A retrospective analysis of the National Cancer Database suggests an overall survival benefit to adjuvant chemotherapy among breast cancer patients with an OncotypeDX score of 25 or less. The findings reinforce the positive results from the RxPONDER study, which showed benefits to invasive disease–free and distant relapse–free survival.
OncotypeDX is a prognostic assay for hormone-receptor–positive, human epidermal growth factor receptor 2 (HER2)–negative and axillary lymph-node–negative breast cancer. It measures expression of 21 different genes and assigns each patient a score between 0 and 100, with higher scores representing a greater risk of recurrence and a worse prognosis. The 2018 TAILORx study validated Oncotype DX and found no benefit of adjuvant chemotherapy added to endocrine therapy in women over 50 with an OncotypeDX score of 11-25, but it did find a benefit in women under 50 years old with a score of 16 or higher.
RxPONDER was a prospective study that randomized women with Oncotype DX scores of 25 or lower and 1-3 positive lymph nodes to adjuvant endocrine therapy with or without chemotherapy. Among premenopausal women, 5-year invasive disease–free survival was 93.9% with chemotherapy and 89.0% with endocrine therapy only (hazard ratio, 0.60; P = .002), while distant relapse–free survival was 96.1% and 92.8%, respectively (HR, 0.58; P = .009).
Overall survival data from RxPONDER has yet to be reported. In the meantime, “We decided to use the National Cancer database to see if this group of patients have an overall survival benefit,” said Prashanth Ashok Kumar, MBBS, who presented the results of the new study at a poster session this month during the 2022 San Antonio Breast Cancer Symposium.
“Our research further supports the findings of the RxPONDER trial showing that this subgroup of patients may also have an overall survival benefit with adjuvant chemotherapy. We can give physicians a little bit more confidence to recommend the findings of the RxPONDER study to their patients and could recommend chemotherapy in this group,” said Dr. Kumar, who is a second-year oncology fellow at Upstate University Hospital. Syracuse, N.Y.
The study is limited by its retrospective nature, but Dr. Kumar said that the researchers used propensity score matching to reduce confounding. “This would need to be confirmed with further prospective clinical trials and also the mature data from the RxPONDER trial is something that we have to look forward to,” he said.
Adjuvant therapy might be particularly beneficial to patients with more high-risk features, such as T4 or N2 or N3 disease. “We have to go with each individual patient’s features, and also the patient’s personal preference and what they want from their quality of life,” Dr. Kumar said.
The study included 8,628 patients from the 2004-2018 National Cancer Database participant user file. They were 18-50 years old with N1-N3 lymph node status, no metastasis, and any T stage. All had an OncotypeDX score of 25 or less and were hormone receptor–positive and HER2-negative while 40.8% underwent adjuvant chemotherapy.
Unadjusted Kaplan-Meier scores showed a slightly higher 10-year survival with adjuvant chemotherapy (93% versus 91%; HR, 0.602; 95% confidence interval, 0.482-0.751). Multivariate subanalyses showed that adjuvant chemotherapy was associated with better survival among White patients (HR, 0.512; 95% CI, 0.348-0.752) between 18 and 40 years old (HR, 0.429; 95% CI, 0.217-0.847), and for patients between 40 and 50 years old (HR, 0.585; 95% CI, 0.394-0.869); among patients with poorly differentiated tumors (HR, 0.404; 95% CI, 0.186-0.874); among patients with well-differentiated tumors (HR, 0.386; 95% CI, 0.165-0.903); and for those with Oncotype DX scores between 12 and 25 (HR, 0.549; 95% CI, 0.379-0.795).
Dr. Kumar has no relevant financial disclosures.