EGFR mutations are most commonly found in patients who have never smoked. In the US of the approximately 220,000 patients who are diagnosed with lung cancer each year, about 10%-15%, or 20,000 to 30,000 are never smokers. Of these, around 40% express egfr so my best guess is that around 8,000 to 12,000 patients in the US have the mutation.
With over 1 million deaths worldwide from lung cancer. obviously, the number is higher worldwide. Also, the non-US numbers may be much higher as the egfr mutation is most common in non-smoking, asian women.