ES08.03 The Magnitude of the Benefit

Abstract

Why do people get screened? The obvious answer is so that cancer can be detected early with a view towards a higher chance of cure with early treatment. Therefore, the critical questions that must be addressed relate to the risk of cancer over time and then, how likely cure will be when screen-detected versus clinically detected. Current approaches to evaluate screening have relied on randomized controlled trials with a view towards demonstrating that a benefit actually exists but are not designed to quantify the magnitude of the benefit. Current trial designs have limited rounds of screening and long-term follow up after screening has stopped. When these parameters change, the results of the trial will also change. Several approaches currently exist to estimate that critical parameter regarding the curability of screen detected lung cancer. This includes modeling approaches which can use data extracted from a variety of sources, they can also be measured directly as was done in the I-ELCAP study which measures directly the reduction in case fatality rate by using long term survival as a measure of cure, and an additional approach would be to screen continuously in the context of a clinical trial and measure the reduction in mortality after several years of screening where the benefit of screening reaches its maximum and becomes equivalent to the reduction in case fatality rate. When applied to lung cancer it can be shown that this benefit is far greater than the 20% so commonly reported and instead is in the 60=80% range for cure. Were this to be fully understood the entire rationale behind requiring shared decision making would be called into question as it was thought that the balance between benefits and harms was so tenuous that shared decision making was necessary. When considering whether a particular type of screening is to be considered beneficial there is also a tendency to compare different types of screening and seeing how many screens are necessary to save a life. Here to, this approach suffers from the same mistake. Each of those screening exams estimates this number based on their own randomized trial and each of these differ in terms of the design parameters, therefore the comparisons are essentially meaningless. benefit, lung cancer screening