Prostate cancer is one of the most common cancers in men in the UK. In the advanced stages - when the cancer has spread (metastisised), commonly to bone - there is no cure. Unlike in other types of cancer, deaths from prostate cancer are often due to bone disease and its complications. Whilst some prostate cancer drugs provide pain relief, they have not been shown to improve patient survival.
This is because their use also suppresses the production of blood cells from the bone marrow, which can lead to severe side effects such as anaemia, bleeding and infections.
With the knowledge that radium-223 selectively targets the spread of cancer cells to bone, researchers from the NIHR Royal Marsden BRC, and the Institute for Cancer Research trialled radium-223 in men with advanced prostate cancer.
The phase 3 trial, which involved 921 patients receiving either radium-223 or a placebo, showed at the point of interim analysis that radium-223 could boost patient survival by 30% in those with advanced prostate cancer.
A short distance goes a long way
The ability of radium-223 to target cancer cells in a much more effective way than previous prostate cancer treatments is in part due to its similarity to calcium. Like calcium, active bone cells take up radium-223 and as cancer cells are more active than normal bone cells, they are more likely to do this. Once inside the bones radium-223 is very targeted in its action. It releases radiation but only over a very short distance, around the equivalent of 2-10 cells. This means the cancer cells that have picked up the radium-223 and those in the close surroundings are killed, but the healthy cells further away are subject to only a very low dose of radiation or none at all. This reduces the likelihood of adverse effects as demonstrated by the safety profile of the drug during this trial.
An early end with a NICE conclusion
Once the effectiveness of radium-223 compared to placebo became clear this trial was stopped. Whilst not a cure for advanced prostate cancer, the drug effectively targets tumours that have spread enabling men to live longer and experience less pain with fewer side effects.
In December 2014, draft NICE guidance approved radium-223 for the treatment of men with bone metastatic castration resistant prostate cancer. It has since been licensed and is now available for use in England via the Cancer Drugs Fund.
Prior to this study at least 20 to 40% of patients with bone metastatic castration resistant prostate cancer didn’t receive chemotherapy, often considered too frail to have the treatment. Through the inclusion of patients who were not thought to be eligible to receive chemotherapy, this study has addressed an important unmet need in a population that was not served by therapies used historically to treat advanced prostate cancer.