Routine Use Of Sentinel Lymph Node Surgery In Patients Undergoing Prophylactic Mastectomy: A Decision Analysis Model.

607 Background: Patients with invasive carcinoma identified following prophylactic mastectomy (PM) require axillary lymph node dissection (ALND) for nodal staging as standard surgical treatment. Since most patients will be node negative, sentinel lymph node (SLN) surgery has been advocated to avoid the sequelae of unnecessary axillary surgery. However, since SLN surgery is not without complications and the incidence of invasive cancer in PM is extremely low, we sought to compare surgical strategies using a decision analysis model in order to define the true risks and benefits of routine SLN surgery versus standard surgical treatment (ALND). Methods: Model estimates were derived by systematic review of the literature. The outcomes examined were: (1) the number of SLN procedures that would need to be performed to avoid one ALND in a pathologically node negative patient; and (2) the probability of long-term axillary complications with each strategy. Occult breast cancer was defined as invasive cancer in the PM specimen and/or SLN metastases. Results: The following weighted averages were used to inform the model: i) incidence of invasive cancer in PM of 1%, ii) incidence of nodal disease of 25% in the presence of invasive breast cancer and 1% in the absence of invasive cancer in the breast, and iii) incidence of complications after ALND of 30% and after SLN surgery of 6%. Routine use of SLN surgery doubled the sensitivity for detection of carcinoma compared to ALND. However, 133 SLN procedures were required to avoid one ALND in a node negative PM patient. Additionally, the probability of complications per breast cancer detected was 10-fold greater with the SLN strategy. When the risk of breast cancer was projected at 10%, 13 SLN procedures were required to avoid one negative ALND and the complication rate per cancer detected was 2-fold greater in the SLN arm. Conclusions: The benefit of adding SLN surgery in patients undergoing PM depends on the probability of detecting invasive cancer. Routine SLN surgery in PM is not warranted given the large number of procedures required to benefit one patient and the complications associated with performing SLN surgery in all patients. However, the SLN strategy may be appropriate for subgroups of patients at higher risk of occult carcinoma. No significant financial relationships to disclose.