Unlike in females, where ovarian reserve is established in utero and declines over time, spermatogenesis commences at puberty and continues throughout life.
Because of this, Semen Analysis is the gold standard for assessing fertility status in the male, and can be performed at any age after puberty. It is an easy, cost-effective, and non-invasive mode of determining fertility potential in the male at any stage following puberty. Important aspects of a semen analysis for review include semen volume, sperm concentration, sperm motility and morphology. It is well established that varying chemotherapeutic regimens can either cause temporary oligo or azoospermia with significant recovery to normospermia with in 24 months  or can cause irreversible oligospermia or azoospermia, as in the case of alkylating agents . Similarly, it has also been shown that quantitative semen characteristics will often return to baseline 24 months after radiation therapy. This however, largely depends on dose and location of radiation therapy being delivered. For instance, Bujan et al demonstrated that 6% of men remained azoospermic at 12 months and 2% at 24 months following radiation therapy for patients with testicular cancer.
Testicular Sperm Extraction would be considered as an option for obtaining sperm in a male cancer survivor who has azoospermia. Success rates largely depend on cancer diagnosis, type and dose of chemotherapy, and location and dose of radiation therapy. With a median time of 18 years from various chemotherapy treatments, Hsiao et al demonstrated a sperm retrieval rate in 37% of post-chemotherapy azoospermic patients with a subsequent 50% clinical pregnancy rate.