The role of high-degree microsatellite instability as a marker to predict benefit from adjuvant chemotherapy remains unclear.
Dr George Kim and colleagues from Florida conducted an analysis of the National Surgical Adjuvant Breast and Bowel Project.
The researchers assessed 542 patients who were randomly assigned to a surgery-alone group and patients assigned to an adjuvant fluorouracil treated group.
Microsatellite instability and other potential markers were evaluated.
|18% of patients exhibited microsatellite instability|
|Journal of Clinical Oncology|
The researchers found that 18% of patients exhibited microsatellite instability.
The team noted that there was a strong inverse relationship between microsatellite instability and mutant p53 status.
The prognostic analyses showed increased recurrence-free survival for microsatellite instability patients.
However, the team noted no difference in overall survival.
The team observed a potential interaction between microsatellite instability and mutant p53 in terms of improved recurrence-free survival.
In the predictive marker analysis, the team observed no interaction between microsatellite instability status and treatment for recurrence-free survival or overall survival.
The hazard ratio for recurrence-free survival with microsatellite instability vs high-degree microsatellite instability was 0.77 in the untreated-patient group.
In the treated-patients group, the hazard ratio was 0.6 for recurrence-free survival.
The team noted that hazard ratios for overall survival were 0.8 for untreated and 1.02 for treated patients.
There was a trend toward improved recurrence-free survival in patients with microsatellite instability and mutant p53.
Dr Kim's team concluded, "These results do not support the use of microsatellite instability as a predictive marker of chemotherapy benefit."