After being diagnosed with prostate cancer, many men will undergo treatment with either surgery or radiotherapy. While both of these treatments are highly effective, a cure is not guaranteed. Because of this, it’s important to have periodic PSA blood tests after prostate cancer treatment (typically every three months for the first year, every six months for years 2 and 3, and annually thereafter). PSA is a very useful marker in men who have undergone prostate cancer treatment. When PSA levels rise following prostate cancer treatment, this is called a “biochemical recurrence.”

For men who initially had radiotherapy as their primary prostate cancer treatment, their PSA level should go down after treatment, though it often doesn’t reach the undetectable levels that we see after surgery. As a result, there have been multiple efforts to define a level of PSA that can identify patients who are likely to have their disease progress and cause issues. The currently used definition is known as the Phoenix criterion for the American city where it was named. The Phoenix criterion defines biochemical recurrence after radiotherapy as a PSA level that is 2 ng/mL above the lowest level it reached after treatment (the so-called “nadir”). That is, if a patient’s PSA goes from 6ng/mL before radiotherapy to 0.4 ng/mL as the lowest level after treatment, they would have biochemical recurrence once their PSA level rises above 2.4 ng/mL.

When there is biochemical evidence of prostate cancer returning (that is, the PSA level is rising), we must distinguish between “biochemical only” recurrence (a rising PSA blood test without any evidence of cancer on physical examination or imaging tests) and “clinical” recurrence (evidence of cancer on physical examination or imaging tests). When PSA levels are low, clinical recurrence is very uncommon and many clinicians will not order imaging tests. However, increasing use of PSMA-PET imaging may allow for the identification of specific spots of disease.

For men who have received radiotherapy as their first prostate cancer treatment, salvage treatment options are not as clear-cut as for those who initially had surgery. One treatment approach is systemic therapy, using androgen deprivation therapy (ADT). A relatively recent study has shown that there may be some benefit to starting ADT early, as compared to waiting for the disease to advance. Importantly, in this setting, ADT may be used intermittently, such that after a period of time when the PSA is low/undetectable, the patient may be a candidate for a “hormone holiday” where ADT is stopped and PSA is continued to be checked every three to six months.

An alternative treatment approach is to pursue local treatments, specifically targeting the prostate. Before undertaking any local salvage treatments, it is important to ensure that the prostate cancer has not spread. This is done by repeating staging investigations. Also, most clinicians will want to repeat a prostate biopsy to better understand the cancer that remains after the initial radiation.

There are many approaches that may be done for salvage local therapy. Salvage radical prostatectomy (surgery) is a possible treatment option for selected men. However, it carries significantly higher complication risks (including urinary incontinence, erectile dysfunction, and rectal injuries) than when surgery is performed as the first treatment. Other ablative approaches may also be used including brachytherapy, cryotherapy, high-intensity focused ultrasound, and stereotactic body RT. These approaches are often relatively specialized and you may need to seek referrals and second opinions to discuss these approaches.

With the increasing use of PSMA-PET/CT and the identification of sites of disease, the option to provide targeted radiation (stereotactic body radiotherapy, SBRT) to these spots in addition to the standard salvage radiation approach is becoming more common.

In conclusion, while all men (and their doctors) hope that the first prostate cancer treatment will be the last, recurrence is not uncommon. Thankfully, there are effective treatment options. For men who have radiotherapy as their first prostate cancer treatment, salvage treatment options include androgen deprivation therapy (ADT) and local therapies such as surgery and ablation.

Zachary Klaassen, MD, MSc
Urologic Oncologist, Georgia Cancer Center, Augusta University, Augusta, GA, USA