Reply To: In situ colorectal cancer rates

Reply To: In situ colorectal cancer rates

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Jim Hofferkamp

A few reasons i can think of that may explain some of the differences.

1. Reporting from surgery centers. If a patient has a colonoscopy with polypectomy and is found to have a low grade in situ tumor, they may not receive any additional treatment. A more invasive tumor would probably be treated with resection. If the central registry doesn’t have good reporting from surgery centers, their in situ cases may be down.
2. High grade dysplasia is a big issue among pathologist. Some pathologist consider high grade dysplasia to be carcinoma in situ and others do not. Each facility is responsible for determining when or if a high grade dysplasia should be abstracted as carcinoma in situ. If some of the larger facilities are reporting some or all of their high grade dysplasia cases as carcinoma in situ, it could impact rates.
3. A less likely explanation might be the AJCC definition of Tis for colon. A Tis for colon includes tumors that invade the lamina propria. They do this because these patients should be treated like in situ cases (not like T1 patients). Even though the T value is Tis, these cases should have a behavior of /3 and summary stage of 1-localized. However, some registrars see that AJCC calls these Tis and assume the behavior should match.

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