Prostate specific antigen (PSA) generally tends to decline linearly after endocrine therapy for prostate cancer. This is because most prostate tumor cells respond to endocrine therapy and undergo apoptosis, leaving some insensitive cells that continue to grow, and these eventually progress to androgen-independent tumors.
So endocrine therapy is not really a cure, but rather a means of temporarily stopping tumor growth, providing patients with 3 to 5 years of effective treatment that may later progress to androgen-independent tumors.
So, an elevated PSA after endocrine therapy for prostate cancer means that the tumor has progressed to androgen non-dependent. At this point, continued endocrine therapy is no longer effective, and radiation, chemotherapy, cryotherapy, and high-energy focused ultrasound therapy can be used, as well as abiraterone in combination with prednisone to control the disease.