It is possible that prostate cancer may progress after a while, even when it has been treated with hormone therapy. This is because the cancer cells can regrow and adapt to the change in the testosterone level. The cancer is then referred to as castrate resistant (or sometimes hormone refractory) because the cancer can progress without a normal level of testosterone in the body. New generation hormonal therapies are constantly being developed, which may still work even with a rising PSA with low testosterone. 

The types of treatment available when this happens depend on what treatments you previously had, your symptoms, and how the cancer is progressing. Although one type of hormone therapy may have stopped being effective for you, a different combination of hormone therapy could stop the cancer from progressing. Some treatments control the cancer while others control the symptoms, and some do both. The best treatment at this point is the one that suits your needs and situation.