Abstract P3-04-01: Molecular determinants of post-mastectomy breast cancer recurrence

Introduction

The management of breast cancer (BC) patients who undergo mastectomy in the setting of 1-3 positive lymph nodes has been controversial. This retrospective Translational Breast Cancer Research Consortium study evaluated the molecular aberrations associated with locoregional recurrence (LRR) or distant metastasis (DM) compared to controls in an effort to identify molecular predictors associated with recurrence.

Methods/Materials

We identified 115 HER2 negative, therapy naïve, T 1-3 and N 0-1 BC patients treated with mastectomy and no post mastectomy radiation therapy from 1997 to present with available FFPE tissue blocks. The cohort included 32 patients with LRR, 34 with DM, and 49 controls (without recurrence) who were matched for stage, grade, hormone receptor status, age ≤ or > 50, chemotherapy receipt, and margin status. Matched primary and recurrent LRR samples were available for 3 patients. Hybrid capture next generation sequencing (NGS) of 142 cancer related genes and RNAseq were performed to identify DNA/RNA alterations associated with LRR or DM. The frequency of common alterations on NGS was compared with Fisher's exact test. Expression of each gene from mRNA-Seq was treated as an explanatory variable. Immunohistochemistry (IHC) was performed for PTEN, Ki-67 and cleaved caspase 3 (CC3). PTEN loss and percentage of Ki-67 and CC3 positive cells were compared between groups with Fisher's exact test and nonparametric methods, respectively.

Results

RNAseq was performed on 115 patients; there was no difference in RNA expression levels between the groups. DNA analysis was performed on 57 patients (17 LRR, 15 DM and 25 controls), NF1 mutation rate was significantly elevated in both the LRR (24%) and DM (27%) samples compared to controls 0%; (p=0.0070). The mitogen activated protein kinase (MAPK) pathway was significantly mutated in both LRR (47%) and DM (40%) samples compared to the controls 0%; (p<0.0001). There was no significant difference in the rate of alterations of the PI3K/Akt/mTOR pathway among the three groups. Of three patients with matched primary vs LRR samples, one had concordant mutations. The second patient had additional mutations in the LRR, including gain of a NF1 mutation. The third patient had complete discordance of mutations identified in primary and LRR and had gain of HER2 amplification, suggestive of a new primary. There was no significant association between the groups and the loss of PTEN expression or CC3 expression. There was a significant difference between Ki 67 positive cells in patients with LRR (mean 29%), DM (mean 26%) versus controls (mean 14%, p= 0.0011). HR+ patients were significantly more likely to have a positive PTEN, lower Ki-67 and lower CC3 expression, p=0.0004, p<0.0001, and p<0.0001 respectively.

Conclusions

In this matched cohort analysis, mutations in the MAPK pathway, specifically NF1, were associated with both LRR and DM, suggesting that alterations in this pathway are associated with a more aggressive tumor phenotype. However, there were no molecular features that discriminated between those likely to recur locally alone versus distantly. Further study is needed to validate these findings, and to determine whether targeting alterations in this pathway could decrease the risk of recurrence.

Citation Format: Keene KS, King T, Hwang ES, Peng B, McGuire K, Tapia C, Zhang H, Bae S, Nakhlis F, Klauber-Demore N, Meszoely I, Sabel MS, Willey SC, Eterovic KA, Hudis C, Wolff A, De Los Santos J, Thompson A, Mills GB, Meric-Bernstam F. Molecular determinants of post-mastectomy breast cancer recurrence [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-04-01.

Evaluating feasibility of an automated 3-dimensional scanner using Raman spectroscopy for intraoperative breast margin assessment

Breast conserving surgery is the preferred treatment for women diagnosed with early stage invasive breast cancer. To ensure successful breast conserving surgeries, efficient tumour margin resection is required for minimizing tumour recurrence. Currently surgeons rely on touch preparation cytology or frozen section analysis to assess tumour margin status intraoperatively. These techniques have suboptimal accuracy and are time-consuming. Tumour margin status is eventually confirmed using postoperative histopathology that takes several days. Thus, there is a need for a real-time, accurate, automated guidance tool that can be used during tumour resection intraoperatively to assure complete tumour removal in a single procedure. In this paper, we evaluate feasibility of a 3-dimensional scanner that relies on Raman Spectroscopy to assess the entire margins of a resected specimen within clinically feasible time. We initially tested this device on a phantom sample that simulated positive tumour margins. This device first scans the margins of the sample and then depicts the margin status in relation to an automatically reconstructed image of the phantom sample. The device was further investigated on breast tissues excised from prophylactic mastectomy specimens. Our findings demonstrate immense potential of this device for automated breast tumour margin assessment to minimise repeat invasive surgeries.

P2-08-02: Magnetic Resonance Imaging as a Predictor of Pathologic Response in Patients Treated with Neoadjuvant Systemic Treatment for Operable Breast Cancer (TBCRC 017)

Background: Increased pathologic complete response (pCR) rates observed with neoadjuvant chemotherapy for invasive breast cancer has prompted interest in whether patients with pCR can be identified preoperatively and potentially spared the morbidity of surgery. This multicenter retrospective study was performed to determine the accuracy of preoperative MRI in predicting pCR in the breast and whether MRI performance differs by molecular subtype, histology, and treatment regimen.

Methods: 770 women from 8 institutions were retrospectively identified as having received neoadjuvant systemic therapy with MRI obtained at baseline and after completion of systemic treatment. Tumor phenotypes were defined on the basis of estrogen and progesterone receptor (ER/PR or HR) and HER2 receptor status. Univariate and multivariate analyses of factors influencing radiographic complete response (rCR) and pCR were recorded, with rCR defined as resolution of any abnormal enhancement, mass, or distortion on MRI, and pCR defined as resolution of both invasive disease and DCIS.

Results: rCR and pCR for the total group were 182/746 (24%) and 179/746 (24%), respectively, with the highest rate of pCR seen among the triple-negative (TN; 57/155; 37%) and HR-/HER2+ (38/101; 38%) subtypes. Covariates significantly associated with rCR included T stage (p=0.0002), tumor grade (p=0.005), IHC phenotype (p=0.005), and chemotherapy regimen (p<0.0001). On multivariate analysis, only tumor phenotype was independently associated with likelihood of rCR, with both TN (OR = 2.00, 95% CI 1.20−3.33) and HR-HER2+ (OR=2.30, 95% CI 1.09–4.83) more likely to achieve rCR than HR+HER- (reference group). Overall accuracy of MRI for prediction of pCR was 74%. Sensitivity, NPV, PPV, and accuracy differed significantly among tumor subtypes, with the greatest NPV in the HR-/HER2+ and TN subtypes (table1). Among patients with rCR, ER- status (OR=6.4, 95% CI 1.1 to 35.6), PR- status (OR=3.8, 95% CI 1.2 to 11.4), and tumor grade of 3 vs 1 or 2 (OR=2.49, 95% CI 1.22−5.07) were independently associated with likelihood of pCR. Discussion: MRI performance for predicting pCR in patients with invasive breast cancer receiving neoadjuvant systemic therapy differed significantly among breast cancer subtypes; however this difference is likely due to subtype differences in frequency of pCR and not to intrinsically better or worse MRI detection. The relatively low NPV of MRI following neoadjuvant systemic therapy does not support using MRI rCR alone to accurately identify those patients that can safely avoid surgery.

Aortoiliac occlusive disease and gastrointestinal malignancy: changing therapeutic options

Treatment of gastrointestinal malignancy encountered unexpectedly during procedures involving the abdominal aorta continues to be debated. Previously, simultaneous vascular procedures with intra-abdominal malignancy were rare. Most underwent vascular reconstruction followed by a delayed aortic procedure. With recent improvement in axillobifemoral graft patency, a one-stage procedure for aortoiliac disease should be entertained. We recently encountered a small bowel lymphoma while beginning an aortic replacement for aortic occlusion. Resection of a near-obstructing small bowel tumor immediately after axillofemoral reconstruction provided treatment of both entities at one time. Since the early description of axillofemoral bypass in 1963, varying success with extra-anatomic bypass has been reported. Early data for axillofemoral bypass were dismal, but with recent technical and graft improvements patency has been improved. Occult malignancy during aortic procedures is uncommon, about 2 to 4 per cent, but when met is usually dealt with after the patient recovers from the vascular procedure. With improvements in extra-anatomic bypass results, a single operative period can be entertained.

Hypothalamic Na(+)-K(+)-ATPase inhibitor characterized in two-sided liposomes containing pure renal Na(+)-K(+)-ATPase

The functional characterization of putative endogenous inhibitors of the Na(+)-K(+)-ATPase has been greatly hindered by spare amounts extractable from biological sources. We therefore used a miniaturized, two-sided test system consisting of ATP-filled liposomes containing dispersed, randomly oriented renal Na(+)-K(+)-ATPase molecules to study effects of a low-molecular-weight, nonpeptidic Na(+)-K(+)-ATPase inhibitor extracted from bovine hypothalamus. With this test system, Na(+)-K(+)-ATPase inhibition produced by a single dose of 0.1 U (congruent to 75 fmol) of the hypothalamic inhibitory factor (HIF) as well as the membrane permeation of a single unit (approximately equal to 750 fmol) became measurable, and an estimation of the minimal number of HIF molecules per unit could be made. By a molecular mechanism involving positive cooperativity, HIF potently and completely blocked active 86Rb+ transport catalyzed by the right-side-out-oriented pump population, with an average 50% inhibitory concentration of 3.5 x 10(-8) M, indicating a roughly 30-fold higher apparent affinity than ouabain. By studying inhibition of the inside-out-oriented pump population, comparison of the membrane permeability of HIF to that of various cardiac glycosides of known hydrophobicity further indicated that HIF is not entirely ouabain-like as HIF penetrates the liposomal membrane, whereas ouabain does not. Besides the cardiac glycosides, HIF is the only compound tested thus far in the purified system that displays such striking transport inhibition. Other known or proposed endogenous Na(+)-K(+)-ATPase inhibitors, including unsaturated fatty acids, palytoxin, dehydroepiandrosterone, and vanadate, produce only partial transport inhibition even at high concentration.