CANCER MORTALITY USA

July 13, 2010 — The latest statistics released by the American Cancer Society (ACS) show that cancer rates — both incidence and mortality — are continuing to decline in the United States.

The new figures, compiled by researchers at the ACS, in collaboration with researchers at the Centers for Disease Control and Prevention, were published online July 7 in CA: A Cancer Journal for Clinicians.

The reduction in the overall cancer death rates from 1991/2 to 2006 means that approximately 767,000 cancer deaths have been prevented.

According to ACS deputy chief medical officer Len Lichtenfeld, MD, MACP, "767,000 people in this country are either alive today or were able to live a fuller measure of their lives because we have been doing something right when it comes to cancer."

Discussing the new statistics in his blog, Dr. Lichtenfeld admits that there are still many areas in which more work is needed. He mentions in particular the controversy surrounding the overdiagnosis and overtreatment of very early breast and prostate cancers that might be "indolent," which has been much in the news lately.

"But the statistics don't lie, and the statistics tell us that for so many people and for several cancers, we have clearly done something right," he comments.

Mortality Rates Continue to Decline

Nevertheless, cancer remains a number 1 killer — cancer still accounts for more deaths than heart disease in people younger than 85 years, the authors of the report note. However, when age is not taken into account, heart disease is the leading cause of death overall in the United States.

"Cancer continues to be the leading cause of death for people in this country between the ages of 40 and 79, while heart disease is far and away the leading cause of death in people age 80 and over," Dr. Lichtenfeld writes.

Cancer accounted for 23% of all deaths — about 1 in 4 — in the United States in 2007, he points out. "There were 562,875 cancer deaths that year, which was 2987 more than in 2006. However, the cancer death rate continued to decline, from 180.7 in 2006 to 178.4 in 2007. The reason for this seeming paradox is that our population is larger and older, meaning a lower rate is spread over more older people, which in turn leads to an increase in the actual number of cancer deaths," he explains.

The report estimates that in 2010, 569,490 Americans will die of cancer, corresponding to more than 1500 deaths from cancer each day of the year.

The most common fatal cancers remain lung, prostate, and colorectal in men, and lung, breast, and colorectal in women, the report notes. These 4 cancers together account for about half of all the deaths from cancer in men and women combined.

The good news is that deaths from cancer are declining, and have been declining steadily since the early 1990s, Dr. Lichtenfeld notes.

For men, death rates from cancer fell 21% from 1990 and 2006. Most of that decline can be explained by decreases in deaths from lung, prostate, and colorectal cancer, which together account for 80% of the observed decrease in cancer deaths in men, he points out.

For women, the data show a 12.3% drop in cancer death rates over the same period of time, with most of the decrease coming from falling breast and colorectal cancer death rates. Unfortunately, Dr. Lichtenfeld notes, deaths from lung cancer have remained steady over the past few years.

Lung cancer surpassed breast cancer as the leading cause of cancer death in women in 1987, and is expected to account for 26% of all female cancer deaths in 2010, the authors note in their report.

Dr. Lichtenfeld writes that this fact is not widely appreciated — that lung cancer is a bigger killer of women than breast cancer, even though breast cancer is more common.

The rate of decline in cancer deaths is a little higher in recent years, the report notes. For men, overall cancer death rates decreased by 2% per year from 2001 to 2006, compared with declines of 1.5% per year from 1993 to 2001. For women, the decline was 1.5% from 2002 to 2006, compared with 0.8% per year from 1994 to 2002.

However, the death rates from some cancers are increasing. Between 1990/1 and 2006, death rates increased for liver cancer in both men and women, for esophageal cancer and melanoma in men, and for lung and pancreatic cancer in women.

Also, there are marked differences with age. Leukemia is the most common fatal cancer in men younger than 40, whereas lung cancer is the most common fatal cancer in men older than 40. In women, leukemia is the leading cause of cancer death before the age of 20 years, breast cancer ranks first from ages 20 to 59, and lung cancer is the largest cancer killer in women older than 60 years.

Incidence Rates Also Declining

The report shows that overall cancer incidence rates are declining in the United States, and the authors, headed by Ahmedin Jemal, DVM, PhD, from the ACS, offer a few explanations for the trend.

In men, the overall cancer incidence rate decreased by 1.3% per year from 2000 to 2006 — largely because of decreases in the incidence of lung, prostate, and colorectal cancer.

In women, the decrease was 0.5% per year from 1998 to 2006 — mainly because of decreases in the incidence of breast and colorectal cancer. However, the incidence rate for lung cancer is still increasing, although at a much slower rate than in previous years, the report authors note.

The fact that lung cancer incidence is decreasing in men but continues to increase in women reflects "historical differences in cigarette smoking between men and women," the authors write, noting that smoking peaked in women about 20 years later than in men.

The accelerated decrease in colorectal cancer incidence rates, seen in both sexes, largely reflects increases in screening that can detect and remove precancerous polyps, the authors write.

The decrease in the breast cancer incidence rate since 1999 largely reflects the drop in hormone replacement therapy used by postmenopausal women, which began in 2001, although it might also reflect delayed diagnosis due to decreased use of mammography, they explain.

"However, close inspection of the incidence rate by individual year shows that after a 6% decrease from 2002 to 2003, the incidence rates from 2003 to 2006 remained relatively unchanged," they point out. This might support the hypothesis that hormonal therapies act as promoters rather than initiators of breast cancer, they add.

"What is really going on here remains [unclear]," Dr. Lichtenfeld notes. "Hormones may not have been the actual cause of breast cancer (if that was the case, then the number of new cases would continue to drop), but instead acted as a breast cancer 'promoter' (in other words, stimulating the growth of an underlying breast cancer that was already in progress). Time will help us understand this issue better."

Some Progress Due to Better Cancer Care

Reflecting on the reasons for the declines in cancer rates that are now being seen, Dr. Lichtenfeld suggests that "not all of this was due to some remarkable breakthrough in medical treatment, although some of it certainly is due to better cancer care. Much of it has to do with stopping smoking, or not starting for that matter, especially among men. Much of it has to do with better screening and early detection of breast and colorectal cancer, and perhaps prostate cancer (although we are not certain about the latter). Some of it may have to do with lifestyle changes, such as increased awareness of the importance of exercise and diet in reducing cancer risk."

He points out that although "in general the news is encouraging," there is still a lot of work ahead.

"We have many people who aren't listening to the messages about screening for cancer, which for many people accounts for their being alive today," he explains.

"We have many people who don't understand that a healthy lifestyle — which includes not smoking, eating a healthy diet, getting regular exercise, maintaining a healthy body weight, and getting screened — can substantially reduce their risk of dying from cancer (and several other major diseases as well)," he adds.

The authors have disclosed no relevant financial relationships.

CA Cancer J Clin. Published online July 7, 2010. Abstract