MammaPrint Pre-screen Algorithm (MPA) reduces chemotherapy in patients with early-stage breast cancer.

Grant KA, Apffelstaedt JP, Wright CA, Myburgh E, Pienaar R, De Klerk M, Kotze MJ.

Source

Department of Biomedical Sciences, Cape Peninsula University of Technology, Cape Town, South Africa. grantk@cput.ac.za

Abstract

BACKGROUND:

Clinical and pathological parameters may overestimate the need for chemotherapy in patients with early-stage breast cancer. More accurate determination of the risk of distant recurrence is now possible with use of genetic tests, such as the 70-gene MammaPrint profile.

OBJECTIVES:

A health technology assessment performed by a medical insurer in 2009 introduced a set of test eligibility criteria - the MammaPrint Pre-screen Algorithm (MPA) - applied in this study to determine the clinical usefulness of a pathology-supported genetic testing strategy, aimed at the reduction of healthcare costs.Methods. An implementation study was designed to take advantage of the fact that the 70-gene profile excludes analysis of hormone receptor and human epidermal growth factor receptor 2 (HER2) status, which form part of the MPA based partly on immunohistochemistry routinely performed in all breast cancer patients. The study population consisted of 104 South African women with early-stage breast carcinoma referred for MammaPrint. For the MammaPrint test, RNA was extracted from 60 fresh tumours (in 58 patients) and 46 formalin-fixed, paraffin-embedded (FFPE) tissue samples.

RESULTS:

When applying the MPA for selection of patients eligible for MammaPrint testing, 95 of the 104 patients qualified. In this subgroup 62% (59/95) were classified as low risk. Similar distribution patterns for risk classification were obtained for RNA extracted from fresh tumours v. FFPE tissue samples.

CONCLUSIONS:

The 70-gene profile classifies approximately 40% of early-stage breast cancer patients as low-risk compared with 15% using conventional criteria. In comparison, more than 60% were shown to be low risk with use of the MPA validated in this study as an appropriate strategy to prevent chemotherapy overtreatment in patients with early-stage breast cancer.