Background: Breast cancer patients at high risk for recurrence are treated with anthracycline-based chemotherapy, but not all patients do equally benefit from such a regimen. To further improve therapy decision-making, biomarkers predicting outcome are of high unmet medical need. Methods: The percent DNA methylation ratio (PMR) of the promoter gene coding for the Paired-like homeodomain transcription factor 2 (PITX2) was determined by a validated methylation-specific real-time polymerase chain reaction (PCR) test. The multicenter study was conducted in routinely collected archived formalin-fixed paraffin-embedded (FFPE) tissue from 205 lymph node-positive breast cancer patients treated with adjuvant anthracycline-based chemotherapy. Results: The cut-off for the PITX2 methylation status (PMR = 12) was confirmed in a randomly selected cohort (n = 60) and validated (n = 145) prospectively with disease-free survival (DFS) at the 10-year follow-up. DFS was significantly different between the PMR ≤ 12 versus the PMR > 12 group with a hazard ratio (HR) of 2.74 (p < 0.001) in the validation cohort and also for the patient subgroup treated additionally with endocrine therapy (HR 2.47; p = 0.001). Conclusions: Early-stage lymph node-positive breast cancer patients with low PITX2 methylation do benefit from adjuvant anthracycline-based chemotherapy. Patients with a high PITX2 DNA methylation ratio, approximately 30%, show poor outcome and should thus be considered for alternative chemotherapy regimens.
Significant evidence has accumulated that DNA-methylation of the paired-like homeodomain transcription factor 2 (PITX2) gene can serve as a prognostic and predictive biomarker in breast cancer. PITX2 DNA-methylation data have been obtained so far from microarray and polymerase chain reaction (PCR)-based research tests. The availability of an analytically validated in vitro methylation-specific real-time PCR assay format (therascreen PITX2 RGQ PCR assay) intended for the determination of the percent methylation ratio (PMR) in the (PITX2) promoter 2 prompted us to investigate whether the clinical performance of these different assay systems generate comparable clinical outcome data. Mathematically converted microarray data of a previous breast cancer study (n = 204) into PMR values leads to a PITX2 cut-off value at PMR 14.73. Recalculation of the data to experimentally equivalent PMRs with the PCR PITX2 assay leads to a cut-off value at PMR 12 with the highest statistical significance. This cut-off predicts outcome of high-risk breast cancer patients to adjuvant anthracycline-based chemotherapy (n = 204; Hazard Ratio 2.48; p < 0.001) comparable to microarray generated results (n = 204; Hazard ratio 2.32; p < 0.0001). The therascreen PITX2 RGQ PCR assay is an analytically validated test with high reliability and robustness and predicts outcome of high-risk breast cancer patients to anthracycline-based chemotherapy.
The therascreen PITX2 RGQ PCR assay is an optimized in vitro DNA methylation-specific quantitative real-time PCR test intended for the determination of the percent methylation ratio (PMR) in the pituitary homeobox 2 (PITX2) transcription factor gene promoter 2. The test uses bisulfite-converted genomic DNA derived from formalin-fixed paraffin-embedded tumor tissues of breast cancer patients. The PMR will aid clinicians in selecting adjuvant systemic chemotherapy, e.g. anthracycline-based chemotherapy in high-risk lymph node-positive, estrogen receptor-positive, HER2-negative breast cancer patients. The assay is intended to be used by qualified users, such as technicians, molecular biologists/clinical chemists, or physicians, trained in molecular biology techniques and in vitro diagnostic procedures. The complete workflow is streamlined for medium sample throughput with highly reliable and robust readout and can be performed in two working days.
The CE-marked therascreen® PITX2 RGQ PCR Kit (QIAGEN Cat No./ID 873211), a PITX2 DNA methylation assay was introduced to the market in 2018, (hereinafter referred to as the “standard therascreen PITX2 workflow) and represents an in vitro diagnostic to predict outcome to anthracycline-based chemotherapy considered standard-of-care systemic treatment in early breast cancer patients. The Intended Use (IUS) of this kit covers lymph node-positive, estrogen receptor-positive and HER2-negative high-risk breast cancer patients treated in the adjuvant setting with anthracycline-based chemotherapy and requires 400 ng genomic DNA as recommended DNA input extracted from 1-2 x 5 µm Formalin-Fixed-Paraffin-Embedded (FFPE) sections with a minimal total tumor tissue surface area of ≥ 100 mm2. In today’s clinical workflow of early high-risk breast cancer patient therapy, increasing number of patients are treated in the neoadjuvant setting after tumor biopsy with anthracycline-based chemotherapy before tumor resection by surgery. Biopsy material size restriction in this clinical area requires for a predictive marker test to be applicable biopsy specimens with tumor tissue surface area’s in the range of 20-50 mm2. Therefore, a modified PITX2 workflow protocol - the so-called “Condensed Efficient Fast (CEF)” PITX2 workflow – was developed to address this need. The required modifications of the standard therascreen PITX2 workflow is described in the “bisDNA Preparation” section. The “PMR Detection & Analysis” section of the standard therascreen PITX2 workflow remains unchanged. The new CEF PITX2 workflow is for Research Use Only (RUO) and intended to be used by qualified users such as technicians, molecular biologists/clinical chemists, or physicians. The complete CEF PITX2 workflow is optimized for medium sample through-put with highly reliable and robust read-out and can be performed in two working days.
<b><i>Background:</i></b> PITX2 DNA methylation has been shown to predict outcomes in high-risk breast cancer patients after anthracycline-based chemotherapy. To determine its prognostic versus predictive value, the impact of PITX2 DNA methylation on outcomes was studied in an untreated cohort vs. an anthracycline-treated triple-negative breast cancer (TNBC) cohort. <b><i>Material and Methods:</i></b> The percent DNA methylation ratio (PMR) of paired-like homeodomain transcription factor 2 (PITX2) was determined by a validated methylation-specific real-time PCR test. Patient samples of routinely collected archived formalin-fixed paraffin-embedded (FFPE) tissue and clinical data from 144 TNBC patients of 2 independent cohorts (i.e., 66 untreated patients and 78 patients treated with anthracycline-based chemotherapy) were analyzed. <b><i>Results:</i></b> The risk of 5- and 10-year overall survival (OS) increased continuously with rising PITX2 DNA methylation in the anthracycline-treated population, but it increased only slightly during 10-year follow-up time in the untreated patient population. PITX2 DNA methylation with a PMR cutoff of 2 did not show significance for poor vs. good outcomes (OS) in the untreated patient cohort (HR = 1.55; <i>p</i> = 0.259). In contrast, the PITX2 PMR cutoff of 2 identified patients with poor (PMR >2) vs. good (PMR ≤2) outcomes (OS) with statistical significance in the anthracycline-treated cohort (HR = 3.96; <i>p</i> = 0.011). The results in the subgroup of patients who did receive anthracyclines only (no taxanes) confirmed this finding (HR = 5.71; <i>p</i> = 0.014). <b><i>Conclusion:</i></b> In this hypothesis-generating study PITX2 DNA methylation demonstrated predominantly predictive value in anthracycline treatment in TNBC patients. The risk of poor outcome (OS) correlates with increasing PITX2 DNA methylation.
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