Our finding that MR1 rare variant carriers had significantly poorer overall survival (p-value = 3.46 × 10−7), with half of those individuals having OS decreased by 1.32 years after diagnosis with UC (despite similar age at diagnosis, histological grade distribution, CCI, and sex distribution to non-carriers) points to the possible significant impact of genetic rare variants to predict clinical outcome and examine causes of cancer-related mortality. Here, MR1 is linked to cancer.