In a population-based cohort study reported in JAMA Network Open, Zhai et al found that adjuvant therapies were associated with improved overall survival among patients with stage I (T1 N0 M0) triple-negative breast cancer, with adjuvant chemotherapy being associated with improved breast cancer–specific survival.
As stated by the investigators, “Adjuvant chemotherapy remains the only recommended treatment for patients with triple-negative breast cancer. However, the existing evidence is not enough to recommend adjuvant therapies to patients with T1 N0 M0 triple-negative breast cancer.”
“The findings of this cohort study suggest that adjuvant therapies could improve overall survival in patients with T1 N0 M0 triple-negative breast cancer, whereas only chemotherapy was associated with better breast cancer–specific survival. Older patients with early-stage triple-negative breast cancer may benefit from adjuvant radiotherapy. Administration of adjuvant therapies to patients with different ages and cancer stages should be discussed carefully, which necessitates guidance from updated guidelines.”— Zhai et al
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Study Details
The study involved data from 7,739 postoperative patients diagnosed with T1 N0 M0 triple-negative breast cancer between 2010 and 2015 in the SEER (Surveillance, Epidemiology, and End Results) cancer registry program. Overall, 755 patients had T1a; 1,979, T1b; and 5,005, T1c disease. Adjuvant therapy consisted of none in 1,286 patients; chemotherapy alone in 2,202; radiotherapy alone in 1,278; and both chemotherapy and radiotherapy in 2,973.
Key Findings
Median follow-up for overall survival was 45 months. Overall survival at 5 years was 91.7% among all patients.
On multivariate analysis, compared with patients who did not receive adjuvant therapy, those who received chemotherapy (adjusted hazard ratio [HR] = 0.475, P < .001), radiotherapy (adjusted HR = 0.725, P = .04), and both (adjusted HR = 0.489, P < .001) had significantly improved overall survival.
Median follow-up for breast cancer–specific survival was 44 months. Breast cancer–specific survival at 5 years was 94.9% among all patients.
On multivariate analysis, compared with patients who did not receive adjuvant therapy, those who received chemotherapy (adjusted HR = 0.657, P = .02)—but not those who received radiotherapy (adjusted HR = 0.805, P = .40) or both (adjusted HR = 0.895, P = .60)—had significantly improved breast cancer–specific survival.
In analyses by type of surgery, consisting of breast-conserving surgery and other surgery (simple mastectomy, radical mastectomy, or other surgical procedures) among patients aged ≥ 70 years, all adjuvant therapies were associated with improved overall survival, except for radiotherapy after other surgery; only radiotherapy after breast-conserving surgery was associated with improved breast cancer–specific survival (adjusted HR = 0.478, P = .03).
Among patients with T1c disease, chemotherapy after breast-conserving surgery or other surgery was associated with improved overall survival, with only chemotherapy after other surgery being associated with improved breast cancer–specific survival (adjusted HR = 0.579, P = .04).
The investigators concluded, “The findings of this cohort study suggest that adjuvant therapies could improve overall survival in patients with T1 N0 M0 triple-negative breast cancer, whereas only chemotherapy was associated with better breast cancer–specific survival. Older patients with early-stage triple-negative breast cancer may benefit from adjuvant radiotherapy. Administration of adjuvant therapies to patients with different ages and cancer stages should be discussed carefully, which necessitates guidance from updated guidelines.”
Zhijun Dai, PhD, of the First Affiliated Hospital, Zhejiang University, Hangzhou, and Huafeng Kang, MD, of the Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China, are the corresponding authors for the JAMA Network Open article.
Disclosure: For full disclosures of the study authors, visit jamanetwork.com.
