Importance of accurate clinical staging in patients with early stage HER2+ and triple negative breast cancer.

Abstract

e12631 Background: Comprehensive radiological evaluation in early-stage breast cancer is essential for accurate staging and subsequent therapeutic decisions. This is especially important in early-stage human epidermal receptor -2 (HER2) positive and triple negative breast cancer (TNBC). For these tumors, current guidelines suggest a neoadjuvant approach for ≥cT2 disease. Standard diagnostic modalities have oftentimes failed to confirm the correct size of these tumors. Misrepresentation of their true size may lead to patients being treated with upfront surgery and potentially missing the added benefits of residual treatment if they were later found to have >T2 disease. Methods: We conducted a retrospective analysis via electronic medical record review of a large institutional database from 2008 to 2020. We reviewed all patients with a diagnosis of early-stage breast cancer (Stage I - III) with triple negative or HER2 positive tumors. Patients who received neoadjuvant chemotherapy were excluded. Data on demographics, comorbidities, receptor status, clinical staging, pathological staging, and mortality were collected. Results: Electronic charts from 448 patients were reviewed. 153 patients had ≤cT1 disease. 33 (21.6%) of the 153 patients were upstaged from cT1 to ≥pT2 tumors. Combined imaging modality with mammogram + ultrasound (US) yielded a statistically significant accuracy in clinical staging compared to US alone (82.6 vs. 44.4%; p = 0.02). Comparisons between other imaging methods were not statistically significant (mammogram + US vs. mammogram only, 74.1 vs. 82.6%, p = 0.41 and mammogram only vs. US only, 74.1 vs. 44.4%, p = 0.13). Magnetic Resonance Imaging (MRI) was only utilized on 2 patients with 50% accuracy. Conclusions: Significant discordance (> 20%) exists between radiological staging and pathological staging of T1 TNBC and HER2 positive breast cancers at our institution. This data has considerable therapeutic implications as landmark studies such as the CREATE-X and KATHERINE trials have provided better survival data with the use of drugs such as capecitabine and trastuzumab emtansine (T-DM1), respectively, in patients with residual disease who have undergone neoadjuvant chemotherapy followed by surgery. Combined imaging with mammography and US yielded the most accurate staging. MRI was utilized on only two patients. MRI has shown to be helpful in evaluation of patients for preoperative systemic therapy, defining the extent of disease, assessing response to treatment and the potential for breast conserving surgery. Several studies have also demonstrated the accuracy of MRI for staging breast cancer. Given the significant discordance seen at our institution, one possible solution may be to employ MRI for staging on patients with inherently aggressive early-stage tumors such as TNBC and HER2+ breast cancers. Further prospective studies are required to validate our findings.