The current standard of care for stage 1 hormone receptor-positive (HR+) breast cancer consists of breast-conserving surgery followed by adjuvant radiotherapy (RT) and endocrine therapy (ET) for at least 5 years. The benefit of adjuvant ET for older patients is mitigated because of their increase risk of death from other causes and shorter time horizon to live. Clinical and pathological factors such as low-intermediate grade, tumor size ≤2 cm, and older age have been used in a few studies to identify patients with a lower risk of recurrence that might benefit from adjuvant therapy de-escalation, i.e. omission of RT or ET. Since there is no dedicated randomized clinical trial (RCT) conducted to evaluate the omission of ET, there is clinical equipoise as to whether we can omit adjuvant ET in older patients with lower-risk early-stage breast cancer. Therefore, we propose a randomised, multicentre trial evaluating harms and benefits of endocrine therapy in patients ≥70 years of age with lower risk breast cancer.
New invasive estrogen and/or progesterone receptor-positive (ER+ and/or PR+), HER2-negative (HER2-) invasive breast carcinoma diagnosis as per ASCO-CAP guidelines
The primary tumour characteristics are either: Grade 1 and ≤3 cm on microscope exam, OR Grade 2 and ≤2 cm on microscope exam, OR Grade 3 and ≤1 cm on microscope exam
Treated with standard loco-regional therapy: breast conserving surgery followed by adjuvant radiotherapy OR total mastectomy
Axillary node-negative (cN0 or pN0)
Metastatic cancer
Parallel
No endocrine therapy
Other interventionNo endocrine therapy given
Endocrine therapy
Other interventionEndocrine therapy given for at least 5 years
Hierarchical composite endpoint (OS, iDFS, MDFS, QoL)
The primary outcome is a hierarchical composite endpoint following the WIN-ratio approach. This composite endpoint includes overall survival (OS), invasive disease free survival (iDFS), metastatic disease free survival (MDFS), quality of life (QoL), joint pain, and hot flashes.
Overall survival
Overall survival (OS) is the time from the date of surgery to the date of death due to any cause.
Invasive disease free survival
Invasive disease free suvival (iDFS) is the time from the surgery until the first occurrence of invasive ipsilateral, loco-regional, contralateral and distant breast tumor recurrence or death due to any cause
Metastatic disease free survival
Metastatic disease free survival (MDFS) is the time from the surgery until the first occurrence of distant breast tumor recurrence of death due to any causes
Health-related quality of life: FACT-B plus ES
Health-related quality of life is measured using the Functional Assessment of Cancer Therapy - Breast (FACT-B) plus the Functional Assessment of Cancer Therapy - Endocrine Symptoms (FACT-ES). The FACT-B has a total score of 0 to 148. FACT-ES has a total score of 0 to 184. Higher scores indicate better quality of life.
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