Stereotactic body radiotherapy in oligorecurrent prostate cancer

The authors aimed to determine the effect of tumor-directed stereotactic body radiotherapy in prostate cancer patients with oligometastases.

The authors concluded that tumor-directed stereotactic body radiotherapy was a useful treatment for both oligorecurrent and oligoprogressive castration-resistant prostate cancer. 

Oligometastatic prostate cancer is cancer that is no longer confined to the prostate gland, but that has not yet become wide-spread to surrounding organs. It is usually treatable with curative therapy. This can include prostate surgery or radiation therapy (targeting a radiation beam at the cancer site to kill cancer cells). Oligometastatic cancer can be classified into various categories, such as oligorecurrent and oligoprogressive castration-resistant prostate cancer (oligo-CRPC).

Oligorecurrent prostate cancer is when there are 1-3 tumors resulting in an increase in prostate specific antigen levels (PSA – protein elevated in the blood in the presence of cancer) following treatment. Oligo-CRPC is when tumors are found after PSA levels increase during hormone therapy (targets the male sex hormones, such as testosterone).

Tumor-directed stereotactic body radiotherapy (SBRT) targets tumors using radiotherapy from different directions. This means that the tumor receives high levels of radiation and the surrounding tissues receive low levels of radiation with minimal damage.

The aim of this study was to determine the effect of tumor-directed stereotactic body radiotherapy in prostate cancer patients with oligometastases.

141 patients were included in this study. 100 patients in group 1 had oligorecurrent cancer. 41 patients in group 2 had oligo-CRPC. 

The average follow-up time was 20.4 months in group 1. Patients underwent prostate surgery alone, radiation alone or a combination of both. The first round of SBRT was carried out in 87 patients (87%) with 1 tumor, 9 patients (9%) with 2 tumors and 4 patients (4%) with 3 tumors. The average distant progression-free survival (DPFS – time from treatment until disease progression in a distant area) was 17.7 months. DPFS at one year was 64.4%. DPFS at two years was 43%. DPFS at three years was 26.6%.  At 2 years local control (LC – the effect of treatment against local cancer) was 92.8%. Two-year overall survival (time from treatment until death from any cause) was 98.1%.

15 patients received a second round of SBRT. These patients had a hormone therapy-free survival (did not undergo hormone therapy after SBRT treatment) of 20.9 months.

The average follow-up time was 23.4 months in group 2. All group 2 patients received the first round of SBRT. The average DPFS was 11 months. DPFS at one year was 43.2%. DPFS at two years was 21.6%. 10 patients received a second round of SBRT. The average systemic treatment-free survival (STFS – time from treatment until the need for further treatment such as chemotherapy) was 22 months. Overall survival at two years was 93.3%. The LC rate at two years was 90.2%.

The authors concluded that tumor-directed stereotactic body radiotherapy was a useful treatment for both oligorecurrent and oligo-CRPC.