Breast cancer: was the treatment up to guideline?

Breast cancer treatment is driven by three lab results: the estrogen receptor (ER), the progesterone receptor (PR), and HER2. Together they sort a tumor into one of four subtypes, and each subtype has its own pathway in the clinical practice guidelines.

Most of what goes wrong after breast surgery traces back to those three results. Either they were never documented, or the therapy that should follow from them never happened. Here is what we check a breast cancer record against.

The decisions that matter

• Receptor testing. Every invasive breast cancer should have ER, PR, and HER2 status documented before treatment decisions are made. It is the fork in the road for everything that follows.
• Endocrine therapy for hormone-positive disease. If the tumor is ER- or PR-positive, the guidelines call for endocrine therapy (tamoxifen or an aromatase inhibitor, usually for five to ten years) after surgery. It is inexpensive, effective, and surprisingly easy to find missing from a record.
• HER2-targeted therapy. A HER2-positive tumor should be treated with HER2-targeted drugs such as trastuzumab (Herceptin), typically alongside chemotherapy. Leaving it out of a HER2-positive treatment plan is a serious gap.
• Chemotherapy for triple-negative disease. Triple-negative tumors lack all three receptors, so endocrine and HER2 drugs do nothing for them. Chemotherapy carries the load, and the guidelines recommend it for most triple-negative tumors beyond a very small size.
• The 21-gene recurrence score. For many hormone-positive, HER2-negative cancers, a genomic assay (Oncotype DX) shows whether chemotherapy adds anything on top of endocrine therapy. The guidelines say to use it in eligible cases. Without it, patients get over-treated or under-treated.
• Metastatic disease. Stage IV treatment should still follow the subtype. The receptors keep steering the choice of therapy even after the cancer has spread.

What a deviation looks like

A HER2-positive cancer treated with chemotherapy alone and no trastuzumab. An ER-positive tumor with no endocrine therapy after surgery, or endocrine therapy stopped after a year with nothing in the record explaining why. Receptor results missing from the chart entirely. Each finding we raise cites the guideline page for that subtype's pathway, so a professional can check the source in seconds.