30-Pack-Year Threshold Too High to Catch At-Risk African American Smokers

September 18, 2020

Low-dose CT scans could catch more cancers if the lung cancer screening threshold were dropped to a history of 20-pack-years.

Current lung cancer screening guidelines could be overlooking African American smokers who are at risk for developing lung cancer.

According to a study published in the Sept. 15 Journal of the American College of Radiology, the current guideline based on the 30-pack-year threshold sets the bar too high, as most African American smokers self-report a less than 30 pack-year history. This determination sounds an alarm bell because African Americans have a high incidence of and worse outcomes from lung cancer.

“There is growing concern that there are healthcare disparities in lung cancer screening guidelines and programs,” said lead study author Anupam Basu, M.D., a diagnostic radiologist in Cook County Health. “Evidence suggests that the National Lung Screening Trial (NLST) and Preventive Services Take Force inclusion threshold of a 30-pack-year smoking history excludes a portion of African American patients at risk for lung cancer.”

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Even though African Americans are more significantly impacted by lung cancer, the team said, they still only account for 4 percent of the NLST. Based on existing evidence this group does have a smoking duration history similar to their white counterparts – but, they actually smoke fewer packs a day. Consequently, they have a shorter pack history – the benchmark providers use to determine who should undergo lung cancer screening.

The team, therefore, suggested lung cancer screenings would be much more accurate and impactful if they adopted a 20-pack-year threshold.

Lung Cancer Incidence by Smoking History and Race

ParticipantsAll< 30 Pack Years≥ 30 Pack Years
African-American2.5 percent2.7 percent2.2 percent
White1.9 percent0.0 percent3.1 percent

To identify a threshold that could better identify more African American smokers who could benefit from lung cancer screening, the team retrospectively reviewed low-dose CT scans from patients in their public hospital between September 2017 to December 2019. Patients were also asked to self-report their smoking histories. Of all patients surveyed, African Americans were more likely to report being active smokers with a less than 30 pack-year history.

All total, they reviewed data from 784 patients, 57.5 percent of whom were men with an average age of 62. The majority were African American (66.2 percent), followed by white (20.4 percent), Hispanic (8.3 percent), Asian (4.8 percent), and Native American (0.3 percent). Participants most commonly reported hypertension, coronary disease, and diabetes, but only 17.5 percent reported a family history of lung cancer.

Of the group, three-quarters – 75.5 percent – were active smokers, and just more than half – 51.5 percent revealed a pack history of fewer than 30 years. Total years smoked did not vary much by race, the team said. But, the African American experience was somewhat different, and it painted a grim picture.

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“African Americans smoked fewer packs per day and had fewer pack-years compared with other races,” the team said. “African Americans were more likely to be active smokers but also more likely to report [less than] 30 pack-years compared with other races.”

Low-dose CT findings determined that lung cancer incidence did not vary by race, but African American had an incidence of 2.5 percent while whites experience 1.9 percent. Fortunately, the majority of cancers identified (75 percent) were Stage 1, and all patients had the cancerous tissues successfully removed with surgery.

Looking at lung cancer diagnosis specifically in the context of smoking brought more bad news. African Americans were the only race diagnosed with lung cancer when their self-reported pack-year history was less than 30. For smokers in this group with more than 30-pack-year histories, the incidence rate was 2.2 percent. For those with less than 30 years, it was 2.7 percent.

These findings, the authors said, corroborates existing investigations that contend lowering the lung cancer screening threshold from 30 pack years to 20 pack years would identify many more African American smokers who could have early-stage lung cancer and benefit from treatment.

“We are concerned that the 30-pack-year threshold in the African American population may exclude a portion of patients who are still at risk for lung cancer,” the team said. “We propose prospective study of African Americans with [less than] 30-pack-year histories to determine the potential benefits and harms of [lung cancer screening] in this unique underserved population.”