What’s your source there? I ask because I was curious and found the exact opposite (but I’ve not done any in-depth dive into this topic):
The scientists found no evidence that frequent ejaculations mark an increased risk of prostate cancer. In fact, the reverse was true: High ejaculation frequency was linked to a decreased risk. Compared to men who reported 4–7 ejaculations per month across their lifetimes, men who ejaculated 21 or more times a month enjoyed a 31% lower risk of prostate cancer. And the results held up to rigorous statistical evaluation even after other lifestyle factors and the frequency of PSA testing were taken into account.