ASCO 2014 Report – Survival not significantly affected by disease site in metastatic colorectal cancer

by Bruce Sylvester – Survival based on primary site of disease is not significantly different among metastatic colorectal cancer patients, Australian researchers reported in a poster presentation at ASCO 2014.

The investigators used the South Australian Registry of  Metastatic Colorectal Cancer to analyze differences in patient characteristics, treatment received, and outcomes out to at least 5 years based on primary site of disease.

The researchers analyzed registry data from 3,121 patients. Of that total, 33.5% had right colon primary site disease, 35.3% left colon primary site disease and 26.7% rectal primary site disease.

There were no major patient characteristic differences between the left colon and rectal groups. There were statistically significant differences between right colon and left colon groups, and right colon and rectal groups, most notably that rectal site disease appeared more in females and in older subjects.

They found that biologic drug treatment, chemotherapy, and metastatectomy were all less common in the rectal primary group. And KRAS mutant tumor rates were greater in right primary vs. left primary (p=0.007).

Analysis for systemic drug treatment showed similar rates of 1st line therapy, but different rates of 2nd line, with 47% right primary use, 60% left primary use and 60% rectal primary use.

The median overall survival was 9.8 months for right primary, 19.2 months for left primary and 17.8 months for rectal primary.

For the “active therapy” patients, defined as chemotherapy with or without metastatectomy, median overall survival was 15.5 months for right primary, 26.2 months for left primary and 26.3 months for rectal primary.

For those patients (n=168) who were eligible to undergo liver resection (with or without prior chemotherapy), 5 year survival was 55% for right primary, 58% for left primary and 55% for rectal primary.

Among patients treated with only chemotherapy, median overall survival was 10.3 months for right primary, 15.1 months for left primary and 15 months for rectal primary.

“There were no major differences noted between L [left] colon and rectal primary. Patients with right primary had more negative prognostic factors and indeed had inferior outcomes when compared to those with left or rectal primary. Patients who were suitable for hepatic surgery had no difference in outcome,” the authors concluded.

Citation: 2014 ASCO Annual Meeting; General Poster Session, Gastrointestinal (Colorectal) Cancer; Abstract Number 3540