It’s rare to encounter a good-news story about cancer — excluding, of course, the individual stories of people who have survived it — and for obvious reasons. Cancer is nasty, awful, scary stuff.

It’s also alarmingly common. Chances are you or someone you know has been affected by it; across Canada, it’s estimated a new case is diagnosed every three minutes.

A statistical report released last week by the Canadian Cancer Society provides some cause for cautious optimism, however. Prepared in collaboration with the Public Health Agency of Canada and Statistics Canada, it found cancer death rates have dropped over the past 20 years, with approximately 100,000 people’s lives saved as a result.

Between 1988 and 2007, overall death rates from all types of cancer declined by 21% in men and by 9% in women — a change attributed to better screening and treatment, and decreasing smoking rates. Death rates have also declined in all four main cancers — i.e., lung, colorectal, breast and prostate, which together account for 54% of all cancers.

The notable exception to this trend is lung cancer deaths among Canadian women, which increased over the same time frame and is one of the reasons for the gender gap in the overall rates. According to the CCS, smoking rates among men began decreasing in the ’60s while smoking rates among women didn’t begin falling until the ’80s, and it takes 20 to 30 years before such changes translate into measurable declines in lung cancer incidence and death rates.

Obviously, less people dying from cancer is a good thing — but less people getting diagnosed with cancer would be an even better thing. Alas, while incidence rates vary depending on age and sex, none have declined much (if at all) since 1983. Cancer continues to be the leading cause of death in Canada. In Manitoba, it will kill an estimated 2,850 people by the end of 2012.

The CCS lists a number of factors that can increase a person’s risk of cancer: tobacco use, yes, but also an unhealthy diet, physical inactivity, excess body weight, alcohol consumption, over-exposure to the sun and exposure to environmental and workplace carcinogens.

You’ll note two of these things are not like the others. (Hint: they have nothing to do with individual choices.)

When we talk about cancer, it’s important to acknowledge that systemic factors beyond our control are also part of the equation — for example, the amount of carcinogenic chemicals with which we come in contact on a near-daily basis, often without even realizing it. (And here I will take a moment to recommend Pink Ribbons Inc., a recent NFB documentary that examines a range of issues related to breast cancer, including this very topic. It’s screening at Cinematheque later this month, and it’s an educational, thought-provoking and, at times, enraging film.)

There’s a fine line between promoting health and blaming people for getting sick. As we continue to confront this awful disease, it’s essential we don’t cross it.

Marlo Campbell dedicates this column to the people in her life who have died from cancer, the people who have survived it and the people who are currently living with it.