Radiation therapy is a common and effective treatment option for prostate cancer, particularly for localized disease where the cancer has not spread beyond the prostate gland. This treatment uses high-energy beams to target and destroy cancer cells while aiming to minimize damage to surrounding healthy tissues. It serves as a primary treatment for many men.
Understanding Treatment Success
Defining “success rate” in prostate cancer treatment involves several key measures beyond simply achieving a “cure.” One common metric is biochemical recurrence-free survival, which indicates that the prostate-specific antigen (PSA) level in the blood remains low after treatment, suggesting the cancer has not returned at a detectable level. For radiation therapy, PSA levels typically decline gradually over months or even years, unlike surgery where they often drop to undetectable levels quickly.
Other important measures include overall survival, which tracks how long patients live after diagnosis, and disease-specific survival, which specifically measures survival related to prostate cancer itself. A “cure” for prostate cancer is complex; success often refers to long-term disease control and good quality of life, as some slow-growing tumors may never be life-threatening.
Key Factors Influencing Outcomes
Several patient-specific and disease-specific factors significantly influence the success rates of radiation therapy for prostate cancer. The initial prostate-specific antigen (PSA) level is a major indicator, as higher PSA levels before treatment can suggest a more advanced or aggressive cancer. The Gleason score, which assesses the aggressiveness of tumor cells based on their microscopic appearance, also plays a substantial role. A higher Gleason score indicates a more aggressive tumor with a greater likelihood of progression.
The clinical stage of the cancer, often referred to as T-stage, describes the extent to which the cancer has grown within the prostate or spread to nearby tissues. Cancer confined within the prostate (lower T-stage) generally has a better prognosis than cancer that has spread locally. The patient’s age and overall health, including the presence of other medical conditions, also influence treatment decisions and outcomes.
The specific type of radiation therapy employed can affect outcomes. External beam radiation therapy (EBRT) delivers radiation from outside the body, while brachytherapy involves placing radioactive sources directly into the prostate. Combining radiation types, such as high-dose-rate brachytherapy with external beam radiation, may offer better outcomes. The radiation dose delivered is also a factor.
Expected Success Rates
The expected success rates of radiation therapy for prostate cancer vary considerably depending on the cancer’s risk stratification. For low-risk prostate cancer, the rate of biochemical recurrence (PSA rising after treatment) is generally low, often less than 10%. This indicates a high likelihood of successful long-term control.
For intermediate-risk prostate cancer, the biochemical recurrence rate after radiation therapy typically falls between 10% and 15%. A study on intermediate-risk localized prostate cancer found a five-year disease control rate of 96% with stereotactic body radiation therapy (SBRT), compared to 95% for conventional radiation.
In cases of high-risk localized prostate cancer, the biochemical recurrence rate after radiation therapy is generally higher, ranging from 15% to 20%. For men with high-risk prostate cancer who received androgen deprivation therapy (ADT) in addition to SBRT, the estimated five-year biochemical recurrence-free survival was 81.4%, compared to 77.2% for those who did not receive ADT. Combining external beam radiation therapy with a brachytherapy boost has also shown superior biochemical control in intermediate and high-risk patients.
Monitoring After Radiation Therapy
Post-treatment surveillance is important for monitoring the success of radiation therapy. Regular prostate-specific antigen (PSA) testing is the primary method of monitoring. After radiation therapy, PSA levels typically decline slowly over several months to a few years before reaching their lowest point, known as the nadir.
A stable and low PSA level generally indicates successful treatment, while a rising PSA may suggest biochemical recurrence. Guidelines often recommend PSA testing every 6 to 12 months for the first five years, followed by annual testing thereafter.
A temporary rise in PSA, called a “PSA bounce,” can occur in the first few years after radiation therapy but does not necessarily indicate cancer recurrence. A subsequent rise of 2 ng/ml or more above the nadir, or three consecutive PSA increases, often prompts further investigation.