Performance of CT scan of abdomen and pelvis in detecting asymptomatic synchronous metastasis in breast cancer.

Background: In many centres in Australia, CT scan of abdomen and pelvis (CTAP) is a commonly used staging investigation to detect asymptomatic synchronous metastasis (ASM) in newly diagnosed breast cancer. However, its routine use is not supported by strong evidence either on its cost effectiveness or on specificity. Despite contrary recommendations by international guidelines this staging investigation is widely used among new early breast cancers(EBC). This retrospective study aims to assess the cost effectiveness and usefulness of CTAP in new breast cancers.

Materials And Methods: All patients with primary invasive breast cancers who underwent breast cancer treatment through Eastern health breast unit during 50-month period from January 2012 were included in the study. All staging CTAP results were reviewed to evaluate its yield, false positive rate and cost of investigation per single positive result. Odds ratio for positive test results were calculated for five possible risk factors (Age less than 40 years, stage III disease, presence of LVI, HER2 positive disease and presence of metastasis in lymph node).

Results: 49% (n = 285) of all breast cancer patient underwent staging CTAP which lead to the detection of 4 ASM. (Over all yield of 1%) Overall false positive rate was 15% because of 42 indeterminate results needing further tests. Based merely on approved billing rates this amounted to $ 40733 per single ASM identified. Presence of lymph node metastasis did not increase the chance of positive test result (OR = 1.3; CI:0.13-12.69).

Conclusion: Staging CTAP is associated with high incidence of false positive rates and low yield, especially among EBCs. It is desirable to choose this investigation more selectively than currently practiced.