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Colon Cancer Appears Deadlier On The Right Side

New research data has suggested that the odds for survival among colon cancer patients may very well depend on which side of the colon the tumor is on, US News reports.

In a study conducted with more than 1,000 men and women colon cancer patients, the patients whose tumors were on the left side survived just over 33 months, while those who had their tumors on the right side survived only a little more than 19 months. These were all cases where the colon cancer had spread.

Lead researcher Dr. Alan Venook from the University of California, San Francisco, says that, “It’s a stunning and surprising finding, and the difference is dramatic.”

According to their data, colon cancer that begins on the right side is different from colon cancer that begins on the left.

Venook explains, “We thought of the colon as a tube that propelled stool out of the body, but it’s not that simple. Each side of the colon starts in a different place, which is why the cancers are biologically different.” He adds,

We don’t have just colon cancer, but varieties of colon cancer, and some have better prognosis than others. The bad ones tend to be on the right side of the colon and the better ones are on the left side.

The research team likewise found that patients with tumors on the left side lived a little longer, an average of 36 months, after the chemotherapy drug cetuximab (Erbitux) was included in their treatment. On the other hand, patients whose tumors were on the right side and had been treated with the same drug lived a little less than 17 months.

A similar pattern appeared among patients who were treated with the drug bevacizumab (Avastin). Those with tumors on the left survived up to 31 months, while patients with tumors on the right lived for around 24 months.

Venook is hopeful that these findings will be able to help find different treatments for colon cancer, depending on which side the tumor is on. “Right now, we don’t know the biology, we just know there is something we need to figure out.”

“Now that we are aware of this, there’s a whole lot more to learn and a lot of digging to do,” Venook says. “People don’t just have colon cancer, they have a particular brand of colon cancer, much as we see with breast cancer.”

Dr. Arun Swaminath, director of the inflammatory bowel disease program at Lenox Hill Hospital in New York City was surprised at the research findings. “I would have never thought that the location of the cancer should have any bearing on how people deal with treatment.” He says that, “Having metastatic [spreading] colon cancer is terrible, regardless of whether it’s right- or left-sided. So, everyone over 50 should have a colonoscopy to decrease the risk of developing cancer.”

The study was released Wednesday during a press conference that presented some of the research to be shown at the American Society of Clinical Oncology meeting in June. All research presented at the meetings are considered preliminary until published in a peer-reviewed medical journal.

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