Evaluation of tartrate-resistant acid phosphatase (TRAP) as serum marker of bone resorption in irradiated bone metastases

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XXI Annual Meeting of the European Society of Therapeutic Radiology and Oncology, Vienna

K.Obert¹, A.Rahn¹, I.Breidert¹, K.Borowsky¹, C.Menzel², F.Grünwald², S.Mose¹, HD.Böttcher¹

Departments of ¹Radiation Oncology, and ²Nuclear Medicine, Johann Wolfgang Goethe University, Frankfurt/Main, Germany

Abstract

Background: The active isoform 5b of TRAP is a specific serum marker of bone resorption. It is typically expressed in osteoclasts and demonstrates low biological variation during 24 hours (±5%). In contrast to alkaline phosphatase (AP) which is a enzymatic marker of osteoblast activity, TRAP 5b is not dependent on liver and kidney function. Our ongoing study is aimed to evaluate if the determination of TRAP provides the possibility to monitor the effect of local radiotherapy in bone metastases and if TRAP will have a predictive value regarding further osseous progress.

Conclusion: In case of local response without any further osseous progress, TRAP is presumably complementary to subjective and objective pain criteria. However, because pain is influenced by therapy, it could not be expected that changes of the TRAP-level would be able to predict pain reduction.

Independent of local treatment response a stable or decreasing TRAP-level may be predictive for a stable osseous situation. Furthermore, a large increase of the TRAP-level during time of radiotherapy seems to point to a progress in the skeleton system.