When I received a letter this summer from Be the Match, I didn't know what would come next. I just knew that I was being presented with the opportunity to save a life.

I knew that no matter how much time and money I did or did not donate to nonprofits and charities doing important work, this was different. Here was a patient with a blood cancer whose particular immune system resembled my own. Turns out I, among potentially everyone in the world, was in the best position to save her life.

It's an awesome responsibility and opportunity.

Now that I've been through the entire experience, including the ominous-sounding procedure called a "bone marrow harvest," it's clear that the most decisive point for me was simply joining the registry in the first place.

Joining is a small time investment -- all it takes is a few cotton swabs of saliva -- but understandably seems to have no pay off. The chances of ever becoming a donor are only about 1 in 540.

But if a donor request letter does come, as it did for me, the tangible opportunity to save someone's life is so compelling and immediate that the next steps seemingly take no effort at all.

Getting the letter

About 1 in 40 registry members will receive a potential donor letter at some point, according to the donor program. This just indicates that based on the saliva sample, you might be the match for somebody.

I was on the registry for five years before I received a potential donor letter.

Here's what happened next.

I called Be the Match and told them I was still willing and able.

A specialist assigned to this case scheduled my initial blood test. This allowed them to determine whether I was really the best match for the intended recipient.

Through the entire process you just call and e-mail with your assigned specialist, which makes things easy.

PBSC vs. Bone Marrow

If the match is a good one, you next get to choose whether to donate actual bone marrow, or what's called peripheral blood stem cells, known as PBSC. The patient's doctor will request one or the other, but ultimately the donor decides which one he or she feels willing to give.

I was curious how the decision would affect my recipient's chances of survival. That's what this is all about, after all.

"When we look at PBSC versus bone marrow, we see comparable outcomes in adults," Dr. John Miller, a medical director at Be the Match and the National Marrow Donor Program, told me.

"When we look at outcomes in children, we see better outcomes with bone marrow, and long-term outcomes in terms of complications are lower with marrow than with PBSC, so most pediatric transplants use marrow as the transplant source."

Because my recipient is an adult, I felt comfortable with picking either of the two options.

A bone marrow harvest is a minor surgical procedure usually done under general anesthesia, so the donor remembers nothing and experiences no pain except in rare cases. A needle is inserted into the back of the pelvic bone, and bone marrow is drawn out with syringes.