Correlation of cancer antigen 15-3 (CA15-3) serum level and bony metastases in breast cancer patients

Background: Cancer antigen 15-3 (CA15-3) is a common tumor marker and the serum level of this tumor marker is evaluated during the treatment period (periodically) in breast cancer patients. Assuming that the elevated serum levels of this tumor marker can be a potential risk, this study was conducted to determine the association between CA15-3 and bone metastasis and CA15-3 and metastasis spreading rate in breast cancer patients. Methods: In this study, 70 women with the mean of age 51.69 (10.77) years who suffered from breast cancer were studied by performing both bone scintigraphy and measuring CA15-3. Independent sample t test, Fisher’s exact test, Spearman rho correlation, and logistic regression were used for inferential section. To determine the new cross section, Roc curve and coordinates of the curve were applied. Also, significance level was set at p<0.05. Data were analyzed by SPSS 16 software. Results: There was no difference among patients in age (p=0.123). Assuming the CA15-3 (≥ 30 U/mL) as a potential risk, there was no association between CA15-3 and bone metastases (p=0.167). Based on Spearman's rank correlation coefficient, there was no significant correlation between CA15-3 and metastasis spreading rate (r=-0.07, p=0.851). Based on ROC curve and Youden's J statistic index, the new cutoff was pointed at CA15-3 ≥21.76 Unit/mL, which correlated with bone metastases (p<0.001). Conclusion: This study found a decreased cutoff point at CA15-3 (≥21.76) against 30 (routine value). Based on CA15-3 (≥21.76), there was a correlation between bone metastases and CA15-3, indicating that patients with CA15-3 (≥21.76) were most likely to experience bone metastases.