Background: Data from many populations show a decrease in the incidence of large cell carcinoma (LCC) of the lung while incidence of lung adenocarcinoma (AC) is decreasing to a lower rate or even increasing from the 1990s. We compared the changes in incidence of lung LCC and AC worldwide to test the hypothesis that at least part of the decline in LCC incidence was due to classification of these tumors as AC.

Methods: We analyzed the annual percent change (APC) in the age-standardized rates (ASRs) of lung LCC and AC incidence between 1996 and 2007 in 78 high-quality cancer registries from Europe, Asia, North America, and South America, using linear regression.

Results: Among women, the median APC of LCC incidence was -5.42, and that of AC incidence was -0.96. There was a positive correlation between the two measures (β=0.29; p=0.01). The APC of LCC incidence was negative in 64 populations (82.1%); that of AC incidence was negative in 50 populations (63.3%, p of the χ2 distribution = 0.07). Among women, the median APC for LCC and AC incidence was -5.06 and +2.11, respectively. The correlation between the two measures was 0.17 (p=0.03). The APC of LCC incidence was negative in 59 populations (76.6%); that of AC incidence was negative in 23 populations (29.9%, p of the χ2 distribution = 0.41).

Conclusions: The decrease in LCC may be, in part, due to changes in histologic classification and triaging towards a diagnosis of adenocarcinoma.

Citation Format: Dana Hashim, Ariana Znaor, William Travis, Paolo Boffetta. Is the decrease in the incidence of large cell carcinoma of the lung due to changes in classification towards adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1208.