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THE letter from Frances Harcourt-Brown (VR , April 15, 2017, vol 180, pp 385-386), in response to my previous letter (VR , February 25, 2017, vol 180, p 204), in which she recommends that all female rabbits should be spayed is a classic example of 'eminence-based medicine'. In her experience, uterine tumours are 'common' in older does, but she cannot say how common, and surgical and anaesthetic complications are 'low', but she cannot say how low. Obviously, spaying rabbits to prevent the tumours must be in their interest.
In human reproductive oncology, implementations of similarly intuitively right, but not evidence-based, policies have become controversial, having caused more harm than good in some people. Examples include prostate-specific antigen screening for prostate cancer, mammography screening of women under the age of 50, and radical mastectomy as a treatment for breast cancer ( Andriole and others 2009 , Barry 2009 , Berry 2013 , Godlee 2013 , Broeders and Paci 2015 , Ireland and O'Shaughnessy 2015 , Prasad and Cifu 2015 , Chetlen and others 2016 ). Human breast and prostate cancers have lifetime incidences of about 12 per cent in women and men, respectively ( Breastcancer.org 2017 , Cancer Research UK 2017a , b, National Cancer Institute 2017 ), probably higher than the lifetime incidence of uterine tumours in pet does. Could widespread spaying of young rabbits be causing more harm than good? We would need evidence to decide, and that is lacking.
What matters is not the number of entire does that develop uterine tumours, but how many suffer morbidity and/or mortality because of the tumours before they die of another condition. From the very limited evidence available, rabbits live to an average of around four years ( Craven and others 2016 ), and the average age of uterine adenocarcinoma diagnosis is five to six years (Saito and others 2002, Walter and others 2010 , Kunzel and others 2015, Whitehead 2017 ). Some uterine tumours are incidental findings, some of which may not have caused morbidity before the rabbit died of other causes. In...