All numbered parenthetical references in this section, are to the References list for the Osteoporosis Screening Guidelines.
Prostate Cancer, Androgen Ablation and Osteoporosis
Prostate cancer is the commonest cause of cancer in men in Canada. In 1999 over 2,600 men were diagnosed with prostate cancer in BC. By 2020 we expect a 50% rise in incidence, because of increasing life expectancy and age of the population.
Fifty years ago hormonal therapy was carried out by orchidectomy. Now the majority of men choose medical castration with LHRH agonists. Androgen ablation (AA) is used for:
- adjunct with radiotherapy (or surgery) [1];
- node positive or metastatic cases; or
- biochemical relapse after first line curative treatment.
This third category is the largest and has the longest potential duration of AA. Specifically, estimates of prostate cancer survival five years after PSA failure from radiotherapy can be as high as 76-78% for patients with a biopsy Gleason score of 6 or less or a pre-treatment PSA 10 or less (4). After radical prostatectomy and PSA relapse the median actuarial time to metastases was eight years from the time of PSA level elevation (5). Once men developed metastatic disease, the median actuarial time to death was five years. This gives a potential total of 13 years of androgen deprivation in patients who fail biochemically.
Osteoporosis is only one of several adverse effects of AA. Others include hot flashes, fatigue, an increase in body fat, memory loss and depression. The premise of this work is that earlier diagnosis and prevention of fractures should decrease the medical problems, as well as improve patients' quality of life (QOL).
Osteoporosis in Men Without Cancer
Osteoporosis can be defined as "a systemic skeletal disease characterized by low bone mass and micro-architectural deterioration of bone tissue with a resultant increase in fragility and risk of fracture".
In Canada 1 in 8 of all men have osteoporosis and with the ageing population this will increase dramatically over the next decade. Estimates of the lifetime risk of an osteoporotic fracture is 13-25% in men – 2-4X less than women. One third of hip fractures occur in men. Men have a gradual age related loss in BMD of about 10% per decade beginning at age 30 years (6).
Many vertebral fractures are occult and asymptomatic but they correlate with a poorer overall survival. Vertebral fractures increase the risk of future fractures. Similarly, osteoporotic hip fractures are associated with increased mortality: being 33% in the year afterwards. In addition, up to 70% of cases with hip fractures never regain to their previous functional status and QOL. Some 20% require long term care.
Early surgical management improves the results. Open vertebral surgery is reserved for rare cases with neurological deficits or instability. Newer procedures include vertebroplasty and kyphoplasty using cement injections into the bone. The care cost for treatment of fractures is estimated at over US$3B in the USA. Most important of all, osteoporotic fractures are preventable.
[1] BC Cancer Agency data shows that testosterone recovery to 5nmol/l takes a year on average with 80% reaching this at two years post cessation of LHRH therapy. Longer acting LHRH formulations may lead to significantly poorer recovery of testosterone.
