The De-escalation of Breast Cancer Therapy
One of the great challenges in modern cancer management is to limit or discontinue traditional therapies that have not proven beneficial in certain populations of patients. Adjuvant radiotherapy is prescribed after breast-conserving surgery to reduce the risk of local recurrence. However, radiotherapy is inconvenient, costly, and associated with both short-term and long-term side effects.
Clinicopathologic factors alone are of limited use in the identification of women at low risk for local recurrence in whom radiotherapy can be omitted. Molecularly defined intrinsic subtypes of breast cancer can provide additional prognostic information.
A prospective cohort study reports results in 500 women who were at least 55 years of age, had undergone breast-conserving surgery for T1N0 (tumor size <2 cm and node negative), grade 1 or 2, luminal A–subtype breast cancer (defined as estrogen receptor positivity of ≥1%, progesterone receptor positivity of >20%, negative human epidermal growth factor receptor 2, and Ki67 index of ≤13.25%), and had received adjuvant endocrine therapy. Among women who were at least 55 years of age and had T1N0, grade 1 or 2, luminal A breast cancer that were treated with breast-conserving surgery and endocrine therapy alone, the incidence of local recurrence at 5 years was low with the omission of radiotherapy.
Radiotherapy of the breast is commonly administered after breast-conserving surgery to reduce the risk of local recurrence and thereby avoid mastectomy. However, radiotherapy is inconvenient for patients, involving 3 to 6 weeks of daily treatments, and is costly. It is also associated with considerable short-term side effects, such as fatigue, skin irritation, and breast swelling, and long-term side effects, such as skin telangiectasia, breast pain, induration, and retraction, that can adversely affect cosmesis and quality of life. Rarely, breast radiotherapy can cause second cancers and ischemic cardiac disease.
The use of Ki67 identifies a potentially useful marker, although not currently captured as an element of TNM staging of breast cancer. It is important to capture these types of markers in our cancer registries for many types of cancers to help in identifying instances in which traditional therapies can be abandoned.
