A trial to determine the effect of glucosamine versus placebo on aromatase inhibitor induced arthralgia (joint pain) in postmenopausal women with early breast cancer who are on letrozole

Arthralgia (joint pain) and other joint related symptoms are common side effects of taking letrozole (hormone therapy). As such, some patients stop taking their hormone therapy earlier than the recommended 5 years after breast surgery. The purpose of this study is to find out if glucosamine can ease joint pain in patients taking letrozole, and therefore reduce the chance that they will stop their hormone therapy early. Participants (ER and/or PR receptor positive, postmenopausal, early breast cancer) will receive either crystalline glucosamine sulphate (1500mg tablet) or placebo that will be taken concurrently with letrozole and will be followed for a total of 24 months (maximum treatment period of 18 months followed by an off study treatment visit 6 months later). The discontinuation rate of letrozole will be determined at 12 months and 18 months. Off study treatment visit should be 24 months post-randomisation or, if discontinued study treatment prior to 18 months post-randomisation, off study visit should be 6 months post permanent cessation of CGS/placebo.