CHANGES IN THE MANAGEMENT OF DUCTAL CARCINOMA IN SITU BEFORE THE RELEASE OF CLINICAL PRACTICE RECOMMENDATIONS IN AUSTRALIA: THE CASE IN VICTORIA

Biology and treatment of ductal carcinomain situ

Ductal carcinoma in situ (DCIS) is responsible for 25% of screen-detected breast cancers. Various prognostic classifications are in use, including the Van Nuys Prognostic Index and the European Organisation for Research and Treatment of Cancer grading system (well, intermediate or poorly differentiated) based on cytonuclear pattern. This has been modified in screening programs to low, intermediate and high grade. In comparison with normal epithelium, DCIS has a tenfold increase in growth and 15-fold increase in apoptosis. Patients with extensive or multifocal DCIS need mastectomy and sentinel node biopsy, together with reconstruction, if requested. Microinvasion associated with DCIS is an indication for sentinel node biopsy. Randomized trials have confirmed the value of breast irradiation after wide excision, in terms of DCIS relapse and progression to invasive disease. Patients with estrogen receptor-positive DCIS benefit from adjuvant tamoxifen after breast-conserving surgery.

Nomogram for predicting the risk of local recurrence after breast-conserving surgery for ductal carcinoma in situ

PURPOSE

While the mortality associated with ductal carcinoma in situ (DCIS) is minimal, the risk of ipsilateral breast tumor recurrence (IBTR) after breast-conserving surgery (BCS) is relatively high. Radiation therapy (RT) and antiestrogen agents reduce the risk of IBTR and are considered standard treatment options after BCS. However, they have never been proven to improve survival, and in themselves carry rare but serious risks. Individualized estimation of IBTR risk would assist in decision making regarding the various treatment options for women with DCIS.

PATIENTS AND METHODS

From 1991 to 2006, 1,868 consecutive patients treated with BCS for DCIS were identified. A multivariate Cox proportional hazards model was constructed using the 1,681 in whom data were complete. Ten clinical, pathologic, and treatment variables were built into a nomogram estimating probability of IBTR at 5 and 10 years after BCS. The model was validated for discrimination and calibration using bootstrap resampling.

RESULTS

The DCIS nomogram for prediction of 5- and 10-year IBTR probabilities demonstrated good calibration and discrimination, with a concordance index of 0.704 (bootstrap corrected, 0.688) and a concordance probability estimate of 0.686. Factors with the greatest influence on risk of IBTR in the model included adjuvant RT or endocrine therapy, age, margin status, number of excisions, and treatment time period.

CONCLUSION

The DCIS nomogram integrates 10 clinicopathologic variables to provide an individualized risk estimate of IBTR in a woman with DCIS treated with BCS. This tool may assist in individual decision making regarding various treatment options and help avoid over- and undertreatment of noninvasive breast cancer.