First described in 1853, prostate cancer was originally thought to be rare. Today, it is the most frequently diagnosed cancer in men in the European Union, and the second most common—after skin cancer — in American men. In 2018, prostate cancer was diagnosed in 1.2 million men, leading to 459,000 deaths worldwide.
Most early cases of prostate cancer are treated with a "watch and wait" approach, but men diagnosed with later stages of prostate cancer have a number of available treatment options, including surgery, radiation, chemotherapy, hormonal therapy, and immunotherapy. New treatments still in clinical trials may also be available soon and may again change the landscape of prostate cancer treatment. In recent years, the field of radiology has generated a great deal of innovation.
Intertwined modalities yield super-targeted treatment
Radiology was first employed at the beginning of the twentieth century as an alternative to surgery. The treatment then involved inserting radium into the urethra and rectum. This crude approach evolved, and by the 1970s, tumor growth was found to slow after radioactive needles were inserted into the prostate gland. The use of localized radiation was improved and finessed, and in the 1980s, the technique brachytherapy, or radioactive implants in tissue using transrectal ultrasonography to guide the procedure, was commonly used.
More sophisticated imaging technology helped clinicians and researchers to target more accurately, using, for example, computerized tomography (CT) and multi parametric MRI (mpMRI) scans to created three-dimensional conformal treatment plans that limit damage to surrounding tissue.
Radiopharmaceuticals to the rescue
In the last few decades, treatment with radiopharmaceuticals has helped many patients with advanced prostate cancer to live longer and more comfortably. A radiopharmaceutical product is one that marries highly effective radiotherapy to specific receptors on cancer cells. Most patients with advanced prostate cancer experience osteoblastic bone metastasis, and this is one of several areas where radiopharmaceuticals can be useful. Bone-seeking radiopharmaceuticals, although not able to cure the cancer, provide significant palliative relief.
In 2013, the US Food and Drug Administration (FDA) approved the radiopharmaceutical radium-223 dichloride for treatment of men with metastatic castration-resistant prostate cancer (mCRPC) that had spread to the bone. Other radiopharmaceuticals had been in use previously, but radium-223 was hailed as being less toxic for patients and offering a survival benefit in addition to palliative action.
The combination of cancer-finding and cancer-treating agents has proven irresistible to investigators. One type of radiopharmaceutical that has resulted from study is “peptide receptor radionuclide therapy” (PRRT). PRRT pairs with a radioactive material that includes a protein called a peptide. The result is a “radiopeptide”. Investigators are looking at different cells and tumor properties that can be targeted in this fashion. They range from the molecular mechanism CXCR4 to biomarkers that are specific to individual patients.
The PSMA pathway
PSMA, or prostate specific membrane antigen, is found on most prostate cancers. As a result, it offers avenues for cancer detection, location, and treatment. PSMA PET/CT scans, for example, are an alternative to conventional imaging that involve patients taking a radioactive substance that attaches to the PSMA antigen. The subsequent PET/CT scans light up the radioactive substance, revealing the cancerous cells. Although success is impacted by the size of the lesions and the patients’ PSMA levels, PSMA PET/CT has been found to be nearly a third more accurate than standard imaging. In some cases it can prompt a change to the patient's treatment plan
For these advances to reach more patients, the clinical trials that determine how treatments are used and for whom must encompass nuclear medicine, immunotherapy, evolving imaging, and more. It’s a daunting task, but we continue to make progress.