Evaluating the risk of secondary cancers after internal radiation therapy in patients with prostate cancer

This study looked at the long-term risk of secondary cancers following brachytherapy (BT; internal radiation therapy) for prostate cancer. It found that treating prostate cancer with BT had a low risk of secondary cancers.

Prostate cancer is a slow-growing cancer of the prostate gland. Men with prostate cancer that has not spread outside the prostate have multiple treatment options and good outcomes. Therefore, it is important to consider long-term side effects.

Brachytherapy (BT) is a treatment for cancer which is confined to one area. During BT, a radiation source in a sealed capsule is surgically inserted at the site of the cancer. BTis given continuously, which requires fewer office visits and allows less time between treatments for cancer cells to grow.

Radiation causes genetic changes to nearby cells, which is one of the ways it kills cancer. However, these changes also increase the risk of developing a second cancer later in life. BT causes less radiation leakage to other areas of the body than external radiation therapy. It is unclear how BT affects the risk of secondary cancer.

This study included records of 241 patients with localized prostate cancer. All patients had been treated with BT. The BT used radioactive iodine-125. The patients were followed for an average of 11.4 years.

34 patients (14.1%) developed another cancer at least six months after BT. Two patients developed more than one additional cancer. These secondary cancers had not metastasized from (come from) the prostate cancer. The most common cancers were lung cancer (6 patients) and colorectal cancers (6 patients). Patients developed additional cancers at a constant rate over the 10 years after treatment.

4 patients (1.7%) developed a secondary cancer in the radiation field of the BT at least five years after treatment. These cancers were considered to be linked to the BT.

The overall 10-year survival was 66.4% for all patients. For patients who developed an additional cancer, the 10-year survival was 50%. The 10-year survival was the also 50% for patients who developed a secondary cancer in the BT radiation field.

This study found that there was a low rate of developing a secondary cancer due to radiation from BT for prostate cancer.

Cancers which developed in the pelvic area during the five years after treatment were not considered related to the BT.