A re-evaluation of isotope screening for skeletal metastases in node-negative breast cancer.

OBJECTIVE

To determine the accuracy and cost-effectiveness of skeletal scintigraphy in women with early, node-negative (T1-2N0M0) breast cancer.

DESIGN

Retrospective, where scintigraphic prediction of metastases was compared with the criterion standard of radiological confirmation during a follow-up of 5 - 10 years.

SETTING

Tertiary referral breast clinic at Groote Schuur Hospital.

PATIENTS

Six hundred and seventy-three women with clinical T1-2N0M0 breast cancer who had skeletal scintigraphy between 1974 and 1987, and who had been followed up for more than 5 years.

INTERVENTIONS

Initial skeletal scintigraphy, annual follow-up with radiological examination of symptomatic areas.

MAIN OUTCOME MEASURES

Correlation of the sites indicated by scintigraphy with the initial presence or later development of metastases at 1 - 10 years, and the cost.

RESULTS

Five hundred and sixty-one (83.4%) scans were normal, 35 (5.2%) indicated benign processes, and 77 (11.4%) were suggestive or diagnostic of metastatic disease, with radiological confirmation in 3 (initial detection rate 3/673, 0.44%; accuracy rate 3/77, 3.9%). Of the remaining 74 abnormal scans without radiological confirmation of metastases, 62 has a focus at a single site, and 45 were of low intensity and equivocal, with no apparent explanation. The cumulative sensitivity for predicting site of metastases at 1 year was 33% (3/9) and the positive predictive value 4.0% (3/75). At 10 years the sensitivity was 5.0% (3/60) and the positive predictive value 5.0% (3/65). The total cost of screening was calculated to be R323 460.00, suggesting that the cost for each patient in whom metastases were detected was R64 629.00.

CONCLUSION

While scintigraphy may be of value in symptomatic or more advanced disease, screening of node-negative women had a minimal detection rate, was expensive and cannot be supported.