To determine the effects of exposure to nonsteroidal antiinflammatory drugs (NSAIDs) on the risk of invasive female breast cancer we carried out a nested case-control study, using the beneficiaries of the Saskatchewan Prescription Drug Plan (SPDP) from 1981 to 1995 with no history of cancer since 1970 as the source population. Four age-matched controls were randomly selected for each case using incidence density sampling. Dispensing rates, calculated over successive time periods, characterized NSAID exposure according to dosage and the timing of exposure. / We accrued 5,882 cases and 23,517 controls. Increasing NSAID exposure during the period 7--12 months preceding diagnosis was associated with a trend towards an increasing rate ratio (RR) for the diagnosis of breast cancer (p trend = 0.003), which was attributed to detection bias because it was markedly reduced by eliminating from the analysis the cases with tumours most likely to have been detected by screening (≤ 2 cm diameter). Increasing NSAID exposure 2--5 years preceding diagnosis was associated with a trend towards a decreasing RR (p-trend = 0.003); for the highest exposure level RR = 0.76, 95% CI: 0.63--0.92. This protective effect could not be attributed to confounding by other risk factors. Confounding by risk factors not in the SPDP database was studied in analyses adjusted with data obtained by interviewing samples of subjects accrued from mid1991 to mid-1995, selected according to both disease and exposure status. / Increasing NSAID exposure 2--5 years and 6--10 years before diagnosis was associated with trends towards decreasing RRs for having a primary tumour >5 cm diameter at diagnosis (p-trend = 0.06 and 0.02, respectively). NSAID exposure did not alter the risk of regional lymph node metastasis. However, increasing NSAID exposure 2--5 years and 6--10 years before diagnosis was associated with trends towards decreasing RRs for having distant metastases at diagnosis (p-trend = 0.0003 and 0.03, respectively). / The use of NSAIDs may retard the growth of established, undiagnosed breast cancers and may decrease the risk of distant metastasis.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36706 |
| Date | January 1999 |
| Creators | Sharpe, Colin R. |
| Contributors | Collet, Jean-Paul (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Epidemiology and Biostatistics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001740500, proquestno: NQ64666, Theses scanned by UMI/ProQuest. |
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