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Question

A 45 year-old woman complaining of breast pain was diagnosed with having HER2-positive breast cancer. The patient underwent lumpectomy followed by a period of chemotherapy including adjuvant treatment. Over the course of their treatment, the patient developed a urinary tract infection that required antimicrobial therapy, which initially consisted of a trimethoprim/sulfametoxazole combination drug. However, the patient during the course of her therapy suffered multiple recurrent infections and was, consequently, enrolled in a clinical trial to test the efficacy of a new mannoside anti-infective agent.

Question: Discuss the mechanisms underpinning current therapeutic strategies for treating HER2-positive breast cancer. In your discussion, you should include details about managing therapeutic resistance and adverse side effects such as cardiotoxicity.

Answer 1

Approximately 25% of breast cancer cases, the cancer cells have an excess of the HER2 protein. This is caused by a mutation in the HER2 -human epidermal growth factor receptor 2 gene. When mutation of HER2 gene occurs, it causes cells in the breast to grow and divide at an uncontrolled pace, resulting to growth of a tumor.

Diagnosis of HER2-positive breast cancer:

1. The Inform Dual ISH test utilizes stains that color HER2 genes in a tissue sample so they can be counted under a microscope.
2. The IHC test utilizes certain antibodies that identify the HER2 protein in a sample of breast cancer tissue.
3. The  FISH test utilizes fluorescent pieces of DNA that stick to the HER2 gene in cells, which are then counted under a microscope.