Adjuvant Chemotherapy Guided by a 21-Gene Expression Assay in Breast Cancer

• The 21-gene recurrence-score assay (e.g., Oncotype DX, Genomic Health):
  • Is one of several commercially available gene-expression assays:
    • That provide prognostic information in hormone-receptor-positive breast cancer
• The assay originally set cut points for:
  • Low risk at a recurrence score < 18
  • Intermediate risk at 18 to 30
  • High risk at > 31
• It is predictive of chemotherapy benefit when:
  • The recurrence score (RS) is high (> 26), and prognostic for very low rates of distant recurrence (2% at 10 years) when the RS is low (< 10)
• The TAILORx prospective randomized clinical trial:
  • Was completed to determine whether chemotherapy is beneficial for women:
    • With an intermediate RS of 11 to 25
  • The cutoffs for this trial were adjusted to ensure all patients in the intermediate range who may benefit were included
  • At 9 years of follow-up:
    • The endocrine therapy only and the chemo-endocrine therapy group:
      • Had similar rates of invasive disease-free survival:
        • 83.3% vs. 84.3% respectively
    • The endocrine therapy alone was noninferior to chemoendocrine therapy for all patients in the intermediate RS study group
    • The two groups also had similar outcomes in freedom from disease recurrence at a distant or locoregional sites
    • However, the chemotherapy benefit for invasive disease-free survival varied with the combination of recurrence score and age (P=0.004):
      • With some benefit of chemotherapy found in women 50 years old or younger with an RS of 16 to 25
      • In women less than 50 receiving chemotherapy demonstrated a lower rate of distant recurrence than endocrine therapy if RS was 16 to 20 (percentage-point difference, 0.8 at 5 years and 1.6 at 9 years) or 21 to 25 (percentage-point difference, 3.2 at 5 years and 6.5 at 9 years)
      • Overall survival however remained similar
  • For this reason, researchers conclude that the 21-gene assay can identify women with ER postive early-stage breast cancer:
    •  Who may be spared chemotherapy if they are over 50 years old with an RS of 25 or lower, as well as women 50 years or younger with RS of 15 or lower
• References
  • Sparano JA, Gray RJ, Makower DF, Pritchard K, Albain KS, Hayes DF, et al. Adjuvant chemotherapy guided by a 21-gene expression assay in breast cancer. N Engl J Med. 2018;379(2):111-121.

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