Metformin and Biliary Tract Cancer in Patients With Type 2 Diabetes

Aim

This retrospective cohort study evaluated whether metformin use in patients with type 2 diabetes mellitus might reduce the risk of biliary tract cancer (BTC); and explored whether metformin use might affect the overall survival in patients who developed BTC.

Methods

New-onset type 2 diabetes patients aged 25–75 years during 1999–2005 were enrolled from the Taiwan’s National Health Insurance and followed up until December 31, 2011. A total of 287,995 ever users and 16,229 never users were identified (unmatched original cohort) and a 1:1 matched pairs of 16,229 ever users and 16,229 never users based on propensity score (PS) were created (matched cohort). Hazard ratios were estimated by three Cox regression models: 1) adjusted for PS; 2) incorporated with the inverse probability of treatment weighting using PS; and 3) all covariates treated as independent variables. Overall survival was compared between ever users and never users of metformin who developed BTC.

Results

In the unmatched cohort, 73 never users and 523 ever users developed BTC, with respective incidence of 100.36 and 38.06 per 100,000 person-years. An overall risk reduction was observed in metformin users in all three regression models with respective hazard ratio (95% confidence interval) of 0.442 (0.344-0.568), 0.377 (0.295-0.481), and 0.477 (0.370-0.615). The tertile analyses showed a dose-response pattern with a neutral effect in the first tertile when metformin use was <2 years and a significant risk reduction in the second and third tertiles. Findings in the matched cohort were consistent with those observed in the unmatched cohort. The overall survival did not differ significantly between ever and never users of metformin among patients who developed BTC.

Conclusions

Metformin significantly reduces the overall risk of BTC by 50%–60%. A dose-response effect is observed and users of approximately 2 years show significantly reduced risk. However, metformin does not affect the overall survival in patients with BTC.

Dementia Risk in Type 2 Diabetes Patients: Acarbose Use and Its Joint Effects with Metformin and Pioglitazone

This population-based retrospective cohort study investigated dementia risk associated with acarbose in patients with type 2 diabetes mellitus by using Taiwan’s National Health Insurance database. A cohort of 15,524 matched pairs of ever and never users of acarbose based on propensity score matching was enrolled from new-onset type 2 diabetes patients from 1999 to 2006. Patients who were alive on January 1, 2007, were followed up for dementia until December 31, 2011. Adjusted hazard ratios were estimated using Cox proportional hazards models. The results revealed that the incident case numbers (incidence rates) of dementia were 264 (407.19 per 100,000 person-years) for never users and 231 (337.94 per 100,000 person-years) for ever users. The hazard ratio for ever users versus never users was 0.841 (95% confidence interval, 0.704-1.005) and 0.918 (0.845-0.998) for every 1-year increment of cumulative duration of acarbose therapy. Subgroup analyses showed that the reduced risk associated with acarbose was only observed in women (adjusted hazard ratio, 0.783; 95% confidence interval, 0.618-0.992) and in non-users of metformin (adjusted hazard ratio, 0.635; 95% confidence interval, 0.481-0.837). A model comparing different combinations of acarbose, metformin, and pioglitazone suggested that users of all three drugs had the lowest risk of dementia (hazard ratio, 0.406; 95% confidence interval, 0.178-0.925). In conclusion, reduced risk of dementia associated with acarbose is observed in the female sex and in non-users of metformin. Moreover, users of all three drugs (acarbose, metformin, and pioglitazone) have the lowest risk of dementia.

Metformin reduces risk of varicose veins in patients with type 2 diabetes

AIM

This population-based retrospective cohort study compared the incidence of varicose veins in an unmatched cohort and a cohort of 1:1 propensity score (PS)-matched pairs of ever and never users of metformin in type 2 diabetes patients.

METHODS

Patients with new-onset type 2 diabetes during 1999 to 2005 were enrolled from Taiwan's National Health Insurance and followed until December 31, 2011. Analyses were conducted in an unmatched cohort of 123 710 ever users and 15 095 never users and in 15 088 PS-matched pairs of ever users and never users. Hazard ratios were estimated by Cox proportional hazards model incorporated with the inverse probability of treatment weighting using the PS.

RESULTS

New-onset varicose veins were diagnosed in 126 never users and 633 ever users in the unmatched cohort and in 126 never users and 80 ever users in the matched cohort. The respective incidences were 191.36 and 110.04 per 100 000 person-years in the unmatched cohort and 191.41 and 115.81 per 100 000 person-years in the matched cohort. The hazard ratio for ever versus never users in the unmatched cohort was 0.57 (95% confidence interval, 0.47-0.69) and was 0.60 (0.45-0.80) for the matched cohort. In the unmatched cohort, the hazard ratios for the first, second, and third tertiles of cumulative duration were 1.03 (0.83-1.28), 0.55 (0.44-0.69), and 0.29 (0.23-0.37), respectively. The respective hazard ratios in the matched cohort were 0.97 (0.65-1.43), 0.79 (0.55-1.15), and 0.24 (0.13-0.42).

CONCLUSION

Metformin use is associated with a lower risk of varicose veins in patients with type 2 diabetes.

Prevalence and Risk Factors of Sensory Symptoms in Diabetes Patients in Taiwan

BACKGROUND

Diabetic sensory neuropathy has rarely been studied in the Asian populations. This study investigated the prevalence and risk factors of sensory symptoms (SS) in the Taiwanese diabetes patients.

METHODS

A total of 1,400 diabetes patients received a health examination together with a structured questionnaire interview for three categories of abnormal sensation of numbness or tingling pain, electric shock, and skin thickness sensation on seven anatomical sites on upper limbs and six sites on lower limbs. Prevalence of SS was defined using nine different criteria, with the least stringent criterion of "any positive symptom on at least 1 site" and the most stringent criterion of "any positive symptom on at least bilateral and symmetrical 2 sites involving the lower limb." Logistic regression was used to estimate the odds ratios and their 95% confidence interval for SS by the different definitions. Fasting plasma glucose and hemoglobin A_1c were entered in separate models to avoid hypercollinearity.

RESULTS

The prevalence of SS was 14.4 and 54.0% when using the most stringent and least stringent criterion, respectively. Women consistently had a significantly higher prevalence than men did. Among the three categories of symptoms, numbness or tingling pain was the most common, and fingers and toes were the most commonly involved anatomical sites. For any symptoms, 37.1% of the patients had any symptoms on the upper limbs and 41.7% had any symptoms on the lower limbs. Female sex, diabetes duration, hemoglobin A_1c, and hypertension were associated with SS in all models.

CONCLUSIONS

Taiwanese diabetes patients may have a high prevalence of SS if a structured questionnaire is used for screening. Female sex, diabetes duration, hemoglobin A_1c, and hypertension are associated with SS.

Metformin Use and Leukemia Risk in Patients With Type 2 Diabetes Mellitus

BACKGROUND

The effect of metformin on leukemia risk remains unknown.

METHODS

The Taiwan's National Health Insurance database was used to enroll 610,089 newly diagnosed type 2 diabetes patients on at least 2 anti-diabetic prescriptions during 1999-2009. We followed-up these patients until 31 December 2011, in order to determine the incidence of leukemia. We used Cox regression model (incorporated with the inverse probability of treatment-weighting using propensity scores) to estimate hazard ratios in both intention-to-treat and per-protocol analyses.

RESULTS

We enrolled 414,783 metformin initiators and 195,306 non-metformin initiators. Among them, 598 and 372 patients developed new-onset leukemia after a median follow-up period of 5.08 years and 6.79 years, respectively. The respective incidence rates were 26.52 and 28.40 per 100,000 person-years. The hazard ratio for metformin initiators versus non-metformin initiators was 0.943 (95% confidence interval 0.828-1.074) in the intention-to-treat analysis and 0.852 (95% confidence interval 0.705-1.031) in the per-protocol analysis. Sensitivity analyses after excluding patients using the exclusion criteria (a follow-up duration < 24 and < 36 months, respectively, patients with incretin-based therapies during follow-up, and patients enrolled during 2 different periods of 1999-2003 and 2004-2009) consistently showed a neutral effect. However, metformin initiators had a significantly higher risk of leukemia in the per-protocol analyses when censoring patients at a time without regular follow-up.

CONCLUSION

Metformin use has an overall neutral effect on leukemia but we cannot exclude a significantly higher risk in patients who persistently use the drug.

Metformin Use Is Associated With a Lower Risk of Hospitalization for Heart Failure in Patients With Type 2 Diabetes Mellitus: a Retrospective Cohort Analysis

Background

A beneficial effect of metformin on heart failure requires confirmation.

Methods and Results

Patients with new‐onset type 2 diabetes mellitus during 1999 to 2005 were enrolled from Taiwan's National Health Insurance database and followed up from January 1, 2006, until December 31, 2011. Main analyses were conducted in an unmatched cohort (172 542 metformin ever users and 43 744 never users) and a propensity score matched‐pair cohort (matched cohort I, 41 714 ever users and 41 714 never users). Hazard ratios were estimated by Cox hazard regression incorporated with the inverse probability of treatment weighting using the propensity score in the unmatched cohort and by naïve method in the matched cohort I. Results showed that the respective incidence rates of heart failure hospitalization in ever users and never users were 304.25 and 864.31 per 100 000 person‐years in the unmatched cohort (hazard ratio, 0.350; 95% CI, 0.329–0.373) and were 469.66 and 817.01 per 100 000 person‐years in the matched cohort I (hazard ratio, 0.571; 95% CI, 0.526–0.620). A dose‐response pattern was consistently observed while estimating hazard ratios for the tertiles of cumulative duration of metformin therapy. Findings were supported by another propensity score–matched cohort created after excluding 10 potential instrumental variables in the estimation of propensity score (matched cohort II). An approximately 40% lower risk was consistently observed among ever users in different models derived from the matched cohorts I and II, but models from the matched cohort II were less subject to model misspecification.

Conclusions

Metformin use is associated with a lower risk of heart failure hospitalization.

P5006Metformin reduces the risk of hospitalization for heart failure in type 2 diabetes patients: a retrospective cohort analysis

Background

A beneficial effect of metformin on heart failure requires confirmation.

Purpose

To investigate whether metformin might affect the risk of heart failure hospitalization in type 2 diabetes patients.

Methods

Patients with new-onset type 2 diabetes during 1999–2005 were enrolled from the reimbursement database of Taiwan's National Health Insurance and followed until December 31, 2011. Analyses were conducted in a propensity score (PS) matched-pair cohort (42,367 ever users and 42,367 never users) and hazard ratios were estimated by Cox's hazard regression analysis incorporated with the inverse probability of treatment weighting using the PS.

Results

A total of 1,592 never users and 987 ever users were hospitalized for heart failure for the first time during follow-up, with a respective incidence of 843.34 and 499.18 per 100,000 person-years. The overall hazard ratio was 0.588 (95% confidence interval: 0.543–0.637), and the hazard ratios for the first (<29.13 months), second (29.13–61.63 months), and third (>61.63 months) tertiles of cumulative duration were 1.018 (0.914–1.135), 0.575 (0.511–0.647), and 0.340 (0.297–0.390), respectively. Sensitivity analyses conducted in an unmatched cohort before and after excluding patients who received an irregular refill of metformin or who were treated with incretin-based therapies during follow-up consistently supported such a protective effect of metformin on heart failure.

Conclusion

Metformin use is associated with a lower risk of hospitalization for heart failure.

Acknowledgement/Funding

The study was partly supported by the Ministry of Science and Technology (MOST 107-2221-E-002-129-MY3) of Taiwan.

Metformin reduces risk of benign nodular goiter in patients with type 2 diabetes mellitus

Background Whether metformin might affect the risk of benign nodular goiter in patients with type 2 diabetes mellitus has not been investigated. Methods Patients with new-onset type 2 diabetes mellitus during 1999-2005 were enrolled from Taiwan's National Health Insurance database. Analyses were conducted in a propensity score matched-pairs of 20,048 ever users and 20,048 never users of metformin. The patients were followed until December 31, 2011, for the incidence of benign nodular goiter. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using the propensity score. Results Among the never users and ever users of metformin, 392 and 221 cases were diagnosed of benign nodular goiter during follow-up, with incidence of 457.88 and 242.45 per 100,000 person-years, respectively. The overall hazard ratio for ever versus never users was 0.527 (95% confidence interval: 0.447-0.621). When cumulative duration of metformin therapy was divided into tertiles, the hazard ratios for the first (<25.3 months), second (25.3-57.3 months) and third (>57.3 months) tertiles were 0.815 (0.643-1.034), 0.648 (0.517-0.812) and 0.255 (0.187-0.348), respectively. Sensitivity analyses estimating the overall hazard ratios for patients enrolled in each specific year from 1999 to 2005 consistently showed a lower risk of benign nodular goiter among users of metformin. Conclusion Metformin use is associated with a lower risk of benign nodular goiter in patients with type 2 diabetes mellitus.

Metformin use is associated with a lower risk of uterine leiomyoma in female type 2 diabetes patients

BACKGROUND

Whether metformin may reduce the risk of uterine leiomyoma in type 2 diabetes patients has not been investigated. This retrospective cohort study compared the risk of uterine leiomyoma in ever versus never users of metformin.

METHODS

Female patients with new-onset type 2 diabetes during 1999-2005 were enrolled from the reimbursement database of Taiwan's National Health Insurance and followed up from 1 January 2006 until 31 December 2011. Analyses were conducted in a propensity score (PS) matched-pair cohort of 10,998 ever users and 10,998 never users of metformin. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using the PS.

RESULTS

A total of 321 never users and 162 ever users developed uterine leiomyoma during follow up, with respective incidence of 704.65 and 329.82 per 100,000 person-years. The overall hazard ratio was 0.467 (95% confidence interval: 0.387-0.564). The hazard ratios for the first (<23.3 months), second (23.3-53.1 months), and third (>53.1 months) tertiles of cumulative duration were 0.881 (0.685-1.132), 0.485 (0.367-0.642), and 0.198 (0.134-0.291), respectively; and were 0.751 (0.576-0.980), 0.477 (0.360-0.632), and 0.277 (0.198-0.386), respectively, for the first (<655,000 mg), second 655,000-1,725,500 mg), and third (>1,725,500) tertiles of cumulative dose. Sensitivity analyses after excluding users of sulfonylurea, users of estrogen, users of insulin, users of incretin-based therapies during follow up, patients with irregular drug refills, patients who discontinued the use of metformin, patients who received metformin prescription less than four times, or redefining uterine leiomyoma by using 'diagnostic code' plus 'procedure codes' consistently supported a lower risk of uterine leiomyoma in ever users of metformin.

CONCLUSION

Metformin use is associated with a lower risk of uterine leiomyoma.

Human Insulin Therapy Is Associated With an Increased Risk of Lung Cancer: A Population-Based Retrospective Cohort Study

Background: Whether human insulin may affect lung cancer risk requires investigation. Methods: All patients with a diagnosis of diabetes mellitus from 1996 to 2009 were enrolled from Taiwan's National Health Insurance. An entry date was set on January 1, 2004, and 1,007,617 patients with type 2 diabetes mellitus diagnosed before 2004 were followed up for new-onset lung cancer until December 31, 2009. Incidence rates of lung cancer for never-users, ever-users, and tertiles of three dose-response exposure parameters (i.e., time since starting insulin, cumulative dose, and cumulative duration) were calculated. Adjusted hazard ratios were estimated by Cox proportional hazards models. The joint effect of insulin and chronic obstructive pulmonary disease was also evaluated. Results: There were 156,720 ever-users and 850,897 never-users. The respective case numbers of incident lung cancer were 3,007 (1.92%) and 13,677 (1.61%), and the respective incidence rates were 424.45 and 313.60 per 100,000 person-years. The adjusted hazard ratio comparing ever-users vs. never-users was 1.545 (95% confidence interval: 1.478-1.614). The hazard ratios for the different subgroups of the three dose-response parameters all suggested a significantly higher risk of lung cancer associated with insulin use (P trend < 0.0001). Compared to patients without insulin use and without chronic obstructive pulmonary disease, insulin users who also had chronic obstructive pulmonary disease had the highest risk of lung cancer (adjusted hazard ratio: 1.891, 95% confidence interval: 1.767-2.024). Conclusions: This study suggests a significant association between human insulin use and lung cancer risk in patients with type 2 diabetes mellitus.

Metformin and risk of hepatocellular carcinoma in patients with type 2 diabetes

BACKGROUND

Whether metformin may reduce hepatocellular carcinoma (HCC) risk requires confirmation.

METHODS

Type 2 diabetes patients newly diagnosed during 1999-2005 and with 2 or more prescriptions of antidiabetic drugs were enrolled from the Taiwan's National Health Insurance database. A total of 173 917 ever-users and 21 900 never-users of metformin were identified (unmatched cohort). A 1:1 matched-pair cohort of 21 900 ever-users and 21 900 never-users based on a propensity score (PS) was created. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using the PS. In addition, interactions with aspirin and statin were evaluated.

RESULTS

In the unmatched cohort, 619 never-users and 2642 ever-users developed HCC, with a respective incidence of 668.0 and 330.7 per 100 000 person-years and an overall hazard ratio of 0.49 (95% confidence interval: 0.45-0.54). The hazard ratios for the first (<25.7 months), second (25.7-56.9 months) and third (>56.9 months) tertile of cumulative duration of metformin therapy were 0.89 (0.81-0.98), 0.50 (0.46-0.56) and 0.23 (0.21-0.26) respectively. Analyses of the matched cohort showed an overall hazard ratio of 0.76 (0.67-0.85), and the hazard ratios for the respective tertiles were 1.39 (1.19-1.62), 0.77 (0.65-0.91) and 0.37 (0.30-0.45). Aspirin and statin were observed to have a significant interaction with metformin.

CONCLUSIONS

Metformin was associated with a reduced risk of HCC in a dose-response pattern. Users of both metformin and aspirin or metformin and statin had the lowest risk.

Pioglitazone Reduces Dementia Risk in Patients with Type 2 Diabetes Mellitus: A Retrospective Cohort Analysis

BACKGROUND

The beneficial effect of pioglitazone on dementia requires confirmation.

METHODS

The database of Taiwan's National Health Insurance was used to enroll a propensity score-matched-pair cohort of patients who had ever used pioglitazone and patients who had never used pioglitazone from Taiwanese patients with newly diagnosed diabetes mellitus during 1999⁻2008. The patients were to be alive on 1 January 2009 and were followed up for dementia until 31 December 2011. Hazard ratios were estimated using the Cox proportional hazards model.

RESULTS

There were 11,011 never users and 11,011 ever users of pioglitazone, with respective numbers of incident dementia of 123 and 91. The overall hazard ratio was 0.716 (95% confidence interval: 0.545⁻0.940) for ever users versus never users. The hazard ratios for the first (<11.0 months), second (11.0⁻19.6 months) and third (>19.6 months) tertiles of cumulative duration were 0.806 (0.544⁻1.193), 0.654 (0.430⁻0.994) and 0.694 (0.469⁻1.026), respectively. When cumulative duration was treated as a continuous variable, the hazard ratio was 0.987 (0.976⁻0.998). In subgroup analyses, the beneficial effect was mainly observed in patients who had not been treated with metformin. Among metformin ever users, the hazard ratio for dementia for pioglitazone ever users versus never users was 0.802 (0.580⁻1.109); and was 0.494 (0.284⁻0.857) among never users of metformin. No interaction between pioglitazone and major risk factors of dementia (i.e., stroke, hypoglycemia, head injury and Parkinson's disease) was observed.

CONCLUSIONS

Pioglitazone use is associated with a lower risk of dementia, especially when it is used in never users of metformin and has been used for more than 20 months.

Metformin and risk of developing nasopharyngeal cancer in patients with type 2 diabetes mellitus

BACKGROUND

Metformin has anticancer effects, but whether it can reduce the risk of nasopharyngeal cancer (NPC) is not known.

METHODS

A total of 15,486 ever-users and 15,486 never-users of metformin matched by propensity score were enrolled from among patients with new-onset type 2 diabetes mellitus diagnosed during the period 1999-2005 and who were found in the reimbursement database of Taiwan's National Health Insurance. The patients were followed until December 31, 2011. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity scores.

RESULTS

NPC incidence was 33.41 and 106.04 per 100,000 person-years in ever-users and never-users, respectively. The overall hazard ratio (95% confidence interval) of 0.312 (0.197-0.494) favored a significantly lower risk among metformin ever-users than in never-users. Hazard ratios comparing the first (<26.03 months), second (26.03-58.03 months) and third (>58.03 months) tertiles of cumulative duration of metformin use to never-users were 0.690 (0.389-1.224), 0.187 (0.076-0.463) and 0.168 (0.068-0.415), respectively. A significantly lower risk of NPC was consistently observed among metformin users in subgroup analyses of age (<50 years and ≥50 years), sex (men and women), and patients with or without nephropathy, liver diseases or diseases of the esophagus, stomach, and duodenum, respectively.

CONCLUSIONS

Metformin use is associated with a significantly lower risk of NPC.

Metformin and Risk of Hypertension in Taiwanese Patients With Type 2 Diabetes Mellitus

Background

Whether metformin use may reduce hypertension risk has not been studied. This study investigated such possibility in patients with type 2 diabetes mellitus.

Methods and Results

Newly diagnosed patients with type 2 diabetes mellitus during 1999–2005 were enrolled from the reimbursement database of the Taiwan's National Health Insurance and followed to December 31, 2011. Hypertension was defined either by a diagnosis or by a diagnosis plus the use of angiotensin converting enzyme inhibitors/angiotensin receptor blockers and/or calcium channel blockers. Analyses were conducted in a propensity score matched‐pair cohort of 4810 ever users and 4810 never users. Cox proportional hazards regression model was used to estimate the hazard ratios. Results showed that when hypertension was defined by a diagnosis, 2261 never users and 1908 ever users developed hypertension. The overall hazard ratio was 0.724 (0.681–0.769) and the hazard ratios for the first (<2.0 months), second (2.0–13.0 months) and third (>13.0 months) tertiles of cumulative duration were 0.820 (0.745–0.903), 0.692 (0.634–0.756), and 0.687 (0.630–0.749), respectively. When cumulative duration of metformin therapy was treated as a continuous variable, the hazard ratio was 0.991 (0.989–0.994) for every 1‐month increment of metformin use. When hypertension was defined by a diagnosis plus the use of antihypertensive drugs, the overall hazard ratio was 0.831 (0.771–0.895), the hazard ratios for the respective tertiles were 0.868 (0.769–0.980), 0.852 (0.767–0.946), and 0.787 (0.709–0.874), and the hazard ratio was 0.994 (0.991–0.997) for every 1‐month increment of metformin use.

Conclusions

A reduced risk of hypertension is observed in metformin users in a dose‐response pattern.

Metformin and lung cancer risk in patients with type 2 diabetes mellitus

This study evaluated whether metformin might reduce lung cancer risk. The reimbursement database of the Taiwan's National Health Insurance was used. A sample of 15414 never users and 280159 ever users of metformin (original sample) and a 1:1 matched-pairs of ever and never users (n=15414 in each group, matched sample) were recruited from patients with newly diagnosed type 2 diabetes mellitus during 1999-2005. They were followed until December 31, 2011. Cox regression incorporated with the inverse probability of treatment weighting using propensity score was used to estimate hazard ratios. Results showed that the respective incidence of lung cancer in ever and never users was 173.36 and 292.65 per 100000 person-years in the original sample; and was 211.71 and 292.65, respectively, in the matched sample. The overall hazard ratios (95% confidence intervals) of 0.586 (0.509-0.674) in the original sample and 0.717 (0.584-0.881) in the matched sample suggested a significantly lower risk among metformin users. Hazard ratios comparing the first (<22.60 months), second (22.60-46.67 months) and third (>46.67 months) tertile of cumulative duration of metformin use to never users was 1.163 (1.005-1.348), 0.612 (0.526-0.711) and 0.176 (0.148-0.210), respectively, in the original sample; and was 1.465 (1.131-1.897), 0.758 (0.566-1.016) and 0.228 (1.460-0.357) in the respective tertile of the matched sample. Sensitivity analyses after excluding patients with certain risk factors of cancer and subgroup analyses supported a favorable effect of metformin. In conclusion, metformin use may reduce lung cancer risk in patients with type 2 diabetes mellitus.

Sitagliptin and heart failure hospitalization in patients with type 2 diabetes

This study evaluated the risk of heart failure hospitalization in a 1:1 matched pair sample of sitagliptin ever and never users derived from the Taiwan's National Health Insurance. A total of 85,859 ever users and 85,859 never users matched on 8 digits of propensity score were followed for the first event of heart failure hospitalization until December 31, 2011. The treatment effect (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. Additionally, adjusted hazard ratios for heart failure were estimated for the baseline characteristics in sitagliptin ever users. Results showed that the incidence of heart failure hospitalization was 1,020.16 and 832.54 per 100,000 person-years, respectively, for ever and never users, with an overall hazard ratio (95% confidence intervals) of 1.262 (1.167-1.364). While compared to never users, the respective hazard ratio for the first, second, and third tertile of cumulative duration < 3.7, 3.7-10.3 and >10.3 months was 2.721 (2.449-3.023), 1.472 (1.318-1.645) and 0.515 (0.447-0.594). Older age, longer diabetes duration, male sex, and use of insulin, sulfonylurea, calcium channel blockers, aspirin, ticlopidine, clopidogrel and dipyridamole were significantly associated with a higher risk in sitagliptin users, but dyslipidemia and use of metformin and statin were protective. In conclusion, sitagliptin increases the risk of heart failure hospitalization within one year of its use, but reduces the risk thereafter. Some factors predisposing to sitagliptin-related heart failure are worthy of attention in clinical practice.

Attitudes and potential barriers towards hepatitis C treatment in patients with and without HIV coinfection

This study aimed to assess attitudes and potential barriers towards treatment in patients with hepatitis C virus (HCV) infection, comparing those with and without HIV coinfection. A cross-sectional survey of 82 HCV-infected adults with and without HIV was conducted in greater Los Angeles between November 2013 and July 2015. Overall, there were 53 (64.6%) with HIV coinfection, 20 (25.0%) with self-reported cirrhosis, and 22 (26.8%) with a history of prior HCV treatment. Of all, 93.2% wanted HCV treatment, but 45.9% were unwilling/unable to spend anything out of pocket, 29.4% were waiting for new therapies, and 23.5% were recommended to defer HCV treatment. HIV/HCV-coinfected patients were more likely to want treatment within one year (90.2% versus 68.2%, p = 0.02), more willing to join a clinical trial (74.5% versus 8.0%, p < 0.01), more willing to take medications twice daily (86.3% versus 61.5%, p = 0.01), and more likely to prefer hepatitis C treatment by an infectious diseases/HIV physician (36.7% versus 4.0%, p < 0.01). Of all, 77.1% of coinfected patients were willing to change antiretroviral therapy if necessary to treat HCV, but only 48.0% of patients were willing to take a medication if it had not been studied in HIV-positive patients. Treatment preferences differ between HIV/HCV-coinfected and HCV-monoinfected patients. Despite a strong willingness among the study cohort to start HCV treatment, other factors such as cost, access to medications, and provider reluctance may be delaying treatment initiation.

Metformin use and cervical cancer risk in female patients with type 2 diabetes

This study evaluated whether metformin may affect the risk of cervical cancer. The reimbursement databases of the Taiwan's National Health Insurance were used. Female patients with type 2 diabetes at an onset age of 25-74 years during 1999-2005 and newly treated with metformin (n=132971, "ever users of metformin") or other antidiabetic drugs (n=6940, "never users of metformin") were followed for at least 6 months until December 31, 2011. The treatment effect of metformin (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. Analyses were also conducted in a 1:1 matched pair cohort based on 8 digits of propensity score. Results showed that the respective numbers of incident cervical cancer in ever users and never users were 438 (0.33%) and 38 (0.55%), with respective incidences of 68.29 and 121.38 per 100,000 person-years. The overall hazard ratio suggested a significantly lower risk in metformin users (0.558, 95% confidence intervals: 0.401-0.778). In tertile analyses, the hazard ratios (95% confidence intervals) for the first (<23.0 months), second (23.0-47.9 months) and third (>47.9 months) tertile of cumulative duration were 1.272 (0.904-1.790), 0.523 (0.366-0.747) and 0.109 (0.070-0.172), respectively. Findings were supported by the analyses in the matched cohort. In conclusion, metformin may significantly reduce the risk of cervical cancer, especially when the cumulative duration is more than 2 years.

Sitagliptin use and thyroid cancer risk in patients with type 2 diabetes

Whether sitagliptin may increase thyroid cancer risk has not been investigated in the Asian populations. This study evaluated the association in Taiwanese patients with newly diagnosed type 2 diabetes from 1999 to 2008 by using the reimbursement database of the National Health Insurance. They should have been followed for at least 6 months after March 1, 2009, the date when sitagliptin was approved for reimbursement. Patients newly treated with sitagliptin (n=58238, "ever users of sitagliptin") or other antidiabetic drugs (n =312853, "never users of sitagliptin") were followed until December 31, 2011. The treatment effect (for ever versus never users, and for tertiles of cumulative duration of therapy) was estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. Results showed that the respective number of incident thyroid cancer in ever users and never users was 28 and 172, with respective incidence of 29.34 and 22.13 per 100,000 person-years. The overall hazard ratio (95% confidence interval) of 1.516 (1.011-2.271) suggested a significantly higher risk associated with sitagliptin use. In tertile analyses, the hazard ratio for the first ( < 6.53 months), second (6.53-14.00 months) and third ( > 14 months) tertile of cumulative duration was 1.995 (1.015-3.919), 2.516 (1.451-4.364) and 0.595 (0.244-1.449), respectively. Analyses after excluding patients with benign thyroid disease and in a subsample matched on baseline characteristics supported the findings in the original sample. In conclusion, sitagliptin use is associated with an increased risk of thyroid cancer, especially during the first year of its treatment.

Metformin and esophageal cancer risk in Taiwanese patients with type 2 diabetes mellitus

This study evaluated whether metformin might reduce esophageal cancer risk. Patients with type 2 diabetes mellitus diagnosed during 1999–2005 were recruited from the reimbursement database of Taiwan's National Health Insurance. Those newly treated with metformin (n = 288013, “ever users of metformin”) or other antidiabetic drugs (n = 16216, “never users of metformin”) were followed until December 31, 2011. Sensitivity analyses were conducted in a matched-pair sample of 16216 never users and 16216 ever users. Hazard ratios were estimated by Cox regression incorporated with the inverse probability of treatment weighting using propensity score. The risk associated with infection of Helicobacter pylori, Epstein-Barr virus, hepatitis B virus and hepatitis C virus was also evaluated. Results showed that the incidence of esophageal cancer in ever and never users was 25.03 and 50.87 per 100,000 person-years, respectively. The overall hazard ratio (95% confidence intervals) of 0.487 (0.347–0.684) suggested a significantly lower risk among metformin users. Hazard ratios comparing the first (< 21.47 months), second (21.47–46.00 months) and third (> 46.00 months) tertile of cumulative duration of metformin use to never users was 1.184 (0.834–1.680), 0.403 (0.276–0.588) and 0.113 (0.071–0.179), respectively. Infection of Helicobacter pylori (but not the other viral infections) significantly increased the risk, which could be ameliorated by metformin. Analyses in the matched sample consistently supported a protective role of metformin. In conclusion, metformin reduces esophageal cancer risk when the cumulative duration is more than approximately 2 years.

Abstract 2296: Metformin reduces colon cancer risk in patients with type 2 diabetes: a retrospective cohort analysis

Background: The effect of metformin on colon cancer is rarely investigated in Asian populations.

Methods: This is a retrospective cohort study. Patients with newly diagnosed type 2 diabetes during 1999-2005 were recruited from Taiwan’s National Health Insurance. A 1:1 propensity score matched-pair sample of 16314 ever users and 16314 never users of metformin were followed until December 31, 2011. Cox regression incorporated with the inverse probability of treatment weighting using propensity score was used to estimate hazard ratios.

Results: The incidence of colon cancer was 272.04 and 392.44 per 100,000 person-years, respectively, in ever and never users. The overall hazard ratio (0.691, 95% confidence interval: 0.578-0.826) suggested a significantly lower risk in metformin users. While compared to never users, the hazard ratio (95% confidence interval) for the first (&lt;20.00 months), second (20.00-45.20 months) and third (&gt;45.20 months) tertile of cumulative duration of metformin therapy was 1.455 (1.165-1.816), 0.683 (0.526-0.885) and 0.224 (0.152-0.331), respectively. The protective effect of metformin on colon cancer was not affected by the use of aspirin and statin or the infection of Helicobacter pylori in additional analyses.

Conclusions: Metformin reduces colon cancer risk in patients with type 2 diabetes. The protective effect is more remarkable when the cumulative duration is more than 20 months.

Citation Format: Chin-Hsiao Tseng. Metformin reduces colon cancer risk in patients with type 2 diabetes: a retrospective cohort analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2296. doi:10.1158/1538-7445.AM2017-2296

Sitagliptin and oral cancer risk in type 2 diabetes patients

The reimbursement database of the Taiwan’s National Health Insurance was used to evaluate oral cancer risk after sitagliptin use. Patients newly diagnosed of type 2 diabetes during 1999–2008 were recruited. A 1:1 propensity score matched-pair sample of 39195 ever users and 39195 never users were followed up until December 31, 2011. Cox regression incorporated with the inverse probability of treatment weighting using propensity score was used to estimate hazard ratios. Results showed that the overall hazard ratio was not statistically significant (0.956, 95% confidence interval: 0.652–1.401). However, in tertile analyses, the hazard ratio for the first (< 7.47 months), second (7.47–15.63 months) and third (> 15.63 months) tertile of cumulative duration was 1.563 (0.963–2.537), 1.236 (0.738–2.071) and 0.345 (0.164–0.725), respectively; and was 1.575 (0.963–2.575), 1.224 (0.738–2.033) and 0.347 (0.165–0.731), respectively, for the first (< 19,600 mg), second (19,600–42,200 mg) and third (> 42,200 mg) tertile of cumulative dose. Sensitivity analyses after excluding patients who developed any other cancer during follow-up did not change the results substantially. Additionally, the risk of oral diseases that may predispose to oral cancer (i.e., “gingival and periodontal diseases" and/or "oral mucosal lesions") paralleled the risk pattern of oral cancer, suggesting a possible explanation for the risk change of oral cancer related to sitagliptin. In conclusion, sitagliptin may reduce oral cancer risk when the cumulative duration is > 15.63 months or the cumulative dose is > 42,200 mg.