Clinical benefit of post-trastuzumab deruxtecan treatment in patients with HER 2-positive unresectable or metastatic breast cancer: A single-institution retrospective observational study.

PURPOSE: Trastuzumab deruxtecan (T-DXd) can improve the prognosis of patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). However, data on treatment recommendations after T-DXd are lacking. Thus, this study aimed to evaluate the treatment options after T-DXd and their effectiveness. METHODS: Patients with HER2-positive MBC were included in this study. Data from clinical records were retrospectively analyzed. The primary outcome was time to treatment failure (TTF). Secondary endpoints were TTF of each treatment and first-line treatment after interstitial lung disease (ILD) and overall survival (OS). RESULTS: A total of 29 patients were included. Among them, 18 (62%) were hormone receptor-positive. All patients had a median TTF (mTTF) of 3.5 months (95% confidence interval (CI) 2.1-10.03). The mTTF of each treatment, including HER2 tyrosine kinase inhibitor (HER2 TKI), other anti-HER2 treatments, and other treatments, was 2.6, 8.8, and 3.8 months, respectively. No significant differences were observed between treatments, but regimens that include trastuzumab showed a longer TTF than TKI. However, the mTTF among patients who developed T-DXd-related ILD was 2.33 months (95% CI 0.7-not reached), which was shorter than that among those who did not develop ILD (3.83 months, 95% CI 2.1-10.03, hazard ratio: 2.046, 95% CI 0.760-5.507, p = 0.258). The median OS was 14.9 months (95% CI 11.07-29.17). CONCLUSION: Treatments after T-DXd showed a shorter mTTF. Regimens that include trastuzumab may be more effective post-T-DXd treatment than HER2 TKI. Further data are needed to establish the best sequential treatment after T-DXd.

Utility of a breast biopsy clip and a point marker system in tailored axillary surgery for patients with breast cancer after neoadjuvant chemotherapy.

BACKGROUND: Tailored axillary surgery (TAS) is a new approach for selective removal of metastatic lymph nodes. This study evaluated the safety and utility of TAS using a breast biopsy clip inserted into a metastatic lymph node and a point marker consisting of a short hook wire and nylon thread to remove the clipped lymph node. METHODS: Patients with breast cancer and clinically confirmed metastases to one-to-three axillary lymph nodes were included in this study. A breast biopsy clip was inserted into the metastatic lymph nodes before neoadjuvant chemotherapy. TAS was performed in patients with ycN0 disease after neoadjuvant chemotherapy. The lymph nodes containing the clips were removed using a point marker. The success criteria for TAS were the removal of the lymph node into which the clip was inserted using a point marker and the identification of the sentinel lymph node. The false-negative rate was calculated for cases in which TAS and axillary lymph node dissection were performed. RESULTS: Thirty individuals from two institutions were enrolled between May 2021 and November 2022, of whom 20 underwent TAS. Ten patients had clinically positive axillary lymph nodes and underwent axillary lymph node dissection. No adverse events were observed in any patient using the clips or point markers. TAS was successful in 18 of the 20 patients (90%). Seven patients underwent TAS and axillary lymph node dissection with a false-negative rate of 0%. CONCLUSION: The use of clips and point markers to perform TAS is clinically feasible.

Single-dose trastuzumab monotherapy achieved pathological complete response (pCR) in a patient with HER2-positive breast cancer: a case report.

BACKGROUND: With advances in breast cancer treatment, the importance of de-escalation therapy to reduce harm during the treatment of elderly patients has attracted attention in recent years. Certain patient populations are expected to have a superior response to anti-HER2 drugs, particularly those with human epidermal growth factor receptor type 2 (HER2)-positive breast cancer. In this report, we describe our experience of dramatic anti-HER2 drug response in a patient who achieved pathological complete response (pCR) with a single dose of trastuzumab. CASE PRESENTATION: An 88-year-old woman presented with a 2-cm palpable mass in the left breast. Vacuum-assisted breast biopsy, ultrasonography, and positron emission tomography-computed tomography revealed estrogen receptor-negative and HER2-positive, T1N0M0, stage I breast cancer. Mastectomy was scheduled within 2 months of the initial visit; however, the patient was anxious about the length of the waiting period and requested medication in the interim. Therefore, prior to surgery, one cycle of trastuzumab monotherapy was administered at the discretion of the attending physician. Postoperative pathology showed no remnant of invasive carcinoma and pCR with only a 0.2-mm ductal carcinoma in situ remnant. The patient refused further medication after surgery because of severe diarrhea after trastuzumab administration. Postoperative treatment was limited to follow-up, and no recurrence was observed at 1 year and 6 months postoperatively. CONCLUSION: This case suggests that trastuzumab monotherapy may be effective in certain patients with HER2-positive breast cancer. In the future, identifying patients who are more likely to respond to trastuzumab, as in this case, will allow for more options regarding de-escalation therapy without chemotherapy, particularly in elderly patients who are concerned about the side effects of chemotherapy.