Abstract P6-03-05: Risk of needle-track seeding with serial ultrasound guided biopsies in triple negative breast cancer

Background: Image-guided percutaneous needle biopsy of the breast is a common procedure. In breast cancer patients (pts) undergoing core biopsies and surgical resection on the same day, the rate of tumor cell displacement along the needle track has been reported to be up to 50%. However, the clinical significance of this finding in triple negative breast cancer (TNBC) patients (pts) undergoing serial biopsies while receiving neoadjuvant chemotherapy (NACT) is unknown. Here we report the incidence of needle-track seeding (NTS) in a cohort of TNBC pts enrolled on a molecular triaging protocol involving serial biopsies of the index breast lesion.

Methods: We reviewed the clinical records of 144 consecutive TNBC pts enrolled on a molecular triaging protocol at MD Anderson Cancer Center. Per protocol, all pts underwent a pre-treatment research biopsy and were initiated on anthracycline based NACT (AC). Pts with inadequate response to front-line NACT were encouraged to undergo additional biopsies of the index breast lesion prior to switching therapies. Serial breast ultrasound (US) was performed to monitor therapeutic response and incidental evidence of needle-track seeding noted on US was documented.

Results: Clinicopathological characteristics of the pts are summarized in Table 1. 89% (128/144) of pts had a diagnostic breast biopsy done at another center prior to presenting at MDACC. To date, we have performed 209 US guided biopsies of index breast lesions in 144 pts. 92% (193/209) of these biopsies were done mainly for research purposes. 1.4% (2/144) of pts were found to have evidence of NTS on follow up US. The first pt had a T1N0 (1.9cm), grade 3, invasive ductal carcinoma (IDC) at diagnosis. She underwent a diagnostic biopsy followed by a research biopsy before initiating AC. She was found to have NTS as well as progression of disease (PD) on follow up US after 2 cycles of AC. The second pt had a T2N0 (3cm), grade 3 IDC at diagnosis. She underwent a diagnostic biopsy at another center, followed by a research biopsy before initiating AC. Like the first pt, she was found to have NTS and PD on follow up US after 2 cycles of AC. Both pts are currently on neoadjuvant clinical trials of novel agents.

Conclusion: The rate of NTS detected on US in TNBC pts undergoing serial biopsies of index breast lesions while receiving NACT is low and further studies are needed to determine the impact of serial biopsies on long term outcomes in TNBC.

Table 1: Patient CharacteristicsCharacteristicN=144Age - Median (years, interquartile range)55 (46-62)Tumor Size Mean (cm, standard deviation)3.4 (2.2)T1 – n(%)35 (24)T2 – n(%)89 (62)T3 – n(%)19 (13)T4 – n(%)1 (1)Clinical Nodal Status Negative – n(%)74 (51)Positive – n(%)70 (49)Grade 1 – n(%)1 (1)2 – n(%)17 (12)3 – n(%)124 (86)Unknown – n(%)2 (1)Histologic Subtype Invasive ductal carcinoma – n(%)121 (84)Invasive lobular carcinoma – n(%)2 (1)Mixed ductal and lobular carcinoma – n(%)3 (2)Metaplastic carcinoma – n(%)13 (9)Not specified – n(%)5 (3)Laterality Right – n(%)72 (50)Left – n(%)72 (50)

Citation Format: Yam C, Santiago L, Candelaria RP, Adrada BE, Rauch GM, Hess KR, Litton JK, Piwnica-Worms H, Mittendorf EA, Ueno NT, Lim B, Murthy RK, Damodaran S, Helgason T, Huo L, Thompson AM, Gilcrease MZ, Symmans WF, Moulder SL, Yang W. Risk of needle-track seeding with serial ultrasound guided biopsies in triple negative breast cancer [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 P6-03-05.

Abstract P3-04-11: Implications of somatic TP53 and PIK3CA mutations in patients with metastatic breast cancer who underwent germline BRCA testing

Background: TP53 and PIK3CA are the most frequently mutated genes in breast cancer. However, there is limited data evaluating the impact of somatic mutations in TP53 and/or PIK3CA patients (pts) with metastatic breast cancer (MBC) who have undergone germline testing for BRCA mutations. Here, we report the frequency of somatic TP53 and PIK3CA mutations in MBC pts who previously underwent germline BRCA (gBRCA) testing and evaluate their impact on long-term outcomes.

Methods: We identified pts with MBC from our prospectively maintained high risk genetics database who underwent gBRCA testing and had somatic mutation testing performed for TP53 and/or PIK3CA through hotspot sequencing of single genes or as part of a next generation sequencing panel. Univariable logistic regression was used to evaluate associations between clinicopathological characteristics, including gBRCA status, and the presence of somatic TP53 and PIK3CA mutations. Overall survival (OS) was defined as the time from diagnosis to death from any cause. Multivariable cox regression analysis was used to identify independent predictors of OS.

Results: 104 pts met all inclusion criteria. Somatic mutations in TP53 and PIK3CA were found in 46% (39/84) and 23% (24/104) of tested pts, respectively. Associations between clinicopathological characteristics and somatic TP53 and PIK3CA mutation status are summarized in Table 1. Pts with hormone receptor positive (HR+) disease were less likely to have TP53 mutations (odds ratio [OR]: 0.28, 95% confidence interval [CI]: 0.11-0.70, p=0.007) but more likely to harbor PIK3CA mutations (OR: 3.27, 95% CI: 1.11-9.62, p=0.031). There were no significant associations between gBRCA mutation status and somatic TP53 or PIK3CA mutations. On multivariable analysis, somatic TP53 mutations (adjusted hazard ratio [aHR]: 1.98, 95% CI: 1.10-3.58, p=0.023) and de novo metastatic disease (aHR=2.88, 95% CI: 1.26-6.58, p=0.012) independently predicted poorer OS, while HR+ disease (aHR: 0.40, 95% CI: 0.21-0.74, p=0.004) and HER2+ disease (aHR: 0.33, 95% CI: 0.13-0.83, p=0.019) were significantly associated with improved OS. PIK3CA mutations (aHR: 1.20, 95% CI: 0.59-2.44, p=0.62) and gBRCA mutations (aHR: 0.78, 95% CI: 0.33-1.83, p=0.57) did not significantly impact OS in this study.

Conclusion: In this study, somatic TP53 mutations independently predicted worse OS in pts with MBC after adjusting for significant covariates, including gBRCA mutation status. These findings should be validated in a larger cohort of pts.

Table 1: Association between patient characteristics and somatic TP53 and PIK3CA mutation status TP53  PIK3CA   TP53 mutant (n=39)TP53 wild type (n=45)p valuePIK3CA mutant (n=24)PIK3CA wild type (n=80)p valueMedian Age – years (Interquartile Range)37 (33-47)39 (36-44)0.93739 (34-46)38 (34-43)0.494gBRCA mutant – n(%)3 (8)11 (24)0.0511 (4)15 (19)0.116ER/PR positive - n(%)17 (44)33 (73)0.00719 (79)43 (54)0.031HER2 positive - n(%)8 (21)6 (13)0.3827 (29)10 (13)0.060De Novo Metastatic – n(%)6 (15)8 (18)0.7693 (13)16 (20)0.409Visceral Disease – n(%)23 (59)26 (58)0.91215 (63)47 (59)0.743

Citation Format: Yam C, Gutierrez Barrera A, Huang D, Lin X, Litton JK, Arun B. Implications of somatic TP53 and PIK3CA mutations in patients with metastatic breast cancer who underwent germline BRCA testing [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 P3-04-11.

Abstract P1-07-22: Androgen receptor positivity is associated with nodal disease in triple negative breast cancer

Background: Gene expression profiling (GEP) has identified several molecularly distinct subtypes of triple negative breast cancer (TNBC). Currently, GEP-based molecular diagnostics are not routinely used in clinical decision making due to the lack of proven benefit, costs involved and long turnaround time. However, two molecularly distinct subtypes of TNBC, the luminal androgen receptor (AR) and mesenchymal subtypes, have surrogate CLIA-certified immunohistochemical (IHC) markers, AR and vimentin (VM), respectively, which have the potential for application in the clinic. Here we report the rates of AR and VM positivity and their association with clinicopathological characteristics in a cohort of TNBC pts receiving NACT.

Methods: As part of an ongoing molecular triaging protocol, 144 pts with stage I-III TNBC underwent a pretreatment biopsy for molecular characterization (MC) prior to initiating neoadjuvant chemotherapy (NACT). IHC for AR and VM were performed using commercially available antibodies. AR+ and VM+ were defined as ≥10% and ≥50% staining, respectively. Pts were randomized 2:1 to know (intervention arm, n=93) and not know (control arm, n=51) the MC results. The charts of pts randomized to the intervention arm were reviewed. Categorical variables were analyzed using Fisher's exact test. Ordinal and continuous variables were analyzed using the Wilcoxon rank-sum test and Student's t test as appropriate.

Results: 31% (29/93) and 16% (15/93) of pts were AR+ and VM+, respectively. Only 4% (4/93) of pts were both AR+ and VM+. Clinicopathological characteristics are summarized in Table 1. AR+ pts were more likely to have clinically node positive disease as compared to AR- pts (66% vs 34%, p=0.007). There were no significant differences in clinical tumor size or grade between AR+ and AR- pts. VM+ and VM- pts had similar clinicopathological characteristics.

Conclusion: Pts with AR+ TNBC were more likely to have node positive disease. The impact of AR+ on long term outcomes should be investigated in prospective studies.

Table 1: Association between patient characteristics and AR/VM status AR  VM   AR+ (n=29)AR- (n=64)p-valueVM+ (n=15)VM- (n=78)p-valueAge - Median (years, interquartile range)58 (48-65)52 (46-61)0.05855 (48-64)56 (47-62)0.88Clinical Tumor Size      Mean (cm, standard deviation)3.5 (1.8)3.0 (1.8)0.2872.7 (1.7)3.3 (1.9)0.31T1 – n(%)5 (17)21 (33)0.2307 (47)19 (24)0.098T2 – n(%)21 (72)36 (56) 7 (47)50 (64) T3 – n(%)3 (10)7 (11) 1 (7)9 (12) Clinical Nodal Status      Negative – n(%)10 (34)42 (66)0.0078 (53)44 (56)1.00Positive – n(%)19 (66)22 (34) 7 (47)34 (44) Grade      2 – n(%)6 (21)5 (8)0.0763 (20)8 (10)0.293 – n(%)23 (79)59 (92) 12 (80)70 (90) 

Citation Format: Yam C, Huo L, Hess KR, Litton JK, Yang W, Piwnica-Worms H, Mittendorf EA, Ueno NT, Lim B, Murthy RK, Damodaran S, Helgason T, Thompson AM, Santiago L, Candelaria RP, Rauch GM, Adrada BE, Symmans WF, Gilcrease MZ, Moulder SL. Androgen receptor positivity is associated with nodal disease in triple negative breast cancer [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 P1-07-22.