Story highlights About 1 in 40 registry members will receive a potential donor letter at some point

Timeline, from first contact to donation, depends on recipient's health and treatment schedule

Minorities have lower chances of finding willing and able donors

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 payoff. 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.

Hudson undergoes the procedure at Medstar Georgetown University Hospital, which does more bone marrow harvests than any other facility in the country.

"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.

"A small percentage (1.3%) of donors experience a serious complication due to anesthesia or damage to bone, nerve or muscle in their hip region," according to Be The Match.

On the whole, it's a very low-risk procedure, and it's the one I chose.

However, the more common option is to donate peripheral blood stem cells. This requires one injection each day for five days of a drug called filgrastim, which moves stem cells out of the bone marrow and into the blood stream. During this process, the donor feels achy and sore.

On the fifth day, the donor is connected to an apherisis machine, which draws blood from one arm, isolates the stem cells now circulating in the blood, and then transfuses the donor's blood right back into the other arm. This typically takes four to six hours.

The drug filgrastim is widely considered to be safe by clinicians, with the one caveat that there's limited data specifically about the long-term effects of the drug on healthy donors.

As a donor, that gave me pause. So I looked into what we do know.

In 2009, researchers found that there's "no evidence of increased cancer risk," though study participants had been followed for, on average, about four years.

Miller, who is also one of the study authors, says the latest data continues to indicate no increased risks from taking filgrastim for a PBSC donation.

Donating PBSC simultaneously enrolls you in an ongoing clinical trial to assess long-term risks and benefits.

Making the donation

Six months passed from the day Be The Match first contacted me to the day of donating. The timeline just depends on the recipient's health and treatment schedule.

Of course, there are lots of consent forms to sign, and a complete physical exam with a chest X-ray, EKG, and blood and urine samples before giving the green light for the donation.

The collection itself often requires traveling to another city, but everything from airfare and taxis to hotels and meals is paid for or reimbursed for you and a companion.

My bone marrow harvest took about an hour. Doctors kept me in the hospital overnight, but not with regular hospital food. Ruth's Chris Steak House caters to marrow donors at my assigned hospital.

The next day I walked out, slowly and a bit sorely, with instructions to take it easy for two weeks, as my body replaces the lost marrow.

Immediately after a bone marrow harvest, a volunteer courier travels -- by plane, train, or automobile -- with the stem cells and personally delivers them directly to the patient's location. At this point, the patient's abnormal bone marrow cells have already been intentionally destroyed by chemotherapy and/or radiation therapy, and the healthy stem cells are given to the patient through an IV drip.

Once infused, the stem cells automatically travel to the recipient's bone cavities and -- if the transplant is successful -- begin making healthy blood cells.

My recipient could be almost anywhere in the world: 51% of transplants through Be The Match involve an international donor or recipient. If we both consent, we can meet after at least one year, but either of us could choose to remain anonymous.

I hope to meet her.

I've created a fairly specific, though imaginary, image in my head of what she looks like, and the teary hug we would share.

Joining the registry is a statement -- that when cancer affects one of us, it affects all of us.

All I know about my recipient is her age, diagnosis, and that she likely shares my English ancestry.

Minorities have lower chances of finding willing and able donors, as minority groups are not as well represented on the donor registry. For African-American patients, there's an estimated 66% likelihood of finding a donor.

The entrepreneur Amit Gupta , who was diagnosed in 2011 with Leukemia, was able to find a donor only after waging an online campaign encouraging more South Asians in the U.S. and abroad to join donor registries.

An average 54,000 people join Be The Match Registry every month.