Abstract OT3-11-01: TK IMPACT: Treatment Monitoring of Hormone Receptor Positive (HR+), HER2 Negative (HER2-) Metastatic Breast Cancer (MBC) Patients Receiving CDK 4/6 Inhibitors (CDK4/6i) with DiviTum® Thymidine Kinase 1 Activity

Background: CDK 4/6i have altered the therapeutic landscape of HR+, HER2- MBC, improving progression free and overall survival (PFS and OS) compared to endocrine therapy (ET) alone. Despite durable responses to CDK 4/6i in a large majority of patients, treatment response monitoring in this population has historically included numerous serial blood-based and imaging studies at frequent time points. There is a growing global interest in utilizing novel non-invasive biomarker-driven disease monitoring assessments to improve patient outcomes and reduce health care costs. Thymidine kinase 1 (TK1), a key cell-cycle regulated enzyme important for nucleotide metabolism during DNA synthesis, is regulated by the E2F pathway, downstream of CDK 4/6. Studies have shown that DiviTum® TK1 activity (TKa) may serve as both a prognostic and predictive biomarker of CDK 4/6i treatment response (McCartney et al, Clin Canc Res, 2020; Malorni et al, Eur J Cancer, 2022; Bagegni et al, Breast Cancer Res, 2017). Early TKa suppression within 2 weeks (wk) post CDK 4/6i therapy initiation is associated with improved PFS, suggesting a subgroup of patients who may be able to de-escalate imaging frequency. Elevated TKa at baseline and post CDK 4/6i may identify patients with CDK 4/6i-resistant disease and disease progression (PD) requiring early therapy modification. TK IMPACT is a prospective, single-arm trial designed to assess the impact of incorporation of DiviTum® TKa on a physician’s decision regarding subsequent timing of routine disease monitoring modalities in patients with advanced HR+, HER2- MBC receiving ET plus CDK 4/6i (NCT04968964). Methods: Blood sample collections will be analyzed using DiviTum® TKa at baseline (bl), wk 2, 4, 6, 8, and Q 4 wks thereafter beginning at wk 8 during the first 24-wk time period of study enrollment (+/- 3 days); followed by Q 12 wks thereafter, until PD or 36 months, whichever occurs first. Optional repeat TKa within 2-4 wks (+/-3 days) is permitted in case of rising TKa. Research blood (bl, wk 2, 12, 24, 48, and PD) and optional archival tumor tissue collection at diagnosis and PD will be obtained for correlatives. The investigator will record intended imaging modalities and timing prior to receipt of TKa, followed by documentation of any changes in imaging testing interval after receipt of TKa. Key eligibility criteria include postmenopausal women age ≥18 years with HR+, HER2- MBC, to initiate (Cohort 1) or are currently receiving (≤24 months, Cohort 2) any FDA approved first line ET plus CDK 4/6i with a life expectancy > 6 months. The primary endpoint is any physician-reported intended change in imaging testing interval post TKa by study cohort, within the first 48-wk period of study participation. Key secondary endpoints are concordance rate between TKa values and progression status at first on-study imaging and longitudinal TKa dynamics. Key exploratory endpoints include plasma and tumor tissue-based biomarkers of CDK 4/6i response and resistance. A total of 40 patients will be enrolled (n=20/Cohort). The expected change rate is 20% with a 95% Wilson confidence interval of 0.105~0.248 across all patients and if within each cohort, with a 95% Wilson confidence interval of 0.081~0.416 for N=20. N=40 allows the lower limit of the 95% CI > 10% and that of the N=20 in Cohort 1 to be ~10%, indicating some clinically meaningful influence of TKa progression on patient management. The study is open to accrual and has presently enrolled 5 patients.

Citation Format: Nusayba A. Bagegni, Isabella Grigsby, Leslie Nehring, Jingqin Luo, Jennifer Powers Carson, David W. Gibson, Meghan Horvath, Katherine K. Clifton, Foluso O. Ademuyiwa, Rama Suresh, Ashley Frith, Andrew A. Davis, Lindsay L. Peterson, Ron Bose, Amy Williams, Mattias Bergqvist, Cynthia Ma. TK IMPACT: Treatment Monitoring of Hormone Receptor Positive (HR+), HER2 Negative (HER2-) Metastatic Breast Cancer (MBC) Patients Receiving CDK 4/6 Inhibitors (CDK4/6i) with DiviTum® Thymidine Kinase 1 Activity [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-11-01.

Early Assessment Window for Predicting Breast Cancer Neoadjuvant Therapy using Biomarkers, Ultrasound, and Diffuse Optical Tomography

PURPOSE

The purpose of the study was to assess the utility of tumor biomarkers, ultrasound (US) and US-guided diffuse optical tomography (DOT) in early prediction of breast cancer response to neoadjuvant therapy (NAT).

METHODS

This prospective HIPAA compliant study was approved by the institutional review board. Forty one patients were imaged with US and US-guided DOT prior to NAT, at completion of the first three treatment cycles, and prior to definitive surgery from February 2017 to January 2020. Miller-Payne grading was used to assess pathologic response. Receiver operating characteristic curves (ROCs) were derived from logistic regression using independent variables, including: tumor biomarkers, US maximum diameter, percentage reduction of the diameter (%US), pretreatment maximum total hemoglobin concentration (HbT) and percentage reduction in HbT (%HbT) at different treatment time points. Resulting ROCs were compared using area under the curve (AUC). Statistical significance was tested using two-sided two-sample student t-test with P < 0.05 considered statistically significant. Logistic regression was used for ROC analysis.

RESULTS

Thirty-eight patients (mean age = 47, range 24-71 years) successfully completed the study, including 15 HER2 + of which 11 were ER + ; 12 ER + or PR + /HER2-, and 11 triple negative. The combination of HER2 and ER biomarkers, %HbT at the end of cycle 1 (EOC1) and %US (EOC1) provided the best early prediction, AUC = 0.941 (95% CI 0.869-1.0). Similarly an AUC of 0.910 (95% CI 0.810-1.0) with %US (EOC1) and %HbT (EOC1) can be achieved independent of HER2 and ER status. The most accurate prediction, AUC = 0.974 (95% CI 0.933-1.0), was achieved with %US at EOC1 and %HbT (EOC3) independent of biomarker status.

CONCLUSION

The combined use of tumor HER2 and ER status, US, and US-guided DOT may provide accurate prediction of NAT response as early as the completion of the first treatment cycle.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02891681. https://clinicaltrials.gov/ct2/show/NCT02891681 , Registration time: September 7, 2016.

Abstract PS18-07: Association between pathological response and tumor genomic profiling in triple negative breast cancer patients treated with neoadjuvant chemotherapy

Background: Triple negative breast cancer (TNBC) has a marked molecular diversity that promotes clinical heterogeneity. Less than 40% of TNBC patients will achieve a pathological complete response (pCR) to standard neoadjuvant chemotherapy. Patients who do not achieve pCR have a high risk of disease recurrence and subsequent death from breast cancer. Molecular characterization may identify TNBC patients unlikely to achieve pCR and subsequently develop recurrent disease. Methods: We are conducting a multicenter prospective study of clinical stages II and III TNBC patients treated with neoadjuvant docetaxel and carboplatin. We performed tumor whole exome sequencing on 56 patients pre-treatment samples to identify somatic mutation associated with pCR. Thirteen matching samples from cycle 1 day 3 (C1D3) were also analyzed to assess changes in somatic mutation profiles. Results: In this biomarker study, thirty-seven (66.1%) patients are Caucasians, 17 (30.4%) African American. Nineteen (33.9%) achieved pCR following six cycles of neoadjuvant docetaxel and carboplatin. 9063 variants were detected in 5386 unique genes. The overall mutation burden for patients who achieved pCR was not significantly different from non-pCR patients (median of 80 variants, IQR 51-135 in pCR, vs median 72, IQR 44-102 in non-pCR, Wilcoxon rank sum test p=0.78). As expected, TP53 is the most frequently mutated gene observed in 48 of all 56 patients (85.7%). There was a non-significant trend with lower TP53 mutations occurring in 78.9% of patients with pCR, versus 89.2% of non-pCR patients (OR 0.46, 95% CI 0.07 - 2.83; p value 0.42). BRCA2 somatic mutations were observed in 5.4% and 5.3% of pCR and non-pCR samples, respectively. No BRCA1 somatic mutations were identified. EGFR, RAD51AP2, SDK2, L1CAM, KPRP, CACNA1S, CFAP58, COL22A1, and COL4A5 were differentially mutated and almost exclusively found in pCR samples. PCDHA1 and TRMT9B were observed in 18.9% and 16.2%, respectively, of non-pCR samples only. There was a trend of higher variant counts in the thirteen matched samples at C1D3 (median of 82, IQR 49-157) versus corresponding pre-treatment samples (median of 72, IQR 42-92), Wilcoxon rank sum test p=0.29, suggesting clone emergence under treatment pressure. Using the Molecular Signatures Database v7.1, several gene families involved in immune related pathways showed differences between pCR and non-pCR samples. Additionally, borderline differences in hedgehog signaling pathway were identified between pCR and non-pCR samples. There were no differences in apoptosis, DNA repair, EMT, inflammatory response, NOTCH signaling pathways. Conclusion: Across TNBC tumors analyzed, TP53 mutation frequency does not differ in pCR versus non-pCR patients. Somatic mutations in EGFR, RAD51AP2, immune pathways genes, and hedgehog signaling pathway genes may predict pCR to docetaxel and carboplatin chemotherapy.

Citation Format: Foluso O Ademuyiwa, Jingqin Luo, Bryan Fisk, Gejae Jeffers, Tracy Summa, Isabella Grigsby, Mothaffar Rimawi, Meenakshi Anurag, Matthew Ellis, Obi Griffith, Malachi Griffith. Association between pathological response and tumor genomic profiling in triple negative breast cancer patients treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS18-07.