Study Identifies Clinicopathologic and Adjuvant Treatment Characteristics Linked to Very Low Risk of Local Recurrence After Breast-Conserving Surgery
Histologic grade, age, margin status, and use of endocrine therapy may identify a subset of women aged ≥ 50 with stage I breast cancer, who are at a very low risk of disease recurrence after breast-conserving surgery plus whole-breast radiotherapy, according to a study by Smith et al in the International Journal of Radiation Oncology • Biology • Physics.This finding suggests that these women may safely forgo radiotherapy, although further study is needed to support this approach.
Breast-conserving surgery plus whole-breast radiation therapy is the current standard of care for women over 50 with stage I breast cancer. Previous studies have attempted to determine whether these patients could forgo whole-breast radiation therapy and still maintain lower rates of disease recurrence, but the results have been mixed. With that in mind, the investigators aimed to identify clinical and pathologic factors that might shed further light on the need for whole-breast radiation therapy after breast-conserving surgery within this patient population.
Study Details and Results
The investigators conducted an analysis of an institutional database of patients with newly diagnosed breast cancer who underwent breast-conserving surgery and whole-breast radiotherapy. Over half of the patients received adjuvant systemic therapy, which was categorized as endocrine therapy alone, chemotherapy alone, or both endocrine therapy and chemotherapy. The primary outcome was local disease recurrence in the ipsilateral breast.
Factors analyzed by the investigators included age, menopausal status at diagnosis, and estrogen receptor status. They also examined tumor factors such as size, histologic type, histologic grade, and lymphovascular tumor invasion.
Among 821 patients treated with breast-conserving surgery plus whole-breast radiation therapy for grade 1 tumors who did not receive endocrine therapy, the rate of 5-year local tumor recurrence was 0.6% (95% confidence interval [CI] = 0.1%–1.2%). The rate of 10-year local tumor recurrence was 2.2% (95% CI = 1.0%–3.4%).
Among 1,038 women with grade 1 tumors treated with breast-conserving surgery, whole-breast radiation therapy, and endocrine therapy, the rate of 5-year local tumor recurrence was 0.2% (95% CI = 0.0%–0.5%) and the 10-year rate was 0.8% (95% CI = 0.1%–1.6%). In comparison, among 843 patients aged ≥ 60 years with grade 2 tumors treated with breast-conserving surgery, whole-breast radiation therapy, and endocrine therapy, the 5-year rate of local tumor recurrence was 0.5% (95% CI = 0.0%–1.1%) and the 10-year local tumor recurrence rate was 0.9% (95% CI = 0.2%–1.6%).
The results of this study indicated that clinicopathologic and adjuvant treatment characteristics (histologic grade, age, margin status, and use of endocrine therapy) can be used to identify subgroups of female patients with stage I breast cancer who have a local tumor recurrence rate ≤ 1.5% at 5 years after breast-conserving surgery and radiotherapy. These findings suggest that these subsets of patients may have a local tumor recurrence risk of < 5% without the inclusion of radiotherapy.
Clinical Implications
Utilizing the advancements in intrinsic subtyping and current findings of very low local tumor recurrence risk based on traditional clinicopathologic characteristics in some patients, the findings from this study may revive the question of whether subtype testing can be used in combination with readily available clinicopathologic characteristics to select patients with a very low risk of local tumor recurrence risk who may be safely treated with adjuvant endocrine therapy without whole-breast radiotherapy.
One concern regarding forgoing radiotherapy in patients with very low risk of local tumor recurrence is the possibility of poor adherence to endocrine therapy. However, previous findings from the same institution indicated that 61.4% of patients continued to take endocrine therapy for ≥ 80% of days prescribed.
The investigators remarked, “Histologic grade, age, margin status, and use of endocrine therapy may identify approximately 45% of female patients, aged ≥ 50 with stage I breast cancer, who have very low recurrence risks after [breast-conserving surgery plus breast radiotherapy].”
Sally L. Smith, BSc, MD, FRCPC, of the Radiation Therapy Program and Breast Cancer Outcomes Unit, British Columbia Cancer Agency, is the corresponding author of the article in the International Journal of Radiation Oncology • Biology • Physics.
The authors reported no potential conflicts of interest.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
