Radical prostatectomy and radiotherapy are preferred treatment options for localized prostate cancer patients. When the level of the prostate-specific antigen rises after radical prostatectomy, that is an indication of recurrence of prostate cancer, and the patients can still be cured with salvage radiotherapy. Chances for a cure can be maximized by surrounding the extent of the disease with irradiated volumes. It is critical to accurately estimate the location of the disease to plan the radiotherapy in the salvage and definitive settings.
The existing first-line imaging for prostate cancer has limited sensitivity when detecting the disease at the initial stages and biochemical recurrence. Integrating PET when evaluating prostate cancer patients will improve the accuracy of staging and radiotherapy planning. 18F-FDG PET/CT is routinely used in radiation planning for several types of cancer, but it has low sensitivity for prostate cancer.
Prospective investigations suggest that PET/CT has a significant impact on the planning of prostate radiation treatment. Trials exposing patients to conventional radiotherapy planning and PET/CT aided planning are likely to show positive outcomes. Incorporating PET/CT can affect radiotherapy in several ways.
- PET/CT-defined gross disease within a target volume can be prescribed a higher dose. PET/CT optimizes the treatment plan to increase the dose of radiation to the tumor and reduce the dose to sensitive organs (improving the therapeutic ratio).
- The CTVs can be expanded to include the areas of the disease that cannot be seen by the current first-line imaging and which are not generally targeted by consensus.
- The evidence of metastatic disease is an indication that local therapy alone is not able to cure cancer. Metastasis directed therapy is currently undergoing clinical trials.
- In other cases where PET/CT shows unexpected diffuse metastatic disease, radiotherapy may be considered abandoned and futile.
Integrating PET/CT into radiation therapy planning is achievable. PET/CT impacts the treatment goal of radiation therapy improved staging. It optimizes the treatment plan to increase the dose of radiation to the tumor and reduce the dose to sensitive organs. After treatment, PET/CT can be used in monitoring the response to treatment and assess for recurrence.