Intermittent Letrozole Therapy in Postmenopausal Women With Metastatic Breast Cancer

Inclusion Criteria: * Female * 18 years of age or older * Postmenopausal * Histologically or cytologically confirmed adenocarcinoma of the breast with locally advanced or metastatic disease this is not considered amenable to curative treatment with elevation of CA 15-3 documented at the time of diagnosis of metastatic disease and prior to initiation of letrozole or anastrozole therapy * Current letrozole or anastrozole monotherapy with a documented CA 15-3 level that has decreased by at least 50% of the patients baseline * Letrozole or anastrozole must be discontinued at the time of study enrollment * Evidence of hormone sensitivity of primary or secondary tissue. * Measurable or nonmeasurable (but evaluable-defined as nontarget lesions) disease according to modified RECIST * Prior antiestrogen therapies including tamoxifen, steroidal AIs, nonsteroidal AIs, or fulvestrant in the adjuvant setting is allowed provided the patient is currently on letrozole or anastrozole monotherapy as first-line therapy for metastatic disease * Life expectancy of greater than 3 months * ECOG (Eastern Cooperative Oncology Group) Performance Status of 0,1, or 2 * Normal organ and marrow function as outlined in protocol Exclusion Criteria: * Premenopausal * Trastuzumab or biologic therapy within 2 weeks * Prior or planned radiation therapy to a site of evaluable disease in the event that the site is the only site of evaluable disease * Concomitant anticancer treatments including trastuzumab, che…