Left or Right Primary Tumor Location Predicts Colon Cancer Survival Rate

Ian C. Langtree - Writer/Editor for Disabled World (DW)
Published: 2016/06/08 - Updated: 2024/11/02
Publication Type: Informative
Topic: Colorectal Cancers - Publications List

Page Content: Synopsis - Introduction - Main

Synopsis: Patients with colorectal cancer whose primary tumor is situated on the left side of the colon survive significantly longer than patients whose cancer starts on the right side.

Why it matters: This article offers valuable insights into colorectal cancer by highlighting the significant impact of tumor location on patient survival outcomes. It presents findings from a large clinical trial that demonstrates patients with left-sided primary tumors have a notably longer median overall survival compared to those with right-sided tumors, suggesting that tumor location is a critical factor in treatment efficacy and prognosis. This research, led by Alan P. Venook and presented at the American Society of Clinical Oncology meeting, challenges existing treatment paradigms and underscores the need for further exploration into the molecular biology behind these differences. The article is particularly useful for medical professionals and researchers as it could influence future colorectal cancer treatment strategies and deepen understanding of cancer biology - Disabled World (DW).

Introduction

A study, the largest of its kind so far to look at tumor location in colorectal cancer, is a retrospective analysis of data from a large clinical trial designed to compare the effectiveness of two drugs for treating metastatic colorectal cancer.

Main Item

The analysis shows that patients whose primary tumor is on the left of the colon (the side comprising the descending colon, sigmoid colon, and rectum) have a significantly longer survival than patients whose primary tumor is on the right side (where the cecum and ascending colon are located).

Lead author Alan P. Venook, a professor of medicine at the University of California-San Francisco (UCSF), explains that while previous studies have suggested tumor site can influence clinical outcomes in colorectal cancer, the effect they observed in their analysis is much bigger than they expected.

The study was presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago, IL, June 3-7, 2016.

ASCO President Julie M. Vose says this unexpected discovery "could answer some long-standing questions about why certain patients do better than others."

The data came from a clinical trial that compared bevacizumab and cetuximab in combination with chemotherapy as initial therapy for metastatic colorectal cancer.

In their main analysis, the researchers used data on 293 patients with right-sided primary tumors and 732 patients with left-sided primary tumors.

This analysis found that patients with left-sided primary tumors had a median overall survival of 33.3 months, compared with 19.4 months in patients with right-sided primary tumors.

Of the patients treated with cetuximab, those with left-sided primary tumors lived 36 months, while patients with right-sided primary tumors lived 16.7 months.

The analysis showed a similar pattern for patients treated with bevacizumab: 31.4 months overall survival for those with left-sided tumors and 24.2 months for those with right-sided tumors.

Another way to look at these results is from the point of view of tumor location first, then treatment. This shows if the tumor was on the right, patients receiving bevacizumab had a longer survival than patients receiving cetuximab (24.2 months and 16.7 months, respectively).

Conversely, patients with left-sided tumors treated with cetuximab lived 36 months, while those receiving bevacizumab lived 31.4 months.

As the clinical trial comparing the two drugs was under way, it was discovered that mutations in the KRAS gene is an important factor in the use of cetuximab.

When the researchers analyzed the data just for patients with KRAS mutations, they found a similar pattern to the previous results: patients with left-sided tumors lived longer compared with patients with right-sided tumors.

The researchers conclude that whether the primary tumor was on the left or the right likely influenced the effectiveness of the treatments the patients received in the trial.

They are now looking into the molecular biology mechanisms that might explain such differences.

"These findings will likely change the way we approach colorectal cancer treatment and research, even as we seek to more deeply understand the biology driving the difference in outcomes between right and left sided cancers."

Author Credentials: Ian was born and grew up in Australia. Since then, he has traveled and lived in numerous locations and currently resides in Montreal, Canada. Ian is the founder, a writer, and editor in chief for Disabled World. Ian believes in the Social Model of Disability, a belief developed by disabled people in the 1970s. The social model changes the focus away from people's impairments and towards removing barriers that disabled people face daily. To learn more about Ian's background, expertise, and achievements, check out his bio.