Faculty Bibliography

Metastatic castrate-resistant prostate cancer (CRPC) refers to the disease state in which metastatic prostate cancer fails to respond to androgen deprivation therapy (ADT). This can be manifest as a rising PSA, increase in radiographically measurable disease, or progression of clinical disease. Roughly 90 % of men with metastatic prostate cancer have bone metastases, which is a predictor of both morbidity and mortality. Historically, treatment has been palliative, consisting of external beam radiation therapy (EBRT) and pharmacological analgesics for pain control and osteoclast inhibitors, such as bisphosphonates and denosumab to mitigate skeletal-related events. Older radiopharmaceuticals, such as Strontium-89 and Samarium-153, are Beta-emitting agents that were found to provide palliation but were without survival benefit and carried high risks of myelosuppression. Radium-223 is an Alpha-emitting radiopharmaceutical that has demonstrated a significant overall survival benefit in men with metastatic CRPC, delay to symptomatic skeletal events (SSEs), and improvement in pain control, with a favorable toxicity profile compared with placebo. Unlike EBRT, Radium-223 has systemic uptake, with the potential to address several bone metastases concurrently and provides overall survival benefit. It is a simple administration with minimal complexity and shielding requirements in experienced hands. EBRT appears to provide a more rapid and dramatic palliative benefit to any given lesion. Because Radium-223 has limited myelosuppression, the two can be thoughtfully integrated, along with multiple agents, for the treatment of men with CRPC with symptomatic bone metastases. Given its excellent safety profile, there is interest and anecdotal safety combining Radium-223 with therapies, such as abiraterone and enzalutamide. Formal recommendations regarding combination therapies will require clinical trials. The use of Alpha-emitting radiopharmaceuticals in castrate-sensitive disease, in metastatic asymptomatic CRPC, the categorical sequencing amongst other treatments for CRPC, as well as the application to other primary pathologies, such as metastatic breast cancer, is currently evolving.

The adrenal gland is a common site of cancer metastasis. Surgery remains a mainstay of treatment for solitary adrenal metastasis. For patients who cannot undergo surgery, radiation is an alternative option. Stereotactic body radiotherapy (SBRT) is an ablative treatment option allowing larger doses to be delivered over a shorter period of time. In this study, we report on our experience with the use of SBRT to treat adrenal metastases using CyberKnife technology. We retrospectively reviewed the Winthrop University radiation oncology data base to identify 14 patients for whom SBRT was administered to treat malignant adrenal disease. Of the factors examined, the biological equivalent dose (BED) of radiation delivered was found to be the most important predictor of local adrenal tumor control. We conclude that CyberKnife-based SBRT is a safe, non-invasive modality that has broadened the therapeutic options for the treatment of isolated adrenal metastases.