Ductal carcinoma in situ (DCIS) of the breast is a pre-malignant lesion of the breast, which is associated with a marked increase in the likelihood of developing invasive breast cancer. Since DCIS tends to be associated with microcalcifications, it is detected with an increased frequency in patients being screened with mammographic techniques. The treatment of DCIS is based on a number of parameters; local treatment depends on the size of the lesion, grade and margins. The only systemic treatment currently available is in the form of endocrine therapy; it depends on the expression of estrogen receptor (ER). Randomized trials have shown that the treatment of DCIS with breast conserving therapy and radiation is as effective as simple mastectomy.~The efficacy of tamoxifen in reducing the incidence of further invasive or non-invasive breast cancer has been established. In addition to surgery (with or without radiation), patients with ER positive disease also receive anti-estrogen therapy. Current guidelines do not recommend any additional therapy for ER-negative DCIS.~The rationale for the proposed study is based on the observations that HER2 is expressed at high levels in higher grades of DCIS, which typically lack ER. In addition, an inverse relationship between ER expression and the expression of EGFR has also been demonstrated. Lapatinib is active against both these receptors and may have therapeutic action in ER negative DCIS.~We propose to treat the patients with drug in the interval between biopsy diagnosis and definitive surgery.
The purpose of this study is to establish the utility of lapatinib in the treatment of DCIS, particularly ER-negative DCIS.