KRAS Made No Difference in Stage III Outcome

Patients with stage III colon cancer didn’t do better or worse if their tumor had mutated KRAS.

Studying KRAS in the tumors of about half the patients in a large clinical trial of chemotherapy for stage III colon cancer, researchers found no differences in disease-free, recurrence-free, or overall survival.  This remained true no matter which chemotherapy the patients received.

Between 1999 and 2001, almost 1,300 patients took part in a clinical trial that compared standard treatment at the time — bolus 5-FU and leucovorin– to adding irinotecan to 5-FU/leucovorin.  That trial didn’t find a difference between the two chemotherapy arms in preventing recurrences or increasing survival for stage III colon cancer.

To see if KRAS status made any difference in outcomes for stage III colon cancer, a research team analyzed tumor tissue from 508 of the 1,264 patients who were enrolled in the CALGB 89803 clinical trial.  They found mutated KRAS in 178 tumors, 35 percent of all participants.

Five-year outcomes between KRAS mutant and KRAS wild-type tumor tissue were very similar:

  • Disease-free survival was 62 percent for KRAS mutant versus 63 percent for KRAS wild-type.
  • Recurrence-free survival was 64 percent for mutant vs wild-type.
  • Overall survival was 75 percent in mutant and 73 percent in wild-type tumors.

In addition, the research team found no correlation between KRAS status and clinical features of the cancer, which chemotherapy arm the patients were on, or microsatellite instability (MSI).

Writing in Clinical Cancer Research, Shuji Ogino and colleagues concluded,

In this large trial of chemotherapy in stage III colon cancer patients, KRAS mutational status was not associated with any significant influence on disease-free or overall survival.

SOURCEOgino et al., Clinical Cancer Research, online first November 24, 2009.

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