Repeated low-dose vs. single high-dose 153Sm-EDTMP treatment. Advantages and disadvantages

153Sm-EDTMP has been proven to be an efficient therapeutic agent for bone pain palliation and even beyond for lesion stabilisation/regression as well as prolongation of survival. The Vienna protocol for repeated (5 times in 3-months intervals) low-dose (1,1GBq [30mCi]) treatment on an outpatient base has been developed specifically to achieve long-lasting pain palliation and beneficial curative effects beyond. Haematological conditions were compared between the conventional (single 37 MBq [1mCi]/kg) and the Vienna protocol therapy in patients suffering from prostate cancer and bone metastasis who did not receive any additional radio- and/or chemotherapeutic intervention. Vienna protocol patients (n=100; 49-93 a) vs. conventional approach (n=15; 52-81 a) were compared finally at 15 and 18 months after therapy, haematology being assessed at 3 months (conventional) and 3 weeks (Vienna protocol) intervals. Low-dose therapy causes a temporary decrease (platelets > red blood cells > white blood cells). No significant difference in pain palliation response between the two schemes was noted. Shortest duration of the palliative effect was 9 weeks with both schemes, the longest 51 weeks with the high-dose regimen. Lesion response after 18 months is significantly better using the Vienna protocol. After 15 months peripheral blood cells are comparable, after 18 months - although insignificant- even above the ones of single therapy. These findings show that beside a longer total pain free period (due to the repeated administration) and a more beneficial effect on lesion stabilisation/regression, the Vienna protocol offers also haematological advantages