Stereotactic body radiotherapy (SBRT) for the treatment of bone metastases in oligometastasised prostate cancer

Abstract

Local radiation therapy of metastases in prostate cancer patients has become increasingly important in recent years. In order to improve the evaluation of the outcome, we have studied oligometastatic prostate cancer patients who were treated with stereotactic radiation therapy. 24 patients with a total of 30 bone metastases were included in the study. We examined the response to SBRT (biochemical and imaging), as well as progression-free survival and time to start of antihormonal therapy (aHT). The mean follow-up interval after completion of SBRT was 32.7 months (1.4 - 84 months). The SBRT was well tolerated, without acute or late adverse effects. In 16 patients, the PSA value decreased from a mean of 4.58 ng/mL (0.05 - 50.25 ng/mL) before SBRT to 1.19 ng/mL (0.01 - 8.85 ng/mL) after completion of SBRT. The mean biochemical progression-free survival of these patients was 17.6 months (0.7 - 85.0 months). Six patients received aHT, either before or during SBRT. In ten patients, the aHT was initiated after a mean interval of 20.6 months (1.8 - 85.0 months) after completion of the SBRT. Another six patients were not given any aHT during the whole period of observation. In 18 of 30 metastases, there was a decrease in PSMA expression within the area of SBRT in the PSMA-PET - in accordance with a partial functional response. In five patients, PSMA hyperexpression was unchanged; in 7 patients there was no PSMA imaging for follow up. In 17 patients, distant metastasis progression was diagnosed by imaging after a mean of 16.2 months (1.6 - 40.6 months). Three patients had a local recurrence in the prostatic fossa. SBRT of bone metastases in oligometastatic prostate carcinoma patients is an effective and well tolerated therapy and can help to achieve high local control in the area of the metastases as well as delay the start or the escalation of systemic therapy. Nevertheless, the high rate of progression of distant metastases shows how important correct patient selection is and that combination with aHT may be necessary.