57 Addressing Barriers to Identifying Patients With HER2-Low Metastatic Breast Cancer in a Large Community Oncology Practice

57 Addressing Barriers to Identifying Patients With HER2-Low Metastatic Breast Cancer in a Large Community Oncology Practice

Background

A large community oncology practice initiated a retrospective quality improvement initiative to address challenges in identifying patients with HER2-low metastatic breast cancer (mBC) based on information available within the electronic medical record (EMR).

Materials

Medical records for patients with mBC treated between January 1, 2023, and August 11, 2023, were queried within OncoEMR and chart reviews were performed. HER2 test results were included regardless of stage when tested. Patients with mBC with an HER2 immunohistochemistry (IHC) score of 1+ or 2+/in situ hybridization–negative (ISH–) were considered “HER2-low,” IHC 0 was considered HER2-negative” (HER2–), IHC 3+ or fluorescence in situ hybridization (FISH)–positive was labeled “HER2-positive” (HER2+) and patients who were referred to as “HER2-negative” in clinical notes but who did not have a HER2 IHC score documented in the EMR or within an embedded pathology report were considered “indeterminate.”

Results

Of 376 patients with mBC, 101 (27%) patients were HER2+, 95 (25%) were HER2– (IHC 0), 120 (32%) were HER2-low (IHC 1+ or 2+/ISH–), 6 (1.5%) patients had conflicting IHC scores, and 54 (14%) were noted as “HER2-negative” in the EMR but did not have documented HER2 IHC scores (ie, indeterminate). Of the indeterminate patient group, the following scenarios attributed to lack of IHC score:

1. 15 (28%) did not have pathology reports within the EMR.
2. 39 (72%) only received HER2 testing by FISH. Most of these cases (> 90%) were prior to the approval of fam-trastuzumab deruxtecan-nxki for HER2-low mBC in August 2022, which underscores the need to reassess HER2 status at progression.
3. HER2 testing was not performed at metastatic diagnosis in about 20% of indeterminate cases; however, 5% had documented supportive rationale (eg, bone-only disease or tissue quantity insufficient for testing).

Conclusions

Most publications to date have explored laboratory barriers to diagnosing HER2-low patients, yet there continue to be major obstacles for community oncology practitioners. Pathology reports are typically PDF documents embedded in the EMR, found under varying tabs or fields, and not easily queried. Community practices send testing to multiple different laboratories with various report formats that may not prominently display the HER2 IHC score. Also, clinicians may not cross-reference the original pathology report while reviewing clinical notes or patient referrals. Finally, certain laboratories perform FISH testing alone up front for HER2 in patients with breast cancer.