Overdiagnosis, Misleading 5-Year Lung Cancer Survival in Taiwan
A population-based study in Taiwan suggests that screening for lung cancer in a predominantly nonsmoking female population is associated to significant overdiagnosis, spuriously high 5-year survival rates and significant overdiagnosis.
“To our knowledge, our findings are the first evidence of LDCT [low-dose computed tomography]-induced lung cancer overdiagnosis on a population level,” Wayne Gao, PhD, Taipei Medical University, Taiwan and colleagues write in their article published online January 18 in JAMA Internal Medicine.
They conclude that “until randomized trials show the benefits in populations with lower risk Our findings suggest that screening for LDCT should be provided to smokers who are heavy and only after a careful presentation of benefits and risks.”
In the early 2000s, Taiwan’s 5-year survival rates from lung cancer among women were within the middle of high-income nations. However, after a decade, “Taiwan attained what is arguably the highest survival rate for lung cancer in the world,” Gao and colleagues write.
The authors discuss how, in the period media outlets and hospital websites in Taiwan started a promotion specifically targeting women who were undergoing lung cancer screening, despite having a smoking rate below five percent. One outlet offered the advice: “Avoid the tragedy and sudden death caused by lung cancer that is fatal like the celebrities (celebrities). People who haven’t done Lung cancer treatment (LDCT), especially women, should consider it now.”
Gao and his colleagues wanted to learn how the incidence of lung cancer rates have changed since Taiwan encouraged lung cancer screening.
The Taiwan National Cancer Registry data was used to calculate the incidence of stage-specific lung cancer. They identified deaths due to lung cancer among women between January 2004 and December 2018 and then analyzed the changes in the incidence of stage-specific lung cancer during that time.
Between 2004 and 2018, a total of 57,898 women were diagnosed with lung cancer among a population of approximately 12 million Taiwanese women. Following the introduction of LDCT screening, Taiwanese women experienced a significant increase in the early stages of disease. Particularly between 2004 and 2018, the rate of stages 0 to I lung cancer was more than six times higher from 2.3 per 100,000 population to 14.4 per 100,000.
Interestingly, however the authors didn’t notice the expected decline in advanced-stage disease. The incidence of lung cancer stage II-IV was virtually unchanged at 18.7 per 100,000 in 2004, compared to 19.3 per 100,000 in 2018.
“Because the sixfold increase in early stage cancer was not associated with an increase in late-stage cancers, we suspect that most of the increase in detection of lung cancer since the introduction of LDCT screening in 2004 is overdiagnosis.” the authors conclude.
Gao and colleagues noticed Gao and colleagues noticed a “dramatic” change in 5-year survival rates as well. The authors write that survival rates for five years more than doubled, going from 18% in 2004 and 40 percent in 2013. This is “arguably the highest lung cancer survival rate in the world,” they write.
Given that the mortality rate for lung cancer in Taiwan was stable between 2004 and 2018, researchers suggest that the 5-year survival rate could be biased, indicating an increase in detection of indolent, early stage lung cancer.
The authors point out that their research “does not exclude the possibility of LDCT screening having an impact that is only marginally beneficial” and acknowledge that screening may have assisted in the early diagnosis of certain cancers that could develop to the stage of late.
They are open to the possibility of alternative explanations for their findings. One possibility is that lung cancer is increasing in Taiwan.
However, evidence suggests the opposite may be true. The dramatic decrease in smoking in men from over 60% in the past to less than 25% in the present indicates that exposure for women has been decreasing. At the same time the quality of air in Taiwan has improved over the past few years due to the decreased use of coal and wood for heating and cooking- factors that would reduce the incidence of lung cancer.
“Furthermore,” the authors note, “it’s difficult to imagine the way in which a rise in the occurrence of disease would not be associated with early stage disease.”
The authors also highlight the financial benefits associated with extensive LDCT screening. Despite being widely promoted for women, Taiwan’s LDCT screening for lung cancer is not covered under National Health Insurance (NHI). The service typically costs $150 to $230. However the authors mention that LDCT has been offered as a free charitable service to certain groups.
Even with no screenings, hospitals still earn money from follow up testing biopsies, procedures and biopsies covered by NHI. For example the claims for thoracotomies of women rose from 800 to 8000 per year between 2000 and 2018. This was mostly due to the increase of video-assisted surgery procedures.
The authors write that these findings “underline the financial incentives for the opportunity-based screening.” With the “evidence of both overdiagnosis as well as overtreatment, we would strongly encourage the NHI to continue not to reimburse the entire population for LDCT screening for lung cancer.”
The authors did not divulge any financial relationships.
JAMA Intern Med. Online publication on January 18 2022. Full Text
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