Current guidelines for screening are based on studies primarily carried out on men in the 1960’s and 1970’s. Despite not being able to extrapolate studies done on men at that time to women today, the current guidelines are the same for men and women. These guidelines do not recommend screening, infact, screening for lung cancer is not currently recommended by any medical organization in Canada.
Survival rates of lung cancer are highest for people who present with early stage disease, but early-stage lung cancer does not have any symptoms. Unfortunately, lung cancers are rarely discovered until they have progressed to a late stage where they are almost untreatable.
Men have tended to develop squamous cell tumours which are central and more likely to present with symptoms early in the course. X-rays are poor at picking up these endobronchial tumours, so radiographic screening may have been no better than checking for symptoms. Women have tended to develop adenocarcinomas which are peripheral and much less likely to present with symptoms early in the course of disease.
Screening includes sputum cytology, chest radiographs and spiral computed tomographs. Spiral CT, introduced in the 1990’s, can pick up tumors well under 1cm in size, while chest X-rays detect tumors about 1 to 2 cm in size. Conventional wisdom suggests that the smaller the tumor, the more likely the chance of survival. But no scientific evidence to date has shown that screening or early detection of lung cancer actually saves lives .
Of the 11 lung cancer screening studies performed up to 1997, only 2 of them included women Most of the screening studies took place in the 1970’s and 1980’s when the prevalence of women with lung cancer was lower and not well documented.
In a 2003 meta analysis of controlled trials, women were excluded from most of the studies.
The National Cancer Institute in the United States sponsored a lung cancer screening trial in September 2002 slated to last eight years. It includes both men and women. This randomized control trial will hopefully be able to provide the evidence needed to determine whether spiral CT scans are better than chest X-rays at reducing a person’s chances of dying from lung cancer.
European countries are in the process of developing randomized control trials for screening, which should include women.
The International Early Lung Cancer Action Program, I-ELCAP, is evaluating low dose CT scanning in individuals at risk. This study is working from the knowledge that cancers found in the early stage are highly curable and that CT screening can possibly find over 80% of lung cancers in this early stage.
Although the Canadian Annual Period Examination does not recommend annual screening chest xrays, this recommendation is not evidence based since evidence does not exist for women or for the current population of men. Fortunately studies utilizing new technologiest are now being carried out.
Screening tests like sputum cytology, chest X-rays and spiral CT can each have false-positives. This makes it important to carefully decide who should and who should not be screened in order to avoid unnecessary worry, testing and surgery.
It is essential that physicians communicate with their patients prior to sending them for lung cancer screening and discuss the advantages and disadvantages of each investigation. It is important to inform them as well that there is no evidence that shows screening to increase life expectancy.