Sperm preservation and neutron contamination following proton therapy for prostate cancer study

Background: The present study investigates the impact of scatter dose radiation to the testis on ejaculate and sperm counts from treatment of prostate cancer with passive-scatter proton therapy.

Material and methods: From March 2010 to November 2014, 20 men with low- or intermediate-risk prostate cancer enrolled in an IRB-approved protocol and provided a semen sample prior to passive-scatter proton therapy and 6–12 months following treatment. Men were excluded if they had high-risk prostate cancer, received androgen deprivation therapy, were on alpha blockers (due to retrograde ejaculation) prior to treatment, had baseline sperm count <1 million, or were unable to produce a pre-treatment sample or could not provide a follow-up specimen. Sperm counts of 0 were considered azoospermia and <15 million/ml were classified as oligospermia.

Results: Four patients were unable to provide a sufficient quantity of semen for analysis. Among the 16 remaining patients, only one was found to have oligospermia (7 million/ml). There was a statistically significant reduction in semen volume (median, 0.5 ml) and increase in pH (median 0.5). Although not statistically significant, there appeared to be a decline in sperm concentration (median, 16 million/ml), total sperm count (median, 98.5 million), normal morphology (median, 9%), and rapid progressive motility (median, 9.5%).

Discussion: Men did not have azoospermia 6–12 months following passive-scatter proton therapy indicating minimal scatter radiation to the testis during treatment. Changes in semen quantity and consistency may occur due to prostate irradiation, which could impact future fertility and/or sexual activity.