Significant pain relief with loading dose zoledronic acid in bone metastases is only seen in patients with elevated initial serum C telopeptide (CTX).

In symptomatic bone metastases with significant pain, refractory to standard analgesics and radiotherapy, loading dose zoledronic acid (ZA) represents a simple and nontoxic treatment to obtain significant pain relief in a very short time. Its analgesic effect is limited to patients with massive osteoclast activation with high initial serum C-telopeptide (CTX). The pain reduction is proportionally correlated with the reduction of CTX.