Advanced and metastatic prostate cancer is associated with a number of pain syndromes. The principal source of pain in metastatic prostate cancer results from skeletal involvement. As many as 50% of men with skeletal metastases from prostate cancer will have uncontrolled pain . Pain in advanced disease can also result from local invasion of pelvic structures, in particular the rectum, bladder and nerve plexi. This chapter will focus on pain management strategies for skeletal metastases. Pain management strategies discussed will include external beam radiotherapy, bone-seeking radionuclide therapy and bisphosphonate therapy. The use of other systemic therapies including cytotoxic chemotherapy is described elsewhere in this book.
EXTERNAL BEAM RADIOTHERAPY
Radiation therapy has been used to control pain from bone metastases for almost 100 years. In the initial years of this modality, the dose of radiation delivered to bone was limited by the tolerance of the normal structures irradiated in the field. For bone metastases this included the overlying skin and soft tissues; however, with the advent of cobalt-60 machines and subsequently megavoltage linear accelerators (Figure 18.1), it became feasible to deliver larger doses of ionizing radiation to areas deep within the body with skin-sparing effects. Irradiation of bony metastatic disease is now one of the most common uses of external beam radiotherapy.
A modern linear accelerator.
External beam radiotherapy (EBRT) is effective in the palliation of painful bone metastases from most solid tumours with published response rates of the order of 40–70% [2, 3]. In some patients the onset of pain relief can be within 2 days; however, in others it may take up to 6 weeks for the full benefit of the treatment to be realized . The onset of pain relief and the likelihood of a clinically useful response will depend a lot on the aetiology of the pain. Nerve or soft tissue compression caused by collapse of a vertebra or pathological fracture of a long bone will be unlikely to respond well to external beam radiotherapy, whereas pain secondary to soft tissue tumour growth will generally have a better outcome. EBRT also has an important role in the treatment of pain caused by pelvic and para-aortic nodal metastases.
EBRT carries a risk of toxicity. Early or acute toxicity, occurring within 3 months of palliative EBRT depends on the region of the body and the surrounding normal tissues being irradiated. The most common side-effects are tiredness, nausea and vomiting and diarrhoea. Patients receiving large single fractions of radiotherapy who are at risk of nausea and vomiting should receive prophylactic antiemetics such as a 5-hydroxytryptamine (5HT) antagonist prior to radiation. In general the toxicity associated with palliative radiotherapy to bone is minimal and ...