A recent study presented at the 2018 Gastrointestinal Cancers Symposium (January 18-20, 2018; San Francisco, CA) identified the difference between right-sided and left-sided tumors in regard to disease-free survival outcomes in patients with late stage, high-risk colorectal cancer.
Registry studies and meta-analyses have shown that patients with right-sided colorectal cancer who develop metastatic disease have a worse prognosis than patients with left-sided tumors. Patients with left-sided tumors may also benefit from treatment with epidermal growth factor receptor (EGFR) inhibitors. However, most data confirming these trends exist only in patients who have relapsed.
One such study (SCOT) randomly assigned 6088 patients between 2008 and 2013 from 244 multinational cancer centers. Results from the study showed that 3-month adjuvant chemotherapy containing oxaliplatin was non-inferior to 6-month adjuvant therapy among patients with stage III and high-risk stage II colorectal cancer.
Mark P Saunders, MD, PhD, MBBS, MRCP, FRCR, consultant clinical oncologist, The Christie NHS Foundation Trust (United Kingdom), and colleagues aimed to determine whether tumor sidedness had an impact on disease-free survival in the SCOT study. Among the 3219 patients in the evaluable study population, 1207 had right-sided tumors (41% tumor size 4; 17% stage II) and 2012 had left-sided tumors (24% tumor size 4; 21% stage II).
Researchers found that 80% of patients with left-sided tumors achieved 3-year disease-free survival, compared with only 73% of patients with right-sided tumors (HR, 1.4; 95% CI, 1.21-1.61). After adjusting for T-stage and N-stage, the hazard ratio was reduced to 1.21 (95% CI, 1.05-1.40).
Researchers acknowledged that the data was not significant for tumor sidedness affecting the impact of 3 months vs 6 months of chemotherapy on 3-year disease-free survival (right-sided, HR, 1.04; 95% CI, 0.84-1.29; left-sided, HR, 0.91; 95% CI, 0.75-1.09).
While Dr Saunders and colleagues admitted that cohort size limited any further subset analysis, the data clearly suggests that right-sided tumors are associated with worse disease-free survival in late stage, high-risk colorectal cancer.
“This is the first study to show that unselected patients with right-sided tumors had a worse DFS compared [with] left-sided tumors,” commented Dr Saunders (January 16, 2018). “This implies that prognosis is influenced primarily by greater recurrence rather than the contributing factors that influence OS.”—Zachary Bessette