HPV-associated base of tongue squamous cell carcinoma incidence increasing in Sweden

The incidence for base of tongue squamous cell carcinoma increased significantly in Sweden between 1998 and 2007, and by 2007, more than 80% of these cases were HPV-positive.

Various studies during the past 20 years have indicated that HPV is a risk factor for oropharyngeal cancer. However, few studies have assessed the specific sub-sites of the oropharynx.

In this study, researchers assessed the increased incidence of base of tongue cancer and the association of HPV in 109 patients diagnosed with base of tongue cancer between 1998 and 2007 in Stockholm, Sweden.

The researchers obtained diagnostic pretreatment paraffin-embedded tumor biopsies from 95 patients. DNA samples were obtained from 30-mcm paraffin-embedded base of tongue biopsy slices. Age at diagnosis ranged from 41 to 85 years.

From 1970 to 2007, the age-standardized incidence of base of tongue squamous cell carcinoma increased from 0.15 per 100,000 person-years between 1970 and 1974 to 0.47 per 100,000 person-years between 2005 and 2007.

HPV DNA was found in 75% of base of tongue cancer cases during this time. Of the HPV-positive tumors, 86% were HPV-16–positive and seven were HPV-33–positive.

During the study period, the incidence of HPV-positive base of tongue cancers persistently increased (see chart). A significant increase was found in the proportion of HPV-positive cancer between 1998 and 2001 compared with 2004 and 2007 (58% vs. 84%; P<.05).

When compared with patients with HPV-negative tumors, patients with HPV-positive tumors were likely to be stage IV (P<.02) and had less advanced T-stage (P<.05 for T2; P<.01 for T3); however, these patients had more advanced N-stage (P<.01 for N0; P<.01 for N2a-c).

Attner P. Int J Cancer. 2010;doi:10.1002/ijc.24994.

It would be interesting to know whether the age of patients has decreased in tandem with the increased incidence of tumors in this cohort. As noted previously in these pages, a marked increase in oral sex activity has been reported in adolescents during the past 20 years. Therefore, oncologists should be rigorous in taking detailed sexual histories in this epidemiologic arena. In this regard, recent conflated reports that adolescent sexual activity can be reduced in teenagers by providing sexual "abstinence" courses are probably misleading. Intercourse may be delayed, but oral sexual activity has not been rigorously examined. We might be trading unwanted pregnancies for later miserable head/neck cancer morbidity and mortality.

- Harry S. Jacob, MD
HemOnc Today Chief Medical Editor