Differences in metastatic potential in HER2 positive and triple negative inflammatory breast cancer

Abstract

Background: Inflammatory breast cancer (IBC) presents the most aggressive form of breast cancer with high metastatic potential. It is initially inoperable form of BC, so the standard treatment is induction chemotherapy (iCT) but is known by low rate of complete remission (CR). High incidence of HER2 positivity has been reported, up to 38%. The aim of this retrospective analysis is to evaluate the metastatic potential, comparatively in groups of HER2 positive (HER2+) and triple negative (TN) IBC patients. Methods: We evaluated 84 medical records of female patients with diagnosed IBC, without distant metastases, registered at Institute for oncology and radiology of Serbia, in period 2008- 2010. IBC is defined as BC with typical clinical signs of cancer-mastitis, with or without pathologically confirmed dermal lymphatic invasion (DLI) and with or without underlying tumor. Responses to iCT have been evaluated clinically and by mammography after 4 cycles of iCT and depending of the registered response, treatment was continued, changed to second line CT or complemented with radiotherapy or surgery. In follow-up period (median 23 months, range 4-42), all first metastatic sites were recorded. Time to progression was calculated from date of diagnosis to date of relapse. Results: The incidence of HER2+ IBC was 47,6% (40/84 patients) and TN IBC 20,2% (17/84 patients). Median age at diagnosis was 57,6 and 54,8 years, respectively. DLI was confirmed in 19/40 patients (47,5%) of HER2+ and 3/17 (17,6%) of TN patients. Response rate (RR) to iCT was observed in 77,5% (31/40 patients) of HER2+ and 70,6% (12/17) of TN patients. In HER2+ group, 9/40 patients (22,5%) experienced disease progression (PD), with average time to progression 14,7 months. Even 4/40 patients (10%) developed CNS metastases. Other metastatic sites were: local recurrence, bones and lung, detected in 2 patients each, and contralateral breast in one patient. Two patients died (5%). In TN group, 7/17 patients (41,2%) had PD, with average time to progression 12,5 months. Most common were liver metastasis, seen in 4 patients (23,5%), local recurrence was seen in 3 patients while lung and CNS were affected in one patient each. Three patients died (17,6%). Conclusion: In this study we showed that triple negative is more aggressive form of inflammatory breast cancer than HER2+ IBC, with lower response rate to iCT, shorter time to disease progression and higher mortality. Interestingly, patients with HER2+ IBC have higher chance to develop CNS metastases. Although the number of patients analyzed in this paper is relatively small and follow up is quite short, we are strongly convinced that this analysis can contribute to the knowledge about IBC at least in the term of its metastatic potential.