S01.04 Lung Cancer Screening: 1999 to Date – What Have We Learnt?

Abstract

In 1999, ELCAP published their initial results from baseline screening. It found that in a cohort of 1000 participants approximately 85% of the cancers could be diagnosed as clinical Stage I, and that compared with chest radiography found many more of the cancers. In a subsequent study the expanded I-ELCAP found that the long term survival as a measure of cure rate approached 80%. The publicity associated with this initial study was quite large and led to the initiation of several other trials including the NLST. The NLST published their results in 2011 and based this, screening was endorsed by insurers in the US and now other countries are similarly following suit. However, despite the positive result of the NLST, and reimbursement from insurers, screening has had extremely limited uptake in the US, with only approximately 2% of those eligible (among a restricted population) are being screened. Thus, we face a situation where the most common cancer killer has been studied in the most expensive screening trial ever performed which had a positive result, insurers are reimbursing for it, and few people are having it done. With lung cancer screening being touted as a major breakthrough in the war on cancer the question naturally arises as to why it is not being performed more frequently. There have been many reasons to explain the poor uptake, ranging from merely a slow start but expected steady increase, lack of awareness by the clinician or potential screenee, obstacles such as the shard decision making requirement, too many potential harms, and lack of significant benefits. This lack of perceived significant benefit is perhaps the most important aspect, since without a substantial benefit, even if the harms were minimized, why would anyone get screened and why would a clinician recommend it. It seems that this is clearly influencing the decision not to be screened as many experts and even guideline organizations consider the benefits to not be sufficient enough so as to recommend the screening. Even CMS considered the balance of the risks and benefits so tenuous that they took the unique step of requiring a shared decision making process to be included as necessary for reimbursement so that a person could balance the risks and benefits. It is this aspect of benefit that needs to be considered more carefully when explaining it to a potential screenee. Current decision aids, which are required as part of a shared decision making process, in the US and Canada rely almost exclusively on the NLST result and attempt to convert its findings into more visual aids. However, in translating those NLST results, it needs to be understood that they were highly dependent on the design parameters of the study itself, namely 3 rounds of screening and 6.5 years of follow-up. When these parameters change so do the benefits. In the US, current recommendations for screening include annual screening over the period of eligibility for the participant (although for Canada it is restricted to 3 years). Under the circumstance of continued annual screening, the reduction in mortality begins to approach the estimated cure rate for the cancer. It is this feature of cure rate that is really what is most important to any person interested in being screened, and it is substantially higher than the mortality reduction seen in a randomized trial where by necessity the mortality reduction is diluted by the time interval after screening has stopped and cancers are still being followed, and also by not including those cancers that are relatively slow growing and cured as a result of early treatment but not counted towards the mortality reduction because the trial has concluded before their counterpart in the control arm has died. Based on these considerations, it is possible to have a cancer that is 100% curable when screen detected, yet the trial may only show a 20% (or even lower) mortality reduction. Thus, there is inherently no incompatibility between the 80% cure rate seen in the I-ELCAP compared with the 20% mortality reduction seen in the NLST. The simple conversion of the 20% mortality reduction found in NLST into a cure rate as is so commonly done when explaining the benefit to a person interested in screening is highly misleading. The cure rate, which is the clinically relevant feature, is higher. This coupled with the way in which harms are currently expressed, based again almost solely on those NLST results has the effect of amplifying harms at the same time the benefits are being underestimated and surely affect the perception of overall value of CT screening both for physicians as well as people who might be interested. mortality reduction, Screening, curability