The history of cancer screening

Mitigating Cancer Overdiagnosis

Overdiagnosis refers to the detection of cancers that pose no threat to life and would never have been detected in the absence of screening. It is now a major public health concern throughout the world because advancements in screening technology have substantially increased the detection rates of non-lethal cancers. Cancer overdiagnosis leads to unnecessary treatments, putting patients unnecessarily at risk for the potential morbidity and mortality that may arise from those treatments, and it wastes healthcare resources. Patients may also suffer unnecessary anxiety, job discrimination, financial hardships, and other detrimental effects on quality-of-life following cancer overdiagnosis. In this article, I provide examples of cancer overdiagnosis as a consequence of screening for thyroid, breast, and pancreatic cancers. To mitigate the adverse effects of cancer overdiagnosis, we should adopt only those screening strategies that have been shown in randomized trials to reduce cancer mortality, and we should inform patients about the potential benefits and risks of cancer screening, particularly the risk for overdiagnosis.

Breast Cancer Screening Trials: Endpoints and Overdiagnosis

Screening mammography was assessed in 9 randomized trials initiated between 1963 and 1990, with breast cancer-specific mortality as the primary endpoint. In contrast, breast cancer detection has been the primary endpoint in most screening trials initiated during the past decade. These trials have evaluated digital breast tomosynthesis, magnetic resonance imaging, and ultrasound, and novel screening strategies have been recommended solely on the basis of improvements in breast cancer detection rates. Yet, the assumption that increases in tumor detection produce reductions in cancer mortality has not been validated, and tumor-detection endpoints may exacerbate the problem of overdiagnosis. Indeed, the detection of greater numbers of early stage breast cancers in the absence of a subsequent decline in rates of metastatic cancers and cancer-related mortality is the hallmark of overdiagnosis. There is now evidence to suggest that both ductal carcinoma in situ and invasive cancers are overdiagnosed as a consequence of screening. For each patient who is overdiagnosed with breast cancer, the adverse consequences include unnecessary anxiety, financial hardships, and a small risk of morbidity and mortality from unnecessary treatments. Moreover, the overtreatment of breast cancer, as a consequence of overdiagnosis, is costly and contributes to waste in health-care spending. In this article, we argue that there is a need to establish better endpoints in breast cancer screening trials, including quality of life and composite endpoints. Tumor-detection endpoints should be abandoned, because they may lead to the implementation of screening strategies that increase the risk of overdiagnosis.

Impact of reduced smoking rates on lung cancer screening programs in Japan

Background

In Japan, lung cancer screening by annual chest radiography has been performed for the past 30 years. However, changes in risk factor status may have influenced the efficiency of current organized lung cancer screening program. The purpose of this study was to clarify whether the reduced smoking rate in younger Japanese affects the efficiency and effectiveness of lung cancer screening.

Methods

We investigated chronological changes in epidemiological indicators, which support lung cancer screening programs offered by the Japan Cancer Society, such as gender- and age-specific numbers of participants and lung cancers detected by the screening by clinical stage, in relation to smoking rates from 1991 to 2016.

Results

Participant age at the time of screening and age at the time of cancer detection have both increased over time. The lung cancer detection rate (LCDR) in younger age cohorts tended to decrease from 1991 to 2016 in both genders, particularly men aged <55 years. Age-adjusted LCDR significantly decreased from 1991 to 2016 in both genders. After 2001, ~45% of overall detected cases in men and 70% in women were found in stage I. Although trends differed between men and women, smoking rate decreased from 1991 to 2016 in most age cohorts in both genders.

Conclusions

These results suggest that organized lung cancer screening in Japan should be limited to higher-risk populations.

Identifying Lung Cancer Risk Factors in the Elderly Using Deep Neural Networks: Quantitative Analysis of Web-Based Survey Data

BACKGROUND

Lung cancer is one of the most dangerous malignant tumors, with the fastest-growing morbidity and mortality, especially in the elderly. With a rapid growth of the elderly population in recent years, lung cancer prevention and control are increasingly of fundamental importance, but are complicated by the fact that the pathogenesis of lung cancer is a complex process involving a variety of risk factors.

OBJECTIVE

This study aimed at identifying key risk factors of lung cancer incidence in the elderly and quantitatively analyzing these risk factors' degree of influence using a deep learning method.

METHODS

Based on Web-based survey data, we integrated multidisciplinary risk factors, including behavioral risk factors, disease history factors, environmental factors, and demographic factors, and then preprocessed these integrated data. We trained deep neural network models in a stratified elderly population. We then extracted risk factors of lung cancer in the elderly and conducted quantitative analyses of the degree of influence using the deep neural network models.

RESULTS

The proposed model quantitatively identified risk factors based on 235,673 adults. The proposed deep neural network models of 4 groups (age ≥65 years, women ≥65 years old, men ≥65 years old, and the whole population) achieved good performance in identifying lung cancer risk factors, with accuracy ranging from 0.927 (95% CI 0.223-0.525; P=.002) to 0.962 (95% CI 0.530-0.751; P=.002) and the area under curve ranging from 0.913 (95% CI 0.564-0.803) to 0.931(95% CI 0.499-0.593). Smoking frequency was the leading risk factor for lung cancer in men 65 years and older. Time since quitting and smoking at least 100 cigarettes in their lifetime were the main risk factors for lung cancer in women 65 years and older. Men 65 years and older had the highest lung cancer incidence among the stratified groups, particularly non-small cell lung cancer incidence. Lung cancer incidence decreased more obviously in men than in women with smoking rate decline.

CONCLUSIONS

This study demonstrated a quantitative method to identify risk factors of lung cancer in the elderly. The proposed models provided intervention indicators to prevent lung cancer, especially in older men. This approach might be used as a risk factor identification tool to apply in other cancers and help physicians make decisions on cancer prevention.

Breast Cancer Screening: a Paradigm Change Is Needed-the PB Desai Oration

This editorial summarizes the key points of the PB Desai Oration, delivered by the author at the National Conference of the Indian Association of Surgical Oncology in Kolkata, India, on September 21, 2019.