Target-based therapeutic matching of phase I trials in patients with metastatic breast cancer in a tertiary referral centre

Molecular profiling of metastatic breast cancer and target-based therapeutic matching in an Asian tertiary phase I oncology unit

Introduction

Molecular profiling of metastatic breast cancer (MBC) through the widespread use of next-generation sequencing (NGS) has highlighted actionable mutations and driven trials of targeted therapy matched to tumour molecular profiles, with improved outcomes reported using such an approach. Here, we review NGS results and treatment outcomes for a cohort of Asian MBC patients in the phase I unit of a tertiary centre.

Methods

Patients with MBC referred to a phase I unit underwent NGS via Ion AmpliSeq Cancer Hotspot v2 (ACH v2, 2014-2017) prior to institutional change to FoundationOne CDx (FM1; 2017-2022). Patients were counselled on findings and enrolled on matched therapeutic trials, where available. Outcomes for all subsequent treatment events were recorded to data cut-off on January 31, 2022.

Results

A total of 215 patients were enrolled with successful NGS in 158 patients. The PI3K/AKT/PTEN pathway was the most altered with one or more of the pathway member genes PIK3/AKT/PTEN affected in 62% (98/158) patients and 43% of tumours harbouring a PIK3CA alteration. Tumour mutational burden (TMB) was reported in 96/109 FM1 sequenced patients, with a mean TMB of 5.04 mt/Mb and 13% (12/96) with TMB ≥ 10 mt/Mb. Treatment outcomes were evaluable in 105/158 patients, with a pooled total of 216 treatment events recorded. Matched treatment was administered in 47/216 (22%) events and associated with prolonged median progression-free survival (PFS) of 21.0 weeks [95% confidence interval (CI) 11.7, 26.0 weeks] versus 12.1 weeks (95% CI 10.0, 15.4 weeks) in unmatched, with hazard ratio (HR) for progression or death of 0.63 (95% CI 0.41, 0.97; p = 0.034). In the subgroup of PIK3/AKT/PTEN-altered MBC, the HR for progression or death was 0.57 (95% CI 0.35, 0.92; p = 0.02), favouring matched treatment. Per-patient overall survival (OS) analysis (n = 105) showed improved survival for patients receiving matched treatment versus unmatched, with median OS (mOS) of 30.1 versus 11.8 months, HR = 0.45 (95% CI 0.24, 0.84; p = 0.013). Objective response rate (ORR) in the overall population was similar in matched and unmatched treatment events (23.7% versus 17.2%, odds ratio of response 1.14 95% CI 0.50, 2.62; p = 0.75).

Conclusions

Broad-panel NGS in MBC is feasible, allowing therapeutic matching, which was associated with improvements in PFS and OS.

Clinical outcomes of patients with metastatic breast cancer enrolled in phase I clinical trials

BACKGROUND

Next-generation phase I clinical trials (Ph1s) investigating targeted therapy (TT) and immunotherapy (IO) led to consistent improvements in outcomes of patients with cancer . Ph1s are mainly designed to enrol patients with different tumour types; hence, scant information on characteristics and outcomes of specific tumours is available. The aim of our study is to evaluate the outcomes of patients with metastatic breast cancer (BC) enrolled in Phs1 testing TT, IO and combinations.

MATERIAL AND METHODS

We retrospectively collected data on clinical characteristics and outcomes of all patients with metastatic BC treated in Ph1s from 2014 to 2019 at our Institution. The primary end-points were progression-free survival (PFS) and overall survival (OS). The secondary objectives were overall response rate (ORR), disease control rate (DCR) and 90-day mortality rate. Univariate and multivariate analyses were performed to assess the impact of different variables.

RESULTS

One hundred fifty-one patients with metastatic BC were treated, including 70 (46%) with hormone receptor-positive (HR+), 18 (12%) with HER2+ and 63 (42%) with triple-negative (TN) BC. The median age was 52.4 years (26.9-77.9). Patients with TNBC were less pretreated than patients with HR+ and HER2+ subtypes. Patients with HR+ tumours were preferentially included in TT rather than IO trials (97% vs. 2.9%, P < 0.001). In 148 patients evaluable for tumour response, DCR and ORR were 51.4% and 18.9%, respectively. Higher response rates have been observed in patients treated with TT (TT vs. IO: 23.5% vs. 3.0%, P = 0.008) and in the HER2+ or TN subtypes (HER2+ vs. TN vs. HR+: 33.3% vs. 24.2% vs. 10.3%, P = 0.032). Improved median PFS was observed in patients treated with TT (P < 0.001), aged ≥ 65 years (P = 0.001) and having fewer than 3 metastatic sites (P = 0.026). Patients with HR+ and HER2+ subtypes presented a numerically higher median PFS than those with TNBC (3.65 vs. 3.58 vs. 2.28 months, P = 0.053). Median OS was longer in HR+ and HER2+ subtypes than that in TNBC (20 vs. 16 vs. 10 months, P = 0.007). Variables independently associated with improved OS were fewer than three metastatic sites (P = 0.014) and a baseline lactate dehydrogenase lower than upper limit of normal (P < 0.001).

CONCLUSION

Our study provides novel insights on the landscape of metastatic breast cancer metasta treated in Ph1s. Patients with TNBC still have poor outcomes, reinforcing the need to better translate preclinical findings into the clinical context. TT-based trials-mainly biomarker-driven-are associated with improved outcomes, suggesting that future IO trials have to be guided by meaningful biomarkers. Finally, patients with low tumour burden can have significant benefit, underling the importance to enrol patients in earlier lines of treatment to maximise the benefit.