This comprehensive population-based study provides detailed and up-to-date data on oral cavity cancer survival in Germany, relying on data of over 15,000 patients diagnosed with oral cavity cancer in 1997–2006 from an underlying population of 33 million people. The according findings indicate an overall five-year age-standardized relative survival of 54.6%. For women, survival generally decreased with age. For men, survival showed a similar pattern up to the age group 65–74 years, but somewhat higher survival among patients of age 75+.
Distinction between different oral localizations proofs relevant: patients with cancer of the lip were shown to have a five-year relative survival of 86.5%. This was almost 40% units higher than the survival of patients with tongue cancer (48.1%), and by about 35% units higher than that of a tumor within other regions of the oral cavity (51.7%). The lowest overall survival was found for cancer in the floor of mouth (49.3%). Only very few lip cancer cases had a distant disease stage or a poorly diffentiated carcinoma (grade 3 or 4) whereas for the tongue as well as other regions of the oral cavity, there was a comparably wide survival range according to tumor stage and grade: Five-year relative survival ranged from more than 60% for localized cancer to less than 10% for cancers with distant metastases. Cancer of the lip also proved as a distinct entity in that it did not exhibit a significant sex difference in age-adjusted cancer survival whereas for the tongue and other regions of the oral cavity age-adjusted cancer survival was significantly higher amongst women than men. The according sex-differences could only partially be explained by differences in tumor stage.
Relative to other developed countries, the results of our study compare as follows: In the US, the overall five-year relative survival (period of diagnosis: 2001–2007; age-standardized estimates according to SEER) for neoplasms of the lip amounted to 90.5%. For cancers of the tongue it was 59.4%. For cancers of the gum and other localizations within the mouth and for cancers of the floor of the mouth five-year relative survival estimates of 58.1% and 51.2% have been reported, respectively 
. Notably, survival in the US differ significantly with respect to ethnicity (higher survival for “Caucasian” than “Afroamerican” patients). In general, the US data indicate a tendency towards higher survival for patients diagnosed with oral cancer than observed for Germany.
According to NORDCAN, five-year relative survival in Scandinavian countries presents as follows (period of diagnosis: 1999–2003; age-standardized estimates reported separately for men/women): Denmark: neoplasm of lip: 86/88%; neoplasm of tongue: 35/45%; neoplasm of other part of oral cavity: 40/49%; Finland: neoplasm of lip: 94/96%; neoplasm of tongue: 50/68%; neoplasm of other part of oral cavity: 43/64%; Norway: neoplasm of lip: 87/98%; neoplasm of tongue: 48/58%; neoplasm of other part of oral cavity: 54/59%; Sweden: neoplasm of lip: 91/91%; neoplasm of tongue: 46/56%; neoplasm of other part of oral cavity: 51/61% 
The overall survival estimates for Germany as reported in the present paper were within a similar range as those from several Scandinavian countries. Our findings of higher survival estimates for patients with cancers of the lip than for cases with cancers of the tongue or other parts of the oral cavity were likewise in agreement with data from both the USA and the Scandinavian countries. For lip cancer, previous literature has not only reported a relatively good surgical operability, but has also shown that most of the cases are localized on the lower lip and are squamous cell carcinomas 
. Such carcinomas have been reported to have relatively low rates of spread to nearby lymph nodes and distant sites. Lip cancer is therefore perceived as having a relatively good prognosis 
. Interestingly, there were similar sex differences between Germany and Scandinavia, i.e. differences in survival between men and women were non-significant for lip cancer but significant for the tongue and other localizations of the oral cavity, except for Norway. One potential explanation for the relatively small sex margin among patients with lip cancer may be that, due to its comparably high visibility, a lip cancer is more likely to be identified by persons other than the affected individual. Consequently, this may mitigate eventual duration differences between women and men until medical advice is sought.
While survival for female patients in Germany continuously decreased with increasing age, our study revealed a tentative re-increase of five-year relative survival of men with oral cavity cancer at age 75+ compared to younger patients. It is tempting to speculate whether this survival pattern is attributable to selection effects due to age-related increases of other potentially fatal co-morbidities (e.g. cardiovascular diseases), many of which are closely related to smoking, the key risk factor for oral cavity cancers. In other words, men at age 75+ may respond relatively positively to oral cancer treatment, simply because a high proportion of multi-morbid, smoking men may already have died in earlier life years.
The focus of the present paper has been on cancer of the oral cavity. Earlier reported survival estimates from Germany were mostly restricted to the Saarland registry and to estimates which aggregated oral and pharyngeal cancer 
. Previous evidence has shown significant survival differences between oral and pharyngeal cancer 
which makes a reliable assessment of temporal trends regarding survival of patients with oral cavity cancer in Germany difficult. Nonetheless, the overall lack or very limited progress of 5-year relative survival for patients with oral cavity and pharyngeal cancers emphasize the pivotal importance of enhanced efforts of primary prevention to limit the burden of these cancers, as a very large proportion of them are smoking related and thus, in principle, avoidable.
Further limitations of the present study should be mentioned. First, the small number of observations for lip cancer in early life years did not enable us to provide survival estimates for more narrowly defined age groups. Second, the proportion of cases first notified by death certificates (7.3%) appears relatively high. This seems partly attributable to the unfavorable prognosis of patients with oral cavity cancer and the fact that several of the included cancer registries have been established only recently, implying that some patients were diagnosed with cancer prior to but died after the respective registry was instituted. As DCO cases were excluded from our analysis, survival estimates may have been slightly overestimated 
. Third, cancer survival could also be under the influence of different treatment approaches used in oral cancer. For example, differential application of elective and therapeutic selective neck dissection could have an impact on survival because neck metastasis is considered an important prognostic factor in oral carcinomas 
. In this respect, however, the present study is limited because our data base does not include treatment information. Moreover, for a considerable proportion of patients (43.3%) cancer stage was unknown. Such a level of incomplete/missing tumor stage information is not uncommon in population-based registries for oral cavity cancer 
. In an attempt to explore the extent to which availability of information about tumor stage is relevant, we have calculated age-standardized survival for patients with known and with unknown cancer stage. The aggregate estimates for oral cavity cancer (ICD-10: C00-C06) were 51.4% (SE
1.2) for patients with known tumor stage and 57.7% (SE
1.2) for patients with unknown tumor stage, suggesting that the latter subgroup may comprise a relatively large proportion of patients with favorable tumor stages. As we also obtained similar results for separate subsites, our findings should, hence be considered with some caution. Finally, our data base was restricted to eleven out of 16 German Federal States and this may raise some concern of limited validity for the entire German population. Nevertheless, all major regions of Germany (e.g. East – West) were represented approximately according to their population share, and the coverage of about 33 million persons living in Germany enabled a not hitherto available level of precision of survival estimates even for less common subgroups of cancers of the oral cavity.
To summarize, the present study is the first to provide comprehensive information about five-year relative survival of oral cavity cancer patients of almost half of the German population. Patients with cancers of the lip (ICD-10: C00) were shown to have a five-year age-adjusted relative survival of 86.5%. The survival with a cancer of the tongue (ICD-10: C01-02) amounted to 48.1%. Patients with cancer at other regions of the oral cavity (ICD-10: C03-06) had a 5-year relative survival of 51.7%. These survival estimates were similar to those observed for several Scandinavian countries but lower than those recently reported from the US. Our findings further emphasize the high relevance of primary prevention and early detection of oral cavity cancer.