Baseline staging tests for breast cancer

The Breast Cancer Disease Site Group of the Cancer Care Ontario Practice Guidelines Initiative has published their recommendations for baseline staging tests in breast cancer.1 I wish to take issue with the recommendation that ultrasonography of the liver be done routinely in patients with stage III breast cancer. The authors suggest that a test that detects metastases in more than 1% of patients is clinically useful and therefore that ultrasonography should be used in this group of patients; however, in their Table 3 the 95% confidence interval for the percentage of patients with stage III cancer who had a positive result with liver ultrasonography ranges from 0.4% to 3.6%.

The papers that they quote do not support the routine use of liver ultrasonography. In the largest study, which is twice as large as all other studies combined, only 28% of patients with stage III cancer were sent for liver ultrasonography.2 This low compliance rate suggests that there may well have been selection biases. The detection rate was 0% in patients with stage IIIA cancer and 0.85% in those with stage IIIB cancer. Furthermore, ultrasonography had a positive predictive value of only 33%, indicating that it represents an expensive wild goose chase 2 out of 3 times.

In another paper referenced by the authors there was only 1 positive liver ultrasound in 24 patients with stage III cancer.3 The authors of this paper suggested that ultrasound should be abandoned in this group of patients.

If the incidence of asymptomatic liver metastases in patients with stage III breast cancer is 1–2%, then approximately $30 000 will be spent in ultrasonography to find 1 case of liver metastasis. Because the patient would probably receive some form of chemotherapy anyway and there would be little if any effect on the patient's life expectancy, there would be no cost saving to the system of any substance and no effect on mortality. Surely, then, routine staging ultrasonography cannot be justified in this group of patients.