancer.

KIFC1 induces resistance to docetaxel and is associated with survival of patients with prostate cancer

OBJECTIVES

Prostate cancer (PCa) is a common malignancy worldwide. Docetaxel has been an important treatment option for patients with metastatic castration-resistant prostate cancer (CRPC). However, nearly all patients with CRPC treated with docetaxel eventually become refractory. In the present study, we analyzed the expression and distribution of kinesin family member C1 (KIFC1) in human PCa by immunohistochemistry and examined the effect of inhibiting KIFC1 expression on docetaxel resistance.

METHODS

Expression of KIFC1 was determined using immunohistochemistry. RNA interference was used to inhibit KIFC1 expression in PCa cell lines. To examine cell viability, we performed 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays.

CONCLUSIONS

These results indicate that KIFC1 plays an important role in PCa progression. Immunohistochemical analysis of KIFC1 would facilitate identification of patients with poor prognoses after radical prostatectomy, as well as patients with poor therapeutic outcomes after docetaxel-based chemotherapy.

In vivo evaluation of a novel albumin-binding prodrug of doxorubicin in an orthotopic mouse model of prostate cancer (LNCaP)

PSA, which is overexpressed in prostate carcinoma, represents a molecular target for selectively releasing an anticancer agent from a prodrug formulation. In this study, we report on the in vivo antitumor efficacy of an efficacious albumin-binding prodrug of doxorubicin (PSA9) that incorporates p-aminobenzyloxycarbonyl (PABC) as a self-immolative spacer in addition to the heptapeptide, Arg-Ser-Ser-Tyr-Tyr-Ser-Leu, which serves as a substrate for PSA. The prodrug is cleaved very efficiently by PSA releasing H-Ser-Leu-PABC-doxorubicin and subsequently doxorubicin in PSA-positive cell lysates and prostate tumor homogenates as the final cleavage product. PSA9 at 3 × 6 mg kg(-1) doxorubicin equivalents (intravenous) was compared with conventional doxorubicin at equitoxic doses (at 3 × 3 mg kg(-1); intravenous) in an orthotopic mouse model of prostate cancer using LNCaP lentiviral luciferase-neomycin cells transduced with luciferase. Whereas doxorubicin did not show any efficacy against the primary tumor or metastases, the prodrug reduced the primary tumor by 30-50% and circulating PSA levels, and in addition, showed a pronounced reduction in lung and bone metastases by ∼77% and ∼96%, respectively, and a positive trend regarding the activity against liver and lymph-node metastases compared with control and doxorubicin-treated animals. The incorporation of PABC as a self-immolative spacer together with a PSA substrate demonstrates superior antitumor effects over doxorubicin attributed to an efficient cleavage by PSA releasing doxorubicin as the final active agent in prostate tumor homogenates. Using this approach for developing effective prodrugs against prostate cancer, is worthy of further preclinical optimization.

Pre-clinical evaluation of 1-nitroacridine derived chemotherapeutic agent that has preferential cytotoxic activity towards prostate cancer

Chemotherapy in prostate cancer (CaP) even as an adjunct has not been a success. In this communication, we report the pre-clinical efficacy of a nitroacridine derivative, C-1748 (9[2'-hydroxyethylamino]-4-methyl-1-nitroacridine) in CaP cell culture and human xenograft animal models. C-1748, a DNA intercalating agent has been derived from its precursor C-857 that was a potent anti-cancer drug, but failed clinical development due to "high" systemic toxicities. Chemical modifications such as the introduction of a "methyl" group imparted novel properties, the most interesting of which is the difference in the IC(50) values between LnCaP (22.5 nM), a CaP cell line and HL-60, a leukemia cell line (>100 nM). Using gammaH2AX as an intervention marker of DNA double strand breaks, we concluded that C-1748 is more efficacious in CaP cells than in HL-60 cells. In hormone dependent cells, the androgen receptor (AR) was identified as an additional target of C-1748. In xenograft studies, administration of C-1748 intra-peritoneally inhibited tumor growth by 80-90% with minimal toxicity. These studies identify C-1748 as a novel acridine drug that has a high therapeutic index and low cytotoxicity on myelocytic cells with potential for clinical development.

Luteinizing hormone-releasing hormone agonists in the treatment of prostate cancer: A review of their discovery, development, and place in therapy

BACKGROUND

Early identification of the biological activity of luteinizing hormone-releasing hormone (LHRH) paved the way for the synthesis of analogues with enhanced potency and biological properties. Early testing in animal models and humans provided insight into the potential clinical uses of these substances, and, within 10 years, LHRH-agonist therapy had become available for use in patients with advanced prostate cancer (PC). Over time, the role of LHRH-agonist therapy has expanded to include use as part of multimodal treatment regimens throughout the course of the disease.

OBJECTIVES

This article reviews the discovery and development of LHRH agonists and summarizes the clinical evidence for their efficacy in PC.

METHODS

Relevant clinical studies were identified through searches of the English-language literature indexed on MEDLINE through May 2006. The main search terms were prostate cancer and LHRH agonist.

RESULTS

Results of the initial therapeutic trials of sustained-release depot formulations of LHRH agonists in patients with PC were reported in the mid-1980s, indicating that these agents were effective and well tolerated in improving clinical symptoms and producing medical castration. Longer-term studies and subsequent meta-analyses of randomized controlled trials in patients with advanced PC found no significant differences in overall survival when single-therapy androgen suppression was achieved through the use of LHRH-agonist therapy or orchiectomy. Randomized trials have reported significant improvements in disease-free and overall survival in patients with locally advanced or high-grade PC treated with LHRH agonists in addition to radiotherapy. Several prospective randomized trials have reported decreases in rates of positive surgical margins with short-term (6 weeks to 4 months) neoadjuvant LHRH-agonist therapy in patients with stage T1 to T3a PC undergoing prostatectomy. Definitive comparisons of immediate and delayed treatment in patients with biochemical relapse have not been reported. However, the results of several studies suggest that immediate LHRH-agonist therapy (or orchiectomy) may improve the course of disease progression and survival. The risks of long-term treatment (eg, osteoporosis; fracture; anabolic loss of muscle mass, with a tendency toward weight gain) must be considered carefully in patients who are likely to receive chronic LHRH-agonist therapy. Intermittent schedules have been developed to reduce the adverse effects associated with LHRH-agonist therapy; some reports support sparing effects on bone and muscle mass and relative improvements in toxicities during off-therapy periods, whereas others have documented continuing decreases in bone mineral density (BMD), with the rate of bone loss highest during the early cycles of therapy. Bisphosphonate therapy has been shown to increase BMD in patients with PC and may therefore be beneficial when overt symptoms of osteopenia or osteoporosis are present.

CONCLUSIONS

LHRH-agonist therapy has been the mainstay of treatment for advanced PC for >20 years. Clinical evidence supports expanding use of these agents at an earlier stage of disease and as part of multimodal regimens that include radiotherapy. There is a need for further study of the efficacy of adjuvant LHRH-agonist therapy along with prostatectomy, in patients with biochemical failure, in intermittent regimens, and in conjunction with cytotoxic therapies in late-stage disease.

Docetaxel induces apoptosis in hormone refractory prostate carcinomas during multiple treatment cycles

Caspase-cleaved proteins are released from disintegrated apoptotic cells and can be detected in the circulation. We here addressed whether caspase-cleaved cytokeratin 18 (CK18-Asp396) can be used as a serum biomarker for assessment of the clinical efficiency of chemotherapy in hormone-refractory prostate cancer (HRPC). A total of 82 patients with HRPC were evaluated during 751 treatment cycles, either with estramustine (EMP)/vinorelbine or with EMP/docetaxel. The levels of CK18-Asp396 and of total CK18 were measured in patient serum before and during therapy by ELISA. Docetaxel induced significant increases in serum CK18-Asp396 (P<0.0001) and total CK18 (P<0.0002), suggesting induction of apoptosis. Similarly, vinorelbine induced increases in both CK18-Asp396 and CK18 (P<0.001 and 0.011). In contrast, EMP induced increases in total serum CK18 (P<0.0001), but not in CK18-Asp396 (P=0.13). The amplitudes of docetaxel-induced increases were associated with baseline prostate-specific antigen (PSA) and CK18 serum levels in these patients, consistent with tumoral origin of caspase-cleaved fragments. Docetaxel induced significant increases in CK18-Asp396 during second-, third- and fourth-line therapy and induced increased levels of CK18-Asp396 during treatment cycles 1–8. In contrast, vinorelbine induced significant increases only during cycles 1–3. In a subgroup of 32 patients that received EMP/vinorelbine in second line followed by EMP/docetaxel in third line, docetaxel induced stronger increases than vinorelbine (P=0.008). These results show that the CK18-Asp396 serum marker can be used to assess tumour apoptosis in vivo and suggest that the clinical efficiency of docetaxel in HRPC is due to induction of apoptosis during multiple treatment cycles.

Pre-clinical toxicology and pathology of 9-(2′-hydroxyethylamino)-4-methyl-1-nitroacridine (C-1748), a novel anti-cancer agent in male Beagle dogs

We have developed a group of 4-substituted-1-nitroacridines with potent anti-tumor activity against prostate cancer and less toxic than parent 1-nitroacridines. The most active 9-(2'-hydroxyethylamino)-4-methyl-1-nitroacridine (C-1748) was selected for pre-clinical studies. The current study was undertaken to evaluate clinical and/or morphological adverse effects of C-1748 as a single intravenous dose at concentrations ranging from 0.16 to 4.6 mg/kg administered to male Beagle dogs. The maximum tolerated dose was 1.5 mg/kg. Emesis was observed in all groups lasting an average of 30 min to 12 h post-dosing. At high dose, extreme aggression was observed in one dog followed by disorientation and depression lasting for 48 h a frequent observation with chemotherapy. Reductions in platelets and white blood cells were observed which was similar to that seen with other chemotherapeutic agents. A compensatory hyperplasia of lymph nodes and a transient and limited extravasation in the intestinal mucosa were also observed. Increases in aspartate aminotransferase, alkaline phosphatase and creatine phosphokinase were transient with normal levels restored by day 9. These enzyme increases were accompanied by epithelial hypertrophy of larger bile ductules in the periportal triads of the liver. The low toxicity profile and high tumor target activity make this novel class of drug a promising chemotherapeutic agent.

Noninvasive Bioluminescence Imaging of Normal and Spontaneously Transformed Prostate Tissue in Mice

Several transgenic mouse models of prostate cancer have been developed recently that are able to recapitulate many key biological features of the human condition. It would, therefore, be desirable to employ these models to test the efficacy of new therapeutics before clinical trial; however, the variable onset and non-visible nature of prostate tumor development limit their use for such applications. We now report the generation of a transgenic reporter mouse that should obviate these limitations by enabling noninvasive in vivo bioluminescence imaging of normal and spontaneously transformed prostate tissue in the mouse. We used an 11-kb fragment of the human prostate-specific antigen (PSA) promoter to achieve specific and robust expression of firefly luciferase in the prostate glands of transgenic mice. Ex vivo bioluminescence imaging and in situ hybridization analysis confirmed that luciferase expression was restricted to the epithelium in all four lobes of the prostate. We also show that PSA-Luc mice exhibit decreased but readily detectable levels of in vivo bioluminescence over extended time periods following androgen ablation. These results suggest that this reporter should enable in vivo imaging of both androgen-dependent and androgen-independent prostate tumor models. As proof-of-principle, we show that we could noninvasively image SV40 T antigen-induced prostate tumorigenesis in mice with PSA-Luc. Furthermore, we show that our noninvasive imaging strategy can be successfully used to image tumor response to androgen ablation in transgenic mice and, as a result, that we can rapidly identify individual animals capable of sustaining tumor growth in the absence of androgen.