When is adjuvant radiation therapy (RT) necessary in breast cancer?

From the Guidelines

Adjuvant radiation therapy (RT) is necessary in breast cancer after breast-conserving surgery for nearly all patients, except for selected older women with low-risk, hormone-positive tumors taking endocrine therapy, where it may be safely omitted. When considering adjuvant RT in breast cancer, several factors come into play, including the patient's age, tumor characteristics, and overall health status.

• The decision to use adjuvant RT should be made on a case-by-case basis, taking into account the individual patient's risk of recurrence and potential benefits from radiation therapy.
• According to the study by 1, adjuvant RT may be omitted in women aged 70 years or older with clinical stage I, estrogen receptor-positive breast cancer who will receive endocrine therapy.
• The study found that the 10-year local recurrence rates were 2% and 10%, respectively, for those who received tamoxifen with RT and those who received tamoxifen alone, with no significant differences in overall survival or breast cancer-specific survival between the groups 1.
• Another study, the PRIME II study, also found that omission of whole-breast RT after breast-conserving surgery could be considered for some women aged 65 years or older with early-stage breast cancer, with a low rate of ipsilateral recurrence (1.3% vs 4.1%) and no difference in overall survival between the groups 1.
• The standard regimen for adjuvant RT involves whole breast radiation delivered over 3-6 weeks, sometimes with an additional boost to the tumor bed.
• Partial breast irradiation may be appropriate for select low-risk patients, and the decision for adjuvant RT should be made in a multidisciplinary setting, considering tumor characteristics, patient age, comorbidities, and preferences.
• It is essential to weigh the potential benefits of adjuvant RT against the potential risks and side effects, particularly in older patients or those with significant comorbidities.
• Ultimately, the decision to use adjuvant RT should be individualized and based on the latest evidence and guidelines, such as those from the NCCN 1.

From the Research

Adjuvant Radiation Therapy in Breast Cancer

• Adjuvant radiation therapy (RT) is an essential component in the management of breast cancer, particularly after breast-conserving surgery (BCS) or mastectomy 2, 3, 4.
• The decision to use adjuvant RT depends on various factors, including the stage of cancer, tumor size, lymph node involvement, and patient age 3, 5.
• For patients with early-stage breast cancer, adjuvant RT is recommended after BCS to reduce the risk of local recurrence and improve breast cancer-specific survival 2, 4.
• Hypofractionated whole breast irradiation (WBI) is a standard approach for adjuvant RT, reducing the duration of treatment to 3-4 weeks 2.
• Partial breast irradiation is an alternative to WBI for selected patients with early-stage breast cancer, reducing the duration of treatment and the volume of breast tissue irradiated 2, 3.
• For patients requiring RT to the regional lymph nodes, hypofractionated approaches are safe and effective 2, 3.
• The use of adjuvant RT in older women with favorable early-stage breast cancer is still being studied, with some evidence suggesting that RT monotherapy may offer comparable overall survival to endocrine therapy monotherapy 5.

Specific Indications for Adjuvant RT

• After conservative surgery for infiltrating carcinoma, RT is systematically performed, regardless of disease characteristics, to decrease local recurrence and specific mortality 3.
• A boost dose over the tumor bed is required for patients younger than 50 years old 3.
• After mastectomy, chest wall irradiation is required for pT3-T4 tumors and axillary nodal involvement 3.
• Axillary irradiation is recommended only if there is no axillary surgical dissection and a positive sentinel lymph node 3.
• Supra- and infraclavicular irradiation is advised in case of positive axillary nodes 3.

Ongoing Research and Future Directions

• Studies are underway to evaluate the safety and efficacy of shorter regimens and omission of RT versus omission of endocrine therapy for favorable-risk patients 2.
• The use of tumor genomics to identify appropriate patients for omission of radiation with limited nodal involvement is being explored 2.
• Further comparisons of RT-only versus ET-only may be warranted in older patients with early-stage, ER+/HER2- breast cancer who undergo lumpectomy 5.