American Board of Internal Medicine (ABIM) Certification Practice Exam

In which case is postoperative chemoradiation indicated for rectal cancer?

1. Stage I cancer

2. T2 tumors

3. Higher T stage than expected or positive lymph nodes

4. All rectal cancers

The correct answer is: Higher T stage than expected or positive lymph nodes

Postoperative chemoradiation is indicated for rectal cancer primarily in situations where there is a higher likelihood of residual disease or recurrence after surgery. This situation typically arises in cases of higher T stages or when positive lymph nodes are identified. In rectal cancer staging, T stage refers to the extent of the tumor invasion into the rectal wall and surrounding tissues. Higher T stages, particularly T3 or T4, indicate greater tumor depth or extraintestinal extension, which significantly raises the risk of local recurrence. Similarly, the presence of positive lymph nodes suggests that the cancer has spread beyond the primary site, which can lead to metastatic disease. Administering chemoradiation in these scenarios aims to eliminate any microscopic disease that may remain after surgical resection and to reduce the chance of local recurrence, which can otherwise occur in as much as 30-50% of patients with advanced disease. In contrast, stage I cancer typically has an excellent prognosis with surgical intervention alone and does not require chemoradiation. T2 tumors, which are invasive but still contained within the rectal wall, may not necessarily warrant postoperative chemoradiation unless there are additional high-risk features present. Finally, while rectal cancers generally benefit from multidisciplinary management,