As multiple myeloma patients, we rapidly become familiar with many concepts from probability and statistics. There are measures such as the probability of a given treatment leading to a complete response, the probability of that treatment producing undesirable side effects, and of course numbers like median progression-free survival and median overall survival.

It can sometimes be difficult to remember that statistical measures such as these usually only apply to an entire population, not to any single indi­vidual. They are therefore useful for drawing general conclusions, but not for predicting the out­come that any one person will experience.

When I was diagnosed in 2006, the median overall survival for multiple myeloma was pretty much always quoted as being three years. I therefore expected it to be my future. For­tu­nately, it was clearly not the case. It is important not to take probability measures as precise values.

Even so, these measures can sometimes be useful for guiding treatment decisions. For instance, when I was about to have my stem cell transplant, a clinical trial involving stem cell transplants was running that my myeloma specialist mentioned to me. Patients in the trial would have tandem transplants, the first always autol­o­gous (using the patient’s own stem cells), but the second randomly selected to be either autologous or allo­geneic (using stem cells from a donor). This trial was set up to investigate whether the potential benefits of the graft versus myeloma effect that can result from an allogeneic transplant would outweigh the associ­ated risk of complications from graft versus host disease.

Eventually, after weighing the trial’s pros and cons, I decided against it. Only then did my oncologist say that he agreed, for two reasons: I was doing so well already (I liked this reason), and I was too old to take full advantage of it (I didn’t care for this one quite so much!).

Another key concept in statistics is the idea of “conditional probability.” This concept is based on the fact that two events (call them A and B) may not be independent from one another; the probability of B happening at all can be very different from the probability that B happens, given that A has already taken place.

For instance, for most readers of this column, the probability that the next person you meet will be a fluent Hungarian speaker is quite low. However, the probability that they will speak Hungarian, given that you are in Budapest, is extremely high.

It often seems to me that there is also a similar concept that should be called “conditional luck.” I remember being struck by this concept back in the 1980s, when a British newspaper front page headline announced “Luckiest man alive: he fell off a cliff and lived!” (Headlines based on someone being the luckiest man alive are pretty much a staple of British tabloids.)

The really striking point was the contrast between the “lucky” in the headline and the large photo under it, which showed the man in his hospital bed, casts covering him virtually from head to toe. Unquestionably, his “conditional luck” of surviving, given that he had fallen off a cliff, was extremely good. However, measured against the entire population, the vast majority of whom did not fall off cliffs, he was extremely unlucky to end up in hospital with such severe injuries.

Dealing with multiple myeloma brings up similar issues. Anyone with myeloma has had really bad luck com­pared to the general population. After all, only about 0.02 percent of the population has multiple myeloma, and it is still an incurable disease. On the other hand, an increasing number of myeloma survivors these days have treatments that go very well, putting them into extended periods of near-complete remission.

I am one of these people, and often think of how lucky I have been to be able to continue leading a basically normal life, seeing our boys grow up, and working at something that I really enjoy. However, whenever a new set of blood test results comes in and I get so nervous before looking at them, or I think of “regular” people who can worry about such things as “outliving their money”, or I remember that myeloma almost always eventually returns, it reminds me that this “luckiness” is really conditional.

I am indeed lucky, but only given that I have multiple myeloma. However, that is still pretty good.