The Effects of Chemotherapy on Male Sperm

Chemotherapy is the use of chemical agents--drugs--to target and kill the rapidly dividing cells of cancer. These medications are highly effective on cancer cells but also affect normal cells, especially the rapidly dividing cells of the reproductive system. Sperm cells are produced in the male testes and are a common target for these cytotoxic--meaning toxic to cells--medications.

Genetic Mutations

Sperm cells are haploid cells, meaning they contain one-half of the chromosomes, or genetic material. Sperm cells are constantly created through the process of spermatogenesis in which immature cells undergo cell division, both mitosis and meiosis, resulting in the haploid reproductive cell.

Chemotherapy agents can disrupt cell division at both meiosis I and meiosis II stages, resulting in cells with an incomplete number of chromosomes. This is referred to as an aneuploidy, and when eggs are fertilized with these mutated sperm, the resulting fetus usually does not survive.

This effect on the sperm cells is usually not permanent, and new sperm cells produced after chemotherapy treatments have ended are normal. Doctors therefore recommend waiting 12 to 24 months after treatment before trying to father a child.

Motility

Sperm must be able to move, and move fast, in order to be fertile. For such a small cell, sperm have big jobs. There are several theories of how chemotherapy interferes with sperm's motility.

First, scientists know that sperm move through the epididymis, a long tube that connects the testes to the penis, and this is crucial for sperm's motility. Sperm removed from the testes are incapable of forward motion. Scientists continue to study why this passage through the epididymis is so important, but they believe that the proteins the sperm must move through are the key. Sperm in ejaculate are covered with proteins which may aid in the motility. Chemotherapy can destroy proteins, which can then leave the sperm immobile.

Secondly, sperm can "swim" by the movement of their tail, or flagella. Chemotherapy can cause defects to the flagella, hindering their motility.

Count

Azoospermia, the absence of sperm in ejaculate, can result from chemotherapy treatments. In fact, according to the British Journal of Cancer, 96 percent of men on chemotherapy become azoospermic. This is because sperm are continually produced by rapid cell division, which is a target for chemotherapeutic agents. Chemotherapy interrupts cell division, thereby halting sperm production. This condition is usually temporary, and sperm production will begin again once treatments have ended.