A population-based case-control study of canine mammary tumours and clinical use of medroxyprogesterone acetate

Authors

  • MERETE STØOVRING,

    1. Department of Morphology, Genetics and Aquatic Biology, The Norwegian College of Veterinary Medicine, Oslo, Norway
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  • LARS MOE,

    Corresponding author
    1. Department of Small Animal Clinical Sciences, The Norwegian College of Veterinary Medicine, Oslo, Norway
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  • EYSTEIN GLATTRE

    1. Department of Morphology, Genetics and Aquatic Biology, The Norwegian College of Veterinary Medicine, Oslo, Norway
    2. The Cancer Registry of Norway, Montebello, Oslo, Norway
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Small Animal Clinical Sciences, Norwegian College of Veterinary Medicine, P.O. Box 8146 Dep., N-0033 Oslo, Norway.

Abstract

We investigated whether or not an association could be found between mammary tumours and prior clinical use of medroxyprogesterone acetate (MPA) in bitches. A population-based retrospective agematched case-control study was designed based on interviews with the owners of the bitches. The proportion of bitches with diagnosed mammary tumours (group MT+, n = 98) that had received progestin injections was compared with the proportion in a control group without mammary tumours (group MT-, n=98). In the case group 39%, and in the control group 21% of the bitches had been treated with MPA. A significantly higher number of bitches with mammary tumours had been exposed to progestins, compared with the control group without mammary tumours (odds ratio = 2.32, Chisquare=7.01, p=0.008). Bitches treated clinically with low doses of MPA to avoid oestrus were at a greater risk of developing mammary tumours, the majority of which were histologically malignant (91%).

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