What do you study? http://itu.sci.cu.edu.eg/guysborough-sketches-and-essays-revised-edition-8ce9.pdf#ancestor road to chlifa essay  That would be people ages 55 through 79 who smoked a pack of cigarettes a day for 30 years or the equivalent, such as two packs a day for 15 years. Whether screening would help younger or lighter smokers isn't known, so scans are not advised for them. They also aren't for people who quit at least 15 years ago, or people too sick or frail to undergo cancer treatment.