Metformin is not associated with improved biochemical free survival or cause-specific survival in men with prostate cancer treated with permanent interstitial brachytherapy

Evaluation of the effect of metformin as a radiosensitiser in solid tumours: A systematic review

Background

Metformin is an antidiabetic drug that has shown its benefit in increasing the effect of radiotherapy in the treatment of solid tumors in preclinical studies. The objective of this systematic review is to study the effect of metformin as a radiosensitizer in studies carried out in clinical practice.

Methods

Systematic review carried out according to PRISMA criteria of clinical trials, systematic reviews and observational studies focused on the influence of metformin as a radiosensitizer in solid tumors. The studies were published between the years 2010 and 2022. The results of the studies have been analyzed in terms of survival (OS, PFS, DFS, DMFS) and response (ORR) between patients treated with metformin and without it.

Results

A total of 16 studies have been found in the literature (the most frequent tumor was prostate cancer, 5 studies). External radiotherapy was administered in all the studies and in two of them to greater brachytherapy. The use of metformin with radiotherapy showed a consistent benefit in terms of survival and response in tumors of prostate, hepatic and gynecological origin. The benefit in the rest of the tumors analyzed (lung, rectal, and head and neck cancer) is doubtful, and the results are contradictory. The greatest benefits were observed in prostate tumors both in OS and SLE.

Conclusions

The use of metformin in combination with radiotherapy in solid tumors is one of the most promising treatments under development in oncology. The benefit observed in real-life studies makes it necessary to develop clinical trials that specifically evaluate its use in clinical practice in the future.

Unraveling Mitochondrial Determinants of Tumor Response to Radiation Therapy

Radiotherapy represents a highly targeted and efficient treatment choice in many cancer types, both with curative and palliative intents. Nevertheless, radioresistance, consisting in the adaptive response of the tumor to radiation-induced damage, represents a major clinical problem. A growing body of the literature suggests that mechanisms related to mitochondrial changes and metabolic remodeling might play a major role in radioresistance development. In this work, the main contributors to the acquired cellular radioresistance and their relation with mitochondrial changes in terms of reactive oxygen species, hypoxia, and epigenetic alterations have been discussed. We focused on recent findings pointing to a major role of mitochondria in response to radiotherapy, along with their implication in the mechanisms underlying radioresistance and radiosensitivity, and briefly summarized some of the recently proposed mitochondria-targeting strategies to overcome the radioresistant phenotype in cancer.

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%).

Current Status and Application of Metformin for Prostate Cancer: A Comprehensive Review

Metformin, an oral biguanide used for first-line treatment of type 2 diabetes mellitus, has attracted attention for its anti-proliferative and anti-cancer effects in several solid tumors, including prostate cancer (PCa). Liver kinase B1 (LKB1) and adenosine monophosphate-activated protein kinase (AMPK) activation, inhibition of the mammalian target of rapamycin (mTOR) activity and protein synthesis, induction of apoptosis and autophagy by p53 and p21, and decreased blood insulin level have been suggested as direct anti-cancer mechanisms of metformin. Research has shown that PCa development and progression are associated with metabolic syndrome and its components. Therefore, reduction in the risk of PCa and improvement in survival in metformin users may be the results of the direct anti-cancer mechanisms of the drug or the secondary effects from improvement of metabolic syndrome. In contrast, some research has suggested that there is no association between metformin use and PCa incidence or survival. In this comprehensive review, we summarize updated evidence on the relationship between metformin use and oncological effects in patients with PCa. We also highlight ongoing clinical trials evaluating metformin as an adjuvant therapy in novel drug combinations in various disease settings.

Preexisting diabetes, metformin use and long-term survival in patients with prostate cancer

OBJECTIVE

To assess prostate cancer-specific and overall survival in prostate cancer patients with or without preexisting type 2 diabetes mellitus (T2DM) with regards to metformin use.

METHODS

Patients diagnosed with prostate cancer in the Lithuanian population between 2001 and 2005 were identified through the Lithuanian Cancer Registry and followed until 2016, date of death, loss to follow-up or whichever came first. Information regarding the diagnosis of T2DM and antihyperglycemic medications were obtained from the National Health Insurance Fund database. Prostate cancer-specific and overall survival outcomes were analysed using univariate and multivariate Cox proportional hazard models.

RESULTS

Out of 6689 men included, 254 (3.8%) had preexisting T2DM. There were 4807 deaths during follow-up, including 2084 from prostate cancer. No differences were found in prostate cancer-specific survival between men with or without T2DM. The risk of overall mortality was higher (HR = 1.24, 95% CI = 1.07-1.43) in diabetic men. Univariate analysis showed cancer stage at diagnosis and age to be significant predictors of survival. After adjustment for age and stage at diagnosis, there was no difference in prostate-specific survival between non-diabetic patients compared to metformin users or metformin non-users. However, overall survival was lower in T2DM patients, with a higher mortality risk for metformin non-users (HR = 1.63, 95% CI = 1.27-2.10). Prostate cancer-specific mortality risk was insignificantly lower in diabetic men on metformin (HR = 0.74, 95% CI = 0.54-1.02).

CONCLUSION

There was no difference in long-term prostate cancer-specific survival in patients with or without T2DM. Overall survival was lower in T2DM patients not treated with metformin.

Metformin: (future) best friend of the radiation oncologist?

Several molecules are being investigated for their ability to enhance the anti-tumor effect of radiotherapy. The widely prescribed antidiabetic drug metformin has been suggested to possess anti-cancer activity; data indicate that metformin could also enhance radiation sensitivity. The purpose of this review is to summarize current knowledge on the specific effect of metformin in the field of RT, while also discussing the many unknowns that persist. Preclinical models point to multiple mechanisms involved in the radiosensitizing effects of metformin that are mainly linked to mitochondrial complex I inhibition and AMP-activated protein kinase. Transposition of results from bench to bedside will be discussed through the lens of the drug concentration, its potential limits in human settings, and possible alternatives. Clinical data suggest metformin improves progression-free and overall survival in patients for many different cancers treated with RT; nevertheless, the results are not always consistent. The main limitations of the reviewed literature are the retrospective nature of studies, and most of the time, a lack of information on MTF treatment duration and the administered dosages. Despite these limitations, the possible mechanisms of the role of metformin and its utility in enhancing radiotherapy treatments are analyzed. Ongoing clinical trials are also discussed.

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.

Statin and metformin therapy in prostate cancer patients with hyperlipidemia who underwent radiotherapy: a population-based cohort study

Purpose

To evaluate the association between the use of statins and/or metformin and patient survival in prostate cancer patients in Taiwan.

Subjects and methods

Newly diagnosed prostate cancer patients who had hyperlipidemia and received radiotherapy were identified from the National Health Insurance Research Database 2000–2010. The survival rate was estimated by the Kaplan–Meier method. Univariate and multivariate Cox regression analyses were performed to examine the association of mortality. Sensitivity analysis was performed to assess the risk of mortality in patients with diabetes.

Results

The study included 567 patients. Patients who used statins or metformin after prostate cancer diagnosis had longer average survival times (9.3 years and 8.1 years, respectively; P=0.001) compared with patients who persistently used or used the medicines prior to cancer diagnosis. Multivariate Cox regression analysis found that patients treated with statins after cancer diagnosis were significantly associated with a lower risk of mortality (aHR =0.24, 95% CI =0.09–0.66) compared to patients who did not use statins during the study period. Patients treated with metformin after cancer diagnosis were significantly associated more with an increased risk of mortality (aHR =6.78, 95% CI =2.45–18.77) compared to patients who did not use metformin during the study period. Sensitivity analysis revealed that the average survival time was similar among different medicine use groups in patients with diabetes.

Conclusion

The finding suggests that statins and metformin use after prostate cancer diagnosis may increase survival in patients with hyperlipidemia and radiotherapy.

Effects of metformin treatment on radiotherapy efficacy in patients with cancer and diabetes: a systematic review and meta-analysis

Purpose

Metformin is a key pharmaceutical for patients with diabetes mellitus (DM). Metformin also can enhance tumor radiosensitivity in vitro and in vivo. Some retrospective cohort studies have indicated that metformin can improve the efficacy of radiotherapy in patients with cancer and DM. The aim of this systematic review was to evaluate the radiotherapy efficacy of metformin in patients with cancer and DM.

Methods

Multiple databases were queried for studies that address the efficacy of metformin in radiotherapy of patients with cancer and DM. Studies were included that involved comparisons of the short-term tumor responses and long-term survival outcomes of these patients who were managed with or without metformin as well as of nondiabetic patients without metformin. The OR and HR with accompanying 95% CI were assessed in a random effects model. The main endpoints were 2-year and 5-year overall survival (2y-OS and 5y-OS, respectively).

Results

The database search yielded 17 cohort studies that met the inclusion criteria. The results indicated that the tumor response was higher in patients who also were treated with metformin than in those who were not (OR, 0.48; 95% CI, 0.22-1.07; P=0.07) and nondiabetic (OR, 0.27; 95% CI, 0.07-0.98; P=0.05). Moreover, patients who received metformin had survival benefits compared with patients not treated with metformin (2y-OS: OR, 0.48; 95% CI, 0.29-0.80; P=0.005; 5y-OS: OR, 0.38; 95% CI, 0.25-0.56; P<0.00001). The metformin-related HRs of OS values were not significantly different.

Conclusion

Metformin appears to improve the tumor response to radiotherapy in patients with cancer and DM and partly yield survival benefits. Despite the apparent advantages provided by metformin treatment on 2y-OS and 5y-OS, these retrospective data are at risk of bias and should be interpreted with caution.

Metformin and improved treatment outcomes in radiation therapy - A review

BACKGROUND

Metformin, a primary treatment for diabetes mellitus (DM) patients, is associated with improved outcomes for diabetic cancer patients fuelling further investigation on its mechanisms of action. The radiosensitising properties of metformin are increasingly reported in pre-clinical studies. This review discusses whether metformin should be offered to radiotherapy (RT) cancer patients as a means to improve their treatment outcomes.

MATERIALS AND METHODS

A database search was conducted for articles published with metformin as the main intervention between 2010 and 2016. Three groups of RT cancer patients were analysed: diabetic patients using metformin, diabetic patients not using metformin and non-diabetic patients not using metformin. Data on survival and recurrence metrics were extracted.

RESULTS

Thirteen studies were included. Conflicting evidence exists with regards to the impact of metformin administration on recurrence and survival outcomes following radiotherapy. Three studies reported improved tumour response determined by recurrence rates while five studies did not observe differences or metformin use was not the associated reason. One study revealed inconsistent tumour response results. Metformin was reported as improving survival outcomes in 2 studies and not improving outcomes in 5 studies. 4 studies showed indefinite results.

CONCLUSION

Although metformin may improve tumour response in the non-randomized, retrospective studies analysed, it may not necessarily confer survival benefits. Future prospective and randomised trials are required to translate the positive impact of metformin documented in pre-clinical and retrospective studies into improve management of RT cancer patients.

Prostate-specific antigen nadir concentration, hypertension and diabetes as risk factors for biochemical failure after permanent 125I seed brachytherapy for prostate cancer

The aim of this study was to evaluate risk factors for biochemical failure (BF) following permanent prostate seed ¹²⁵I brachytherapy for prostate cancer. The study reviewed the medical records of 607 patients with biopsy-proven prostate adenocarcinoma who were treated at Oulu University Hospital between 2001 and 2014. Clinical characteristics at diagnosis, treatment-related data and follow-up data were collected to identify potential risk factors for BF, which was defined using the Phoenix criteria [prostate-specific antigen (PSA) increase >2 µg/l from the PSA nadir concentration, which defined as the lowest PSA concentration observed after BT]. The median follow-up was 81 months. BF was detected in 117 (19.3%) patients. The PSA nadir concentration was associated with BF. The mean times to BF were 114 [95% confidence interval (CI): 112-116] and 55 (95% CI: 47-63) months for patients with PSA nadir concentrations <0.5 and ≥0.5 µg/l, respectively (P<0.001). Patients with underlying hypertension or diabetes tended to develop BF more rapidly. For patients without and with hypertension, the mean times to BF were 104 (95% CI: 100-107) and 98 (95% CI: 93-103) months, respectively (P=0.035). For patients without and with diabetes, the mean times to BF were 103 (95% CI: 100-106) and 89 (95% CI: 77-102) months, respectively (P=0.006). The overall survival and prostate cancer-specific survival rates were 90.3 and 98.0%, respectively. The mean overall survival and prostate-cancer specific survival times were 147 and 158 months, respectively. Therefore, PSA nadir level was identified as a clear risk factor for BF. In addition, BF tended to develop more rapidly among patients with underlying hypertension or diabetes. These risk factors should be considered, and individually tailored follow-up may be useful for identifying patients requiring more intense follow-up for early BF detection.

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.

Prostate Cancer Patients With Unmanaged Diabetes or Receiving Insulin Experience Inferior Outcomes and Toxicities After Treatment With Radiation Therapy

BACKGROUND

The purpose of the study was to determine the effect of type 2 diabetes mellitus (T2DM) on outcomes and toxicities among men with localized prostate cancer receiving definitive radiation therapy.

PATIENTS AND METHODS

We performed a retrospective review of 3217 patients, from 1998 to 2013, subdivided into 5 subgroups: (I) no T2DM; (II) T2DM receiving oral antihyperglycemic agent that contains metformin, no insulin; (III) T2DM receiving nonmetformin oral agent alone, no insulin; (IV) T2DM receiving any insulin; and (V) T2DM not receiving medication. Outcome measures were overall survival, freedom from biochemical failure (BF), freedom from distant metastasis, cancer-specific survival, and toxicities. Kaplan-Meier analysis, log rank tests, Fine and Gray competing risk regression (to adjust for patient and lifestyle factors), Cox models, and subdistribution hazard ratios (sHRs) were used.

RESULTS

Of the 3217 patients, 1295 (40%) were low-risk, 1192 (37%) were intermediate-risk, and 652 (20%) were high risk. The group I to V distribution was 81%, 8%, 5%, 3%, and 4%. The median dose was 78 Gy, and the median follow-up time was 50 (range, 1-190) months. Group V had increased mortality (sHR, 2.1; 95% confidence interval [CI], 0.66-1.54), BF (sHR, 2.14; 0.88-1.83), and cause-specific mortality (sHR, 3.87; 95% CI, 1.31-11). Acute toxicities were higher in group IV versus group I (genitourinary: 38% vs. 26%; P = .01; gastrointestinal: 21% vs. 5%; P = 001). Late toxicities were higher in groups IV and V versus group I (12%-14% vs. 2%-6%; P < .01).

CONCLUSION

Men with T2DM not receiving medication and men with T2DM receiving insulin had worse outcomes and toxicities compared to other patients.

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.