Trends in the Management of Small HER2-Positive Breast Cancers

The treatment approach for small HER2-positive (+) breast cancers seeks to optimize efficacy while minimizing potential overtreatment and associated toxicities. This study aims to evaluate recent trends in treatment patterns for small HER2+ tumors.

Patients diagnosed with HER2+, cT1, cN0/pN0 breast cancer treated at a single institution from January 2018 to December 2022 were included. Clinicopathological, treatment, and follow-up data were collected and analyzed.

A total of 207 patients were included. Mean age was 63 (± 12.0) years. T category included cT1a in 12.1% (n = 25), cT1b in 28.0% (n = 58), and cT1c in 57.5% (n = 119), while 2.4% (n = 5) had clinical T1 category without further specification. Moreover, 74.4% (n = 154) were hormone receptor positive. Also, 66.7% (n = 138) received adjuvant therapy, 12.6% (n = 26) received neoadjuvant systemic therapy (NAT), and 12.1% (n = 25) received no systemic therapy. Administered regimens included: trastuzumab monotherapy in 6.1% (n = 10), taxane/trastuzumab in 55.5% (n = 91), taxane/carboplatin/trastuzumab in 18.9% (n = 31), and taxane/carboplatin/trastuzumab/pertuzumab in 15.2% (n = 25). In the 26 patients who received NAT, pathological complete response (pCR) was noted in 69.2% (n = 18). Overall, use of NAT increased from 2018 (7.1%) to 2021 (30.2%) and then decreased in 2022 (9.1%). The overall mastectomy rate was 35.3% (n = 73). Young age and multiple tumors were associated with a higher rate of mastectomy (age p < 0.001; multiple tumors p = 0.006). Upstaging of clinically node-negative patients occurred in 14.1% of patients at surgery.

The treatment for cT1N0 HER2+ breast cancers includes primary surgery with adjuvant HER2-targeted therapy in combination with chemotherapy. Primary surgery may allow for an opportunity to deescalate adjuvant therapy with no impact on surgical plan.