Changes in lung cancer histological types in Varese Cancer Registry, Italy 1976-1992.

Shifts in histological tumour type distribution, chiefly an increase in adenocarcinoma, have been reported to accompany changes in lung cancer incidence in the last two decades in the United States and several other developed countries. To elucidate this phenomenon further, we analysed population-based lung cancer incidence rates in the period 1976-1992 from the Varese province, an area with 788,000 inhabitants in Northern Italy. Rates were age-standardised on the world standard population. Overall, lung cancer had stopped increasing in males since the late 1980s, and had started declining in middle-aged men. Conversely, upward trends persisted in females up to 1991-1992. Although it decreased from 13 to 9, the male-to-female incidence ratio was, in 1991-1992 still substantially higher than in the U.S. and North Europe. Specific trends emerged according to histological type(s), with declines (males) or stabilisation (females) for squamous-cell carcinoma and gradual increases for small-cell carcinoma in males. Adenocarcinoma was the only lung cancer type whose incidence rates increased similarly (2.5-fold) in males and females thus approaching, in 1991-1992, in the two sexes combined, the rate for squamous-cell carcinoma. Although advances in diagnostic techniques may have played a role, the absolute and relative increases in the adenocarcinoma rate reflect changes in cigarette manufacture (i.e. spread of filter tips and low-nicotine low-tar cigarettes) and the decrease in smokers.