Cancer mortality rates in the United States have continued to steadily decline, with 2.4 million fewer cancer-related deaths reported in 2015 than in 1991, when rates started to decrease. This represents a 26% decrease since the early 1990s, the American Cancer Society (ACS) reported.

The number of lung cancer deaths decreased by 45% in men from 1990 to 2015, and by 19% in women from 2002 to 2015.

The statistics were published in the ACS’s annual report on cancer incidence, mortality, and survival, titled “Cancer Facts & Figures 2018.”

The report notes that the cancer death rate dropped by 1.7% from 2014 to 2015. In numbers, the death rate decreased from a peak of 215.1 cancer-related deaths per 100,000 U.S. citizens in 1991 to 158.6 deaths per 100,000 in 2015.

The report estimates that in 2018, more than 1.7 million new cases of cancer will be reported in the U.S., along with 609,640 cancer-related deaths.

Researchers behind the report believe some of the primary causes of this significant drop are steady reductions in smoking and advances in the early detection and treatment of cancer.

“This new report reiterates where cancer control efforts have worked, particularly the impact of tobacco control,” Otis W. Brawley, chief medical officer at the ACS, said in a press release.

“A decline in consumption of cigarettes is credited with being the most important factor in the drop in cancer death rates. Strikingly though, tobacco remains by far the leading cause of cancer deaths today, responsible for nearly three in ten cancer deaths,” Brawley added.

In addition to lung cancer, the report cites three other major oncological conditions that are driving the decreasing death rates:

• Female breast cancer, which declined by 39% from 1989 to 2015
• Prostate cancer, which declined by 52% from 1993 to 2015
• Colorectal cancer, which declined by 52% from 1970 to 2015.

But not all of the news is positive. The report highlights the persistent racial gap in cancer mortality in the U.S. Although that gap continues to narrow, progress is mostly seen in older populations and may mask persistent inequalities among younger and middle-aged black Americans.

Factoring all ages, cancer death rates in 2015 were 14% higher among non-Hispanic blacks than non-Hispanic whites. That percentage is down from 33% observed in 1993. However, while the gap narrowed to 7% for those 65 and older —likely due to universal healthcare access for seniors through Medicare — mortality rates were still 31% higher for black citizens under 65 than white citizens of the same age group.

The report also discussed the cancer diagnosis rate in the U.S., the most common cancers for men and women (with lung cancer at the top of both groups), and lifetime probabilities of a cancer diagnosis depending on gender, among other topics.

A more in-depth version of the report, titled “Cancer statistics, 2018,” was published in CA: A Cancer Journal for Clinicians.