The cancer death rate had its largest one-year decline ever from 2016 to 2017, falling 2.2 percent, according to a new study.

The report from the American Cancer Society finds that the drop was driven largely from declining death rates from lung cancer, which is the leading cause of death from cancer.

The decline in the death rate from cancer is due in part to advances in a new form of treatment called immunotherapy, which trains a person’s immune system to fight cancer, said Dr. William Cance, chief medical and scientific officer for the American Cancer Society. 

“The accelerated drops in lung cancer mortality as well as in melanoma that we're seeing are likely due at least in part to advances in cancer treatment over the past decade, such as immunotherapy," Cance said in a statement. “They are a profound reminder of how rapidly this area of research is expanding, and now leading to real hope for cancer patients.”

Between 1991 and 2017, the cancer death rate fell by 29 percent, the report finds. That drop translates to 2.9 million fewer cancer deaths than if the rate had stayed steady, the report says.

Still, there are expected to be 1.8 million new cancer cases and 606,520 deaths from cancer in 2020, according to the report.

Melanoma of the skin also saw significant declines in the death rate after a breakthrough treatment was approved in 2011. The death rate dropped 7 percent per year from 2013 to 2017 for people between ages 20 to 64, the report found.

In contrast, progress slowed in preventing death from colorectal, breast and prostate cancer, the report found, all of which can be significantly curtailed with early detection.

“The exciting gains in reducing mortality for melanoma and lung cancer are tempered by slowing progress for colorectal, breast, and prostate cancers, which are amenable to early detection,” said Rebecca Siegel, the lead author of the report.