Some colon cancer patients don’t benefit from treatment with 5-FU based chemotherapy and may even have worse outcomes than if they no chemo at all.

Of every 100 people with colon cancer, about 15 will have cancers that arise when mistakes in DNA during cell division are not caught and fixed.  Scientists call this defective mismatch repair or dMMR.

More often, colon cancer occurs when mutations in chromosomes accumulate but DNA repair pathways remain intact and mismatch repair is proficient (pMMR). This is true for about 85 percent of colon cancer.

Both prognosis and the potential benefit from FU-based chemotherapy appear to be very different for these two types of colon cancer. Knowing mismatch repair status of colon tumors can help patients and their doctors make better treatment decisions.

Patients with defective mismatch repair have better disease-free and overall survival and don’t seem to benefit from 5-FU at either stage II or stage III.  Stage II patients with dMMR have significantly poorer overall survival if they get chemo after surgery.

Caution:  These results come from studies of 5-FU plus levamisole or 5-FU plus leucovorin.  They don’t include any information from the current standard treatments of FOLFOX or FLOX which contain oxaliplatin in addition to 5-FU and leucovorin.

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Although being obese increases risk for most colon and rectal cancers, the connection isn’t true in all types of colorectal cancer.

Cancers that are linked to microsatellite instability (MSI) don’t appear to be influenced by obesity, strengthening the belief that MSI cancers come about differently than the average colorectal cancer.

Overall, in a recent study, body mass index and weight gain during adult life increased risk of colorectal cancer by about 30 percent for men and 20 percent for women. However, increased risk was limited to microsatellite stable or microsatellite low tumors. Read the rest of this entry »

Briefly This Week

• Acupuncture didn’t reduce prolonged post-operative ileus.
• Large numbers of retrieved lymph nodes predict MSI in stage I and II colon cancer.
• Sarcomas found in families with Lynch syndrome.
• Changes in the weekly briefs. Read the rest of this entry »

Colon cancers that are caused by defects in genes that repair damaged DNA don’t respond well to 5-FU treatment after surgery.

However, a new analysis of patients treated with FOLFOX (oxaliplatin, leucovorin, and 5-FU) found no differences between patients with deficient mismatch repair tumors and those with normal gene expression.

In this small study of 135 patients, the research team concluded that adding oxaliplatin to 5-FU and leucovorin may overcome resistance to chemotherapy in mismatch repair deficient and microsatellite instable (MSI) colon cancer. Read the rest of this entry »

Two gene changes that occur in some colorectal cancers can forecast chances for good or poor survival.

Patients whose cancers had high microsatellite instability (MSI) had significantly better outcomes at every stage, but mutations in the KRAS gene predicted poorer survival. Read the rest of this entry »