American Board of Internal Medicine (ABIM) Certification Practice Exam

When is chest wall radiation therapy recommended after a mastectomy in patients with invasive breast cancer?

1. For tumors smaller than 1 cm and negative margins

2. For tumors greater than 5 cm, positive margins, or involvement of the chest wall

3. For patients with no axillary lymph node involvement

4. Only for patients who choose breast-conserving surgery

The correct answer is: For tumors greater than 5 cm, positive margins, or involvement of the chest wall

Chest wall radiation therapy is recommended after a mastectomy in patients with invasive breast cancer primarily when there are specific adverse features that indicate a higher risk of local recurrence. The correct choice highlights scenarios that necessitate the use of radiation based on tumor characteristics and surgical findings. When tumors are greater than 5 cm, there is a presence of positive margins, or there is chest wall involvement, these factors significantly increase the likelihood of residual cancer cells at the surgical site. As a result, the addition of radiation therapy aims to eliminate any residual microscopic disease and thus reduce the risk of recurrence. It serves as an important adjunctive treatment in these high-risk situations. In contrast, smaller tumors (like those under 1 cm) with negative margins typically present a far lower risk of locoregional recurrence, thus often making radiation therapy unnecessary in those cases. Similarly, if a patient has no axillary lymph node involvement, they might also be considered at lower risk for recurrence, making radiation therapy less critical. Choosing breast-conserving surgery does not directly correlate with the need for chest wall radiation, as that decision is based more on the tumor's characteristics and extent of disease rather than the type of surgery performed. Therefore, the recommendation for chest wall radiation therapy is subst