Association of diabetes mellitus and metformin use with biochemical recurrence in patients treated with radical prostatectomy for prostate cancer

Effect of metformin on incidence, recurrence, and mortality in prostate cancer patients: integrating evidence from real-world studies

PURPOSE

Metformin has been suggested to reduce the risk of cancer. However, previous studies have been inconsistent regarding the relationship between metformin use and the risk of occurrence of prostate cancer (PCa). The purpose of this study was to assess the effect of metformin on clinical outcomes in patients with PCa in a meta-analysis and to explore the possible dose-response relationship.

METHODS

A systematic literature search was conducted in 10 electronic databases and 4 registries. The combined relative risks (RRs) were calculated using a random-effects model with 95% confidence interval (CIs) to assess the effect of metformin on the risk of PCa. Relevant subgroup analyses and sensitivity analyses were performed.

RESULTS

The across studies results show that metformin use associated with lower incidence of PCa (RR: 0.82, 95% CI: 0.74-0.91). Metformin use was also found to reduce PCa recurrence, but the results were not statistically significant (RR: 0.97, 95% CI: 0.81-1.15). Metformin use was not associated with PCa mortality (RR: 0.94, 95% CI: 0.81-1.09). The results of subgroup analyses indicated that the type of study was a cohort study and the population came from both Asia and Europe showed that taking metformin reduced the incidence of PCa. A linear correlation was found between the duration of metformin use and its protective effect.

CONCLUSIONS

This meta-analysis revealed an independent correlation between metformin use and reduced incidence of PCa. Metformin use was not associated with either PCa recurrence rate or mortality. Furthermore, the effect of metformin on PCa incidence was found to be related to duration.

Metformin Overcomes the Consequences of NKX3.1 Loss to Suppress Prostate Cancer Progression

BACKGROUND

The antidiabetic drug metformin has known anticancer effects related to its antioxidant activity; however, its clinical benefit for prostate cancer (PCa) has thus far been inconclusive. Here, we investigate whether the efficacy of metformin in PCa is related to the expression status of NKX3.1, a prostate-specific homeobox gene that functions in mitochondria to protect the prostate from aberrant oxidative stress.

OBJECTIVE

To investigate the relationship of NKX3.1 expression and metformin efficacy in PCa.

DESIGN, SETTING, AND PARTICIPANTS

Functional studies were performed in vivo and in vitro in genetically engineered mouse models and human LNCaP cells, and organotypic cultures having normal or reduced/absent levels of NKX3.1. Correlative studies were performed using two independent retrospective tissue microarray cohorts of radical prostatectomies and a retrospective cohort of prostate biopsies from patients on active surveillance.

INTERVENTION

Metformin was administered before or after the induction of oxidative stress by treatment with paraquat.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Functional endpoints included analyses of histopathology, tumorigenicity, and mitochondrial function. Correlative endpoints include Kaplan-Meier curves and Cox proportional hazard regression models.

RESULTS AND LIMITATIONS

Metformin reversed the adverse consequences of NKX3.1 deficiency following oxidative stress in vivo and in vitro, as evident by reduced tumorigenicity and restored mitochondrial function. Patients with low NKX3.1 expression showed a significant clinical benefit from taking metformin.

CONCLUSIONS

Metformin can overcome the adverse consequences of NKX3.1 loss for PCa progression by protecting against oxidative stress and promoting normal mitochondrial function. These functional activities and clinical correlates were observed only with low NKX3.1 expression. Thus, the clinical benefit of metformin in PCa may depend on the status of NKX3.1 expression.

PATIENT SUMMARY

Prostate cancer patients with low NKX3.1 are likely to benefit most from metformin treatment to delay disease progression in a precision interception paradigm.

Post-diagnostic metformin and statin use and risk of biochemical recurrence in Veterans diagnosed with prostate cancer

OBJECTIVE

To evaluate the impact of post-diagnostic metformin or statin use and duration on risk of biochemical recurrence in a racially-diverse cohort of Veterans.

METHODS

The population consisted of men diagnosed with prostate cancer in the Veterans Health Administration and treated with either radical prostatectomy or radiation (Full cohort n = 65,759, Black men n = 18,817, White men n = 46,631, Other = 311). The association between post-diagnostic (1) metformin and (2) statin use with biochemical recurrence was assessed using multivariable, time-varying Cox Proportional Hazard Models for the overall cohort and by race. In a secondary analysis, metformin and statin duration were evaluated.

RESULTS

Post-diagnostic metformin use was not associated with biochemical recurrence (multivariable-adjusted hazard ratio [aHR]: 1.01; 95% confidence interval [CI]: 0.94, 1.09), with similar results observed for both Black and White men. However, duration of metformin use was associated with a reduced risk of biochemical recurrence in the cohort overall (HR: 0.94; 95% CI: 0.92, 0.95) as well as both Black and White men. By contrast, statin use was associated with a reduced risk of biochemical recurrence (HR: 0.83; 95% CI: 0.79, 0.88) in the overall cohort as well as both White and Black men. Duration of statin use was also inversely associated with biochemical recurrence in all groups.

CONCLUSION

Post-diagnostic metformin and statin use have the potential to prevent biochemical recurrence in men diagnosed with prostate cancer.

Targeting lipid metabolism in metastatic prostate cancer

Despite key advances in the treatment of prostate cancer (PCa), a proportion of men have de novo resistance, and all will develop resistance to current therapeutics over time. Aberrant lipid metabolism has long been associated with prostate carcinogenesis and progression, but more recently there has been an explosion of preclinical and clinical data which is informing new clinical trials. This review explores the epidemiological links between obesity and metabolic syndrome and PCa, the evidence for altered circulating lipids in PCa and their potential role as biomarkers, as well as novel therapeutic strategies for targeting lipids in men with PCa, including therapies widely used in cardiovascular disease such as statins, metformin and lifestyle modification, as well as novel targeted agents such as sphingosine kinase inhibitors, DES1 inhibitors and agents targeting FASN and beta oxidation.

Metabolic syndrome and its components predict the biochemical recurrence and adverse pathological features of patients following radical prostatectomy: a propensity score matching study

BACKGROUND

To investigate the predictive value of metabolic syndrome (MetS) and its components in biochemical recurrence (BCR) and adverse pathological features of patients with prostate cancer (PCa) after radical prostatectomy (RP).

METHODS

A total of 525 PCa patients who underwent RP between 2010 and 2019 at Peking University Third Hospital were analyzed retrospectively. The Kaplan-Meier method was performed to assess BCR-free survival (BCRFS). Univariate and multivariate Cox regression models and multivariate logistic regression models were conducted to identify the predictive factors of BCRFS and adverse pathological features respectively before and after propensity score matching (PSM).

RESULTS

Enrolled patients were allocated into MetS group (n = 136) and non-MetS group (n = 389) according to the presence or absence of MetS, and 127 new matched pairs were identified to balance the baseline characteristics after 1:1 PSM. In propensity matched patients, the Kaplan-Meier analysis revealed that MetS (P = 0.020), hyperglycemia (P = 0.015) and hypertriglyceridemia (P = 0.001) were significantly associated with worse BCRFS; the results of multivariate Cox analyses showed that hyperglycemia (P = 0.040), hypertriglyceridemia (P = 0.017), percentage of positive biopsy cores (P = 0.041) and prostate specific antigen (P = 0.019) were identified as independent prognostic factors for BCRFS. In addition, hypertriglyceridemia was independently associated with non-organ confined disease (NOCD) (P = 0.010), extra-capsular extension (ECE) (P = 0.010) and upgrading (P = 0.017) in the multivariate logistic analyses.

CONCLUSIONS

Hyperglycemia and hypertriglyceridemia are the two effective MetS components both identified as independent risk factors for worse BCRFS after RP, while hypertriglyceridemia was independently associated with NOCD, ECE and upgrading as well.

Are Diabetic Patients at Increased Risk for Biochemical Recurrence After Radical Prostatectomy?

Introduction Diabetic patients are at a lower risk for prostate cancer. However, the relationship between diabetes mellitus (DM) and biochemical recurrence (BCR) after radical prostatectomy (RP) is less clear. The goal of our study was to determine diabetes's value as a biochemical recurrence predictor. Materials and methods We conducted a retrospective analysis of 117 patients who had undergone open radical prostatectomy between 1999 and 2021 at our institution. Univariate and multivariate statistical analyses were used to identify factors associated with biochemical recurrence. Results On univariate analysis, factors associated with biochemical recurrence were diabetes (p=0.002), preoperative prostate-specific antigen (PSA) levels (p=0.022), positive digital rectal exam (p=0.035), number of positive biopsy cores (p<0.001), unfavorable intermediate risk group (p=0.014), peri-neural invasion (PNI) on RP specimen (p=0.043), tumor volume (p=0.011), and positive surgical margins (p<0.001). Multivariate analysis showed that factors independently associated with biochemical recurrence were diabetes (p=0.039; OR=2.788), number of positive cores (p=0.016; OR=4.124), and positive surgical margins (p=0.008; OR=3.876). Conclusion A history of diabetes mellitus should be taken into consideration when assessing patients' risk of biochemical recurrence after radical prostatectomy. More research on a larger scale is needed to determine diabetes' value as a biochemical predictor.

The Impact of Metformin Use with Survival Outcomes in Urologic Cancers: A Systematic Review and Meta-Analysis

Background

Conflicting results exist between the potential protective effects of metformin and the prognosis of urologic cancers. This meta-analysis summarized the effects of metformin exposure on the recurrence, progression, cancer-specific survival (CSS), and overall survival (OS) of the three main urologic cancers (kidney cancer, bladder cancer, and prostate cancer).

Methods

We systematically searched PubMed, Embase, Web of Science, Wanfang, and China National Knowledge Infrastructure databases (January 2010 to December 2019), which identified studies regarding metformin users and nonusers with urologic cancers and extracted patient data. A random effect model or fixed effect model was used to analyze hazard ratios (HRs) and 95% confidence intervals (CIs).

Results

Among the 1883 confirmed studies, 27 eligible studies were identified, including 123,212 participants. In prostate cancer, patients using metformin have significant benefits for recurrence (HR = 0.74; 95% CI: 0.61-0.90; P = 0.007; I² = 56%), CSS (HR = 0.74; 95% CI: 0.61-0.91; P = 0.002; I² = 79%), and OS (HR = 0.76; 95% CI: 0.65-0.90; P < 0.001; I² = 86%). Moreover, further subgroup analysis showed that the beneficial effects of metformin may be more significant for patients receiving radical radiotherapy. For kidney cancer, metformin was beneficial for progression (HR = 0.80; 95% CI: 0.65-0.98; P = 0.14; I² = 46%). Analysis revealed that the effect of metformin on the overall survival of kidney cancer patients may be related to nationality (American: HR = 0.76; 95% CI: 0.59-0.98; P = 0.88; I² = 0%). For bladder cancer, no obvious benefits of metformin use were identified. However, subgroup analysis indicated that metformin may improve the recurrence of bladder cancer, but this improvement was only found in patients with a median follow-up time of more than 4 years (HR = 0.43; 95% CI: 0.28-0.67; P = 0.61; I² = 0%).

Metformin addition to androgen deprivation therapy effect on cancer prostate patients with type 2 diabetes

AIMS

Patients with prostate cancer (PC) have a higher rate of non-cancer mortality than cancer-related, which could be partially attributed to the treatment they receive. We aimed to evaluate the effect of metformin addition to androgen deprivation therapy (ADT) among cancer prostate patients with type 2 DM.

METHODOLOGY

This prospective, two-arm study included 95 PC patients with type 2 DM who had ADT. The patients were divided into 2 groups: the Metformin group includes 48 patients and the non-metformin group includes 47 patients. We compared the anthropometric, diabetic status; tumour status, survival rate, and biochemical relapse between metformin and non-metformin groups.

RESULTS

We observed significant differences in fold changes of anthropometric parameters including weight, BMI, and waist circumference between both groups. We found significant differences in fold change of PSA levels in metformin groups in comparison with non-metformin groups. Overall survival comparison between metformin users and non-users showed better statistically insignificant survival in the metformin users group. We observed a significantly lower relapse rate in the metformin group in comparison with the non-metformin.

CONCLUSION

Metformin could decrease some of the unfavourable metabolic consequences of ADT. Moreover, Metformin could enhance the tumour-suppressive effect of ADT and decrease the PSA relapse rate.

Impact of poor glycemic control upon clinical outcomes after radical prostatectomy in localized prostate cancer

To evaluate the clinical impact of preoperative glycemic status upon oncological and functional outcomes after radical prostatectomy in patients with localized prostate cancer, we analyzed the data of 2664 subjects who underwent radical prostatectomy with preoperative measurement of hemoglobin A1c within 6 months before surgery. The possible association between high hemoglobin A1c (≥ 6.5 ng/dL) and oncological/functional outcomes was evaluated. Among all subjects, 449 (16.9%) were categorized as the high hemoglobin A1c group and 2215 (83.1%) as the low hemoglobin A1c group. High hemoglobin A1c was associated with worse pathological outcomes including extra-capsular extension (HR 1.277, 95% CI 1.000–1.630, p = 0.050) and positive surgical margin (HR 1.302, 95% CI 1.012–1.674, p = 0.040) in multi-variate regression tests. Kaplan–Meier analysis showed statistically shorter biochemical recurrence-free survival in the high hemoglobin A1c group (p < 0.001), and subsequent multivariate Cox proportional analyses revealed that high hemoglobin A1c is an independent predictor for shorter BCR-free survival (HR 1.135, 95% CI 1.016–1.267, p = 0.024). Moreover, the high hemoglobin A1c group showed a significantly longer incontinence-free survival than the low hemoglobin A1c group (p = 0.001), and high preoperative hemoglobin A1c was also an independent predictor for longer incontinence-free survival in multivariate Cox analyses (HR 0.929, 95% CI 0.879–0.981, p = 0.008). The high preoperative hemoglobin A1c level was independently associated with worse oncological outcomes and also with inferior recovery of urinary continence after radical prostatectomy.

The beneficial effects of metformin on cancer prevention and therapy: a comprehensive review of recent advances

Metformin is a widely used drug in today’s prescriptions by physicians due to its specific effects in treating and curing type II diabetes. Diabetes is a common disease that may occur throughout human life, and can increase the likelihood of the occurrence of various types of cancer, such as colon, rectum, pancreas and liver cancers, compared to non-diabetic patients. Metformin inhibits mTOR activity by activating ATM (ataxia telangiectasia mutated) and LKB1 (liver kinase B1) and then adenosine monophosphate-activated kinase (AMPK), and thus prevents protein synthesis and cell growth. Metformin can activate p53 by activating AMPK and thereby ultimately stop the cell cycle. Given the potential of metformin in the treatment of cancer, it can be used in radiotherapy, chemotherapy and to improve the response to treatment in androgen derivatives (ADT), and also, according to available evidence, metformin can also be used to prevent various types of cancers. Generally, metformin can: 1) reduce the incidence of cancers, 2) reduce the mortality from cancers, 3) increase the response to treatment in cancer cells when using radiotherapy and chemotherapy, 4) optimize tumor movement and reduce the malignancy, 5) reduce the likelihood of relapse, and 6) reduce the damaging effects of ADT. Therefore, this drug can be used as a complementary therapeutic agent for cancer treatment and prevention. In this review, we have summarized the data from various experimental and clinical studies and highlight the possible potential effects of metformin on cancer therapeutic responses.

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The effect of metformin therapy on incidence and prognosis in prostate cancer: A systematic review and meta-analysis

The relationship between metformin and prostate cancer (PCa) remains controversial. To clarify this association, the PubMed, Embase and Cochrane library databases were systematically searched from their inception dates to May 23, 2018, using the keywords "metformin" and "prostate cancer" to identify the related studies. The results included incidence, overall survival (OS), PCa-specific survival (CSS) and recurrence-free survival (RFS), which were measured as hazard ratios (HR) with a 95% confidence interval (95% CI) using Review Manager 5.3 software. A total of 30 cohort studies, including 1,660,795 patients were included in this study. Our study revealed that metformin treatment improves OS, CSS and RFS in PCa (HR = 0.72, 95% CI: 0.59-0.88, P = 0.001; HR = 0.78, 95% CI: 0.64-0.94, P = 0.009; and HR = 0.60, 95% CI: 0.42-0.87 P = 0.006, respectively) compared with non-metformin treatment. However, metformin usage did not reduce the incidence of PCa (HR = 0.86, 95% CI: 0.55-1.34, P = 0.51). In conclusion, compared with non-metformin treatment, metformin therapy can significantly improve OS, CSS and RFS in PCa patients. No association was noted between metformin therapy and PCa incidence. This study indicates a useful direction for the clinical treatment of PCa.

Antidiabetic drugs influence molecular mechanisms in prostate cancer

Background: We investigated the role of diabetes mellitus (DM) and the molecular mechanisms of antidiabetic drugs in prostate cancer (PCa).

Patients and Methods: 167 patients with both DM and PCa underwent radical prostatectomy (RPE). We divided our patient collective into “metformin” users, “insulin” users, “other antidiabetic drug” users and those with “no antidiabetic drug/diet only” (control group) and analyzed differences in PCa aggressiveness and laboratory parameters among treatment groups. In addition, we generated a tissue-micro-array (TMA) from RPE specimens for the analysis of candidate target pathways of antidiabetic drugs by immunohistochemistry (IHC).

Results: Gleason score of both biopsy and RPE, biopsy undergrading, tumor stage as well as positive resection margins did not significantly change among groups. Preoperative body mass-index, PSA, fPSA and prostate volume/weight did not change among the treatment groups. As well, CRP, GOT, GPT, yGT, LDH, amylase, hemoglobin, TSH, FT3 and FT4 did not differ. Metformin or insulin use was not associated with changes in biochemical tumor recurrence or PCa specific mortality rates. However, tissue TMA analyses by IHC showed decreased mTOR activation, as indicated by phospho-mTOR in cancer tissue of patients with metformin and also with insulin use compared to the control group. In addition, we were able to show that the androgen receptor and the epithelial-cell contact marker E-cadherin decreased upon metformin use compared to the control group.

Conclusion: We did not find a connection between antidiabetic drugs and PCa aggressiveness or progression. However, tumor biology seems to be different among patients with and without antidiabetic drugs.

The impact of metformin use on the risk of prostate cancer after prostate biopsy in patients with high grade intraepithelial neoplasia

Purpose

We report our experience on metformin use in diabetic patients and its impact on prostate cancer (PCa) after a high-grade prostatic intraepithelial neoplasia (HGPIN) diagnosis.

Materials and Methods

We retrospectively analyzed 551 patients with a diagnosis of HGPIN without PCa in a first prostate biopsy. The cohort of the study consisted of 456 nondiabetic subjects, and 95 diabetic patients. Among the patients with diabetes 44 were treated with metformin, and 51 with other antidiabetic drugs. A transrectal ultrasound prostate biopsy scheme with 22 cores was carried out 4-6 months after the first diagnosis of HGPIN.

Results

Among 195 (35.4%) patients with cancer, there were statistically significant differences in terms of PCa detection (p<0.001), Gleason score distribution (p<0.001), and number of positive biopsy cores (p<0.002) between metformin users and non-users. Metformin use was associated with a decreased risk of PCa compared with neveruse (p<0.001). Moreover, increasing duration of metformin assumption (≥2 years) was associated with decreasing incidence of PCa and higher Gleason score ≥7 compared with assumption <2 years.

Conclusions

This preliminary experience suggests that metformin use may have some beneficial effects in patients with diabetes and HGPIN; metformin should not be overlooked in these patients because it is neither new nor expensive.

An update of research evidence on nutrition and prostate cancer

BACKGROUND

Prostate cancer (PCa) remains a leading cause of mortality in US and other countries. Preclinical and clinical studies have examined the role of nutrition and dietary intake on the incidence and progression of PCa with mixed results.

OBJECTIVE

The objective of this chapter is to provide an update of recent published literature and highlight progress in the field.

MAIN FINDINGS

Low carbohydrate intake, soy protein, ω3 fat, green teas, tomatoes and tomato products and the herbal mixture-zyflamend showed promise in reducing PCa risk or progression. On the contrary, a higher animal fat intake and a higher β-carotene status may increase risk. A "U" shape relationship may exist between folate, vitamin C, vitamin D and calcium with PCa risk. Conclusion Despite the inconclusive findings, the potential for a role of dietary intake for the prevention and treatment of PCa remains promising. Maintaining a healthy body weight and following a healthy dietary pattern including antioxidant rich fruits and vegetables, reduced animal fat and refined carbohydrates, should be encouraged.

CONCLUSION

Despite the inconclusive findings, the potential for a role of dietary intake for the prevention and treatment of PCa remains promising. Maintaining a healthy body weight and following a healthy dietary pattern including antioxidant rich fruits and vegetables, reduced animal fat and refined carbohydrates, should be encouraged.

The Association of Diabetes and Obesity With Prostate Cancer Progression: HCaP-NC

BACKGROUND

The role of race in modifying the association among diabetes, obesity, and prostate cancer (CaP) progression is not well studied. We evaluated diabetes and obesity in association with time to CaP progression in White Americans (Whites) and Black Americans (Blacks).

METHODS

Our study sample consisted of 363 White and 284 Black research participants from the Health Care Access and CaP Treatment in North Carolina (HCaP-NC) cohort. The association between self-reported diabetes or obesity and CaP progression (mean follow-up time approximately 5 years) was assessed using Cox proportional hazards modeling, with adjustment for potential confounders. Stratum-specific hazard ratio (HR) estimates for Whites and Blacks were evaluated.

RESULTS

Self-reported diabetes was not associated with CaP progression in the cohort as a whole (HR: 0.86, 95%CI: 0.54, 1.35), or among racially defined groups (Whites, HR: 1.03, 95%CI: 0.50, 2.13 or Blacks, HR: 0.77, 95%CI: 0.43, 1.39). Obesity was positively associated with CaP progression among Whites, in models including (HR: 1.79, 95%CI: 1.08, 2.97), and excluding (HR: 1.80, 95%CI: 1.09, 2.96) diabetes as a covariate. No association was observed between obesity and CaP progression in Blacks or the cohort as whole.

CONCLUSIONS

Self-reported diabetes was not associated with CaP progression In HCaP-NC. Obesity was associated with CaP progression only among White research participants. Prostate 77:878-887, 2017. © 2017 Wiley Periodicals, Inc.

A spatiotemporal hypothesis for the regulation, role, and targeting of AMPK in prostate cancer

The 5'-AMP-activated protein kinase (AMPK) is a master regulator of cellular homeostasis. Despite AMPK's known function in physiology, its role in pathological processes such as prostate cancer is enigmatic. However, emerging evidence is now beginning to decode the paradoxical role of AMPK in cancer and, therefore, inform clinicians if - and how - AMPK could be therapeutically targeted. Spatiotemporal regulation of AMPK complexes could be one of the mechanisms that governs this kinase's role in cancer. We hypothesize that different upstream stimuli will activate select subcellular AMPK complexes. This hypothesis is supported by the distinct subcellular locations of the various AMPK subunits. Each of these unique AMPK complexes regulates discrete downstream processes that can be tumour suppressive or oncogenic. AMPK's final biological output is then determined by the weighted net function of these downstream signalling events, influenced by additional prostate-specific signalling.

The Effect of Metformin and GANT61 Combinations on the Radiosensitivity of Prostate Cancer Cells

The anti-diabetes drug metformin has been shown to have anti-neoplastic effects in several tumor models through its effects on energy metabolism and protein synthesis. Recent studies show that metformin also targets Hedgehog (Hh) signaling, a developmental pathway re-activated in several tumor types, including prostate cancer (PCa). Furthermore, we and others have shown that Hh signaling is an important target for radiosensitization. Here, we evaluated the combination of metformin and the Hh inhibitor GANT61 (GLI-ANTagonist 61) with or without ionizing radiation in three PCa cell lines (PC3, DU145, 22Rv1). The effect on proliferation, radiosensitivity, apoptosis, cell cycle distribution, reactive oxygen species production, DNA repair, gene and protein expression was investigated. Furthermore, this treatment combination was also assessed in vivo. Metformin was shown to interact with Hh signaling by inhibiting the effector protein glioma-associated oncogene homolog 1 (GLI1) in PCa cells both in vitro and in vivo. The combination of metformin and GANT61 significantly inhibited PCa cell growth in vitro and enhanced the radiation response of 22Rv1 cells compared to either single agent. Nevertheless, neither the growth inhibitory effect nor the radiosensitization effect of the combination treatment observed in vitro was seen in vivo. Although the interaction between metformin and Hh signaling seems to be promising from a therapeutic point of view in vitro, more research is needed when implementing this combination strategy in vivo.

Metformin as an adjuvant treatment for cancer: a systematic review and meta-analysis

BACKGROUND

Metformin use has been associated with a reduced risk of developing cancer and an improvement in overall cancer survival rates in meta-analyses, but, to date, evidence to support the use of metformin as an adjuvant therapy in individual cancer types has not been presented.

PATIENTS AND METHODS

We systematically searched research databases, conference abstracts and trial registries for any studies reporting cancer outcomes for individual tumour types in metformin users compared with non-users, and extracted data on patients with early-stage cancer. Studies were assessed for design and quality, and a meta-analysis was conducted to quantify the adjuvant effect of metformin on recurrence-free survival (RFS), overall survival (OS) and cancer-specific survival (CSS), to inform future trial design.

RESULTS

Of 7670 articles screened, 27 eligible studies were identified comprising 24 178 participants, all enrolled in observational studies. In those with early-stage colorectal cancer, metformin use was associated with a significant benefit in all outcomes [RFS hazard ratio (HR) 0.63, 95% confidence interval (CI) 0.47-0.85; OS HR 0.69, CI 0.58-0.83; CSS HR 0.58, CI 0.39-0.86]. For men with early-stage prostate cancer, metformin was associated with significant, or borderline significant, benefits in all outcomes (RFS HR 0.83, CI 0.69-1.00; OS HR 0.82, CI 0.73-0.93; CSS HR 0.58, CI 0.37-0.93); however, there was significant heterogeneity between studies. The data suggest that prostate cancer patients treated with radical radiotherapy may benefit more from metformin (RFS HR 0.45, CI 0.29-0.70). In breast and urothelial cancer, no significant benefits were identified. Sufficient data were not available to conduct analyses on the impact of metformin dose and duration.

CONCLUSIONS

Our findings suggest that metformin could be a useful adjuvant agent, with the greatest benefits seen in colorectal and prostate cancer, particularly in those receiving radical radiotherapy, and randomised, controlled trials which investigate dose and duration, alongside efficacy, are advocated.

A review for clinicians: Prostate cancer and the antineoplastic properties of metformin

OBJECTIVES

Metformin has numerous antineoplastic effects including an AMP-activated protein kinase-dependent mechanism, AMP-activated protein kinase-independent mechanisms, alteration of insulin and insulin-like growth factor signaling pathways, and suppression of androgen signaling pathways that trigger prostate cancer growth and proliferation. In contrast to other malignancies that are associated with increased incidence among patients with obesity and type II diabetes mellitus (T2DM), epidemiological studies suggest that obesity and T2DM may impart a protective effect on prostate cancer incidence by creating a set of metabolic conditions that lower androgen levels.

METHODS AND MATERIALS

The PubMed and Web of Science databases were searched using the terms "prostate cancer," "metformin," "antineoplastic," "antitumorigenic," and "diabetes" up to the first week of August 2016. Articles regarding metformin's antineoplastic properties on prostate cancer were reviewed.

RESULTS

Treating T2DM with metformin may reverse the metabolic conditions that suppress androgen levels, thereby enabling higher levels of androgens to stimulate prostate growth, proliferation, and tumorigenesis. Thus, the antineoplastic properties of metformin may not be appreciable in the early stages of prostate cancer development because metformin corrects for the metabolic conditions of T2DM that impart a protective effect on prostate cancer. These findings, although inconclusive, do not support the use of metformin as a preventive agent for prostate cancer. However, the future appears bright for metformin as either a monotherapy or an adjunct to androgen deprivation therapy, external-beam radiation therapy, prostatectomy, or chemotherapy. Support for this includes meta-analyses that suggest a mortality benefit to patients with prostate cancer on metformin, a clinical trial that demonstrates metformin leads to significant improvement in metabolic syndrome parameters for patients with prostate cancer on androgen deprivation therapy, and a clinical trial that shows metformin has modest activity in the treatment of some patients with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer.

CONCLUSIONS

This review summarizes the literature regarding the antineoplastic mechanisms, clinical implications, and future trajectory of clinical research for metformin in prostate cancer.

Diabetes Mellitus Type 2: A Driving Force for Urological Complications

Type 2 diabetes mellitus (T2DM) is a growing epidemic associated with many adverse complications. Urological complications of diabetes mellitus in men are gaining recognition. Previously unknown associations between T2DM and risk for prostate cancer, bladder cancer, renal cell carcinomas, urinary tract infections, nephrolithiasis, penile lesions, androgen deficiency, and erectile dysfunction have been discovered. Significantly, metformin could play a role in the management of urological malignancies, and therapies used for management of these cancers could in return lead to increased risk for diabetes. In this review, we aim to bridge the gap between T2DM and urological complications by discussing the latest findings in these fields, with the ultimate goal being improved patient care on both fronts.

Metformin association with lower prostate cancer recurrence in type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Accumulating evidence suggests that metformin possesses anticarcinogenic properties, and its use is associated with favorable outcomes in several cancers. However, it remains unclear whether metformin influences prognosis in prostate cancer (PCa) with concurrent type 2 diabetes (T2D).

MATERIALS AND METHODS

We searched PubMed, EMBASE, and the Cochrane Library from database inception to April 16, 2014 without language restrictions to identify studies investigating the effect of metformin treatment on outcomes of PCa with concurrent T2D. We conducted a meta-analysis to quantify the risk of recurrence, progression, cancer-specific mortality, and all-cause mortality. Summary relative risks (RRs) with corresponding 95% confidence intervals (CIs) were calculated. Publication bias was assessed by Begg's rank correlation test.

RESULTS

A total of eight studies fulfilled the eligibility criteria. We found that diabetic PCa patients who did not use metformin were at increased risk of cancer recurrence (RR, 1.20; 95%CI, 1.00-1.44), compared with those who used metformin. A similar trend was observed for other outcomes, but their relationships did not reach statistical significance. Funnel plot asymmetry was not observed among studies reporting recurrence (p=0.086).

CONCLUSIONS

Our results suggest that metformin may improve outcomes in PCa patients with concurrent T2D. Well-designed large studies and collaborative basic research are warranted.

Involvement of metformin and AMPK in the radioresponse and prognosis of luminal versus basal-like breast cancer treated with radiotherapy

Metformin is under evaluation as a potential anticancer agent. Expression of total and phospho(Thr172)-adenosine monophosphate-activated kinase-α (AMPKα and pAMPKα(Thr172) respectively), a main metformin target, was examined in radiotherapy treated breast cancers and metformin's ability to modulate Trx system expression and breast cancer radiosensitivity evaluated in vitro.

AMPKα and pAMPKα(Thr172) expression was assessed using a discovery (n=166) and validation cohort (n=609). Metformin's role in regulating radioresponse, and Trx family expression, was examined via clonogenic assays and Western blots. Intracellular reactive oxygen species (ROS) levels, cell cycle progression and apoptosis were assessed by flow cytometry.

High AMPKα expression associated with improved local recurrence-free (P=0.019), relapse-free (P=0.016) and breast cancer-specific survival (P=0.000065) and was, from multivariate analysis, an independent prognostic factor from the discovery cohort. From the validation cases AMPKα expression associated with relapse-free and breast cancer-specific survival in luminal breast cancers. Metformin substantially increased radiosensitivity, intracellular ROS levels and reduced Trx expression, in luminal breast cancer cells, but had little effect on basal phenotype cells.

In conclusion, high AMPKα expression associates with improved prognosis, especially in luminal breast cancer. Metformin preferentially radiosensitises luminal breast cancer cells, potentially due to alterations to intracellular ROS levels via modulation of Trx family protein expression.

Metformin effects on biochemical recurrence and metabolic signaling in the prostate

BACKGROUND

Metformin has received considerable attention as a potential anti-cancer agent. Animal and in-vitro prostate cancer (PCa) models have demonstrated decreased tumor growth with metformin, however the precise mechanisms are unknown. We examine the effects of metformin on PCa biochemical recurrence (BCR) in a large clinical database followed by evaluating metabolic signaling changes in a cohort of men undergoing prostate needle biopsy (PNB).

METHODS

Men treated for localized PCa were identified in a comprehensive clinical database between 2001 and 2010. Cox regression was performed to determine association with BCR relative to metformin use. We next identified a separate case-control cohort of men undergoing prostate needle biopsy (PNB) stratified by metformin use. Differences in mean IHC scores were compared with linear regression for phosphorylated IR, IGF-IR, AKT, and AMPK.

RESULTS

One thousand seven hundred and thirty four men were evaluated for BCR with mean follow up of 41 months (range 1-121 months). "Ever" metformin use was not associated with BCR (HR 1.12, 0.77-1.65), however men reporting both pre/post-treatment metformin use had a 45% reduction in BCR (HR = 0.55 (0.31-0.96)). For the tissue-based study, 48 metformin users and 42 controls underwent PNB. Significantly greater staining in phosphorylated nuclear (p-IR, p-AKT) and cytoplasmic (p-IR, p-IGF-1R) insulin signaling proteins were seen in patients with PCa detected compared to those with negative PNB (P-values all <0.006). When stratified by metformin use, IGF-1R remained significantly elevated (P = 0.01) in men with PCa detected whereas p-AMPK (P = 0.05) was elevated only in those without PCa.

CONCLUSION

Metformin use is associated with reduced BCR after treatment of localized PCa when considering pre-diagnostic and cumulative dosing. In men with cancer detected on PNB, insulin signaling markers were significantly elevated compared to negative PNB patients. The finding of IGF-1R elevation in positive PNBs versus p-AMPK elevation in negative PNBs suggests altered metabolic pathway activation precipitated by metformin use.

Preoperative glycemic control status as a significant predictor of biochemical recurrence in prostate cancer patients after radical prostatectomy

Background

The effect of diabetes mellitus (DM) on prostate cancer (PCa) outcome remains controversial. Thus, we investigated the association of DM history, glycemic control, and metformin use with oncologic outcomes after radical prostatectomy (RP).

Methods

We reviewed the records of 746 contemporary patients who had hemoglobin A1c (HbA1c) measured within the 6 months preceding RP. The associations between clinical variables and risk of adverse pathological features and biochemical recurrence (BCR) were tested using a multivariate logistic regression and multiple Cox-proportional hazards model, respectively. BCR was defined as prostatic specific antigen (PSA) > 0.2 ng/mL in 2 consecutive tests.

Results

There were no significant differences in the rates of adverse pathologic features and BCR-free survival between patients with (n = 209) and without (n = 537) a history of DM diagnosis (all p > 0.05). In multivariate analyses, high HbA1c level (≥ 6.5%) was significantly related with high pathologic Gleason score (≥ 4+3; odds ratio [OR] 1.704, p = 0.019) and BCR-free survival (OR 1.853, p = 0.007). Metformin use was not associated with BCR-free survival (OR 0.662, p = 0.125).

Conclusions

Poor glycemic control was significantly associated with BCR after RP. Meanwhile, metformin use was not associated with biochemical outcome after RP. Further investigation would be needed to identify exact mechanism underlying the impact of glycemic control on PCa treatment outcome.

The impact of obesity on prostate cancer recurrence observed after exclusion of diabetics

PURPOSE

Although overall there is a positive association between obesity and risk of prostate cancer (PrCa) recurrence, results of individual studies are somewhat inconsistent. We investigated whether the failure to exclude diabetics in prior studies could have increased the likelihood of conflicting results.

METHODS

A total of 610 PrCa patients who underwent radical prostatectomy between 2005 and 2012 were followed for recurrence, defined as a rise in serum PSA ≥ 0.2 ng/ml following surgery. Body mass index (BMI) and history of type 2 diabetes were documented prior to PrCa surgery. The analysis was conducted using Cox proportional hazard models.

RESULTS

Obesity (25.6 %) and diabetes (18.7 %) were common in this cohort. There were 87 (14.3 %) recurrence events during a median follow-up of 30.8 months after surgery among the 610 patients. When analyzed among all PrCa patients, no association was observed between BMI/obesity and PrCa recurrence. However, when analysis was limited to non-diabetics, obese men had a 2.27-fold increased risk (95 % CI 1.17-4.41) of PrCa recurrence relative to normal weight men, after adjusting for age and clinical/pathological tumor characteristics.

CONCLUSIONS

This study found a greater than twofold association between obesity/BMI and PrCa recurrence in non-diabetics. We anticipated these results because the relationship between BMI/obesity and the biologic factors that may underlie the PrCa recurrence-BMI/obesity association, such as insulin, may be altered by the use of anti-diabetes medication or diminished beta-cell insulin production in advanced diabetes. Studies to further assess the molecular factors that explain the BMI/obesity-PrCa recurrence relationship are warranted.

Impact of metformin on clinical outcomes among men with prostate cancer: a systematic review and meta-analysis

BACKGROUND

Conflicting evidence exists regarding the beneficial effects of metformin in prostate cancer. To determine the association between metformin and clinical outcomes in prostate cancer using systematic review and meta-analysis.

METHODS

Original articles published in English until third week of July, 2014 were searched in electronic databases (Medline-Ovid, Scopus, The Cochrane Library, Web of Science, ProQuest) for studies on metformin use in prostate cancer. The clinical outcomes assessed were: development of biochemical recurrence, metastases or castration-resistant metastatic cancer, all-cause and prostate cancer-specific mortality. Meta-analysis was performed to calculate the pooled hazard ratio (pHR) and their 95% confidence interval (95% CI). Heterogeneity between the studies was examined using I2 statistics. Sensitivity analysis was conducted to assess the robustness of findings and publication bias was assessed by the Egger's regression asymmetry test and contour plot.

RESULTS

Out of 230 retrieved citations, eight retrospective cohort studies and one nested-case-control study met the inclusion criteria. Metformin use was marginally associated with reduction in the risk of biochemical recurrence (pHR: 0.82, 95% CI: 0.67, 1.01, P-value=0.06, I2=25%, five studies). Metformin use was not significantly associated with metastases (pHR: 0.59, 95% 0.30-1.18, P-value=0.14, I2=74%, three studies), all-cause mortality (pHR: 0.86; 95% CI, 0.67, 1.10, P-value=0.23, I2: 73%, six studies) and prostate cancer-specific mortality (pHR: 0.76, 95% CI: 0.43, 1.33, P-value = 0.33, I2=60%, four studies). Pooled estimates for all outcomes varied in sensitivity analysis by diabetes status and primary treatment of prostate cancer. Systematic review revealed mixed findings on metformin use and the risk of CRPC.

CONCLUSIONS

Metformin may reduce the risk of biochemical recurrence in prostate cancer. Given the potential of selection bias in the observational studies, randomized trials should be designed to assess the efficacy of metformin use in prostate cancer.

Nutrition, dietary interventions and prostate cancer: the latest evidence

Prostate cancer (PCa) remains a leading cause of mortality in US men and the prevalence continues to rise world-wide especially in countries where men consume a 'Western-style' diet. Epidemiologic, preclinical and clinical studies suggest a potential role for dietary intake on the incidence and progression of PCa. 'This minireview provides an overview of recent published literature with regard to nutrients, dietary factors, dietary patterns and PCa incidence and progression. Low carbohydrates intake, soy protein, omega-3 (w-3) fat, green teas, tomatoes and tomato products and zyflamend showed promise in reducing PCa risk or progression. A higher saturated fat intake and a higher β-carotene status may increase risk. A 'U' shape relationship may exist between folate, vitamin C, vitamin D and calcium with PCa risk. Despite the inconsistent and inconclusive findings, the potential for a role of dietary intake for the prevention and treatment of PCa is promising. The combination of all the beneficial factors for PCa risk reduction in a healthy dietary pattern may be the best dietary advice. This pattern includes rich fruits and vegetables, reduced refined carbohydrates, total and saturated fats, and reduced cooked meats. Further carefully designed prospective trials are warranted.

Effect of metformin on cancer risk and treatment outcome of prostate cancer: a meta-analysis of epidemiological observational studies

Background

Laboratory studies have shown the anti-tumor effect of metformin on prostate cancer. However, recent epidemiological studies have yielded inconclusive results.

Methods

We searched PubMed database from the inception to May 30 2014 for studies which assessed the effect of metformin use on cancer risk of prostate cancer, biochemical recurrence (BCR) and all-cause mortality of patients with prostate cancer. The pooled results and 95% confidence intervals (CIs) were estimated by random-effect model.

Results

Twenty-one studies were eligible according to the inclusion criteria. Based on the pooled results of available observational studies, metformin use was significantly associated with a decreased cancer risk (14 datasets, 963991 male subjects, odds ratio: 0.91, 95% CI: 0.85–0.97) and BCR (6 datasets, 2953 patients, hazard ratio: 0.81, 95% CI: 0.68–0.98) of prostate cancer. However, the association of metformin use with all-cause mortality of patients with prostate cancer was not significant (5 datasets, 9241 patients, hazard ratio: 0.86, 95% CI: 0.64–1.14).

Conclusion

Results suggest that metformin use appears to be associated with a significant reduction in the cancer risk and BCR of prostate cancer, but not in all-cause mortality of patients with prostate cancer.

Influence of metformin use on PSA values, free-to-total PSA, prostate cancer incidence and grade and overall survival in a prospective screening trial (ERSPC Aarau)

PURPOSE

To analyze the effect of the oral antidiabetic drug metformin on PSA level, free-to-total PSA ratio (f/t-ratio), PCa incidence and grade as well as mortality in men participating in a population-based screening trial.

METHODS

Data from 4,314 men aged 55-70 years from a population-based PSA-screening trial (ERSPC Aarau) were analyzed. Information on metformin exposure was obtained by a self-administered questionnaire. Serum PSA threshold at ≥3 ng/ml triggered prostate biopsy. Data on PCa incidence and mortality were obtained through registry linkages.

RESULTS

Median follow-up time was 7.6 years. Mean age at baseline was 65.5 years (±SD 4.4). In all, n = 150 (3.5 %) men used metformin [metf+]. Mean baseline PSA levels were comparable between both groups ([metf+] 1.6 ng/ml ± 2.4 vs. [metf-] 1.8ug/l ± 2.2, p = 0.4) while f/t-ratio was slightly higher in metformin users ([metf+] 30.7 % ± 10.9 vs. [metf-] 27.3 % ± 10.9, p = 0.01). Overall, n = 372 (8.6 %) PCa cases were detected. Neither cumulative PCa incidence (n = 11; 7.3 % [metf+] vs. n = 361 8.7 % [metf-]; p = 0.5) nor d`Amico risk groups were significantly different between both groups. One man in each group (metf+ 0.7 % and metf- 0.02 %) died from PCa (p < 0.0001), respectively. All-cause mortality was significantly higher among met + compared to met- (adjusted OR 2.50, 95 %CI 1.59-3.82; p = 0.0001).

CONCLUSION

No significant differences in PSA levels or PCa incidence and grade were observed. The slightly higher f/t-ratio did not result in lower PCa detection rate. Metformin users were at significantly higher risk of all-cause mortality. The relatively small number of men on metformin is a main limitation of the study.