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Urinary n-telopeptide (NTX) predicts palliative pain response in metastatic breast cancer patients receiving second-line zoledronic acid.

679 Background: A substantial number of breast cancer patients will have bony progression or develop skeletal related events (SRE) despite treatment with a bisphosphonate (BP) such as clodronate or pamidronate. What could be of use to the practicing oncologist is a marker for predicting which patients will derive palliative benefit with the second-line use of a more potent BP such as zoledronic acid. In this study, we assessed the clinical utility of using early changes in urinary NTX as a predictor of palliative response to second-line zoledronic acid.


METHODS
30 patients with either a documented SRE or bony progression while on either clodronate or pamidronate were switched to infusions of zoledronic acid (4 mg) every 4 weeks for 12 weeks. Urinary NTX and worst pain score using the Brief Pain Inventory were evaluated weekly for the first 4 weeks & again at week 8. No change in systemic anti-cancer treatment was allowed in the month before or after commencing study treatment. A palliative response was defined as a reduction of at least two units in the worst pain score. Logistic regression analysis was used to determine if a decrease in urinary NTX at week 1 relative to baseline was a significant predictor of palliative response to zoledronic acid when measured at week 8.


RESULTS
At week 1, 23 of 30 (76.7%) had a drop in their urinary NTX excretion relative to baseline. At week 8, these 23 patients experienced a 2.4 unit decline in their worst pain score, compared to only a 0.28 unit reduction in the 7 patients whose week 1 urinary NTX increased relative to baseline (P=0.11). A week 1 drop in urinary NTX was identified as an important predictor for palliative response to zoledronic acid when measured at week 8 (OR=9.4; 95%CI: 2.28 to 79.8, P=0.014).


CONCLUSIONS
Our findings imply that a decline in urinary NTX at week 1 is a useful marker for identifying which patients will derive palliative benefits from second-line zoledronic acid. Additional data on a larger sample of patients is needed to validate the clinical utility of using early changes in urinary NTX as a rapid predictor of patient benefit. [Table: see text].