Inflammatory Breast Cancer: Clinical Characteristics and Influence of Molecular Subtypes on Treatment Response

Introduction: Inflammatory Breast Cancer (IBC) is a rare and very aggressive breast cancer with poor prognosis. The prevalence is different from a country to another. In Tunisia, it is about 5 to 7% of breast cancer. The aim of this study is to describe the epidemiological and histopathological features of patients with inflammatory breast cancer and to evaluate the treatment response according to the molecular subtypes. Methods: This retrospective review identified 31 patients with no metastatic IBC treated in our radiotherapy department between December 2019 and November 2020. IBC was confirmed using the clinical criteria. Baseline clinic-pathological and treatment information was retrieved from medical records. Statistical analysis was performed with IBM SPSS V.20. Results: Median age was 51.3 years [27-68]. 48% of tumors were grade 3. The average tumor size was 36mm [10-90]. The histological type was ductal carcinoma in 97%. Vascular invasion was noted in 24 patients (77%). Thirty patients were classified as stage IIIB and one patient was IIIC. 74% were hormone receptor positive and 45% were HER2 positive. Luminal B was the predominant subtype (52%) followed by Her2 positive (32%), Luminal A (23%), and triple negative (3%) All patients had chemotherapy: neoadjuvant for 26 patients (84%) and adjuvant for 5 patients (16%). Nine patients (29%) had tumor pathological complete response (pCR). Partial response was observed in 18 patients (58%). Lymph node pCR was noted in 16% of cases (n=5). Endocrine therapy and trastuzumab were given to 76% and 45% of patients, respectively. The influence of the molecular subtype was not statistically significant on the response to neoadjuvant treatment. The highest rate of pCR were 43% for Her2positive, then 27%, 21% and 9% for Luminal B, Luminal A and Triple negative, respectively (p=0.2). Conclusion: Our study showed a high percentage of hormone receptor and Her2+ (74% and 45% respectively) in IBC. Luminal B was the most frequent subtype. Anthracycline-based chemotherapy and trastuzumab improved the pCR rate: 44% for Her2positive. Triple negative showed poorer pCR than other breast cancer subtype without a significant difference. A larger study is warranted to confirm our findings.