SIX2 and non-small cell lung carcinoma: SIX2, SIX4, and SIX6 showed significant correlation with the poor OS of NSCLC (SIX2: pooled HR = 1.14, 95 % CI, 1.00–1.31, p = 0.711, and I2 = 0.0 %; SIX4: pooled HR = 1.39, 95 % CI, 1.16–1.66, p = 0.749, and I2 = 0.0 %; SIX6: pooled HR = 1.18, 95 % CI, 1.00–1.38, p = 0.242, and I2 = 21.9 %; Fig. 6a, c, e).