Epidemiological evaluation of sunlight as a risk factor of lip cancer

Actinic cheilitis and lip squamous cell carcinoma: Literature review and new data from Brazil

Background

To investigate the prevalence of malignant and potentially malignant lesions of the lip in an oral pathology service and to compare these data with a literature review.

Material and Methods

A total of 3173 biopsy reports and histopathological records were analyzed. Cases with a histological diagnosis of actinic cheilitis (AC) with or without epithelial dysplasia, in situ carcinoma, or lip squamous cell carcinoma (LSCC) were included. A comprehensive literature review was conducted to investigate the prevalence of AC and/or LSCC.

Results

124 cases (3.91%) were included, 75 (60.5%) had some degree of epithelial dysplasia and 31 (25.0%) were LSCC. Clinically, most of the lesions were diagnosed as AC (50.8%); however, eight cases clinically reported as AC were histologically diagnosed as LSCC. Regarding clinical characteristics, most individuals were fair-skinned male, with mean age of 54.3±12.3 years, and with a history of long-term solar exposure. Furthermore, 18 articles were selected from the literature, showing that the lower lip was predominantly affected and that most individuals were males, fair-skinned, and older than 40 years.

Conclusions

Since most of the cases diagnosed clinically as AC presented some degree of epithelial dysplasia, it is important to emphasize the value of biopsy and the histological evaluation of this lesion.

Key words:Actinic cheilitis, Precancerous conditions, In situ carcinoma, Oral diagnosis, Mouth neoplasms.

High dose rate brachytherapy in early stage squamous-cell carcinoma of the lip

INTRODUCTION AND GOALS

To analyze the results obtained after treatment of early stage (T1-T2) squamous cell carcinoma of the lip with high dose rate brachytherapy and evaluate the efficacy of this treatment in both local and regional control.

MATERIALS AND METHODS

Retrospective analysis of the treatments performed at our department from March 1999 to March 2013 with high dose rate brachytherapy with rigid needles. We included 68 patients, 63 men and 5 women; 37 patients (54.4%) presented a T1 tumour, less than or equal to 2cm, while the other 31 (45.6%) were classified as T2. Median total dose was 45Gy, with a median dose per fraction of 5Gy x 9 fractions twice a day for 5 days.

RESULTS

With a mean follow-up of 56.4 months, local control was 96.9%. Stratifying by tumour size, local control of T1 cases was 100%, while T2 achieved 93.2% (2 local recurrences). Regional control at 5 years was 93.8% for T1, and 80.8% for T2. In 11 cases with elective cervical treatment, no regional failure happened. As for toxicity, no patient presented soft tissue, or bone, necrosis. All patients achieved good or excellent cosmetic and functional results.

CONCLUSIONS

High dose rate brachytherapy allows effective, safe treatments for squamous cell carcinoma of the lip, with good aesthetic and functional results. It can be considered a valid alternative for surgery in early stage tumours.

Surgical management of squamous cell carcinoma of the lower lip: an experience of 109 cases

Objectives: We are presenting our experience collected from a series of 109 cases with SCC of the lower lip focusing on clinical features of patients and surgical approach. Study Design: We retrospectively analyzed medical records of patients diagnosed with Squamous Cell Carcinoma (SCC) of the lower lip at the Oral and Maxillofacial surgery at Xi’an Jiaotong University during a period between 1999 and 2008. Results: A total of 109 patients with lip cancer were included in the study. When no frozen-section test was performed, the neoplasia was removed with a margin of at least 6 mm. Different surgical techniques were used for lip reconstruction after tumor excision. Neck dissection was performed in all patients with clinically palpable lymph nodes. Median follow-up was 38 months. During follow-up, recurrence occurred in 5 patients, 3 patients developed neck metastases, distant metastases developed in 1 patient. Five patients died during observation period. Conclusions: The patient-related and defect-related issues must be taken into consideration during reconstruction for surgical defect. For N0 patients, we recommend wait-and-see policy. Early detection, careful follow-up and prompt neck is essential for the successful treatment.

Key words:Lip cancer, surgical management, reconstruction.

Significant differences in nonmelanoma skin cancers of the upper and lower lip

BACKGROUND

Squamous cell carcinomas (SCCs) generally have been reported to be more prevalent on the lips than basal cell carcinomas (BCCs), but in our experience, BCCs of the lips are common, particularly in women.

OBJECTIVES

To determine the tumor characteristics of lip SCCs and BCCs, including tumor type, anatomic location, and size; and to identify the relationship between patient characteristics, including age and sex, and lip tumor characteristics.

METHODS AND MATERIALS

Retrospective review of all BCCs and SCCs located on the lip treated between January 1995 and October 2010.

RESULTS

Of 470 lip nonmelanoma skin cancers (NMSCs) identified, 71.4% were BCCs, and 28.6% were SCCs. Lower lip tumors were predominantly SCCs (79.8%, p < .01), whereas upper lip tumors were predominantly BCCs (85.7%, p < .01). Patients with lower lip tumors were significantly older (68.8 vs. 64.7, p = .02) and were largely male (70.8%, p < .01). Patients with SCCs were mostly male (62.2%, p = .02), whereas those with BCCs were predominantly female (68.8%, p < .01). Subgroup analysis showed that upper lip tumors were 98.1% cutaneous or more than 50% cutaneous, whereas 56.3% of lower lip tumors were mucosal or more than 50% mucosal; 87.1% of mucosal tumors were SCCs, whereas 83.6% of cutaneous tumors were BCCs (p < .01). Seventy-one percent of patients with mucosal tumors were men, whereas 67% of patients with cutaneous only tumors were women (p < .01).

CONCLUSION

These data provide evidence of significant differences in patient and tumor characteristics between NMSCs of the upper and lower lips.

Queilite actínica: avaliação comparativa estética e funcional entre as vermelhectomias clássica e em W-plastia

FUNDAMENTO: A queilite actínica crônica é a ceratose actínica localizada no vermelhão labial. O tratamento é de crucial importância, devido ao potencial de transformação maligna. OBJETIVO: Avaliar os resultados estéticos e funcionais das vermelhectomias clássica e em W-plastia na queilite actínica. Na técnica clássica, a cicatriz é linear; na W-plastia, em linha quebrada. MÉTODOS: Foram tratados 32 pacientes com diagnóstico clínico e histopatológico de queilite actínica. Quinze deles foram submetidos à técnica em W-plastia e 17, à técnica clássica. Avaliaram-se parâmetros como retração cicatricial e alterações funcionais. RESULTADOS: Houve associação estatisticamente significativa entre a técnica utilizada e a presença de retração cicatricial, sendo a associação positiva com a clássica (p=0,01 com correção de Yates). O risco relativo (odds ratio - OR) calculado foi de 11,25, ou seja, houve maior chance de retração nos pacientes submetidos à técnica clássica. Nenhuma das técnicas apresentou alterações funcionais. Avaliaram-se complicações pós-operatórias como presença de crostas, lábios secos, parestesia e deiscência de sutura. Não houve associação estatisticamente significante entre as complicações e a técnica utilizada (p=0,69). CONCLUSÃO: Concluiu-se que a vermelhectomia em W-plastia oferece melhores resultados estéticos e índices de complicações semelhantes.

Actinic cheilitis: clinical and histological features

PURPOSE

The purpose of this study was to analyze the clinical and histological features of actinic cheilitis (AC).

PATIENTS AND METHODS

A total of 29 patients with AC were clinically evaluated, and incisional biopsies were performed to confirm the clinical diagnosis. Histological features were analyzed, and dysplasia was classified as mild, moderate, or severe. The chi(2) test was used for the following variables: gender, age, race, and smoking habits. The degree of dysplasia was related to these variables (Fisher's test) to test for independence between them (P < .05).

RESULTS

Of the patient group, 72.41% were male, 75.86% were over age 40 years, 93.10% were white, and 72.41% were nonsmokers. Clinically, all patients presented with multifocal lesions. The following manifestations were seen: dryness, atrophy, scaly lesions, swelling of the lip, erythema, ulceration, blurred demarcation between the lip vermilion border and the skin, marked folds along the lip vermilion, white spots or plaques, crusts, blotchy areas, and areas of pallor. Keratosis, granulosis, hyperplasia, acanthosis, or atrophy and dysplasia were found in the epithelial tissue; elastosis, inflammatory infiltrate, and vasodilatation were found in the connective tissue. Dysplasia was mild in 10.34% of the patients, moderate in 27.59%, and severe in 62.07%. Absence of sample homogeneity was observed in regard to gender, age, race, and smoking habits. It was not possible to reject the hypothesis of independence between mild, moderate, or severe dysplasia and gender, age, race, and smoking habits.

CONCLUSIONS

Dryness, atrophy, and scaly lesions were the most common clinical findings observed. Dysplasia, inflammatory infiltrate, and vasodilatation, as well as elastosis, were the most common histological findings observed. Gender, age, race, or smoking habits were not related to the degree of dysplasia in the sample.

The epidemiology of lip cancer: a review of global incidence and aetiology

Lip cancer (140 ICD-9) is a form of oral cancer that has a distinctive global epidemiology. This review summarises global incidence rates for male and female lip cancer with the aid of cancer atlases. High male lip cancer rates are reported for regions of North America (12.7 per 100 000 per annum), Europe (12.0 per 100 000 per annum) and Oceania (13.5 per 100 000 per annum), while it is virtually unknown in parts of Asia. Factors commonly cited as important in the aetiology of lip cancer include solar radiation, tobacco smoking and viruses. An attempt is made to summarise the evidence for factors that may be important in lip carcinogenesis. While incidence rates are generally stable or falling among males worldwide, they are rising in many female populations. The aetiology of the disease is far from established and much information regarding its pathogenesis is based on anecdotal rather than case-controlled epidemiological evidence. The epidemiology of lip cancer supports the proposal that the lip should be considered as a distinct cancer site, rather than being included with other forms of intraoral cancer.

Trends in the incidence of lip, oral, and pharyngeal cancer: Connecticut, 1935-94

Using Connecticut Tumor Registry data we explored trends in age-adjusted (AARs) and age-specific (ASRs) incidence rates for lip, oral, and pharyngeal cancer over the 60-year period 1935-94. Particular attention was given to findings from the most recent series of 5-year periods that have not been previously analyzed. There was a long-term decline in lip cancer AARs by period, and ASRs generally fell over time and with successive birth cohorts. This notable decrease in rates continued through 1990-94 and with the more recent cohorts, particularly among males. Oral cancer AARs for males peaked in the early 1960s and the late 1970s while rates for pharyngeal cancer increased into the late 1970s. For each of these sites, rates began to decline in 1980-84 and have continued to fall into the first half of the 1990s. Among females AARs for oral and pharyngeal cancer increased more than threefold between 1935-39 and 1980-84; however, encouragingly, and in sharp contrast to the earlier trend, rates fell during the most recent 10-year period. ASRs for oral and pharyngeal cancer were increasing by the birth cohort of 1900 and tended to increase through the cohort of 1920 for males and the cohorts of 1920-30 for females. ASRs for subsequent cohorts have remained relatively unchanged or decreased modestly. It is doubtful that the observed trends in lip, oral and pharyngeal cancer incidence are primarily artifactual, but more likely represent secular changes in exposure to environmental risk factors.

Radiotherapy for cancer of the lip. A long-term evaluation of 85 treated cases

The results of radiation therapy, both as a single treatment modality and after radical surgery for squamous cell carcinoma of the vermilion surface/border of the lip, are retrospectively analyzed in 85 patients. All recurrences (7%) occurred in T2 and T3 tumors treated with external beam radiotherapy only. The long-term esthetic result and functional morbidity are evaluated. Referral patterns are discussed, and the need for a multidisciplinary treatment protocol is emphasized.

Etiology of cancer of the lip. A review

A range of environmental and host factors has been identified to explain the etiopathogenesis of squamous cell carcinoma of the lip. However, the definitive pathogenic pathway remains unclear. Carcinogenesis does not seem to be limited to a single agent, but rather to a complex multistep process of interactions between putative risk factors. In this paper, the currently available data regarding risk factors, considered to be causally related to the onset of lip cancer, are reviewed.

Solar radiation, lip protection, and lip cancer risk in Los Angeles County women (California, United States)

A population-based case-control study of 74 women with lip cancer diagnosed from 1978 to 1985 in Los Angeles County (California, United States) and frequency matched to 105 controls investigated the risk of solar radiation and protection from lip sunscreening agents to explore the hypothesis that excess incidence of lip cancer seen in men is due partly to lower rates in women, conferred by frequent use of lip protection. We confirm the importance in women of risk factors similar to those found in men, i.e., fair complexion, sun exposure, and smoking. Risk was related strongly to lifetime solar radiation (odds ratio [OR] = 13.5 for highest quartile of exposure, 95 percent confidence interval [CI] = 4.5-40.6, P trend < 0.0001) and time spent outdoors (OR = 4.7 for highest quartile of average yearly hours, CI = 1.9-12.1, P trend = 0.01). Further, among women with high lifetime solar-radiation exposure, those who used lip protection once a day or less had twice the risk of lip cancer than women who used lip protection more than once a day (OR = 7.3, CI = 1.9-27.2 cf OR = 3.2, CI = 1.1-9.2). These findings show that solar radiation is a major risk factor for lip cancer and suggest that lip sunscreening is protective, thereby supporting the hypothesis that use of lipstick and other sunscreening agents by women has contributed to their lower incidence of this disease.

Malignant oral tumours in Sweden 1960-1989--an epidemiological study

Epidemiological data from the Swedish Cancer Registry of new cases of malignant oral tumours in Sweden 1960-1989 are presented, including the total number and the age-standardised incidence rate per 1 million population, by site and sex, (I(s)). An analysis of the various histopathological types of malignant oral tumours in the different sublocations is also given. A comparison is made between the three 10-year periods 1960-1969, 1970-1979 and 1980-1989 regarding total number and I(s). The total number of cases, 17,158, represented 1.8% of all newly diagnosed cancers in Sweden. The following relative frequencies were noted for the respective sites: intra-oral region 0.7%, lip 0.6% and pharynx 0.5%. The results indicated an increase in total number and a statistically significant increase of I(s) for malignant lip tumours in females over the whole period. A corresponding increase in total number during the periods 1960-1969 and 1980-1989 and a decrease in I(s) during the periods 1970-1979 and 1980-1989 in lip tumours for males was observed. For males there was an increase in total number and a statistically significant increase in I(s) for malignant tongue tumours, while the corresponding figures for females remained constant. For malignant floor of the mouth tumours there was an increase in total number and a statistically significant increase in I(s) for both men and women. In the intra-oral region, including the sublocations oral cavity-other sites, tongue and floor of the mouth, the male:female ratio was 1.8:1 and I(s) changed from 22.8 (1960-1969) to 29.6 (1980-1989).(ABSTRACT TRUNCATED AT 250 WORDS)

Cancers of the lip and oropharynx in different social and occupational groups in Finland

Social status and occupation-specific risks of cancers of the lip, tongue, mouth and pharynx were studied in a nationwide series of 2369 men and 809 women diagnosed in Finland in 1971-1985 and recorded in the files of the Finnish Cancer Registry. Codes for social status (four classes) and occupation (336 categories) were drawn from the files of the 1970 Population Census. The standardised incidence rates (SIR) were defined as the ratios of observed and expected numbers of cases, the expected ones being based on the sex, age, site and calendar period-specific incidence rates in the Finnish population. The SIR of lip cancer in the lowest social class was five times that of the highest one, thus indicating the effects of social class differences in smoking habits. The effect of outdoor work on the development of lip cancer was also strongly supported by this study. The social class-adjusted SIR for fisherman was 2.7 (95% C.I. 1.3-5.0), for forestry managers 2.2 (1.2-3.6), for timber workers 1.9 (1.2-2.9) and for farmers 1.8 (1.2-2.6). For cancers of the oral cavity and pharynx there was no clear correlation with social class. However, the SIR for these cancers among farmers was significantly reduced. The occupation-specific SIRs pointed more to alcohol than smoking aetiology. In the case of cancer of the tongue, no aetiological clues whatsoever could be found. The role of direct occupational factors in the aetiology of any of these cancers seemed to be minimal.

The descriptive epidemiology of pharyngeal cancer in Scotland

There have been recent reports of substantial increases occurring in the incidence of and/or mortality from tongue and mouth cancers in several countries. In this paper using data from Scotland (1960-89) we report on time trends in pharyngeal cancer. Similar increases in rates are evident for cancers of the oropharynx and hypopharynx while there has been little change in the occurrence of nasopharyngeal cancer (which has distinct aetiological factors). It therefore seems that reported changes in the incidence of and mortality from oral cancer may be real, and in Scotland, this is most probably due to changes in alcohol consumption.

Epidemiological aspects of lip cancer in Scotland

The purpose of this paper is to present the descriptive epidemiology of lip cancer in Scotland. The incidence and mortality of lip cancer are found to be higher in men than in women and to have fallen remarkably among men. This decline has been the result of cohort effects indicating that the risk of lip cancer is decreasing among successively younger people.

Lip cancer. Incidence trends in Connecticut, 1935-1985

Suspicions have recently arisen that cancer of the lip may exert an undue influence on overall oral cancer statistics and, therefore, possibly distort the true image of intraoral cancer. The authors investigated this question through epidemiologic analysis. A total of 2291 cases of lip cancer accessioned by the Connecticut Tumor Registry (CTR) from 1935 to 1985 (23.6% of all oral cancer) were analyzed. Occurrence trends for males and females had different patterns: for men, the age-adjusted incidence rates showed a fivefold decrease during the 51-year study; for women, the rates were relatively low and constant during the same period. Analysis for age-specific rates revealed that the older the age group, the higher the incidence rates for both sexes. Squamous cell carcinoma accounted for at least 87.4% of all lip cancers (96.2% if nonspecified epithelial neoplasms are assumed to be squamous cell carcinoma). The vermilion border of lower lip was the most common site. Moderately differentiated tumors were most common (48.5%), closely followed by well-differentiated tumors (44.2%). Analysis by county showed that the crude incidence rates for males in New London and Windham counties exceeded the average Connecticut statewide rates. The authors concluded that the epidemiology of Connecticut lip cancer differs significantly from that of intraoral squamous cell carcinoma in the same population studied within the same period of time. Epidemiologic studies involving "oral cancer" should direct attention to anatomic subsite to consider differences in disease trends according to specific location.

Oral cancer

In the U.S. oral cancer accounts for 2.1% of all cancers and 1% of cancer deaths. Two to three times as many males as females are affected. Blacks have more intra-oral cancer than whites, and their incidence and mortality rates have increased in recent years. The etiologic process very likely involves several factors. The major etiologic agents are tobacco (all types) and alcoholic beverages. Herpes simplex virus, human papilloma virus, and Candida have been implicated. Host factors include poor state of dentition, nutritional aberrations, cirrhosis of liver, lichen planus, and immunologic impairmant. Cellular changes include amplification of some oncogenes, alterations in antigen expression, production of gamma-glutamyl transpeptidase, and disturbance of keratin and involucrin production. Experimentally, cancer is readily produced on the hamster cheek pouch and rat oral mucosa. Unlike oral cancer in humans, most experimental lesions are exophytic, and they rarely metastasize.

The surgical management of lip cancer

The history of surgical reconstruction of the lips is outlined and a series of procedures described, which together enable lip reconstruction to be successfully undertaken in a variety of different circumstances.

Actinic cheilitis: a review of the etiology, differential diagnosis, and treatment

With today's increase in sun worshippers, the number of sun-induced skin lesions is increasing. Actinic cheilitis is the counterpart of actinic keratosis of the skin and can also develop into squamous cell carcinoma. In this article we review the etiology, clinical spectrum, histology, differential diagnosis, and treatment of actinic cheilitis. Actinic cheilitis needs to be differentiated from many other lip conditions, and the dermatologist must be attune to its possibility whenever assessing scaly lips. Because of its potential to develop into squamous cell carcinoma, treatment should be instituted as soon as possible.

Reassessing the epidemiology of lip cancer

The risk factors associated with carcinoma of the lip are reviewed with an aim toward reassessing the epidemiology of the disease. Descriptive studies show lip cancer to occur most commonly in aging white men. The geographic distribution of the disease varies widely, both nationally and internationally; recent studies show that at the national level there is not a uniformly high risk of lip cancer across the sunny states, as has been believed. Secular disease trends show a decline in both morbidity and mortality while survival rates have remained stable. The risk factors consistently associated with lip cancer are rural residence and outdoor occupation, but the latter does not apply to all outdoor workers. In addition, both actinic radiation and tobacco smoking have long been considered to be causally related to lip cancer. An extensive review of the literature, however, reveals that the studies evaluating the association between these exposure variables and the disease do not yield consistent results; in addition, many recent, well-designed studies fail to support independent causal hypotheses. We conclude that (1) any risk factors considered to be causally related to lip cancer must be congruent with the descriptive factors (geographic distribution, secular disease trends, etc.) and (2) although sunlight and smoking are highly likely risk factors, their interrelationship as well as their interaction with other factors, such as genetic predisposition, needs reassessment.

An epidemiologic study of malignant oral tumors in Sweden 1958-77

The paper presents epidemiologic data of malignant oral tumors in Sweden 1958-77 including the total number of cases, the number and relative frequency of cases in different sublocations of the oral region and the mean annual age standardized incidence rate, all ages, per one million population, by site and sex. An analysis of different histopathologic types of oral tumors is also presented. A comparison is made between the two 10-yr periods 1958-67 and 1968-77. Errors involved in epidemiologic studies are discussed.

Basal-cell carcinoma of the vermilion border of the upper lip. A case report

Basal-cell carcinoma mostly occurs in patients of advanced age, between the 5th and the 7th decades of life. The lesion is usually located on areas that have exposure to the sun and is extremely rare on the oral mucosa. A case of basal-cell carcinoma on the vermilion border of the upper lip in a 62-year-old-male is described. An excisional biopsy under local anaesthesia was followed by a radical wedge excision of the upper lip.

Occupations with low risk of lip cancer show high risk of skin cancer of the head

The standardized morbidity ratios (SMR) of lip and non-melanomatous skin cancer (basal-cell carcinoma excluded) of the head and neck in males were determined for different occupational groups in Finland. The data on all cases of these types of cancer diagnosed in Finland in the age group 35-69 years in 1971-75 were supplemented by information on occupations from the 1970 census (Central Statistical Office of Finland). The expected numbers of cases were based on the age and occupation-specific numbers of person-years computed by the Central Statistical Office, and the age-specific incidence rates of lip and skin cancers among the economically active population. The highest SMR of lip cancer among all the occupational groups was found in agriculture, forestry and fishing (1.64). In contrast, the SMR of skin cancer was not higher than expected in occupations related to agriculture and forestry. Significantly lower than expected risks of lip cancer were observed among highly educated white-collar workers, among whom the risk of contracting skin cancer was the highest (technical, scientific, humanistic and artistic work, SMR 1.78). The morbidity of both lip and skin cancers varies considerably by occupation, and the risks seem to be, at least in part, inversely related. Thus, it is probable that there are also differences in the risk factors, contrary to several earlier suggestions. The nature of these factors are discussed.

Is upper lip cancer "true" lip cancer?

A description is given of the occurrence of upper and lower lip cancers in Finland in the period 1953-1974 with the aim of reaching conclusions on the possible differences in the etiological factors involved. Substantial differences with respect to various epidemiological parameters, such as incidence rates, trends in the incidence with time, male/female ratios of the incidence rates, age-incidence curves, urban/rural ratios of the incidence rates, and geographical distribution, were demonstrated between upper and lower lip cancers. On the other hand, similarities in the occurrence of upp]er lip cancer and non-melanomatous skin cancer of the head and neck could be observed. It was concluded that in terms of etiology upper lip cancer could be regarded as a separate entity and different from "true" lip cancer of the lower lip. The role of recurrent herpetic infections of the lips is also discussed.

Second primary cancers in patients with carcinoma of the lip

The occurrence of second primary cancers in patients with lip cancer was evaluated in order to test certain etiologic hypotheses. All cases of lip cancer reported to the Finnish Cancer Registry in 1953-74 (3303 men, 320 women) were followed up for a second (or third) primary cancer through the files of the Registry either to death or to 31 December 1974 (a total of 25 510 person-years). The expected numbers of cases were calculated on the basis of the incidence rates specific for sex, age, time and residence (urban or rural) in Finland. A higher than expected risk of cancer was found among both urban and rural male lip cancer patients; among women the observed number of new primary cancers did not differ from that expected. A significant excess risk among males was noted for cancers of the lung and larynx (rural patients) and for non-melanomatous skin cancer in locations other than the head and neck (urban patients). The association of cancers of the lip, lung and larynx found earlier on a geographic level supports the hypothesis that tobacco smoking is a common risk factor in these cancers. The differences in the relative risks between urban and rural patients, however, suggest that the risk factors in lip cancer in urban areas might be partially different from those prevalent in the rural population. The results do not support the hypothesis that sunlight is an important risk factor in lip cancer.

Risk factors of lip cancer: a critical evaluation based on epidemiological comparisons

A description is given of the occurrence of lip, skin, and intraoral cancers in Finland in the period 1953-1973 with the aim of testing certain etiologic hypotheses. In addition, data on lip cancer were correlated with those of some other types of cancer. Substantial differences with respect to various epidemiologic parameters were found between lip and skin cancers. However, there were similarities between lip cancer and cancers of the upper gastrointestinal canal and respiratory organs (especially lung cancer). Negative geographic correlation was found between the age-adjusted incidence rate of lip cancer and that of cancers of the colon and prostate. In addition, the correlation was highly negative for the median income per capita (p less than 0.001). It was concluded that, in terms of cancer etiology, lip cancer is more closely related to cancer of the oral cavity than to that of the skin. Moreover, some specific socioeconomic factors associated with a low standard of living must be considered as noteworthy risk factors of lip cancer.