Metaplastic Breast Cancer Characteristics and Patterns of Recurrence: A Single Institution Experience.
Background Metaplastic breast cancer (MtBC) is a rare type of aggressive breast cancer. MtBChas multiple pathological subtypes, including squamous,sarcomatoid, spindle,adenosquamous, and mixed metaplastic. Given the rare nature of the disease, there is limited information available on the behaviour of this cancer and no well-defined recommendations for treatment. We aim to investigate the clinicopathological characteristics ofMtBC,including overall survival and patterns of recurrence. Methods We conducted asingle-institutionretrospective review of 91 patients with MtBC who presented from 2009 to 2024. We collected patient-specific, clinicopathological, and survival data. Recurrence-free interval, medical and surgical treatment, follow-up, and time to death were also collected.Dataisdescribed with frequency counts and percentages. Product-limit survival estimates were calculated from the time from diagnosis to last follow-up or death. Results Our population consisted of 91 patients; the mean age at diagnosis was 60 years. All patients were female; the majority were Caucasian (59, 67.1%), followed by African American (24, 27.3%). Sixty-six patients (72.5%)hada BMI >25,and 69 (78.4%) were postmenopausal. MtBCwasestrogen, progesterone, and humanepidermal growth factor(Her2)negative in 82 (90.1%), 88 (96.7%), and 80 (88.9%) of the patients, respectively. Forty-five patients(49.5%) underwent alumpectomy, 41 (45.1%) amastectomy, and one (1.1%) nosurgery. Sixty-four patients (73.6%) had undergone sentinel lymph node biopsy (SLNB), 16 (18.4%) hadaxillarylymph nodedissection (ALND), three (3.4%) had targeted axillarysurgery, and four (4.6%) had no axillary surgery. Sixty-six patients(76.7%) underwent chemotherapy,of which 27 (40.9%) were in theneoadjuvant chemotherapy (NACT) setting. Of the patients who underwent NACT, seven had a completepathological response. Twoof thepathologic complete response (pCR) groupreceived Keynote-522. In ourpopulation, 29 (36.3%)patients hada recurrence, of which 12 (41.4%) haddistant recurrence,with amedian time to recurrenceof12 months. The 12-month, 36-month, and 60-month overall survival rates were 93.9% (Standard Error (SE): 2.7%), 81.3% (SE: 4.8%), and79.2% (SE: 5.1%), respectively.There wasno significant difference inthe survivalrates (p= 0.88)or recurrencerates (p=0.19)for NACT versus adjuvantcases.Subgroupanalysis comparing patients with and without recurrence who received NACT revealed no statistically significant differences in clinicopathologic featuressuch as grade, ER, PR,HER2 status,or metaplastic subtype.Moreover, 20 patientsinthis study received both chemotherapy and immunotherapy,and six (33.3%) experienced recurrences, withno significant differences in recurrence rates,recurrence pattern (p=0.40),or timing (p=0.32) between NACT and adjuvant groups. Conclusion We demonstratedthatMtBCexhibits aggressive oncologic behaviour, often with triple-negative receptor status and high Ki-67. The most common pattern ofrecurrenceis distant, mainly involving the lungs; hence, a chest tomography was essential during the one-year follow-up to detect these lesions. Seven patients (25.9%) whoreceivedNACT achieveda pCR,indicatingthatNACT can be highly beneficial for a subset of patients.Further studies investigating the effects ofNACT, especially keynote-522, in a larger population are necessary tocreate standardized treatment.
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