It turned out, that the response to Ra-223-treatment could be best assessed with sodium fluoride-18 PET. The local reactions in the metastatic bone were seen in the PET studies.
However, it was not possible to predict the outcome of the therapy after the first Ra-223-therapy cycle, but after the 6th cycle. All 10 patients demonstrated at least minor skeletal response in sodium fluoride-18 PET. Also flare phenomenon was sometimes associated with early interim imaging after the first cycle.
Now, these findings have been characterized by other investigators, by introducing quantitative PET interpretation criteria . Our modified PERCIST criteria for response assessment in Ra-223-treatment are useful and simple, and can be used in the clinical routine. According to our experience Ra-223 is an essential part of treatment of metastatic castration resistant prostate cancer, if the disease is mainly in the skeleton.
Written by: Kalevi Kairemo, Docrates Cancer Center, Helsinki, Finland & MD Anderson Cancer Center, Houston, TX, USA
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