From the Guidelines
Measuring type 1 collagen C-terminal telopeptide (CTX) has limited direct utility in cancer diagnosis, and its primary clinical application is monitoring bone metastasis activity in patients with established cancer, particularly breast, prostate, and lung cancers that commonly spread to bone. CTX is primarily a biomarker for bone resorption and turnover, not a specific cancer diagnostic tool. Its levels may become elevated when cancer metastasizes to bone because tumor cells can stimulate osteoclast activity, increasing bone breakdown and releasing CTX fragments into circulation. However, CTX elevation is not cancer-specific as it can also occur in non-malignant conditions with increased bone turnover such as osteoporosis, Paget's disease, hyperparathyroidism, and hyperthyroidism.
Key Points
- CTX levels can be used to monitor treatment response in patients receiving anti-resorptive therapies like bisphosphonates or denosumab, where decreasing CTX levels may indicate effective suppression of bone metastatic activity 1.
- The test involves a simple blood draw, with samples typically collected in the morning after fasting for most accurate results.
- While CTX can complement other diagnostic methods in cancer management, it should not be used alone for cancer diagnosis due to its lack of specificity.
- Serum type 1 collagen C-terminal telopeptides (CTx), B-ALP, osteocalcin and procollagen type 1 N-terminal propeptides (P1NP) have been identified as sensitive predictors of bone metastases in patients with advanced tumors 1.
Clinical Application
CTX measurement can be useful in the following clinical scenarios:
- Monitoring bone metastasis activity in patients with established cancer
- Evaluating treatment response to anti-resorptive therapies
- Identifying patients at risk of developing bone metastases or skeletal-related events (SREs) However, it is essential to consider the limitations of CTX measurement, including its lack of specificity and potential elevation in non-malignant conditions. Therefore, CTX should be used in conjunction with other diagnostic methods and clinical evaluation to guide cancer management. As noted in the most recent and highest quality study, CTX is most valuable for monitoring treatment response in patients receiving anti-resorptive therapies 1.
From the Research
Utility of Measuring Type 1 Collagen C-terminal Telopeptide (CTX) in Cancer Diagnosis
- The measurement of CTX has been found to be useful in the diagnosis and prognosis of bone metastases in patients with malignant tumors 2.
- CTX levels have been shown to be higher in patients with bone metastases, particularly in those with prostate cancer, and have been found to correlate with the number of bone metastatic sites 2.
- The utility of CTX in predicting bone metastasis has been demonstrated, with a high sensitivity and negative predictive value (NPV) reported in one study 2.
- In multiple myeloma, CTX-1 has been found to be a useful marker for predicting relapse and monitoring myeloma bone disease (MBD) 3.
- The measurement of CTX has also been found to be useful in assessing bone remodeling and has been recommended as a reference marker for bone resorption in research studies 4.
Factors Affecting CTX Measurement
- The measurement of CTX can be affected by factors such as age, gender, and renal function 3, 5, 6.
- The stability of CTX in serum and plasma samples has been found to be a concern, with significant differences in results between methods reported 5, 4.
- The use of standardized assays and collection of samples at a well-defined time of day has been recommended to minimize biological variation and ensure accurate results 5, 4.
Reference Ranges for CTX
- Reference ranges for CTX have been established for healthy individuals, with levels found to peak between 15-19 years of age and decline throughout adulthood 6.
- The establishment of reference ranges for CTX has been found to be important for the diagnosis and monitoring of bone diseases such as osteoporosis and multiple myeloma 3, 6.