Which isotope is commonly used for LDR brachytherapy to treat prostate cancer?

I-125 is commonly used for low-dose-rate (LDR) brachytherapy to treat prostate cancer due to its favorable physical and biological properties. This isotope emits low-energy gamma radiation, which allows for a localized treatment effect while minimizing damage to surrounding healthy tissue. The half-life of I-125 is approximately 60 days, providing a prolonged dose delivery that aligns well with the goals of LDR brachytherapy, where seeds are implanted directly into the prostate.

In the context of prostate cancer treatment, the use of I-125 allows for precise targeting of the tumor, leading to effective management of the cancer while preserving quality of life for the patient. The biological result of this treatment includes a gradual decrease in tumor size and control of disease progression over time.

The isotopes mentioned in the other options—Cs-137, Ir-192, and I-131—are typically used for different purposes. Cs-137 has been used in some brachytherapy applications but is less common for prostate cancer specifically compared to I-125. Ir-192 is more commonly associated with high-dose-rate (HDR) brachytherapy due to its shorter half-life and higher energy output, which makes it unsuitable for the LDR approach where prolonged, low-dose