Clinicians are pushing back against simple "negative" HER2 pathology reports, demanding detailed Immunohistochemistry (IHC) scores (0, 1+, 2+, 3+) and the criteria used. This granular data is crucial for determining eligibility for modern treatments like antibody-drug conjugates (ADCs), where even low protein expression can be clinically relevant and actionable for patient care.
To qualify patients for HER2-directed therapies, clinicians pragmatically review all available historical biopsies (e.g., from the primary tumor or a prior recurrence). If any sample shows a positive result, they use it to justify insurance approval. This strategy prioritizes getting the patient the drug and avoids the need for a new, potentially invasive biopsy on the current metastatic lesion.
The mechanism of antibody-drug conjugates (ADCs) changes the purpose of HER2 testing. Unlike older therapies needing HER2 amplification to interrupt a functional pathway, ADCs only need the HER2 protein as an "anchor" to deliver their payload. This means even low protein expression is relevant, and follow-up amplification tests like FISH are often unnecessary for determining ADC eligibility.
When a gynecologic cancer recurs, the decision to perform a new biopsy for HER2 testing is often time-dependent. Clinicians may use a ~12-month interval as a practical threshold. A longer time since initial diagnosis increases the likelihood of tumor evolution, making a new biopsy necessary to accurately guide therapy for the current tumor rather than relying on historical data.