Radiopharmaceuticals: A Modern-day Trojan Horse
Treatment Options Mediaplanet sat down with Dr. Andrew Loblaw to talk radiopharmaceutical drug therapy.
Mediaplanet: What treatment options are available for metastatic prostate cancer?
Dr. Andrew Loblaw: Hormonal therapy is the standard treatment for metastatic disease when men are first diagnosed or if the cancer spreads after local treatment like surgery and/or radiation. These therapies block the tumour’s access to testosterone (the hormone feeds the tumour) or decrease testosterone production. Hormone therapy is given as pills taken by mouth (antiandrogens) or injected into the skin of the belly or hip muscle (luteinizing hormone-releasing hormones). This therapy is very effective in cancer control for almost all men and usually keeps it in remission for many years. However, if a man lives longer, the prostate cancer will progress and he might need other treatments that may include external beam radiation, intravenous chemotherapy, second generation hormone therapies taken by mouth, or radiopharmaceuticals.
MP: How does traditional radiation therapy differ from radiopharmaceutical therapy for the treatment of bone metastases?
AL: Traditional radiation therapy can be administered from outside the body (external beam radiotherapy), inside (brachytherapy), or through the veins (radiopharmaceuticals). Brachytherapy is not given for bone metastases. External beam radiotherapy is very effective for reducing bone pain associated with metastases. The standard for uncomplicated bone metastasis is a single treatment, which usually reduces pain partially or completely for about four to six months. Newer (stereotactic) treatments are being tested that appear to give more pain control for a longer time. Radiopharmaceuticals are delivered into the tumour by infusion through the veins. The bone cells trying to repair bone damaged by the tumour take up the medicine mistaking it for calcium, a key building block in normal bone. The radioactive material destroys the tumour in bone metastasis like a modern-day Trojan horse.
MP: What is the benefit of using radiopharmaceutical drug therapy to treat bone metastatic prostate cancer?
AL: The main advantage of radiopharmaceuticals is that they are delivered in the veins and can therefore affect tumours in the bone that are visible or invisible on X-rays. They can also help a man who has many areas of bone metastases, whereas external beam radiotherapy generally has to be given to a few areas at a time and the amount of normal tissue that can be safely radiated is smaller.