The American Cancer Society recently released the 2020 edition of Cancer Statistics and it contains some pretty good news: The risk of cancer-related mortality is dropping faster than ever before.

During the decade between 2008 and 2017, cancer death rates dropped by 1.5% annually. During the latest 12-month period in the study, though, the rate of cancer-related mortality dropped by 2.2%, driven by a decline in deaths from lung cancer.

Doctor holding a chest x-ray.

Image source: Getty Images.

While 2.2% might not seem like a big deal, the American Cancer Society has been publishing mortality statistics since 1991 and the drop off recorded between 2016 and 2017 is the largest 12-month decline ever reported.

What happened?

Different factors led to the recent improvement, including the emergence of cancer immunotherapy drugs from health companies including Merck (MRK -0.33%) Bristol-Myers Squibb (BMY)

The American Cancer Society expects around 135,000 lung cancer deaths in 2020, which makes it the most lethal malignancy of all. Less tobacco consumption, earlier screening of at-risk patients, and increasing use of new cancer drugs play an important role in the reported lung cancer mortality risk improvement. In next year's report, we can probably look forward to more dramatic improvements. After lung cancer, the most common types of cancer are colorectal, breast, and prostate.

In 2018, sales of Merck's Keytruda spiked in response to lung cancer study results that showed adding it to standard chemotherapy reduced the risk of death by half, and sales are still soaring. In the third quarter of 2019, Keytruda sales grew 62% year over year to an annualized $12.4 billion and it's not the only immunotherapy with blockbuster sales. Opdivo's a similar drug that added an annualized $7.3 billion to Bristol-Myers Squibb's top line in the third quarter.