Salvage radiation therapy (SRT) is a treatment option for prostate cancer. It is administered when initial therapies, such as surgery or primary radiation, do not completely eliminate the cancer or if the cancer returns.
What is Salvage Radiation Therapy?
Salvage radiation therapy is a form of external beam radiation therapy (EBRT). It is used when prostate-specific antigen (PSA) levels begin to rise following a prostatectomy, indicating a biochemical recurrence of the cancer. SRT specifically targets the prostate bed, the area where the prostate gland was located, or sometimes includes nearby lymph node tissue.
SRT aims to eradicate microscopic cancer cells that may have been left behind after the initial treatment or have reappeared locally. Unlike primary radiation therapy, which is the first treatment for newly diagnosed cancer, SRT is a “second-line” treatment. It controls localized disease and helps prevent its further spread.
When is Salvage Radiation Recommended?
Salvage radiation therapy is considered when rising PSA levels indicate biochemical recurrence after initial treatment, such as radical prostatectomy. A PSA level of 0.2 ng/mL or higher after prostate removal surgery indicates biochemical recurrence. The timing of SRT is important, with studies suggesting improved outcomes when initiated at lower PSA levels, ideally before 0.5 ng/mL.
Factors such as PSA doubling time (PSADT) and PSA velocity also influence the recommendation for SRT. A rapid PSADT, less than 6 months, indicates more aggressive disease and a higher risk of metastasis, making early intervention with SRT relevant. Conversely, a longer PSADT, such as 15 months or more, is associated with a lower risk of metastasis.
Before SRT, healthcare providers ensure there is no evidence of distant metastasis through imaging tests like a PSMA PET scan, MRI, or CT scan. PSMA PET scans can detect prostate cancer recurrence at low PSA levels, often as low as 0.2 to 0.5 ng/mL, and can help guide treatment decisions. Other factors considered include the initial Gleason score, with higher scores suggesting earlier treatment, and the status of surgical margins from the initial pathology report.
The Salvage Radiation Treatment Process
The salvage radiation treatment process begins with an initial consultation with a radiation oncologist. Next, diagnostic imaging, such as a CT or MRI scan, is performed to precisely map the treatment area. These scans help the medical team identify the prostate bed and any surrounding organs that need to be spared from radiation.
A “simulation” session positions the patient’s body to ensure consistent positioning for each treatment. Small tattoos may be placed on the skin to serve as markers for accurate targeting. This planning process ensures that the radiation dose is calculated to maximize effectiveness on the target area while minimizing exposure to healthy tissues.
Patients typically undergo daily radiation sessions five days a week, with the entire course of treatment lasting approximately four to eight weeks. Each daily session usually takes 20-40 minutes and is administered on an outpatient basis. Sometimes, hormone therapy, also known as androgen deprivation therapy (ADT), may be given in conjunction with SRT to improve treatment effectiveness, particularly in high-risk cases.
Outcomes and Potential Side Effects
The effectiveness of salvage radiation therapy in achieving biochemical control, meaning stabilizing PSA levels, varies depending on several factors. Lower PSA levels before SRT, typically below 0.5 ng/mL, are associated with better outcomes. Higher Gleason scores and a shorter PSA doubling time can also influence treatment success, as these factors may indicate more aggressive disease.
Patients undergoing SRT may experience short-term or long-term side effects. Short-term side effects often include fatigue, which can worsen as treatment progresses, and temporary irritation of the bladder and bowel. Bladder irritation may manifest as increased urinary frequency, urgency, or a burning sensation during urination, while bowel changes can include loose stools or rectal bleeding.
Long-term side effects, while less common, can include urinary incontinence, rectal bleeding, and erectile dysfunction. Urinary incontinence may range from occasional dribbling to a more significant loss of control, and urethral strictures, a narrowing of the urethra, can develop over time. Rectal issues, such as proctitis (inflammation of the rectum) and fecal leakage, are possible. Erectile dysfunction is a known side effect, and its severity can vary among individuals.
Post-treatment monitoring with regular PSA tests is standard to track the patient’s response to SRT and detect any further recurrence. These tests are typically performed every 6 to 12 months for the first five years, then annually for at least 10 years, or as determined by the healthcare team based on individual risk.