'Unprecedented' Drop in US Cancer Deaths, Driven by Lung Cancer

Mortality from cancer in the United States has been falling continuously since 1991, when cancer-related death rates peaked, resulting in a 29% overall decline in mortality from cancer through 2017, notes a new report from the American Cancer Society.

"The big news is that despite slowing progress for other leading causes of death, the cancer death rate is not only continuing to drop but had the largest one-year drop ever from 2016 to 2017," lead author Rebecca Siegel, MPH, American Cancer Society, Atlanta, Georgia, told Medscape Medical News in an email.

"This is driven by accelerating progress against lung cancer," she added — a reflection of both steady reductions in smoking cessation in the past several years and major advances in treatment.

The observed reductions in cancer-related mortality seen in the United States are primarily being driven by long-term declines in mortality from the four leading malignancies in the United States today: lung, breast, colorectal, and prostate cancer.

For example, as of 2017, the mortality rate from lung cancer has dropped by more than 50% among men since 1990 and by 26% among women since 2002. (That said, lung cancer still causes more deaths than breast cancer, colorectal cancer [CRC], and prostate cancer combined and remains the leading cause of cancer-related mortality for both men and women today, Siegel observed.)

Death from female breast cancer has dropped by 40% from 1989 levels, and death from prostate cancer has dropped by 52% since 1993.

Reductions in mortality from CRC have been of the same order of magnitude, dropping by 53% among men since 1980 and by 57% among women since 1969.

"Recent mortality declines are even more rapid for melanoma of the skin, most likely reflecting improved survival in the wake of promising new treatments for metastatic disease," the authors note.

However, this trend did not hold true among men younger than 65 who live in poor counties across the country, where no acceleration in mortality declines from melanoma were detected following new drug approvals.

Decline in Lung Cancer Attributed to Treatment

The progress that has been made in the treatment of lung cancer ― and the impact this has had on the cancer mortality statistics ― is emphasized in an op-ed piece in the Cancer Letter written by Otis Brawley, MD, currently Bloomberg Distinguished Professor of Oncology and Epidemiology at Johns Hopkins University and former chief medical officer at the American Cancer Society.

"As I look through just-published tables of age-adjusted cancer mortality, I recognize an unprecedented development," he writes.

"Immunotherapy is showing such a dramatic impact in the treatment of locally advanced and advanced non–small cell lung cancer that this effect elevates the statistics for all lung cancer and ― this I find astonishing ― you can even see its effect in age-adjusted cancer mortality overall.

"It was a dominant driver in the 2.2% decline in overall age-adjusted death rate," he points out.

"Lung cancer has always been the biggest driver in the 26-year trend of declining age-adjusted cancer mortality. However, the decline we are seeing between 2016 and 2017 is unprecedented: Lung cancer age-adjusted death rate for men dropped by 5%. For women, it dropped by 4%."

Brawley attributes the dramatic decline to changes in treatment.

He acknowledges the role of prevention: "it is undeniable that tobacco control dating back to the 1960s is a major element in the decline in lung cancer deaths," he writes, but adds that this decline is small and steady. And so far, screening for lung cancer has had little impact, mainly because it is still not widely used (in fewer than 2% of smokers).

So that leaves treatment, he says. This includes improvements in imaging and staging, in radiotherapy, but also in the many new drugs that have been approved for the treatment of lung cancer, in particular, the immunotherapies.

Several lung cancer experts have also emphasized the impact of new therapeutics on the treatment of lung cancer on Twitter posts about this new cancer mortality statistics report.

Vinay Prasad, MD, assistant professor of medicine, Department of Hematology and Oncology, Oregon Health and Science University, Portland, takes issue with this interpretation in a Twitter thread. He asserts that immunotherapy had only a "tiny" impact and that targeted drugs aimed at mutations (eg, ALK, EGFR) did not have much, if any, impact. "I suspect lifestyle/smoking is the big driver," he says.

Cancer Incidence

The ACS report notes that, in total, approximately 1,806,590 new cancer diagnoses will be made in 2020, and an estimated 606,520 Americans will die from cancer in thise same year.

These statistics do not include new cases of ductal carcinoma in situ of the breast in women (an expected 48,530 cases), nor new cases of melanoma in situ of the skin (an expected 95,710 cases), the researchers point out.

Among men, the overall incidence rate of cancer declined rapidly between 2007 and 2014, then stabilized through 2016, reflecting slower declines in the incidence of CRC among men and stabilizing rates of prostate cancer.

Siegel noted that slowing declines in mortality from CRC may reflect a reduction in first-time screening. A large spike in colonoscopy rates occurred during the 2000s, but the rise in screening uptake since 2010 has been much slower.

Among women, "the overall cancer incidence rate...has remained generally stable over the past few decades because lung cancer declines have been offset by a tapering decline for CRC and increasing or stable rates for other common cancers," Siegel and colleagues point out.

Most notably, the incidence of lung cancer continues to decline twice as fast in men than in women, reflecting differences in smoking uptake and cessation between men and women, as well as an upturn in the prevalence of smoking among women in some birth cohorts.

In contrast, the incidence of CRC is generally similar in men and women, although the overall incidence of CRC in adults younger than 55 years has been increasing by 2% a year since the mid-1990s.

Bucking the declining trend in cancer incidence is liver cancer, which increased by 2% to 3% a year from 2007 through 2016, although the pace of the increase has slowed from that of previous years. This is "very good news," commented Siegel. It is likely the result at least in part of new antiviral therapies for the treatment of liver cancer caused by chronic hepatitis C infection.

Cancer Survival

For all cancers combined, the 5-year relative survival rate for those diagnosed with cancer between 2009 and 2015 was 67%.

"For all stages combined, survival is highest for prostate cancer (98%), melanoma of the skin (92%), and female breast cancer (90%) and lowest for cancers of the pancreas (9%), liver (18%), lung (19%), and esophagus (20%)," the researchers report.

However, survival rates are still lower for black patients than for white patients for every cancer type with the exception of kidney and pancreatic cancer, for which they are the same.

Blacks also have lower stage-specific survival odds for most cancers, the investigators add. After adjusting for sex, age, and stage at diagnosis, "the relative risk of death after a cancer diagnosis is 33% higher in black patients than in white patients," they point out.

The discrepancy in survival rates is even larger between whites and American Indians/Alaska Natives, among whom the risk for mortality from cancer is 51% higher than it is for white patients.

The authors point out that survival rates following a cancer diagnosis have largely improved since the mid-1970s for most of the common cancers except cervical and uterine cancer, for which there have been no major breakthroughs in the treatment of recurrent or metastatic disease.

In contrast, great progress has been made in treatment protocols and targeted therapies for hematopoietic and lymphoid malignancies. For example, for most patients diagnosed with chronic myeloid leukemia today who receive treatment with a tyrosine kinase inhibitor, life expectancy is nearly normal.

Outcomes Vary by Racial/Ethnic Groups

The authors also point out that the occurrence of cancer and patient outcomes varies considerably between racial and ethnic groups, a reflection of inequalities in wealth and barriers to high-quality cancer prevention, detection, and treatment.

"Overall cancer incidence rates are highest among non-Hispanic whites (NHWs) because of their high rates of lung and female breast cancer," the authors note.

However, sex-specific incidence rates are highest in non-Hispanic black (NHB) men, which were 85% higher than rates in Asian/Pacific Islander men and 8% higher than rates in NHW men.

NHB women have the highest cancer mortality risk of any ethnic group. The risk is 13% higher, for example, than for NHW women.

On the other hand, the black-white disparity in overall cancer mortality among men and women combined has declined from a peak of 33% in 1993 to 13% in 2017 — progress that the authors attribute to more rapid declines in death from smoking-related cancers among blacks.

The authors have disclosed no relevant financial relationships.

CA Cancer J Clin. Published online January 8, 2020. Full text

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