Managing mCRC

CE / CME

Opportunities and Challenges in Management of Metastatic Colorectal Cancer

Physician Assistants/Physician Associates: 1.00 AAPA Category 1 CME credit

Nurse Practitioners: 1.00 Nursing contact hours, includes 1.00 hour of pharmacotherapy credit

Released: May 02, 2023

Expiration: May 01, 2024

Robert Lentz
Robert Lentz, MD

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Tumor Sidedness 

Tumor sidedness, meaning right-sided vs left-sided tumors, is of great importance in both prognosis and guiding treatment options. A right-sided tumor is defined as one in the ascending colon and the transverse colon up to the splenic flexure. A left-sided tumor is defined as occurring at the splenic flexure or more distally all the way through the rectum.11 

Patients with right-sided tumors have a worse prognosis, are more likely to have a KRAS or BRAF mutation, and to have MSI-high tumors. Right-sided tumors are more often seen in younger patients and in those with Lynch syndrome. For reasons that are not fully understood, right-sided disease does not respond as well to EGFR inhibitors, and typically these would not be used to treat right-sided disease. By contrast, patients with left-sided tumors have better survival and EGFR inhibitors can be used.4,11 

Selecting the optimal treatment for patients with mCRC depends on several considerations. These include clinical status, including previous treatments, comorbidities, performance status, and age; characteristics of the tumor, including sidedness, resectability, and tumor burden; and molecular characteristics. Equally important as these disease characteristics are patient-centered concerns about quality of life, toxicity of treatment, ability to adhere with treatment, and psychosocial issues.12,13

Which of these is the recommended first-line option for patients with left-sided, microsatellite-stable (MSS), wild-type RAS disease?