Abstract
BackgroundInvasive ductal carcinoma (IDC) is often accompanied by ductal carcinoma in situ (DCIS). Whether the DCIS component affects the 21-gene recurrence score (RS) is unclear.MethodsConsecutive ER-positive, HER2-negative, N0–1 patients with RS results were included. Patients were divided into pure IDC and IDC with DCIS (IDC/DCIS) groups. The RS, the expression of its 16 cancer genes and prognosis were compared between IDC and IDC/DCIS patients.ResultsA total of 1458 patients were enrolled, 320 of whom had concomitant DCIS. DCIS component was independently associated with lower RS (P = 0.038). IDC/DCIS patients more often had a low-risk RS (P = 0.018) or intermediate-risk RS (P = 0.024). Regarding individual genes in the RS panel, Ki67, CCNB1 and MYBL2 in the proliferation group and MMP11 and CTSL2 in the invasion group were significantly lower among IDC/DCIS patients than pure IDC patients. Among IDC/DCIS patients, lower RS was independently correlated with a higher DCIS proportion and lower DCIS grade. Within a median follow-up of 31 months, the DCIS component in IDC did not significantly influence prognosis.ConclusionsIDC with DCIS component is associated with a lower 21-gene RS, possibly due to lower expression of proliferation and invasion genes. DCIS proportion and grade independently influenced the 21-gene RS in IDC/DCIS patients. Due to the relatively short follow-up period and low recurrence rate, the impact of the DCIS component in IDC on prognosis needs further evaluation.
Highlights
Invasive ductal carcinoma (IDC) is often accompanied by ductal carcinoma in situ (DCIS)
Based on the above questions, this study aims to explore whether and how the DCIS component in IDC impacts the 21gene recurrence score (RS) by analysing individual gene expression between IDC and IDC/DCIS groups
ER expression ≥50% was found in 1,355 patients (92.9%), while progesterone receptor (PR) expression ≥20% was found in 1006 patients (69.0%)
Summary
Invasive ductal carcinoma (IDC) is often accompanied by ductal carcinoma in situ (DCIS). The RS, the expression of its 16 cancer genes and prognosis were compared between IDC and IDC/DCIS patients. Regarding individual genes in the RS panel, Ki67, CCNB1 and MYBL2 in the proliferation group and MMP11 and CTSL2 in the invasion group were significantly lower among IDC/DCIS patients than pure IDC patients. CONCLUSIONS: IDC with DCIS component is associated with a lower 21-gene RS, possibly due to lower expression of proliferation and invasion genes. DCIS proportion and grade independently influenced the 21-gene RS in IDC/DCIS patients. Since the 21-gene assay genetically assesses the proliferative and invasive propensity of the tumour, it would be reasonable to assume that the DCIS component may affect the 21-gene assay result. Whether and how the DCIS component in IDC affects 21-gene RS assay testing remains unknown
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