Gabapentin and Risk of Pancreatic Cancer and Renal Cancer (GPRD)

Study Overview
=================
Brief Summary
-----------------
High doses of gabapentin are associated with pancreatic acinar cell tumors in rats, but there has been no post marketing pancreatic carcinogenicity signal with gabapentin as reported by spontaneous reports in the Adverse Events Reporting System or in the published literature. In a published case-control screening study of the association of gabapentin with 55 cancers, the only cancer that met the screening criteria for possibly increased cancer risk with gabapentin exposure was renal (including renal pelvis) cancer. This association was judged to be likely due to or substantially accentuated by confounding by cigarette smoking, hypertension, and lifestyle (Cancer Causes Control 2009;20:1821-1835). The primary objective of this study is to determine whether exposure to gabapentin is associated with an increased risk of developing pancreatic cancer or renal cancer in the United Kingdom (UK) General Practice Research Database (GPRD). Almost all members of the UK population are registered with a General Practice, which centralizes the medical information not only from the general practitioners themselves but also from specialist referrals and hospital attendances. Over 487 General Practices contribute data to the GPRD. The study cohort from which cases and controls are drawn is all subjects in the GPRD 1993-2008. Gabapentin was approved in the UK in May 1993. Entry into the study cohort begins Jan 1, 1993 for all those who are registered in GPRD before that time, and at the time of registration if later than Jan 1, 1993. Patients with a first diagnosis of the respective cancer 1995-2008 are risk set matched with up to 10 controls within the same General Practice for age at cohort entry (within two years), sex, and year of entry into the study cohort (within one year). For cases, the index date is the date of first diagnosis of the respective cancer. The index date for controls is set as the date at which the follow-up time from cohort entry is the same as the case. The index date is chosen so as to give the control equal follow-up time to that of the case for ascertainment of use of gabapentin. Cases and controls will be required to have at least 2 years of follow-up in the study cohort before their index date. Data on gabapentin prescriptions are obtained for cases and controls from study cohort entry to the index date. Crude and adjusted odds ratios and 95% confidence intervals (CI) will be produced from conditional logistic regression models, with additional analyses evaluating for latency and dose-response. For pancreatic cancer, covariates are smoking, body mass index, diabetes, epilepsy, neuropathic pain, and chronic pancreatitis. For renal cancer, covariates are smoking, body mass index, diabetes, hypertension, diuretic use, epilepsy, and neuropathic pain.

Detailed Description
-----------------
Patients were not recruited for nor enrolled in this study. This study is a retrospective observational study. Data from medical records or insurance claims databases are anonymised and used to develop a patient cohort. All diagnoses and treatment are recorded in the course of routine medical practice. Actual number of patients could be less than , as it is possible for a patient to be represented in more than one of the four arms (See Participant Flow: Overall Study Table) because of the risk set sampling.

Official Title
-----------------
Risk of Pancreatic Cancer and Renal Cancer in Patients Exposed to Gabapentin in the United Kingdom General Practice Research Database

Conditions
-----------------
Renal Pelvis Cancer, Restless Legs Syndrome, Epilepsy, Neuropathic Pain, Chronic Pancreatitis, Hypertension, Pancreatic Cancer, Diabetes, Renal Cancer, Renal Cell Carcinoma

Intervention / Treatment
-----------------
* Drug: Gabapentin prescriptions


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: The study cohort from which cases and controls are drawn is all subjects in the UK GPRD 1993-2008. Entry into the study cohort begins Jan 1, 1993 for all those who are registered in GPRD before that time, and at the time of registration if later than Jan 1, 1993. Follow-up ends Dec 31, 2008, or earlier if the respective cancer is diagnosed, or if the subject leaves the GPRD for any reason including death. Exclusion Criteria: Cases and controls will be required to have at least 2 years of follow-up in the study cohort before their index date (For cases, the index date is the date of first diagnosis of the respective cancer. The index date for controls is set as the date at which the follow-up time from cohort entry is the same as the case.)
Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| UK GPRD 1993-2008<br>The study cohort from which cases and controls are drawn is all subjects in the United Kingdom (UK) General Practice Research Database (GPRD) 1993-2008. Each member of the UK population is registered with a General Practice, which centralizes the medical information not only from the general practitioners themselves but also from specialist referrals and hospital attendances. Over 487 General Practices contribute data to the GPRD. Entry into the study cohort begins Jan 1, 1993 for all those who are registered in GPRD before that time, and at the time of registration if later than Jan 1, 1993. | Drug: Gabapentin prescriptions<br>* The exposure of interest is gabapentin use as defined by prescriptions recorded by the GPRD general practitioner (British National Formulary codes). Data on prescriptions for gabapentin will be extracted for each case and control from entry into the study cohort up to the index date (the exposure window). Gabapentin exposure will be parameterized as follows: (1) Ever versus never exposed; (2) Number of prescriptions; (3) Duration of exposure; and (4) Cumulative dose. These parameterizations will also be examined with a 2 year lag time from the index date, limiting the exposure window from entry into the study cohort up to 2 years prior to the index date.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Number of Pancreatic Cancer Cases and Matched Controls With the Indicated Exposure to Gabapentin | Incident pancreatic cancer. Gabapentin Exposure Description: Without 2 year lag = Gabapentin prescription from cohort entry to index date. With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). | The case index date (ID) was the date of incident pancreatic cancer diagnosis ascertained in the GPRD study cohort 1995-2008. The matched control ID was the date at which the follow-up time from his/her cohort entry was the same as that for the case | 
| Number of Pancreatic Cancer Cases and Matched Controls With the Indicated Number of Gabapentin Prescriptions | Incident pancreatic cancer. Gabapentin Exposure Description: Without 2 year lag = Gabapentin exposure from cohort entry to index date. With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Tertiles without 2 year lag: Tertile 1 (1-2 prescriptions),Tertile 2 (3-8 prescriptions), and Tertile 3 (9-218 prescriptions). Tertile's with 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-10 prescriptions),Tertile 3 (11-191 prescriptions). | The case index date (ID) was the date of incident pancreatic cancer diagnosis ascertained in the GPRD study cohort 1995-2008. The matched control ID was the date at which the follow-up time from his/her cohort entry was the same as that for the case | 
| Number of Pancreatic Cancer Cases and Matched Controls With the Indicated Duration of Exposure to Gabapentin | Incident pancreatic cancer. Gabapentin Exposure Description: Without 2 year lag = Gabapentin exposure from cohort entry to index date. With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Tertile's without 2 year lag: Tertile 1 (0.01 - 1.55 months), Tertile 2 (1.56 - 6.44 months), and Tertile 3 (6.45 - 78.36 months). Tertile's with 2 year lag: Tertile 1 (0.01 - 1.78 months), Tertile 2 (1.79 - 7.20 months), and Tertile 3 (7.21 - 64.13 months). | The case index date (ID) was the date of incident pancreatic cancer diagnosis ascertained in the GPRD study cohort 1995-2008. The matched control ID was the date at which the follow-up time from his/her cohort entry was the same as that for the case | 
| Number of Pancreatic Cancer Cases and Matched Controls With the Indicated Cumulative Dose of Gabapentin | Incident pancreatic cancer. Gabapentin Exposure Description: Without 2 year lag = Gabapentin exposure from cohort entry to index date. With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Tertile's without 2 year lag: Tertile 1 (0.01 - 33.6 grams), Tertile 2 (33.7 - 185.0 grams), and Tertile 3 (185.1 - 7500.2 grams). Tertile's with 2 year lag: Tertile 1 (0.01 - 39.0 grams), Tertile 2 (39.1 - 210.0 grams), and Tertile 3 (210.1 - 5623.8 grams). | The case index date (ID) was the date of incident pancreatic cancer diagnosis ascertained in the GPRD study cohort 1995-2008. The matched control ID was the date at which the follow-up time from his/her cohort entry was the same as that for the case | 
| Number of Renal Cancer Cases and Matched Controls With the Indicated Exposure to Gabapentin | Incident renal cancer. Gabapentin Exposure Description: Without 2 year lag = Gabapentin prescription from cohort entry to index date. With 2 year lag = Gabapentin prescription from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). | The case index date (ID) was the date of incident renal cancer diagnosis ascertained in the GPRD study cohort 1995-2008. The matched control ID was the date at which the follow-up time from his/her cohort entry was the same as that for the case. | 
| Number of Renal Cancer Cases and Matched Controls With the Indicated Number of Gabapentin Prescriptions | Incident renal cancer. Gabapentin Exposure Description: Without 2 year lag = Gabapentin exposure from cohort entry to index date. With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Tertiles without 2 year lag: Tertile 1 (1-2 prescriptions),Tertile 2 (3-8 prescriptions), and Tertile 3 (9-218 prescriptions). Tertile's with 2 year lag: Tertile 1 (1-2 prescriptions), Tertile 2 (3-10 prescriptions),Tertile 3 (11-191 prescriptions). | The case index date (ID) was the date of incident renal cancer diagnosis ascertained in the GPRD study cohort 1995-2008. The matched control ID was the date at which the follow-up time from his/her cohort entry was the same as that for the case. | 
| Number of Renal Cancer Cases and Matched Controls With the Indicated Duration of Exposure to Gabapentin | Incident renal cancer. Gabapentin Exposure Description: Without 2 year lag = Gabapentin exposure from cohort entry to index date. With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Tertile's without 2 year lag: Tertile 1 (0.01 - 1.55 months), Tertile 2 (1.56 - 6.44 months), and Tertile 3 (6.45 - 78.36 months). Tertile's with 2 year lag: Tertile 1 (0.01 - 1.78 months), Tertile 2 (1.79 - 7.20 months), and Tertile 3 (7.21 - 64.13 months). | The case index date (ID) was the date of incident renal cancer diagnosis ascertained in the GPRD study cohort 1995-2008. The matched control ID was the date at which the follow-up time from his/her cohort entry was the same as that for the case. | 
| Number of Renal Cancer Cases and Matched Controls With the Indicated Cumulative Dose of Gabapentin | Incident renal cancer. Gabapentin Exposure Description: Without 2 year lag = Gabapentin exposure from cohort entry to index date. With 2 year lag = Gabapentin exposure from cohort entry to 2 years prior to index date (to control for prediagnostic prescribing for pain symptoms possibly related to cancer). Tertile's without 2 year lag: Tertile 1 (0.01 - 33.6 grams), Tertile 2 (33.7 - 185.0 grams), and Tertile 3 (185.1 - 7500.2 grams). Tertile's with 2 year lag: Tertile 1 (0.01 - 39.0 grams), Tertile 2 (39.1 - 210.0 grams), and Tertile 3 (210.1 - 5623.8 grams). | The case index date (ID) was the date of incident renal cancer diagnosis ascertained in the GPRD study cohort 1995-2008. The matched control ID was the date at which the follow-up time from his/her cohort entry was the same as that for the case. | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
renal cell carcinoma, epidemiology, pancreatic cancer, renal cancer, renal pelvis cancer, GPRD, case-control, Gapabentin