Adjuvant systemic therapy and T1 breast cancer prognosis

This article explored the characteristics and outcomes of T1 breast cancer in an attempt to further improve survival among these early stage patients.

Staging of breast cancer is classily based on the size of the tumor (often marked as T), whether the cancer has spread to the surrounding lymph nodes (often marked as N) and whether the cancer has spread to other organs (or has metastasized, often marked as M). According to this staging system, called the TNM staging, T1 breast cancer is considered a small, early stage breast tumor, with three subtypes; T1a refers to a tumor size of 5mm or less, T1b refers to a tumor size of between 0.5cm and 1cm, and T1c refers to a tumor size greater than 1cm but smaller than 2cm.

Although T1 breast cancers carry a good prognosis, studies have shown that recurrence following treatment occurs in up to 20% of women. Therefore, additional treatments following the surgical removal of the tumor (referred to as adjuvant systemic therapy), such as targeted receptor therapies or hormonal treatments, are often recommended. This large analysis attempts to clarify the role of adjuvant treatments among different T1 breast cancer subtypes.

This study analyzed the medical records of 5423 women diagnosed with T1 breast cancer. It was found that T1a tumors were more likely to be hormone receptor-negative (referring to a tumor not dependent on estrogen or progesterone for growth), and HER2 positive (referring to a tumor whose growth is stimulated by growth hormones), compared to larger T1 tumors.  While HER2-positive breast cancers allow for the use of targeted biological therapies, hormone receptor-negative cancers are generally associated with worse prognosis.

84.7% of women with T1a breast cancer were found to receive adjuvant systemic therapy, compared to 91.2% of T1b patients and 95.3% of T1c patients. Analysis of cancer outcomes after an average follow-up of 60.5 months showed recurrence free survival to be significantly longer among T1b patients, with 95.9% of patients cancer-free at the end of the study follow-up, compared to 93.2% of T1a patients. 5-year recurrence free survival rates were significantly greater among patients receiving adjuvant treatments, especially among hormone receptor-positive patients receiving hormonal therapy.

Overall survival rates among all T1 patients were 97.6% at 5-years, 95.4% at 7-years and estimated as 90.7% at 10-years. No significant difference in overall survival was noted between T1a, T1b and T1c patients.

This study concluded that T1a tumors are associated with an increased risk of negative prognostic factors and worse overall prognosis compared to T1b and T1c tumors. The importance of adjuvant systemic therapy should be stressed among all early stage breast cancer patients, including women with T1a tumors.