A retrospective analysis of clinical trial data reveals that in patients with metastatic colorectal cancer, primary tumor location is predictive of their response to various treatment strategies for the disease. This builds on previous data that tumor “sidedness” is indicative of overall survival within this same patient population, with patients with left-sided primary tumors having significantly better prognosis than those with right-sided tumors.
The study analyzed data of patients with RAS wild-type metastatic colorectal cancer from the Cetuximab and/or Bevacizumab Combined With Combination Chemotherapy in Treating Patients With Metastatic Colorectal Cancer (CALGB/SWOG 80405) clinical trial. Patients with left-sided primary tumors responded significantly better to cetuximab, which had an average survival of 39 months as opposed to 32 months with bevacizumab. Conversely, patients with right-sided primary tumors responded more favorably to bevacizumab.
“The molecular differences between left and right-sided tumors in the colon are such that they are essentially two different diseases,” said Heinz-Josef Lenz, MD, chair of the Gastrointestinal Oncology Program and co-director of the Colorectal Center at USC Norris Comprehensive Cancer Center and co-chair of the SWOG 80405 clinical trial. “More research is needed to determine why there is such a vast prognostic difference; but for the time being, tumor sidedness should be heavily considered when developing a treatment plan for metastatic colorectal cancer patients, and future clinical trials should first stratify participants by primary tumor location.”
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Lenz presented the data at the European Society for Medical Oncology Congress on October 10. He was also a co-author on a paper published in JAMA Oncology online that illustrated similar findings through the CRYSTAL and FIRE-3 clinical trials. At the American Society of Clinical Oncology, Lenz’s colleague and co-chair of the SWOG 80405 trial, Alan Venook, MD, first presented research that illustrated the significant difference in overall survival between patients based on primary tumor location.
by Mary Dacuma