Docetaxel for the treatment of hormone-refractory metastatic prostate cancer

The prostate gland is present only in men. It is located just below the bladder exit, surrounding the urethra, and is subdivided into 3 zones: central, transition and peripheral. The peripheral zone, at the back of the prostate, is the part most susceptible to prostate cancer. The extent of prostate cancer is classified into stages 1 to 4. At stages 1 and 2, the disease is confined to the prostate. At stage 3, the tumour is more locally advanced and at stage 4 either it is locally advanced and invading local adjacent structures, or it has associated distant metastases.

The growth of most prostate cancers is stimulated by testosterone, and hormonal therapies that modify levels of, or responses to, testosterone are standard treatment for men with metastatic disease. Hormonal therapies are initially effective in 80% of men with metastatic prostate cancer, but after around 18 months the disease usually becomes unresponsive to hormone treatment and will progress.

Hormone-refractory metastatic prostate cancer is defined on the basis of biochemical testing (prostate-specific antigen, PSA), findings of imaging studies, or using clinical criteria of progressive metastatic disease despite castrate serum levels of testosterone.

Data on the epidemiology of hormone-refractory metastatic prostate cancer are limited; therefore, inferences must be drawn from available data for prostate cancer. In the UK, prostate cancer is the most common male cancer, excluding non-melanoma skin cancer. In 2001, there were 26,067 new cases in England and 1746 in Wales, giving age-standardised incidence rates of 89.8 and 92.6 per 100,000 men respectively. Prostate cancer is the second most common cause of male cancer deaths, accounting for 13% of them. In 2003, there were 8,582 deaths in England and 579 in Wales from prostate cancer, giving age-standardised mortality rates of 27.3 and 28.6 per 100,000 men respectively. It has been estimated that most of the deaths are in patients with hormone-refractory metastatic prostate cancer.

Prostate cancer is associated with substantial morbidity that can have a significant impact on the patients, and on their families and carers. Prostate cancer was responsible for almost 40,000 hospital episodes in 2003 to 2004, although it is unknown how many of these related to patients with hormone-refractory metastatic prostate cancer. The symptoms of hormone-refractory metastatic prostate cancer may be related to compression of the urethra, metastases to bone and other sites, and adverse effects of treatment. Urinary symptoms include difficulty starting the flow of urine, passing urine more often, and discomfort while passing urine. More than 90% of patients with late-stage prostate cancer develop metastases to bone, and this can cause debilitating and sometimes uncontrollable pain, pathological fractures and spinal cord compression. Patients may receive surgery, radiotherapy, steroids and analgesics as well as hormonal treatment and chemotherapy, and they may suffer adverse effects related to all of these.

The primary risk factor for prostate cancer is increasing age: 90% of cases are in men older than 60, and 42% in men older than 75. Worldwide, the highest rates are observed in African-American men, with much lower rates seen in men of Asian origin. The cause of prostate cancer is probably multifactorial, involving environmental and genetic factors. Prostate cancer does not occur in castrated men, so testosterone is implicated. High levels of insulin-like growth factor (IGF-1), a protein involved in cell metabolism, may also be involved. About 9% of cases are thought to have a genetic component. Diets high in animal fats and dairy products appear to be associated with increased risk of prostate cancer.

The prognosis is poor for patients with hormone-refractory metastatic prostate cancer: survival is not expected to exceed between 9 and 12 months. Hormone-refractory metastatic prostate cancer cannot be cured. The aim of treatment is to improve symptoms, prolong life and slow progression of the disease.

There is no gold standard treatment for hormone-refractory metastatic prostate cancer in the UK. Clinical management is acknowledged to be multimodal rather than sequential and patients may receive a combination of palliative treatments.

Treatment options include second-line hormonal therapy, chemotherapy with or without corticosteroids, and best supportive care. The choice of therapy depends on the symptoms, the site of relapse, the performance status (see appendix B) of the patient and the presence of other comorbidities. Best supportive care can be provided with radiotherapy, bisphosphonates, steroids and analgesics, and is the only option for patients who are too ill to tolerate further active intervention. Tolerability of chemotherapy is of concern, particularly because most patients with prostate cancer are elderly and many have other medical problems.

Chemotherapy regimens that have been used to treat the cancer include those based on mitoxantrone, estramustine and taxanes such as docetaxel. Mitoxantrone is widely used in the UK for hormone-refractory metastatic prostate cancer patients who are fit for chemotherapy, even though it is not licensed for this indication. NICE was informed by several consultees that a combination of mitoxantrone and prednisolone has come to be accepted as the standard care for this group of patients.

NICE's previous cancer service guideline on improving outcomes in urological cancers (now replaced by NICE's guideline on colorectal cancer) stated that chemotherapy should be considered for men with symptomatic hormone-refractory prostate cancer, trials of chemotherapy should be supported, and that palliative radiotherapy should also be available. There are a number of guidelines produced by professional organisations.