SDHB and gastrointestinal stromal tumor: Mean MGMT promoter methylation level for the 65 GIST studied varied by GIST subgroup: mean MGMT methylation was 2.905% (SEM=1.758) for TK mutant GIST (N=21), 3.143% (SEM=0.4041) for NF1 (N=7) vs 2.25% (SEM=0.75 SEM) for quadruple negative GIST (N=4) and 8.091% (SEM=1.786) for SDH-deficient GIST (N=33) (p=0.0449)(table 2).