I think that's due to HPV exposure, not from busting a load. So say hypothetically you marry your highschool sweetheart and fuck her 25,000 times over a lifetime; you'd have a much lower chance of prostate cancer than fucking 25 women 1,000 times each.
The opposite, actually: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1464-410X.2008.08030.x
I think that's due to HPV exposure, not from busting a load. So say hypothetically you marry your highschool sweetheart and fuck her 25,000 times over a lifetime; you'd have a much lower chance of prostate cancer than fucking 25 women 1,000 times each.