Background, Reasons and Benefits Using the Vienna Protocol for the Treatment of Painful Bone Recurrences with ¹⁵³Samarium-EDTMP

Methods and Results

When ¹⁵³Sa-EDTMP was introduced into bone pain palliation it fast became evident that the strategy ‘the sooner, the better’ is preferable. Based upon the finding that a dose of 1 mCi/kg is not more beneficial (Table I) as compared to 0.5 mCi/kg (we generally use 30 mCi) concerning bone pain palliation (Table II) but does significantly more affect the bone marrow, in 1994 we started to treat patients according to the Vienna protocol (Table III) for the first time based on repeated treatments (Table IV) on a given schedule (3). Contraindication for the treatment is a platelet count <100.10³/μl, a white blood cell count <3.10³/μl and a red blood cell count <3.10⁶/μl, hematocrit <30% and hemoglobin <12 g/l. However, if an abnormally low blood cell count is due to bone marrow suppression by tumor cell infiltration, a beneficial response and even an increase in peripheral blood cell count after therapy has been seen (4). Platelets are most affected by ¹⁵³Sm-EDTMP treatment followed by white and red blood cells. Usually, within 3 months (mainly between weeks 10 and 12) the peripheral blood cell count almost completely returns to the pre-values.

Therapy is performed 5 times at 3-month intervals (Table V), followed by 6-, 9- and 12- month intervals with 5 treatments each. The respective treatment intervals are shortened in case of proven disease progression (scintigraphy, magnetic resonance imaging (MRI)). Blood cell count is performed 3 and 6 weeks after therapy as well as immediately before the next scheduled one. Treatment is already indicated when more than 1 bone lesion and/or bone pains exist (Table VI) on an outpatient base (Table VII).

Repeated application clearly shows benefits beyond pain palliation such as tumor marker decrease and lesion regression, as monitored and proven by various imaging techniques (scintigraphy, MRI) (5, 6) (Figure 1 A-C). Prostate-specific antigen (PSA) after a few weeks may show a temporary increase, while in the majority of the patients (71%) it decreased after 3 months. Older bone lesions show a better therapeutic response as compared to new ones appearing after first therapy (Table VIII). As yet, however, there is no individual predictor of response available. While the interindividual ¹⁵³Sm-EDTMP uptake varies greatly (~ 30% up to ~90%), the intraindividual one is rather stable (<7% deviation). Concomitant or even repeated application of biphosphonates does not significantly affect the uptake. Bone uptake does not correlate with treatment response. This indicates that pretherapeutic dosimetry is of low prospective value. A significant improvement in quality of life, pain score, Karnofsky score, WHO questionnaire results and reduction of analgesic consumption has been documented.