This prospective, multicenter observational cohort study evaluates long-term outcomes in patients with early-stage invasive breast cancer who undergo breast-conserving surgery without sentinel lymph node biopsy or other axillary surgery and subsequently receive adjuvant radiotherapy. The study will evaluate recurrence, survival, radiotherapy-related toxicities, and quality of life. Radiotherapy will be delivered according to routine clinical practice at each participating institution without protocol-mandated treatment assignment. Detailed radiotherapy characteristics, including treatment volume, technique, dose and fractionation, tumor-bed boost, and radiation dose to axillary lymph node levels I-III, will be prospectively collected to evaluate their associations with clinical outcomes.
Recent clinical trials have supported the omission of sentinel lymph node biopsy in selected patients with clinically node-negative early breast cancer. However, radiotherapy approaches after sentinel lymph node biopsy omission vary in routine clinical practice, and prospective data regarding the relationship between radiotherapy characteristics, radiation dose delivered to the axillary lymph nodes, and long-term clinical outcomes remain limited. Depending on patient and tumor characteristics and institutional practice, radiotherapy may include whole-breast or partial-breast irradiation with different treatment techniques, dose-fractionation schedules, and tumor-bed boost strategies. The APROOB Cohort is designed to prospectively characterize these variations and evaluate their associations with recurrence, survival, treatment-related toxicity, and quality of life following omission of sentinel lymph node biopsy. No radiotherapy technique, treatment volume, dose, or fractionation schedule is assigned by the study.
Study Type
OBSERVATIONAL
Enrollment
500
Adjuvant radiotherapy is delivered after breast-conserving surgery according to routine clinical practice at each participating institution. Radiotherapy may include whole-breast irradiation or partial-breast irradiation, with treatment technique, dose, fractionation, and tumor-bed boost determined by the treating physician. The study does not assign or mandate a specific radiotherapy regimen.
Samsung Medical Center
Seoul, South Korea
RECRUITING5-Year Recurrence-Free Survival Rate
Recurrence-free survival is defined as the time from study enrollment to the first occurrence of ipsilateral invasive breast recurrence, ipsilateral regional lymph node recurrence, distant metastasis, or breast cancer death. The 5-year recurrence-free survival rate will be estimated using the Kaplan-Meier method.
Time frame: From study enrollment to 5 years
5-Year Axillary Recurrence Rate
Axillary recurrence is defined as newly diagnosed breast cancer recurrence in the ipsilateral axillary lymph nodes after study enrollment. The 5-year cumulative incidence of axillary recurrence will be estimated.
Time frame: From study enrollment to 5 years
5-Year Locoregional Recurrence Rate
Locoregional recurrence is defined as the first occurrence of one or more of the following after study enrollment: ipsilateral invasive breast recurrence; ipsilateral axillary lymph node recurrence; ipsilateral supraclavicular or infraclavicular lymph node recurrence; or ipsilateral internal mammary lymph node recurrence. The 5-year cumulative incidence will be estimated.
Time frame: From study enrollment to 5 years
5-Year Distant Metastasis Rate
Distant metastasis is defined as breast cancer metastasis occurring in organs or non-regional lymph nodes outside the ipsilateral breast and ipsilateral regional lymph node regions. The 5-year cumulative incidence of the first distant metastasis after study enrollment will be estimated
Time frame: From study enrollment to 5 years
5-Year Overall Survival Rate
Overall survival is defined as the time from study enrollment to death from any cause. The 5-year overall survival rate will be estimated using the Kaplan-Meier method.
Time frame: From study enrollment to 5 years
Incidence of Acute Grade 2 or Higher Radiotherapy-Related Toxicity
The proportion of participants experiencing at least one grade 2 or higher acute radiotherapy-related adverse event will be assessed using the Common Terminology Criteria for Adverse Events (CTCAE), version 6.0. CTCAE grades range from 1 to 5, with higher grades indicating greater severity. Acute toxicity is defined as toxicity occurring from the start of radiotherapy through 90 days after completion of radiotherapy.
Time frame: From the start of radiotherapy through 90 days after completion of radiotherapy
Incidence of Late Grade 2 or Higher Radiotherapy-Related Toxicity
The proportion of participants experiencing at least one grade 2 or higher late radiotherapy-related adverse event will be assessed using the Common Terminology Criteria for Adverse Events (CTCAE), version 6.0. CTCAE grades range from 1 to 5, with higher grades indicating greater severity. Late toxicity is defined as toxicity newly occurring or persisting more than 90 days after completion of radiotherapy.
Time frame: From more than 90 days after completion of radiotherapy to 5 years after radiotherapy
Change From Baseline in Global Health Status/Quality of Life Score Assessed by the EORTC QLQ-C30
Global health status and quality of life will be assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30). The Global Health Status/Quality of Life scale is transformed to a score ranging from 0 to 100. A higher score indicates better global health status and quality of life. The change from baseline will be evaluated at each scheduled follow-up assessment.
Time frame: Baseline and up to 5 years after radiotherapy
Change From Baseline in Breast Symptoms Score Assessed by the EORTC QLQ-BR23
Breast symptoms will be assessed using the Breast Symptoms scale of the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Breast Cancer Module 23 (EORTC QLQ-BR23). The score is transformed to a scale ranging from 0 to 100. A higher score indicates more severe breast symptoms and therefore a worse outcome. The change from baseline will be evaluated at each scheduled follow-up assessment.
Time frame: Baseline and up to 5 years after radiotherapy
Change From Baseline in Arm Symptoms Score Assessed by the EORTC QLQ-BR23
Arm symptoms will be assessed using the Arm Symptoms scale of the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Breast Cancer Module 23 (EORTC QLQ-BR23). The score is transformed to a scale ranging from 0 to 100. A higher score indicates more severe arm symptoms and therefore a worse outcome. The change from baseline will be evaluated at each scheduled follow-up assessment.
Time frame: Baseline and up to 5 years after radiotherapy
Change From Baseline in Body Image Score Assessed by the EORTC QLQ-BR23
Body image will be assessed using the Body Image scale of the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Breast Cancer Module 23 (EORTC QLQ-BR23). The score is transformed to a scale ranging from 0 to 100. A higher score indicates better body image and therefore a better outcome. The change from baseline will be evaluated at each scheduled follow-up assessment.
Time frame: Baseline and up to 5 years after radiotherapy
This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.