Medical therapy of prostate cancer. A review.
Androgen ablation or blockade of androgen action through the androgen receptor (AR) has been the cornerstone of treatment of advanced prostate cancer. The relative merits of monotherapy or combined androgen blockade (CAB) are still the subject of debate. Each treatment strategy/hormonal agent has favourable and unfavourable effects. Patients with advanced prostate cancer will clearly benefit androgen deprivation-based treatment for palliating their symptoms and for improving their quality of life (QOL). However, whether these therapies prolong survival when administered before there are symptoms caused by disease progression remains controversial. Data from multiple recent studies indicate that an earlier treatment in patient's disease course likely leads to better outcome, but it is not easy to predict the best timing of hormonal therapy for asymptomatic advanced disease. For the purpose of delaying the onset of androgen-independent growth of prostate cancer, different regimen of intermittent androgen blockade (IAB) have been applied to patients. The use of IAB is increasing but, despite theoretical advantages in terms of patient QOL, clinical studies have yet to prove superiority over continuous therapy. The role of androgen deprivation in combination with surgery or radiotherapy has been also evaluated. While neoadjuvant hormonal therapy (NHT) can significantly decrease the incidence of positive margins at the time of radical prostatectomy (RP), 3 months of treatment is not long enough to have any significant effect on biochemical recurrence rates. The results of studies investigating longer courses (8 months) of NHT are awaited. High-risk patients should be considered for early adjuvant hormonal therapy (AHT) after surgery, as they may be most likely to benefit. The rationale for the use of NHT in combination with radiotherapy is that it reduces tumour volume and therefore the amount of radiation therapy that is needed to treat the tumour. It has been found that 3-4 months of hormonal treatment reduces prostate volume by 25-50%. Intermediate-risk patients treated with NHT and concomitant hormonal therapy have been found to have a 94% freedom for biochemical failure after 4 years, suggesting that this group is the ideal patient population to receive short-term hormonal therapy in combination with brachytherapy. Several studies suggested the current consensus that patients with clinically localized or locally advanced high-grade tumours benefit from definitive radiation therapy and long-term AHT. The current treatment for advanced prostate cancer remains essentially palliative. However, an increased understanding of the heterogeneous nature of the disease, the mechanisms that lead to hormone-refractory prostate cancer (HRPC) has identified novel therapeutic targets and led to the development of selective new therapies, that may help to prolong survival and maintain QOL for patients with HRPC.