Supplement File 2 show the forest plots of the result. We also explored the prognostic value of XRCC1 expression in cancer patients regardless of treatment. Surprisingly, the results showed that high XRCC1 expression was significantly associated with better OS (HR = 0.88, 95% CI: 0.82–0.94, P = 0.00038), which was contrary to our results related to radiotherapy (Figure 2). Here, XRCC1 is linked to cancer.