Abstract P2-13-21: Improved central nervous system outcomes in patients with early-stage HER2-positive breast cancer who receive neratinib for the recommended duration: Findings from the phase 3 ExteNET trial

Background: Non-adherence or early discontinuation from systemic adjuvant therapy is associated with an increased risk of disease recurrence and mortality. In the phase 3 ExteNET trial, neratinib (NERLYNX®), an oral irreversible pan-HER tyrosine kinase inhibitor, significantly improved invasive disease-free survival (iDFS) when given for 12 months in patients with early-stage HER2-positive (HER2+) breast cancer after trastuzumab-based therapy. Anti-diarrheal prophylaxis was not mandated by protocol and 17% of patients discontinued neratinib early because of diarrhea. Improved iDFS, distant disease-free survival, and overall survival (OS) have since been reported in patients who completed the planned duration of neratinib therapy compared with all randomized patients [ASCO 2021]. Here we assess central nervous system disease-free survival (CNS-DFS) in 3 discrete groups of patients who completed planned therapy with neratinib in ExteNET: intent-to-treat (ITT) population; patients with hormone receptor-positive disease who initiated neratinib within 1 year after prior trastuzumab (HR+/≤1 year, the population for which neratinib is approved in the EU); and HR+/≤1 year with residual disease post-neoadjuvant therapy (i.e. no pathologic complete response [pCR]). Methods: Patients with early-stage HER2+ breast cancer received oral neratinib 240 mg/day or placebo after trastuzumab-based (neo)adjuvant therapy for 12 months. Patients who completed neratinib therapy (defined as treatment duration ≥11 months or cessation of neratinib if recurrence occurred prior to 11 months) were compared with placebo (all randomized patients). CNS-DFS was defined as time from randomization to any CNS recurrence or death from any cause (exploratory endpoint). Kaplan-Meier methods were used to estimate CNS-DFS and OS rates. Hazard ratios (HR) with 95% confidence intervals (CI) for neratinib versus placebo were estimated using a Cox proportional hazards model. Data cutoffs: March 2017 (CNS-DFS); July 2019 (OS); median follow-up 8.0 (range 0-9.8) years. Results: 2840 patients were included in the ITT population (1420 per group). Among patients who completed neratinib therapy, CNS-DFS was improved versus placebo in each of the 3 patient groups (see Table). For CNS-DFS, the magnitude of effect of neratinib versus placebo was consistently greater in patients who completed neratinib therapy than in the corresponding overall randomized patient group: ITT HR, 0.70 vs 0.73; HR+/≤1 year HR, 0.27 vs 0.41; HR+/≤ 1 year no pCR HR: 0.16 vs 0.24, respectively.

Conclusions: These descriptive findings suggest that, in addition to improved OS, patients who receive the recommended 12-month course of neratinib may have improved CNS outcomes. A dose-escalation strategy, which was shown to improve the tolerability of neratinib, decrease the proportion of patients who discontinue treatment due to diarrhea (3.3%), and allow more patients to stay on treatment for 11 months or longer in the CONTROL trial (NCT02400476) compared with ExteNET, may help to realize these benefits in the real-world setting.

Table: CNS-DFS and OS in patients who completed planned therapy with neratinib (ITT, HR+/≤1 year and HR+/≤1 year no pCR)NCNS-DFS rate (5 years)OS rateaPopulation/group NeratinibPlaceboDifference, %bHR (95% CI)Difference, %bHR (95% CI)ITT14201420+1.10.73 (0.45-1.17)-0.10.95 (0.75-1.21)cCompleted therapyd8721420+1.20.70 (0.40-1.19)+2.00.78 (0.58-1.04)HR+/≤1 yeare670664+2.70.41 (0.18-0.85)+2.10.79 (0.55-1.13)Completed therapyd402664+3.20.27 (0.08-0.69)+5.80.49 (0.29-0.78)HR+/≤1 yearb no pCRf131164+6.40.24 (0.04-0.92)+9.10.47 (0.23-0.92)Completed therapyd92164+6.90.16 (0.01-0.81)+13.20.29 (0.10-0.68)aOS analysis after a median follow-up of 8.0 (range 0-9.8) years; bDifference (neratinib vs placebo); cStratified by randomization stratification factors; dDefined as ≥11 months of therapy or ended treatment due to disease recurrence (neratinib arm), and all randomized subjects (placebo arm); eHR+ and ≤1 year after prior trastuzumab; fResidual disease post-neoadjuvant therapy. Abbreviations: CI, confidence interval; CNS-DFS, central nervous system disease-free survival; HR, hazard ratio; HR+, hormone receptor-positive; OS, overall survival; pCR, pathologic complete response.

Citation Format: Frankie Ann Holmes, Debra Patt, Yvonne Manalo, Julie C Smith, Steven W Papish, Noa Efrat, Ana Arance, Bo Zhang, Deepa Lalla, Alvin Wong, Miguel Martin. Improved central nervous system outcomes in patients with early-stage HER2-positive breast cancer who receive neratinib for the recommended duration: Findings from the phase 3 ExteNET trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-21.

Abstract P4-12-09: Low-level constitutional mosaicism of a de novo BRCA1 gene mutation

Background:

Germline mutations in the BRCA1 and BRCA2 genes detected in some high-risk breast/ovarian families are used to estimate cancer risk, plan cancer early detection schemes, and make decisions about risk reducing surgeries. The gold standard for detecting BRCA sequence changes has long been Sanger sequencing, but recently next-generation sequencing (NGS) technologies have emerged as an accurate and efficient alternative, with improved sensitivity for detection of mosaic events. Here we report the detection of low-level constitutional germline mosaicism (∼5%) for a de novo pathogenic BRCA1 mutation detected using deep sequencing of three different non-cancerous tissues; and a corresponding high-level detection (∼50%) in cancerous breast tissue. This is the first reported case of multiple tissue constitutional mosaicism in BRCA1 at this level of detection.

Patient and Methods:

The patient is a woman of mixed Jewish Ashkenazi - Bulgarian heritage, diagnosed with a large (8x10 cm), triple negative, high-grade invasive breast cancer in the right breast at age 43 years. Her cancer family history includes a daughter with acute lymphatic leukemia at age 18 months, a brother with a Central Nervous System (CNS) tumor at age 45 years, a father with a malignant CNS tumor at age 58 years, a maternal grandfather with a malignant tumor in his 70's, and two of this maternal grandfather's sisters who were diagnosed with breast cancer. The patient underwent neoadjuvant chemotherapy followed by bilateral mastectomy (therapeutic mastectomy for the right breast and a contralateral risk-reducing mastectomy). The patient underwent germline testing using NGS, sequencing of 29 hereditary cancer genes in DNA extracted from blood using Invitae’s Hereditary Cancer Panel. This testing was followed up with additional NGS testing of buccal and contralateral healthy breast tissue. The patient also underwent somatic mutation testing on her breast tumor.

Results:

NGS of DNA extracted from blood identified a pathogenic BRCA1 mutation, c.1953dupG (p.Lys652GlufX21), in 5% of reads (X450 coverage). No other pathogenic mutations were detected in other genotyped cancer susceptibility genes. Analysis of buccal tissue and normal breast tissue removed at initial surgery also identified this mutation in ∼5% of reads, and confirm that this individual is a constitutional mosaic for this mutation. Genetic analyses were subsequently performed on the breast cancer tissue using Genome Health platform (Foundation One) and the same mutation, c.1943dupG was detected in 47% of molecules. Sanger sequencing of BRCA1 and BRCA2 in DNA extracted from peripheral blood had not detected this mutation. Analysis of the maternal DNA did not reveal this mutation, and analysis of the father was not possible.

Conclusion:

This is the first reported case of a de novo constitutional mosaicism in BRCA1 at this level of detection and confirmed across multiple tissue types, and highlights the need to perform deep sequencing in individuals clinically suspected of having cancer predisposition, prior to considering risk-reducing surgery.

Citation Format: Eitan Friedman, Noa Efrat, Lior Soussan-Gutman, Addie Dvir, Yulia Kaplan, Tali Ekstein, Keith Nykamp, Martin Powers, Marina Rabideau, Scott Topper. Low-level constitutional mosaicism of a de novo BRCA1 gene mutation [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-12-09.

Economic implications of 21-gene breast cancer risk assay from the perspective of an Israeli-managed health-care organization

OBJECTIVE

Oncotype DX, a 21-gene assay, was clinically validated as a predictor of 10-year recurrence-free survival and treatment response in patients with early-stage estrogen-receptor-positive, lymph-node negative breast cancer (ER+ LN- ESBC). This study determined "real-life" alteration in treatment decision and economic implications of Oncotype DX use in women with ER+ LN- ESBC.

METHODS

Clalit Health Services (CHS, Tel Aviv, Israel), determined the proportion of women in low, intermediate and high-risk groups in the first 368 Oncotype DX assays performed, the change of adjuvant therapy recommendation following the recurrence (RS) results from Oncotype DX use, and associated chemotherapy costs. The risk of recurrence-free survival was derived from prespecified statistical protocols of NCI-sponsored trials conducted by NSABP (B-14 and B-20). Utilities were literature based. A 3% discount rate was employed.

RESULTS

Oncotype DX altered recommendations of 40% of patients, 84% of whom were changed from hormone + chemotherapy to hormonal therapy alone. Among high-risk women, 8% switched actual treatment from hormonal therapy to hormone + chemotherapy. By reducing the chemotherapy disutility, quality-adjusted life-years (QALY) increased 0.170 years. Use of Oncotype DX costs $10,770 per QALY gained. Sensitivity analyses revealed that risk reduction in the low-risk population, the cost of adverse events, and the relative risk reduction of recurrence were the most influential variables.

CONCLUSION

Oncotype DX resulted in net QALY gain and increased overall costs, with an incremental cost-effectiveness ratio of $10,770. For CHS, Oncotype DX represents an effective and affordable approach to favorably affect the lives of women with ESBC.

Preliminary safety and activity results of trabectedin in a phase II trial dedicated to triple-negative (ER-, PR-, HER2-), HER2+++, or BRCA1/2 germ-line-mutated metastatic breast cancer (MBC) patients (pts)

1010

Background: Trabectedin ([T]; Yondelis) binds to the minor groove of DNA; its cytotoxicity is determined by the synergistic action of two DNA repair mechanisms, the efficient nucleotide excision repair (NER) and deficient homologous recombination repair (HRR) machinery. T has EMEA authorization in soft tissue sarcoma after failure of standard treatment. Preliminary data have shown activity of T as single agent in MBC. Clinical and preclinical data suggested T may display specific activity among certain NER-intact or HRR-deficient MBC, and prompted this phase II trial dedicated to 3 subgroups: triple-negative (TN), HER-2-overexpressed, and BRCA1/2 germline-mutated MBC. Methods: T was given at 1.3 mg/m2 as a 3- hour iv infusion every 3 weeks to pts with pretreated progressive MBC: Group A: TN; Group B: HER-2+++; Group C: BRCA1/2 mutation carriers. Endpoints were objective response (OR) rate by RECIST, duration of response, progression free survival (PFS), tumor volume changes, safety and exploratory pharmacogenomics (PGx). Results: A total of 95 women (median [med] age 52, ECOG 0/1 48/52%) have been enrolled (A:50, B:24, C:21) with data available for 72 pts. Med number of prior chemotherapy regimens: 4 (1–10). Med number of T cycles administered: 2 (1–12) for all groups. The most commonly reported grade 3/4 AEs are neutropenia (29/21%), ALT (28/2%) and AST (13/0). Alopecia/stomatitis, only G1, was reported in <2% each. Long-lasting disease stabilizations were described in all groups. While OR were rare among TN MBC pts (2PR/43 evaluable), preliminary analysis by investigator shows efficacy in group C (4PR/11 evaluable). Tissue samples from 36 pts were collected for RNA expression analysis (XPG + ERCC1 + BRCA1). Preliminary results show high XPG is associated with longer PFS: 4.1 months (95% CI 2.6-not reached) versus 1.3 months (95% CI 1.2–3.7), p = 0.01. Analyses are ongoing. Conclusions: Trabectedin shows a manageable safety profile in the 3 groups of MBC with promising efficacy in certain DNA-repair machinery sub-categories defined molecularly. TN group was closed due to low response. More mature PGx results will be discussed to help selecting the patients who are at highest chance for response.

[Table: see text]