This is ReachMD, and you’re listening to Conversations on Colorectal Cancer, sponsored by Lilly. On this episode, titled The The Importance of Tumor Sidedness, we will hear from Dr. Benjamin Weinberg from Georgetown University in Washington, DC.
There is overall a prognostic advantage from the left side over the right side and potentially the rectum over the left side over the right side, and why these patients do better we don’t really know. We do think maybe patients with left-sided cancers present earlier due to bleeding, whereas right-sided cancers may also cause obstruction or bleeding, and this could amount to a differential in when patients get diagnosed. But in studies controlling for this delay in diagnosis, it does seem that right-sided colon cancers seem to be more aggressive and potentially have a poor prognostic impact due to their tumor biology.
We do know that there are subsets of cancers on both sides that do better. For instance, right-sided cancers tend to have higher levels of microsatellite instability-high tumors, and we now know that these patients respond to immunotherapy, not approved in the first or second line; but for patients who have already been exposed to chemotherapy with MSI-high right-sided colon tumors, they respond well to either single-agent checkpoint blockade or double-agent checkpoint blockade, for instance with nivolumab and ipilimumab. So that’s a viable therapeutic option for patients with right-sided MSI-high tumors, and they would have a better prognosis overall than all patients with right-sided colon tumors. So there are exceptions to the right versus left versus rectal divide.
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