Patients with stage III and high-risk stage II colorectal cancer had worse DFS if they had right-sided tumors compared with left-sided tumors, according to results of a study scheduled for presentation at the Gastrointestinal Cancers Symposium.
“This is the first study to show that unselected patients with right-sided tumors had a worse DFS compared [with] left-sided tumors,” Mark P. Saunders, MD, PhD, MBBS, MRCP, FRCR, consultant clinical oncologist at The Christie NHS Foundation Trust in Manchester, United Kingdom, and colleagues wrote. “This implies that prognosis is influenced primarily by greater recurrence rather than the contributing factors that influence OS.”
Registry studies and meta-analyses have shown that patients with right-sided colorectal tumors who develop metastatic disease have a worse prognosis than patients with left-sided tumors. Those with left-sided tumors also may have greater benefit from treatment with epidermal growth factor receptor inhibitors. The PETACC8 study recently confirmed these findings, but only after patients had relapsed.
Results from the SCOT study showed 3 months of oxaliplatin-containing adjuvant chemotherapy was noninferior to 6 months among patients with stage III and high-risk stage II colorectal cancer. The study comprised 6,088 patients from 244 cancer centers from six countries, who were randomly assigned between March 27, 2008, and Nov. 29, 2013.
Saunders and colleagues sought to determine whether tumor sidedness had an impact on DFS in the SCOT study. Researchers divided the evaluable study population of 3,219 patients (median age, 65 years) based on whether they had right-sided (n = 1,207; 53% men; 41% tumor size 4; 17% stage II) or left-sided (n = 2,012; 66% men; 24% T4; 21% stage II) tumors.
Significantly fewer patients with right-sided tumors achieved 3-year DFS (73% vs. 80%; HR = 1.4; 95% CI 1.21-1.61).
Adjusting for T- and N-stage reduced the HR to 1.21 (95% CI, 1.05-1.4).
The data did not suggest that sidedness affected the impact of 3 months vs. 6 months of chemotherapy on 3-year DFS (right-sided, HR = 1.04; 95% CI, 0.84-1.29; left-sided, HR = 0.91; 95% CI, 0.75-1.09).
Researchers noted the cohort size limited further subset analysis. – by Chuck Gormley
Disclosures: Cancer Research UK and Medical Research Council funded this study. Saunders reports honoraria and consultant/advisory roles with Amgen, Merck, Roche and Servier. Please see the abstract for all other authors’ relevant financial disclosures.