After surgery or radiation for localized prostate cancer, your PSA will likely fall. After surgery, your PSA should be undetectable (<0.1 ng/dl) after about 30 days and should remain at this level. A rising PSA can be a sign of early recurrence, and given that radiation is more effective if given when the PSA is low after surgery, checking on your PSA every 3 months is recommended for several years. If it remains low, checking the PSA less frequently is reasonable. After radiation, the PSA will drop but often not to undetectable levels. If the PSA starts to rise, sometimes this is called a PSA “blip” or “bump” that is not truly cancer progression but rather a phenomenon that one can see with radiation. However, if the PSA rises about 2 ng/dl or rises on 3 consecutive measures over several month, this is likely a sign of cancer recurrence. Thus, after radiation, checking the PSA every 3 months for several years is also reasonable.
For a man starting hormonal therapy, visits are usually timed with the LHRH injection, along with PSA and other lab checkups such as the testosterone levels and liver and kidney function tests. There is a wide variety of practice patterns, but typically, checking bone mineral density before starting hormonal therapy and once per year to assess the loss of bone density is reasonable given that there are medications that can be used to reduce the risk of fracture.
Bone scans and CT scans are done for men with high or intermediate risk disease at diagnosis, and then again at the time of PSA progression or symptom development. Repeat scans are then performed typically once a year if a man’s disease remains under control, as there are some rare circumstances where cancer can progress without the PSA rising. However, whether a man needs a bone scan and CT scan every year is controversial, and omitting the CT scan in the absence of a PSA rise or any symptoms is reasonable to spare the radiation exposure.
Detecting and Following Metastases
When they spread outward, away from the prostate, prostate cancer cells tend to settle first locally, affecting the pelvic bone, the lower spine, and the upper thighs. Many men experience pelvic area pain as a first sign that the cancer might have spread to the bone, and aggressive management strategies are used to manage the pain, minimize the effects of the metastases, and avoid complications caused by the metastases.
For men with suspected bone metastases, or for men with advanced disease who are considered at risk for developing bone metastases, detection tools will be used to pinpoint the location of the metastases in order to better assess how to treat it.
The “gold standard” test for bone metastases is the bone scan. A radioactive substance that acts like a dye is injected in a vein, and images of the entire skeleton are taken. The dye-like material highlights areas where bone tissue is changing rapidly—a hallmark effect of prostate cancer bone metastases.
Bone scans can detect even small amounts of increased bone metabolism, but not all changes are caused by prostate cancer bone metastases. The dye might be detecting changes in the bone due to a previous fracture, infection, arthritis, or even bone loss that can result from the use of hormone therapy. A complete medical history can help doctors better assess the results of the bone scan and therefore determine the best treatment approach.
During chemotherapy, checking a bone scan and CT scan every 3-4 cycles is reasonable to assess response and the benefit of continuing chemotherapy. Interpreting these scans can be challenging, given that bone scans can sometimes look worse (ie brighter spots or new spots) even when the cancer is regressing. This is called bone scan flare, or healing, and chemotherapy should not be stopped in this situation. Your doctor may repeat these scans later to see if your cancer continues to respond, and take account of other factors, such as your pain, PSA, CT scan results, and quality of life, in determining whether to continue or stop chemotherapy. You generally should be seen by a provider every cycle during chemotherapy to assess toxicities.