MKI67 and digestive system neuroendocrine tumor, grade 1/2: By analyzing data from 252 advanced gastrointestinal neuroendocrine tumor patients who were given chemotherapy, Sorbye found that the 30-month survival rate was 23% when the patients had a Ki-67 labeling index < 55%, which was only 7% for those with a Ki-67 labeling index ≥ 55% [19].