SIX4 and SIX6 expressions approached statistical significance on poor RFS in NSCLC (SIX4: pooled HR = 1.28, 95 % CI, 0.98–1.67, p = 0.363, and I2 = 5.9 %; SIX6: pooled HR = 1.14, 95 % CI, 0.94–1.39, p = 0.468, and I2 = 0.0 %; Fig. 7c, e). Here, SIX6 is linked to non-small cell lung carcinoma.