Myrthe P. P. van Herk-Sukel

Lower Risk of Cancer in Patients on Metformin in Comparison With Those on Sulfonylurea Derivatives Results from a large population-based follow-up study

OBJECTIVE Numerous studies have suggested a decreased risk of cancer in patients with diabetes on metformin. Because different comparison groups were used, the effect magnitude is difficult to estimate. Therefore, the objective of this study was to further analyze whether, and to what extent, use of metformin is associated with a decreased risk of cancer in a cohort of incident users of metformin compared with users of sulfonylurea derivatives. RESEARCH DESIGN AND METHODS Data for this study were obtained from dispensing records from community pharmacies individually linked to hospital discharge records from 2.5 million individuals in the Netherlands. The association between the risk of cancer in those using metformin compared with those using sulfonylurea derivatives was analyzed using Cox proportional hazard models with cumulative duration of drug use as a time-varying determinant. RESULTS Use of metformin was associated with a lower risk of cancer in general (hazard ratio 0.90 [95% CI 0.88–0.91]) compared with use of sulfonylurea derivatives. When specific cancers were used as end points, similar estimates were found. Dosage-response relations were identified for users of metformin but not for users of sulfonylurea derivatives. CONCLUSIONS In our study, cumulative exposure to metformin was associated with a lower risk of specific cancers and cancer in general, compared with cumulative exposure to sulfonylurea derivatives. However, whether this should indeed be seen as a decreased risk of cancer for the use of metformin or as an increased risk of cancer for the use sulfonylurea derivatives remains to be elucidated.

New opportunities for drug outcomes research in cancer patients: The linkage of the Eindhoven Cancer Registry and the PHARMO Record Linkage System

BACKGROUND Insight into co-morbidity and treatment effects is pivotal to improve quality of care for cancer patients. OBJECTIVES To determine whether linkage of the Eindhoven Cancer Registry (ECR) and the PHARMO Record Linkage System (RLS) was technically feasible and to assess which patient-centric data would result from this linkage. METHODS The ECR records data on tumour stage and primary treatment of all newly diagnosed cancer patients in the southeastern Netherlands including co-morbidity at diagnosis, whereas the PHARMO RLS includes data from multiple linked observational databases such as data on drug utilisation (for both in- and out-patients, including chemotherapy), hospitalisations and clinical laboratory measurements. All patients who lived or had been living in the overlapping area served by the ECR and the PHARMO RLS during 1998-2006 were selected for linkage which was performed with probabilistic medical record linkage. RESULTS The linkage resulted in an ECR-PHARMO cohort of 40,004 cancer patients with a total of 42,767 primary tumours. The cancer patients in the linked ECR-PHARMO cohort were representatives for the cancer patients included in the total ECR during 1998-2006. Cancer patients included in the cohorts had a mean history of 5 years and a mean follow-up ranging from 2 to more than 4 years (dependent on the survival rate of the specific cancer type). CONCLUSIONS Linkage of ECR and the PHARMO RLS creates the possibility to study patient-centric drug utilisation, health resources utilisation and their costs, in addition to the effectiveness and safety of pharmaceuticals in routine daily practice in cancer patients.

Expression of HLA Class I Antigen, Aspirin Use, and Survival After a Diagnosis of Colon Cancer

IMPORTANCE Use of aspirin (which inhibits platelet function) after a colon cancer diagnosis is associated with improved overall survival. Identifying predictive biomarkers of this effect could individualize therapy and decrease toxic effects. OBJECTIVE To demonstrate that survival benefit associated with low-dose aspirin use after a diagnosis of colorectal cancer might depend on HLA class I antigen expression. DESIGN, SETTING, AND PARTICIPANTS A cohort study with tumor blocks from 999 patients with colon cancer (surgically resected between 2002 and 2008), analyzed for HLA class I antigen and prostaglandin endoperoxide synthase 2 (PTGS2) expression using a tissue microarray. Mutation analysis of PIK3CA was also performed. Data on aspirin use after diagnosis were obtained from a prescription database. Parametric survival models with exponential (Poisson) distribution were used to model the survival. MAIN OUTCOMES AND MEASURES Overall survival. RESULTS The overall survival benefit associated with aspirin use after a diagnosis of colon cancer had an adjusted rate ratio (RR) of 0.53 (95% CI, 0.38-0.74; P < .001) when tumors expressed HLA class I antigen compared with an RR of 1.03 (0.66-1.61; P = .91) when HLA antigen expression was lost. The benefit of aspirin was similar for tumors with strong PTGS2 expression (0.68; 0.48-0.97; P = .03), weak PTGS2 expression (0.59; 0.38-0.97; P = .02), and wild-type PIK3CA tumors (0.55; 0.40-0.75; P < .001). No association was observed with mutated PIK3CA tumors (0.73; 0.33-1.63; P = .44). CONCLUSIONS AND RELEVANCE Contrary to the original hypothesis, aspirin use after colon cancer diagnosis was associated with improved survival if tumors expressed HLA class I antigen. Increased PTGS2 expression or the presence of mutated PIK3CA did not predict benefit from aspirin. HLA class I antigen might serve as a predictive biomarker for adjuvant aspirin therapy in colon cancer.

Unjustified prescribing of CYP2D6 inhibiting SSRIs in women treated with tamoxifen

Tamoxifen is a largely inactive pro-drug, requiring metabolism into its most important metabolite endoxifen. Since the cytochrome P450 (CYP) 2D6 enzyme is primarily involved in this metabolism, genetic polymorphisms of this enzyme, but also drug-induced CYP2D6 inhibition can result in considerably reduced endoxifen formation and as a consequence may affect the efficacy of tamoxifen treatment. Selective serotonin reuptake inhibitors (SSRIs) and selective serotonin and norepinephrine reuptake inhibitors (SNRIs) have been effectively used for the treatment of depression and hot flashes, both of which occur frequently in tamoxifen-treated women. Due to the drug–drug interaction considerably reduced endoxifen concentrations by inhibition of CYP2D6 will be the result. Evidence of a significant influence of strong CYP2D6-inhibiting drugs on the pharmacokinetics of tamoxifen has resulted in recommendations to avoid potent CYP2D6-inhibiting antidepressants (e.g., paroxetine, fluoxetine) in patients treated with tamoxifen for breast cancer. Nevertheless, dispensing data for tamoxifen and seven regularly used SSRIs/SNRIs in the period between 2005 and 2010, obtained from a large community pharmacy database in the Netherlands (3,000,000 people), show that the potent CYP2D6-inhibiting drug paroxetine remains one of the most frequently used antidepressants in tamoxifen-treated patients. Moreover, trends in the use of SSRIs/SNRIs in the population of all women were similar with trends in women using tamoxifen. Apparently, the recommendations to avoid paroxetine in tamoxifen-treated women have not been implemented into clinical practice. Several reasons may underlie continued use of this drug–drug combination. Contrary to CYP2D6 polymorphisms, drug-induced CYP2D6 inhibition can easily be avoided, since alternative drugs are available. In clinical practice, one should strive to avoid potent CYP2D6 inhibitors as much as possible in tamoxifen-treated patients to reduce the risk of compromising the efficacy of the hormonal therapy. Co-medication should be reviewed by both physicians and pharmacists and potent CYP2D6 inhibitors ought to be switched to weaker alternatives.

Three-year dispensing patterns with long-acting inhaled drugs in COPD: A database analysis

BACKGROUND Long-acting muscarinic antagonists (LAMA), long-acting β2-agonists (LABA) and fixed dose combinations (FDC) of inhaled corticosteroids (ICS) and LABA are used as inhaled maintenance therapies for COPD. OBJECTIVE To estimate persistence rates from dispensing patterns of long-acting inhaled drugs for COPD. METHODS From the PHARMO-database, COPD patients starting LAMA, LABA or LABA-ICS FDC between 2002 and 2006 were selected. Persistence with the initial as well as with any long-acting inhaled drug was determined, defined as time between start and stop of initial/any therapy, allowing ≤ 60-days gaps between refills. For patients who did not continue to receive dispensings of the initial therapy for at least one year, the first change in therapy was determined. RESULTS The study included 2201 LAMA, 1201 LABA and 4146 LABA-ICS FDC users. Persistence rates with initial therapy alone at 1, 2, and 3 years were 25%, 14%, 8% for LAMA, 21%, 10%, 6% for LABA and 27%, 14%, 8% for LABA-ICS FDC. Of patients who did not persist with LAMA alone for one year, 15% added and 13% switched therapy (both mostly LABA-ICS FDC). Of patients not persisting with LABA alone, 9% added therapy (mostly LAMA) and 31% switched therapy (mostly to LABA-ICS FDC). In patients not persisting with LABA-ICS FDC, add-on and switch occurred equally frequent (11%, mostly LAMA). Persistence rates with any long-acting drug at 1, 2 and 3 years were 36%, 23% and 17% respectively. CONCLUSION Persistence with the initial as well as with any long-acting inhaled drug in COPD is low, with a substantial proportion of patients changing therapy.

Patterns of metachronous metastases after curative treatment of colorectal cancer.

BACKGROUND This study aimed to provide information on timing, anatomical location, and predictors for metachronous metastases of colorectal cancer based on a large consecutive series of non-selected patients. METHODS All patients operated on with curative intent for colorectal cancer (TanyNanyM0) between 2003 and 2008 in the Dutch Eindhoven Cancer Registry were included (N=5671). By means of active follow-up by the Cancer Registry staff within ten hospitals, data on development of metastatic disease were collected. Median follow-up was 5.0 years. RESULTS Of the 5671 colorectal cancer patients, 1042 (18%) were diagnosed with metachronous metastases. Most common affected sites were the liver (60%), lungs (39%), extra-regional lymph nodes (22%), and peritoneum (19%). 86% of all metastases was diagnosed within three years and the median time to diagnosis was 17 months (interquartile range 10-29 months). Male gender (HR=1.2, 95%CI 1.03-1.32), an advanced primary T-stage (T4 vs. T3 HR=1.6, 95%CI 1.32-1.90) and N-stage (N1 vs. N0 HR=2.8, 95%CI 2.42-3.30 and N2 vs. N0 HR=4.5, 95%CI 3.72-5.42), high-grade tumour differentiation (HR=1.4, 95%CI 1.17-1.62), and a positive (HR=2.1, 95%CI 1.68-2.71) and unknown (HR=1.7, 95%CI 1.34-2.22) resection margin were predictors for metachronous metastases. CONCLUSIONS Different patterns of metastatic spread were observed for colon and rectal cancer patients and differences in time to diagnosis were found. Knowledge on these patterns and predictors for metachronous metastases may enhance tailor-made follow-up schemes leading to earlier detection of metastasized disease and increased curative treatment options.

Prescribing of Rosiglitazone and Pioglitazone Following Safety Signals Analysis of Trends in Dispensing Patterns in the Netherlands from 1998 to 2008

I read with interest the article by Ruiter et al. [1]. I must say that I found it odd that the results of this study differ from those of other studies in European regions in terms of the use of glitazones [2]. Other European studies have found that rosiglitazone was still used more than pioglitazone in early 2008, despite cardiovascular safety warnings, while this study results were shown differently. In figure 2 of the study by Ruiter et al. [1], a sharp drop in the data series in mid 2007 caught my attention. At that point, a strong diminution in the use of all glitazones can be seen, especially for rosiglitazone, which falls more than 50 %. Before that point, rosiglitazone was being used more than pioglitazone; afterwards, it was the opposite. That led me to suspect that, on that date, an intervention other than the safety warning may have occurred, perhaps some kind of administrative measure regarding the prescription of glitazones. For example, Carracedo-Martı́nez et al. [3] found that no decrease in the use of piroxicam was observed after a health safety warning; however, the month after mandatory prior authorization for piroxicam was introduced (6 months after the safety warning), its use declined sharply (more than 95 %). According to prior authorization rules, the medicine would not be reimbursed for a certain patient if it was not authorized by a health authority, which would only authorize treatment with such medicine if certain prerequisites were met. Indeed, after searching, I found that, in the Netherlands, from 1 July 2007, a measure similar to prior authorization was implemented regarding the prescription of glitazones, and health insurers would be more stringent [4]. The use of glitazones by patients with diabetes who do not meet certain conditions according to health insurance regulations would no longer be reimbursed [4]. Ruiter et al. [1] make no mention of this change in the administrative status of glitazone prescriptions that took place in July 2007. It is neither included in the study design nor mentioned in the discussion. In particular, some safety warnings that were released near July 2007 have proved statistically significant in the study. Ruiter et al. [1] conclude that, in their study, it was difficult to disentangle the effect of Direct Healthcare Professional Communications and European Medicines Agency press releases from the effect of reports published in the literature. I believe that not only that, but also changes in the administrative status of medicines (for instance, if a medicine goes from normal prescription to prescription requiring prior authorization, or if health insurance for a particular medicine changes) should also be taken into account. The fact that, according to figure 2, the strongest diminution by far in the use of glitazones takes place just after such a change in their administrative status in July 2007 [4] is very suggestive.

Prescribing of Rosiglitazone and Pioglitazone Following Safety Signals

AbstractBackground: Relevant safety signals in the EU are regularly communicated in so-called ‘Direct Healthcare Professional Communications’ (DHPCs) or European Medicines Agency (EMA) press releases. Trends of a decrease in the use of rosiglitazone following regulatory safety warnings have been described in the US. In the EU, however, relatively little is known about dispensing patterns following DHPCs or other safety signals such as EMA press releases. Objective: The objective of this study was to analyse trends in dispensing patterns of rosiglitazone and pioglitazone following DHPCs and EMA press releases in the EU member state, the Netherlands. Methods: Data for this study were obtained from the PHARMO Record Linking System, which includes drug dispensing records from community pharmacies of approximately 2.5 million individuals in the Netherlands. Over the period 1998–2008 an auto-regressive, integrated, moving average model (ARIMA) was fitted. The DHPC letters or EMA press releases were used as determinants. Adjustments were made for publication of certain literature. Stratification was performed for dispensings prescribed by general practitioners (GPs) and those prescribed by specialists. Results: for rosiglitazone, four EMA press releases and two DHPCs were issued; for pioglitazone, one DHPC was issued. The number of rosiglitazone dispensings prescribed by GPs decreased significantly after publication of DHPCs and EMA press releases concerning the risk of macular oedema and risk of fractures (both p-values 0.001). The number of rosiglitazone dispensings decreased statistically significantly after publication of EMA press releases 2 and 3 concerning cardiovascular risks but not for EMA press release 4. Adjustment for certain publications in the literature reduced the effect of communicated safety issues on the proportion of dispensings. Conclusions: Although it is difficult to disentangle the effect of DHPCs and EMA press releases from the effect of reports published in the literature, our results suggest that prescribers may react to such safety communications.

Aspirin use after diagnosis improves survival in older adults with colon cancer: a retrospective cohort study.

To assess survival in relation to aspirin use after diagnosis in older adults with colon cancer.

Record linkage for pharmacoepidemiological studies in cancer patients.

An increasing need has developed for the post‐approval surveillance of (new) anti‐cancer drugs by means of pharmacoepidemiology and outcomes research in the area of oncology.