American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the appropriate adjuvant therapy for patients with stage III colon cancer?

1. Chemotherapy with capecitabine and oxaliplatin

2. Chemotherapy with methotrexate and cyclophosphamide

3. Chemotherapy with doxorubicin and vincristine

4. Chemotherapy with leucovorin, 5-fluorouracil, and oxaliplatin

The correct answer is: Chemotherapy with capecitabine and oxaliplatin

In stage III colon cancer, the cancer has spread to nearby lymph nodes but not to distant sites, and the goal of adjuvant therapy is to eliminate any residual disease after surgical resection. The most appropriate regimen for adjuvant therapy in this setting is chemotherapy that includes capecitabine and oxaliplatin, which is supported by clinical guidelines and research showing its effectiveness in reducing the risk of recurrence. Capecitabine is an orally administered prodrug of 5-fluorouracil, featuring a similar mechanism to 5-fluorouracil but with improved convenience and tolerability. Oxaliplatin is a platinum-based drug that adds synergistic benefits when combined with capecitabine, leading to enhanced efficacy. The combination has been extensively studied in clinical trials, such as the CALGB 89803 and X-ACT trials, which demonstrated improved overall survival and disease-free survival compared to prior regimens that did not include these agents. Other combinations listed, like methotrexate and cyclophosphamide or doxorubicin and vincristine, are not standard for colon cancer treatment and are more commonly associated with other malignancies or are not effective against colon cancer. Furthermore, while leucovorin