Efficacy of samarium 153 and strontium 89 treatment for bone metastases in prostate cancer patients: monotherapy vs. treatment combined with external beam radiotherapy. Preliminary report

SummaryBackgroundApproximately 60–80% of metastatic prostate cancer patients suffer from pain caused by bone metastases. Bone metastases have a negative impact on patient performance status.AimThe aim of study was to compare the efficacy of treatment with strontium 89 or samarium 153 in monotherapy vs. radioisotope treatment combined with external beam radiotherapy (EBRT) in prostate cancer patients with bone metastases.Materials/MethodsWe retrospectively analyzed one hundred (n=100) metastatic prostate cancer patients aged between 53 and 84 years, who we divided into four treatment groups: 30 pts received Sr-89 monotherapy; 30 patients received Sm-153 monotherapy; 20 pts received Sr-89 combined with EBRT; and 20 pts received Sm-153 combined with EBRT. Follow-up was 4 months. All patients prior to therapy had their bone metastases confirmed by bone scan examination. Pathologic fractures were excluded and the nature of metastases (osteoblastic/mixed) was evaluated with X-ray films and/or CT and/or MRI. Sr-89 therapy consisted of a standard dose of 150MBq, while Sm-153 was administered proportionally to body weight (37MBq/kg). In combined treatment groups EBRT was given to the dominant metastatic site with 8Gy in one fraction or 20Gy in five daily fractions. Treatment efficacy was determined by change in pain intensity evaluated according to visual analogue scale (VAS), changes in Karnofsky performance status (KPS) and in the use of analgesics.ResultsComplete pain relief (VAS<3) was observed in 33% and 40% of patients in Sr-89 and Sm-153 monotherapy groups and in 50% and 60% of patients treated with Sr-89 and Sm-153 therapy combined with EBRT, respectively. Unsatisfactory response to treatment (VAS>5) was noted in 20% of patients in both monotherapy groups and in 10% and 15% of patients in Sm-153 and Sr-89 combined with EBRT, respectively. Decrease in pain intensity and in the use of analgesics as well as improvement in performance status were statistically significant for combined therapy vs. monotherapy (p<0.05). Treatment was well tolerated, with 3 patients suffering from severe pancytopenia and 22 patients with mild leucopenia and/or thrombocytopenia.ConclusionsRadioisotope therapy with Sr-89 or Sm-153 combined with external beam radiotherapy in comparison with radioisotope monotherapy improves efficacy of treatment. Treatment toxicity is low.