Dr. Maria Ignez Braghiroli on Impact of Tumor Side in mCRC

Maria Ignez Braghiroli, MD, medical oncologist, Instituto do Câncer do Estado de São Paulo, discusses clinical characteristics and outcomes of patients with metastatic colorectal cancer (CRC) harboring NRAS mutations.

Previous studies have shown that patients with right-side tumors have worse outcomes than patients with left-side tumors, says Braghiroli.

The CALGB/SWOG 80405 phase III trial demonstrated that survival outcomes in patients with KRAS wild-type metastatic mCRC were significantly longer among those with tumors originating on the left versus the right side of the colon.

In the analysis, the primary tumor location of all patients enrolled in the 80405 trial was identified either right (293), left (732), transverse (66), or uncertain (46). Across both treatment arms, the median overall survival (OS) was 19.4 months (95% CI, 16.7-23.6) among patients with right-sided tumors compared with 33.3 months (95% CI, 31.4-35.7) for patients with left-sided tumors (HR, 1.60; 95% CI, 1.37-1.86; P <.001). Progression-free survival (PFS) was 8.9 versus 11.5 months, respectively (HR, 1.26; 95% CI, 1.096-1.453; P = .002).

Braghiroli presented data at the recent 2016 ESMO Congress, which examined the clinical characteristics and associated outcomes of patients with mCRC who were also harboring NRAS mutations. She and her colleagues found that NRAS-mutant mCRC is an aggressive subset of CRC with worse overall survival outcomes than that for patients with RAS wild-type tumors or KRAS-mutant mCRC.

Interestingly, this subgroup of patients with NRAS-mutant mCRC tend to have increased left-sided colon primary tumors, and these patients may also have a distinct molecular pathogenesis. So the correlation between better prognosis and left sided tumors is still up for debate, says Braghiroli.