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Locoregional recurrence in women with early stage triple negative breast cancer (pT1 or pT2, cN0 and pN0) treated with mastectomy and sentinel lymph node biopsy with systemic therapy without radiation: an exploratory study
Kara Button
*1, Paige Teller
3, Ian Bristol
21General Surgery , MaineHealth, Portland , ME; 2Radiation Oncology, Spectrum Healthcare Partners, South Portland, ME; 3Breast Surgery, New England Cancer Specalists, Scarborough, ME
Triple negative breast cancer (TNBC) is an aggressive type of breast cancer, associated with higher rates of metastatic disease, locoregional, and distant recurrence compared to other breast cancer types. The absence of receptor targets hinders the use of targeted systemic therapies. Its treatment can be additionally complicated by TNBC subtype heterogeneity. Current NCCN guidelines recommend treatment of early stage (stage I-IIA) TNBC with breast conserving surgery (partial mastectomy) with chemotherapy (neoadjuvant and or adjuvant) and adjuvant whole breast radiation therapy or mastectomy with chemotherapy (neoadjuvant and or adjuvant) usually omitting radiation in node negative disease. Standard guidelines generally do not recommend post-mastectomy radiation therapy (PMRT) for early-stage, node-negative TNBC patients treated with mastectomy. However, limited data exist regarding whether specific clinical or pathological features could identify subsets of these patients who might benefit from PMRT. Retrospective case series to determine the locoregional recurrence rate in women aged 18 years or older with early-stage (pT1-2, clinically node-negative) TNBC treated by mastectomy and systemic therapy within a single health system. Patients were identified through institutional cancer registries and electronic medical records. Eligibility was based on mastectomy with nodal sampling, clinically node-negative status, and triple-negative pathology. Outcomes, demographic, and clinical variables are being analyzed using descriptive statistics. Preliminary review of 63 out of 91 potentially eligible individuals identified 45 patients who met inclusion criteria. Of the 18 who did not meet inclusion criteria, 2 were excluded because they received PMRT for micro metastatic nodal disease. Among the 45 eligible patients who met inclusion criteria, 3 (0.6%) experienced locoregional recurrence along the chest wall or axilla. All 45 patients included in the study had a ductal carcinoma. Of those 3 with locoregional recurrence, 1 (33%) demonstrated a complete pathologic response to neoadjuvant therapy and 1 (33%) had a deleterious genetic mutation. All the patients identified in our study sample identified as white/Caucasian. Subgroup analysis (pT classification, margin status, EIC component, LVSI, genetic mutation, chemotherapy regimen, immunotherapy regimen) of the 2 groups is ongoing. Although a low recurrence rate (0.6%) in our small homogenous sample size appears to support the current practice of omitting PMRT in early-stage TNBC patients, the observed variability in the group highlights the need for further investigation. Well powered studies with a diverse patient population and large datasets are essential to better identify patient and tumor specific factors that increase locoregional recurrence risk, thereby elucidating subgroups that may benefit from PMRT.
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