What tumor marker determines whether trastuzumab (Herceptin) treatment is appropriate?

The correct answer focuses on the HER2/neu tumor marker, which is crucial in determining eligibility for trastuzumab (Herceptin) treatment. HER2/neu is a gene that plays a significant role in the growth and spread of cancer cells. In certain breast cancers, the HER2/neu protein is overexpressed, indicating that the tumor may be more aggressive and could benefit from targeted therapies like trastuzumab.

Trastuzumab is specifically designed to target HER2-positive breast cancer cells, effectively slowing down their growth or causing their death. Thus, assessing the expression level of this marker is essential for oncologists, as it helps them decide if trastuzumab will likely be an effective treatment option for patients with breast cancer that overexpresses the HER2 protein.

Other markers listed, such as beta-hCG, LDH, and PSA, are associated with different cancers and are not relevant for the treatment decision regarding trastuzumab. Beta-hCG is used primarily for germ cell tumors and trophoblastic disease, LDH is a general marker of tissue breakdown, and PSA is specific to prostate cancer. Therefore, they do not inform decisions related to trastuzumab treatment in the context of HER2-overexpressing breast cancer