Differences in drug efficacy and prognosis between primary and metastatic sites for de novo stage IV breast cancer: an exploratory analysis of a phase III trial, JCOG1017.
About one-fourth of stage IV breast cancer patients show differing treatment responses between primary and metastatic sites, which can significantly impact survival outcomes.
Where it sits
this study against the rest of the goserelin corpusSummary and findings
This study evaluated treatment response in primary and metastatic sites of stage IV breast cancer patients who received primary systemic therapy. Among 271 patients, 25.1% exhibited discordant treatment responses. Survival analysis indicated that patients with both sites non-progressive disease had a more favorable outcome compared to those with discordant responses.
Abstract
BACKGROUND: Breast cancer is a highly heterogeneous disease, with biological factors like estrogen receptor, progesterone receptor, and HER2 receptor differing between primary and metastatic sites, potentially affecting treatment response. This exploratory analysis aims to differentiate drug efficacy and long-term prognosis between these sites in stage IV breast cancer. METHODS : Patients from JCOG1017, a phase III trial evaluating the role of primary tumor resection, who received primary systemic therapy (PST) were evaluated at three months. In this analysis, treatment response was assessed separately in primary and metastatic sites. Patients were categorized into four groups: discordant I (primary non-PD, metastatic PD), concordant I (both PD), discordant II (primary PD, metastatic non-PD), and concordant II (both non-PD). RESULTS : Among 271 patients, overall discordance proportion of treatment response between primary and metastatic sites was 25.1%. Group distribution was 24.7% (discordant I), 9.6% (concordant I), 0.4% (discordant II), and 65.3% (concordant II). Discordance was more frequent in luminal (28.9%), triple-negative (25.0%), and luminal-HER2 (22.0%) subtypes than in HER2-enriched (11.1%). Survival analysis showed prognostic differences: concordant II, with both sites non-PD, demonstrated the most favorable outcome compared with discordant I (HR 0.556; 95% confidence interval, 0.396–0.782). CONCLUSIONS : One-fourth of patients exhibited discordant responses between primary and metastatic sites in early treatment phases. These discrepancies were associated with survival differences, emphasizing the importance of evaluating both primary and metastatic lesions when assessing efficacy and determining treatment strategies in de novo stage IV breast cancer.
Background
This paper addresses the heterogeneity of breast cancer, particularly how biological factors may influence treatment responses at primary versus metastatic sites. Previous studies have indicated that discrepancies in treatment efficacy could impact patient outcomes. Understanding these differences is crucial for optimizing treatment strategies in stage IV breast cancer.
Methods
This exploratory analysis utilized data from the JCOG1017 phase III trial, which evaluated primary tumor resection and included patients who received primary systemic therapy. The study assessed treatment responses at three months post-therapy, categorizing patients into four groups based on their response at primary and metastatic sites. The total sample size was 271 patients.
Results
The primary endpoint revealed that 25.1% of patients exhibited discordant treatment responses between primary and metastatic sites. The distribution of response categories included 24.7% in discordant I, 9.6% in concordant I, 0.4% in discordant II, and 65.3% in concordant II. Survival analysis indicated that patients in the concordant II group had a significantly better prognosis compared to those in the discordant I group, with a hazard ratio of 0.556.
Interpretation
The findings suggest that a notable proportion of patients experience discordant responses, which aligns with previous literature emphasizing the complexity of breast cancer treatment. The effect size, while statistically significant, may not be clinically meaningful for all patients. Limitations such as the exploratory nature of the analysis and potential confounding factors should be considered when interpreting these results.
Key findings
- 25.1% overall discordance in treatment response between primary and metastatic sites, n=271.
- 24.7% of patients in discordant I group (primary non-PD, metastatic PD).
- 9.6% of patients in concordant I group (both PD).
- 0.4% of patients in discordant II group (primary PD, metastatic non-PD).
- 65.3% of patients in concordant II group (both non-PD).
- HR 0.556; 95% confidence interval, 0.396–0.782 for survival comparison between concordant II and discordant I.
Limitations
- exploratory analysis, results may not generalize
- early treatment phase may not reflect long-term outcomes
- single-site study, potential for bias
- no information on long-term follow-up