The prognosis in cancer patients has improved over the years. Survivor rates have increased significantly, and paternity has become an important concern in more than 50% of young male survivors. Sperm cryopreservation before cancer treatment is highly recommendable in these patients, as a strategy to preserve their fertility due to is not possible to predict how the chemo or radiotherapy treatment will affect the spermatogenesis.

The objective of this study is to evaluate if sperm after an antineoplastic treatment can be safely used. To determine the possible effects of oncological treatments in the spermatogenesis, three parameters will be analyzed, aneuploidy frequencies, DNA fragmentation in single and double-strand breaks and methylation levels to determine epigenetic changes before and after the therapy.

If cancer treatment affect sperm genetic integrity, it would have a clinical impact in the offspring of these patients. Identify the different side effects of antineoplastic treatments in DNA sperm will provide a clinical improvement in order to select the best sperm sample in an IVF treatment and it will facilitate genetic counseling

Inclusion Criteria:

Patients with previous history of cancer Patients with several sperm samples cryopreserved to be able to thaw a part without damaging their future options, in case they need them.

Patients treated with chemotherapy and/or radiotherapy Patients have finished their oncological treatment. Patints recovered spermatogenesis after the oncological treatment to be able to obtain a sperm sample.

Exclusion Criteria:

Patients with only one sperm sample cryopreserved Patients that are not be able to obtain a fresh sample post treatment Patients with less than 3 million sperm per milliliter

Sperm samples before treatment will be used as a control