SHORT REPORT INCIDENCE AND SURVIVAL OF SQUAMOUS CELL CARCINOMA OF THE TONGUE IN SCANDINAVIA, WITH SPECIAL REFERENCE TO YOUNG ADULTS Karin ANNERTZ 1 * , Harald ANDERSON 2 , Anders BI ¨ ORKLUND 1 , Torgil M¨ OLLER 2 , Saara KANTOLA 3 , Jon MORK 4 , Jo ¨rgen H. OLSEN 5 and Johan WENNERBERG 1 1 Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital, Lund, Sweden 2 Department of Cancer Epidemiology, University Hospital, Lund, Sweden 3 Department of Oral Diagnostics and Oral Medicine, Institute of Dentistry, University of Oulu, Oulu, Finland 4 Cancer Registry of Norway, Oslo, Norway 5 Division of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark In several countries, increased incidence of squamous cell carcinoma (SCC) of the tongue in young adults has been suspected during the last decades. Some reports indicate a lower survival rate for young patients compared to older patients. In other reports, there has not been any consider- able difference in survival when comparing young adults to older patients, whereas some authors have shown better survival for young adults. This disease is rare in young adults, and early reports were based on comparable small numbers and selected patients. Our aim was first to perform a popu- lation-based study to determine if an increased incidence in SCC of the tongue could be verified in a larger population comprising the Scandinavian countries Denmark, Finland, Sweden and Norway. A second aim was to determine sur- vival rates for young adults compared to older patients. The material was based on the annual cancer incidence and sur- vival reports from the Scandinavian cancer registries. The study period was 1960 –1994. During that period, 5,024 SCCs of the tongue were reported. Of these, 276 (5.5%) were young adults (20 –39 years). The incidence increased at all ages except for women 65–79 years old. The increase was most pronounced in young adults: 0.06 – 0.32 for men and 0.03– 0.19 for women, counted by 100,000 person-years. Rel- ative survival was significantly better for young adults com- pared to older patients. © 2002 Wiley-Liss, Inc. Key words: squamous cell carcinoma; epidemiology; etiology; tongue; Scandinavia During the past decades, an increased incidence of squamous cell carcinoma (SCC) of the tongue in young adults has been reported from several countries. 1–4 In some of these studies, the male-to-female ratio was lower in young than in older adults. Unlike the older patients, many of the young patients had never used tobacco or overconsumed alcohol. However, the time of exposure to these well-known carcinogens in most cases would not have been long enough for malignant transformation. This sug- gests that other external or internal factors play a role in the development of the disease in young adults. Hereditary effects may play a role in this type of early-onset cancer, though reports in the literature are contradictory. 5–7 In several reports published since 1975, carcinoma of the tongue in young adults has been described as an aggressive disease. Some reports indicate a lower survival rate for young patients than for older patients suffering from the same disease. 8,9 Other clinical studies comparing young adults with groups of older patients report no significant differences in survival. 10 –15 Some authors, in fact, show better survival for young patients. 4,16 In Sweden, tongue cancer constitutes 12% of all head-and-neck carcinomas. We have previously published results indicating a higher incidence of tongue cancer in young adults in Sweden during the past few decades. 4 Due to the low incidence of the disease in the young population (only 4 –5% of all patients with tongue carcinomas are under 40 years old at the time of diagnosis), earlier reports were based on very small numbers. Greater tumor material can be obtained from all of the Scandinavian countries combined (Denmark, Finland, Norway and Sweden), where cancer registration is compulsory and nearly all-inclusive. The registra- tion process started in Denmark in 1942, and the other Nordic countries followed in the 1950s. An estimated 95% of all diag- nosed tumors in these countries have been registered; therefore, a joint Scandinavian study provides an excellent opportunity for population-based studies regarding incidence and survival. Our aim was first to determine whether an increased incidence in SCC of the mobile tongue in young adults over a 35-year period could be verified in a population of over 20 million Nordic people. A second aim was to compare the survival rates for young adults and older patients diagnosed with SCC of the tongue. MATERIAL AND METHODS The material consists of data on primary SCCs of the mobile tongue reported to the Danish, Finnish, Norwegian and Swedish cancer registries during the study period, 1960 –1994. Population and mortality data were obtained from national statistical yearbooks. In the cancer registries, carcinoma of the tongue is coded ac- cording to the ICD-7 coding system with subsites. Base of the tongue is a subsite of the oropharynx category and therefore was not included in our study. Prior to 1978, histology was not reported in Denmark. For incidence and estimates of numbers of cases of SCC of the tongue in Denmark for the period 1960 –1977, see the following section. For survival analyses, only data from Denmark reported during 1978 –1994 were used. Cases were divided into 3 age groups: 20 –39, 40 – 64 and 65–79 years at the time of diagnosis. The 20 –39 group will be referred to as “young adults”. Cases diagnosed in patients younger than 20 years were excluded from the study since different mechanisms may play a role in carcinogenesis during childhood and adoles- cence. Most earlier reports used 40 years of age as the upper limit for young adults, and this limit was also used in the present study. Grant sponsor: Swedish Cancer Society; Grant numbers: 4478-B00- 01PAB, 1304-B00-14XCC; Grant sponsor: King Gustaf V Jubilee Fund; Grant number: 00:530; Grant sponsor: Swedish Department of Education. *Correspondence to: Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital, S-221 85 Lund, Sweden. Fax:+46-46-2110968. E-mail: karin.annertz@onh.lu.se Received 29 December 2001; Revised 28 May 2002; Accepted 10 June 2002 DOI 10.1002/ijc.10577 Published online 16 July 2002 in Wiley InterScience (www.interscience. wiley.com). Int. J. Cancer: 101, 95–99 (2002) © 2002 Wiley-Liss, Inc. Publication of the International Union Against Cancer