Swedish nationwide cancer registry data from 1961 to 2021 were used to count second primary lung cancers and describe their histology and risk. The number rose close to linearly from 1980 onwards for both sexes and across the four main histological types, with adenocarcinoma accounting for 63.9% of second tumours. Relative risk versus a first lung cancer was 3.59 overall, 4.16 in women and 2.99 in men, rising to 6.68 among those first diagnosed before 55.
Why it is interesting: As more first lung cancers are survived, the second primary becomes a countable and growing component of lung cancer incidence, concentrated in younger women with adenocarcinoma.