After stratifying the patients with Parkinson’s disease according to whether they had cancer or not, we only found that Parkinson’s disease patients with cancer had a statistically significant increase in the length of ATXN2 CAG repeats compared with Parkinson’s disease without cancer for the short allele (22.04 ± 0.41 versus 21.94 ± 0.64; P = 0.016; d = 0.17). This evidence concerns the gene ATXN2 and Parkinson disease.