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Risk of colorectal cancer after initiation of orlistat: matched cohort study

BMJ 2013; 347 doi: (Published 27 August 2013) Cite this as: BMJ 2013;347:f5039
  1. Jin-Liern Hong, doctoral student1,
  2. Christoph R Meier, professor234,
  3. Robert S Sandler, professor15,
  4. Susan S Jick, director and professor4,
  5. Til Stürmer, professor1
  1. 1Department of Epidemiology, UNC Gillings School of Global Public Health, University of North Carolina at Chapel Hill, McGavran-Greenberg, CB # 7435, Chapel Hill, NC 27599-7435, USA
  2. 2Basel Pharmacoepidemiology Unit, Division of Clinical Pharmacy and Epidemiology, Department of Pharmaceutical Sciences, University of Basel, Basel, Switzerland
  3. 3Hospital Pharmacy, University Hospital, Basel, Switzerland
  4. 4Boston Collaborative Drug Surveillance Program, Boston University School of Public Health, Boston, MA 02421, USA
  5. 5Department of Medicine, UNC School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill NC 27599-7555, USA
  1. Correspondence to: J L Hong jlhongtw{at}
  • Accepted 17 July 2013


Objective To examine the risk of colorectal cancer after orlistat initiation in the UK population.

Design Retrospective matched cohort study.

Setting Data from the UK Clinical Practice Research Datalink from September 1998 to December 2008.

Participants 33 625 adults aged 18 years or over who started treatment with orlistat; each orlistat initiator was matched to up to five non-initiators (n=160 347) on age, sex, body mass index, and calendar time.

Main outcome measures Associations between orlistat initiation and the risk of colorectal cancer, assessed by calculating hazard ratios with propensity score adjusted Cox proportional hazard models.

Results Of 193 972 patients with a median age of 47 (interquartile range 37-57) years, 77% were women and approximately 90% were obese (body mass index ≥30). Orlistat initiators were more likely to have a previous history of diabetes or hypertension and to receive prescriptions for anti-diabetes drugs, statins, and aspirin compared with non-initiators. In the intention to treat analysis, 57 colorectal cancer events were identified among orlistat initiators and 246 among non-initiators, with median follow-up times of 2.96 and 2.86 years, respectively. The calculated incidence rate of colorectal cancer per 100 000 person years was 53 (95% confidence interval 41 to 69) for orlistat initiators and 50 (44 to 57) for non-initiators. Orlistat initiation was not associated with a higher risk of colorectal cancer (adjusted hazard ratio 1.11, 95% confidence interval 0.84 to 1.47). Findings were robust in the as treated analyses and in patients who were aged 50 years or over, were morbidly obese, or had a history of diabetes.

Conclusions This study found no evidence of an increased risk of colorectal cancer after the initiation of orlistat. It is limited by the relatively short follow-up time, and the possibility of adverse effects of long term orlistat use on risk of colorectal cancer cannot be excluded.


  • We thank Pascal Egger for help with data management.

  • Contributors: J-LH, TS, RSS, and CRM conceived and designed the study. TS oversaw the conduct of the study. CRM and SSJ provided the data and oversaw the database programming. J-LH did the data analysis. J-LH and TS interpreted the results and drafted the manuscript. TS, RSS, CRM, and SSJ contributed to critical revision of the manuscript for important intellectual content. All authors approved the final manuscript. TS is the guarantor.

  • Funding: The study was funded by the population research award from the Lineberger Comprehensive Cancer Center (LCCC) at the University of North Carolina at Chapel Hill and R01 AG023178 from the National Institute of Aging at the National Institutes of Health. The funding agencies had no role in the design of the study; in the analysis and interpretation of the data; in the writing of the report; or in the decision to submit the paper for publication.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare: JLH and TS receive(d) salary support from the Center for Pharmacoepidemiology, Department of Epidemiology, the University of North Carolina at Chapel Hill, currently funded by GlaxoSmithKline (a pharmaceutical company that produces Alli, the brand name of orlistat 60 mg); no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This study was approved by the Independent Scientific Advisory Committee for MHRA database research in the UK and was exempt from the Institutional Review Board review at the University of North Carolina at Chapel Hill.

  • Data sharing: No additional data available.

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