Abstract P4-13-23: Next-generation sequencing (NGS), array comparative genomic hybridization (aCGH) and patient-derived tumor xenograft (PDX) for precision medicine in advanced breast cancer: A single-center prospective study

Background

Genomic-based approaches in advanced breast cancer (ABC) were recently demonstrated as feasible in the clinical practice, but only a limited number of patients were actually treated with targeted therapies matching genomic alterations, with low antitumor activity. We conducted a pilot study to evaluate whether precision medicine using NGS and aCGH could be implemented prospectively at a single center in ABC patients. In addition, we examined whether PDX could be derived from ABC and thus could help inform therapeutic decision.

Methods

ABC patients accessible to tumor biopsy were prospectively enrolled at the Institut Paoli-Calmettes in the BC-BIO study (ClinicalTrials.gov, NCT01521676). Tumor tissue from locally recurrent or metastatic disease was immediately frozen after dedicated biopsy. Genomic profiling included high-resolution 4x180K aCGH (Agilent Technologies, Massy, France) and DNA sequencing, using a library of 365 cancer candidate genes (HaloPlex target enrichment kit, Agilent technologies, Santa Clara, CA, USA) and MiSeq analyzer (Illumina, San Diego, CA, USA) with 2x150-bp, paired-end at about 300x coverage. In a subset of patients, fresh tumor was implanted orthotopically in humanized cleared fat pads of NSG mice for establishing xenotransplants.

Results

A total of 34 ABC patients were included, with the following characteristics: median age 54 years (35-77); molecular subtypes: 11 triple-negative (32%), 12 luminal non-HER2 (35%), 4 luminal HER2 (12%), 3 HER2 non-luminal (9%), and 4 unknown (12%); 33 with previous chemotherapy (97%); 22 with previous endocrine treatment (35%); 7 with previous anti-HER2 (21%). Tumor biopsies were obtained from liver (15), skin (6), peritoneum (4), breast (3), node (3), lung (1), pleura (1), and ascitis (1), with a median tumor cellularity of 70% (range 10-90%). aCGH and NGS were available from 34 and 33 patients, respectively. An actionable target was found in 28 patients (82%), corresponding to 66 targets, including 37 mutations (8 in PIK3CA, 7 TP53, 4 ESR1, 2 AKT1, 2 BRCA2, 2 HER2), 22 amplifications (7 for CCND1, 2 CCNE1, 2 FGFR1, 2 IGF1R) and 7 homozygous deletions (3 for PTEN, 2 CDKN2A/B,1 BRCA2, 1 STK11). A targeted therapeutic proposal was possible, either in a clinical trial (N=18, 52%) or using already registered drugs (N=17, 50%). Ten patients actually received a targeted treatment, 1 of them experienced objective response and 1 showed stable disease for more than 6 months. Of 26 patients subjected to mouse implantation, 10 had successful xenografting (6 triple-negative, 2 HER2, 1 luminal non-HER2, 1 subtype non-attributed), with a median time to reach 10 mm of 148 days. These PDX will be used as models to understand the patient's therapeutic response.

Conclusion

Precision medicine using high-throughput DNA sequencing and aCGH can be implemented at a single center in the context of clinical practice and may allow direct therapeutic proposal in 1/3 of patients, but antitumor activity was minimal. PDX may be obtained in a significant fraction of patients, especially in triple-negative and HER2 subtypes, and could phenotypically complement genomic data.

Citation Format: Gonçalves A, Bertucci F, Chaffanet M, Guille A, Garnier S, Adelaide J, Carbuccia N, Brunelle S, Piana G, Cabaud O, Thomassin-Piana J, Paciencia-Gros M, Chereau-Ewald E, Lambaudie E, Sabatier R, Tarpin C, Provansal M, Jalaguier-Coudray A, Extra J-M, Sarran A, Pakradouni J, Viens P, Lopez M, Ginestier C, Charafe-Jauffret E, Birnbaum D. Next-generation sequencing (NGS), array comparative genomic hybridization (aCGH) and patient-derived tumor xenograft (PDX) for precision medicine in advanced breast cancer: A single-center prospective study. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-23.