Throwing a wrench in the machinery of sperm production…
I have to admit, the testis “mapping” procedure that I developed some years ago has truly been a workhorse technique for my male infertility practice. And for the practices of other male reproductive specialists around the world as well. Creating fertility from sterility. I bring it up again because it is gathering more attention in the press as this week we recently published another paper that highlights its utility—this time in cancer survivors.
In a related study from 2002, we published that the majority of men who had been exposed to chemotherapy for cancerous or non-cancerous disease and who were “sterile” afterwards have sperm in the testis that can be safely used for fatherhood with assisted reproduction. Fine needle aspiration (FNA) mapping was employed in this study and its potential to help cancer survivors to conceive was convincingly demonstrated. The recent paper expands that group of men to include those who received not only chemotherapy and radiation therapy but also a relatively extreme treatment for certain cancers termed bone marrow transplantation.
Let’s back up a minute for a biology lesson. How does chemotherapy affect a man’s fertility? Well, the basis of its effectiveness in curing cancer is that chemotherapy preferentially kills rapidly dividing cells more than slowly dividing cells. In general, cancer cells divide more rapidly than do normal body cells. The term for this difference in cell susceptibility is “therapeutic index”. Unfortunately, sperm are also produced very rapidly (about 1200 sperm are made every heartbeat) and therefore sperm precursor cells are also very sensitive to the effects of chemotherapy. Think of sperm production as a rapidly turning set of gears and chemotherapy as a wrench being thrown into them. Ka-chunk! Machine comes to a loud and crashing halt. Sperm production is over, or tremendously slowed down. The same action is true for radiation therapy treatment.
Now, imagine not just one small wrench being thrown into the gears, but a huge wrench (or many wrenches) being suddenly thrown into the machine of sperm production. The result? More damage to the sperm-making machinery and a much higher chance of sterility. This is the essential difference between the patients from the 2002 paper on mapping and the most recent one. The cancer survivors in this week’s paper got blasted with the heaviest doses of chemotherapy imaginable, and topped off with a dollop of radiation therapy just to be sure. Hard to believe, but they also had usable pockets of sperm in their testicles. And normal babies as a result.
So, with techniques like FNA sperm mapping, there continues to be hope and good news about fertility after the storm of cancer treatment has passed.
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