My own sluggish path towards a diagnosis continues. I had an ultrasound yesterday which will apparently have results available within five days (although my clinic's office said 14 days, so who knows?). Judging the size and shape of the one node I did glimpse by craning my neck towards the screen (2.0 x 0.6 cm), it's not exactly great news. On the other hand, it's always possible I'll luck out.
In the meantime, I know that one of the most worrying periods in any person's life is the one in which they're not quite sure (yet) whether they're really sick. In the vast majority of cases, we actually aren't – or at least, not seriously. So, on the assumption that some such nervous readers will eventually find their way here, I thought I'd share some potentially comforting statistics.
Public statistics on cancer in Canada, like the annual Canadian Cancer Statistics of the Canadian Cancer Society, are not nearly as detailed as their American counterparts. They do illustrate some similarities, mind you. One that stands out is that the lymphoma incidence rates are climbing in both countries. Since 1978, according to the CCS, Canadian non-Hodgkin's lymphoma rates increased by 50%, but the increase has stabilized in the past decade.
Which leaves us with a disease that, at least for younger patients, is still quite rare. This year, there will be about 20 new lymphoma cases per 100,000 in Canada; that compares with 19.6 in the U.S., based on the SEER database.
I can't find any easily available data in Canada on age distribution of these cases, but the American situation is probably similar – and we do have information about the Americans, thanks to a 2006 Blood article by Lindsay M. Morton et al. They divide the population into ten-year blogs: 0-15, 15-24, 25-34, 35-44, and so on up to 75 and over. Overall, it looks as though the total lymphoma incidence rate starts a little shy of 1 in 10,000 per year for teenagers, and climbs up to almost 0.3% per year in seniors.
Most helpful about the Blood article, though, is that you can see rates for specific types of cancer. The headline Canadian and American data usually just lumps it all together as "non-Hodgkin lymphoma," which of course is not very helpful. This article shows that the most common "aggressive" form of NHL, diffuse large B-cell lymphoma (DLBL or DLBCL) occurs in about 1 in 100,000 people in their teens and 20s, and climbs up to around 0.03% in seniors.
Note that all of these statistics are person-years. So, your likelihood of developing lymphoma within any of these age groups is roughly ten times the above figures.
In contrast, the most common "indolent" or slow-growing variant, follicular lymphoma (FL or fNHL), is extremely rare prior to 30 (at which point it's still only about 0.6 in 100,000 people), climbing up to around 0.01% in seniors. It seems that there are no statistically significant number of cases of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) prior to the mid-20s, although it climbs steeply from there to around 0.01% by late middle age.
For anyone with an anxiety issue, the most disturbing part of the chart is undoubtedly Section P, which reveals that anywhere from 1 in 100,000 to 1 in 10,000 people will be diagnosed with an "unknown" lymphoma each year.
As always, one has to know what statistics mean before bothering to read these things. In this case, what they mean is that the likelihood of a person getting lymphoma in a given year are very, very small – so if you're worried, it's probably not you. Of course, some of us do still win the lottery. In the case of follicular lymphoma, for instance, only about 6 in a million people in their teens and 20s will get lymphoma. That makes about 200 young Canadians per year with this single, still-incurable form of lymphoma.
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