Introduction: adjuvant therapy for colon cancer
Approximately 70–80% of patients with newly diagnosed cases of colorectal cancer undergo curative resection. However 40% of these develop incurable recurrent disease due to undetected micrometastases.
In particular, patients with stage III (T1 to T4, N1-2) or Dukes C colon cancer have a 5-year survival rate of 42–92%, varying substantially depending on the T and N stage. Patients with stage II (T3 or T4, N0) or Dukes B colon cancer have a 5-year survival rate of 62–88%. The poorest outcomes are seen in those with high risk clinicopathological features, which include a presentation with perforation or obstruction and pathology findings of T4 stage, less than 12 lymph nodes sampled, poor differentiation, neural or vascular invasion, and proficient mismatch repair.
The inability to cure all such patients is a direct consequence of residual disease left behind after surgery. Over the last two decades, adjuvant chemotherapy has been offered to such high-risk patients with the aim to decrease relapse and improve overall survival, by attempting to eliminate this microscopic residual disease.
As the median age of diagnosis for colon cancer is just over 70 years, older patients constitute a large proportion of the stage II and III population.
Adjuvant therapy is any treatment that is given in addition to a standard curative cancer treatment such as surgery. By convention, the term ‘adjuvant’ is reserved for postoperative treatment, while ‘neoadjuvant’ refers to treatment given prior to the definitive surgery.
Chemotherapy is cytotoxic drug treatment. Systemic chemotherapy affects the entire body, and is given with the intent of killing residual cancer cells that may lodge and grow in distant organs such as the liver and lungs.
Chapter subsections[edit source]
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