Smoking and alcohol are well-known etiological factors in
tonsillar cancer. However, as in
cervical cancer, human papillomavirus (HPV) is currently found in a sizable proportion of
tonsillar cancer. Recent reports from the U.S. and Finland show an increase in the incidence of
tonsillar cancer, without a parallel rise in smoking and alcohol consumption. This study investigates whether the incidence of
tonsillar cancer has also changed in Sweden and whether a possible explanation of the increase is a higher proportion of HPV-positive
tonsillar cancer. The incidence of
tonsillar cancer between 1970 and 2002 in the Stockholm area was obtained from the Swedish
Cancer Registry. In parallel, 203 pretreatment
paraffin-embedded
tonsillar cancer biopsies taken during 1970-2002 from patients in the Stockholm area were tested for presence of HPV
DNA by PCR. The incidence of
tonsillar cancer increased 2.8-fold (2.6 in men and 3.5 in women) from 1970 to 2002. During the same period, a significant increase in the proportion of HPV-positive
tonsillar cancer cases was observed, as it increased 2.9-fold (p < 0.001). The distribution of HPV-positive cases was 7/30 (23.3%) in the 1970s, 12/42 (29%) in the 1980s, 48/84 (57%) in the 1990s and 32/47 (68%) during 2000-2002. We have demonstrated a highly significant and parallel increase both in the incidence of
tonsillar cancer and the proportion of HPV-positive
tumors. Hence, HPV may play an important role for the increased incidence of
tonsillar cancer. This should definitely influence future preventive strategies as well as treatment for this type of
cancer.