Familial relationships in squamous cell carcinoma of the skin

Non melanoma skin cancer and subsequent cancer risk

INTRODUCTION

Several studies have shown an increased risk of cancer after non melanoma skin cancers (NMSC) but the individual risk factors underlying this risk have not been elucidated, especially in relation to sun exposure and skin sensitivity to sunlight.

PURPOSE

The aim of this study was to examine the individual risk factors associated with the development of subsequent cancers after non melanoma skin cancer.

METHODS

Participants in the population-based New Hampshire Skin Cancer Study provided detailed risk factor data, and subsequent cancers were identified via linkage with the state cancer registry. Deaths were identified via state and national death records. A Cox proportional hazard model was used to estimate risk of subsequent malignancies in NMSC patients versus controls and to assess the potential confounding effects of multiple risk factors on this risk.

RESULTS

Among 3584 participants, risk of a subsequent cancer (other than NMSC) was higher after basal cell carcinoma (BCC) (adjusted HR 1.40 [95% CI 1.15, 1.71]) than squamous cell carcinoma (SCC) (adjusted HR 1.18 [95% CI 0.95, 1.46]) compared to controls (adjusted for age, sex and current cigarette smoking). After SCC, risk was higher among those diagnosed before age 60 (HR 1.96 [95% CI 1.24, 3.12]). An over 3-fold risk of melanoma after SCC (HR 3.62; 95% CI 1.85, 7.11) and BCC (HR 3.28; 95% CI 1.66, 6.51) was observed, even after further adjustment for sun exposure-related factors and family history of skin cancer. In men, prostate cancer incidence was higher after BCC compared to controls (HR 1.64; 95% CI 1.10, 2.46).

CONCLUSIONS

Our population-based study indicates an increased cancer risk after NMSC that cannot be fully explained by known cancer risk factors.

The effect of having an affected parent or sibling on invasive and in situ skin cancer risk in Sweden

Studies suggest that skin cancer aggregates within families; however, the risk of skin cancer associated with having an affected sibling or parent by subtype, tumor site, and age at diagnosis has not been established. The 2006 update of the Swedish Family-Cancer Database was used to calculate standardized incidence ratios (SIRs), representing the ratio of cancer risk among individuals with affected parents or siblings to the general population. Risk of invasive squamous cell skin cancer for individuals with an affected sibling or parent was increased between two- and three-fold compared with that in the general population. For in situ skin tumors, increased SIRs of 1.95-4.30 for squamous cell, Bowen's disease, and actinic keratosis were observed for individuals with affected siblings or parents, and SIRs were generally higher for tumors at sun-exposed versus covered sites. Finally, SIRs for in situ and invasive squamous cell skin cancer increased by increasing number of parental tumors (P< or =0.01). In conclusion, having an affected sibling or parent was associated with an increased risk of skin cancer of varied subtypes compared with that in the general population, and for some subtypes, these familial risks were increased for tumors at sun-exposed sites or by an increasing number of parental tumors.

Squamous cell carcinoma in situ of the skin: History, presentation, biology and treatment

Squamous cell carcinoma in situ (SCCIS) of the skin is a problem commonly dealt with by dermatologists. The classic presentation, originally described by Bowen, is easily recognized, but presentation on some anatomical surfaces may be associated with less than typical features. Major aetiological factors for this disease are UV light, human papillomavirus infection and immunosuppression. The natural course of SCCIS is usually prolonged, with treatment being appropriate, but not urgent. The choice of therapy requires consideration of the location of the lesion, and a desire for a high cure rate without causing loss of form, function or cosmesis. The immunomodulatory agent imiquimod has offered a significant advance for the topical treatment of SCCIS. Our improved understanding of the underlying biology of SCCIS permits us to make rational choices of treatment. In the future we may be able to determine which of these lesions may progress to invasive disease, and help us select the most effective therapy.

Genetic epidemiology of cancer: From families to heritable genes

A reliable determination of familial risks for cancer is important for clinical counseling, prevention and understanding cancer etiology. Family-based gene identification efforts may be targeted if the risks are well characterized and the mode of inheritance is identified. Medically verified data on familial risks have not been available for all types of cancer but they have become available through the use of the nationwide Swedish Family-Cancer Database, which includes all Swedes born in 1932 and later with their parents, totaling over 10 million individuals. Over 150 publications have emanated from this source. The familial risks of cancer have been characterized for all main cancers and the contribution of environmental and heritable effects to the familial aggregation has been assessed. Furthermore, the mode of inheritance has been deduced by comparing risks from parental and sibling probands. Examples are shown on familial clustering of cancers, for which heritable susceptibility genes are yet unknown, such as squamous cell carcinoma of the skin, intestinal carcinoids, thyroid papillary tumors, brain astrocytomas and pituitary adenomas. Some common cancers, such as lung and kidney cancers, appear to show an early-onset recessive component because familial risks among siblings are much higher than those in families where parents are probands. Many of the cancer sites showing high familial risks lack guidelines for clinical counseling or action level. In conclusion, we recommend that any future gene identification efforts, either using linkage or association designs, devise their strategies based on data from family studies. Clinical genetic counseling would benefit from reviewing established familial risks on all main types of cancer.

Familial invasive and in situ squamous cell carcinoma of the skin

We used the updated nation-wide Swedish Family-Cancer Database to examine familial risks in data from 1961 to 1998 on 1252 invasive and 2474 in situ squamous cell carcinoma (SCC) of the skin among offspring, and over 10 times more among parents. In 259 families a parent and an offspring had skin SCC. The familial standardised incidence ratios (SIRs) were 2.72 for invasive and 2.40 for in situ skin cancers in offspring. Multiple skin cancers in parents were associated with increased SIRs for invasive SCC in offspring, being 2.55 for one and up to 14.93 for two invasive and two in situ cancers in parents; the corresponding in situ SCC risks were 2.28 and 7.49. The population attributable fraction for any familial skin SCC, invasive or in situ, was 4.1%. Melanoma was the only discordant tumour that was associated with invasive and in situ skin SCC. These results provide evidence that there is an underlying hereditary susceptibility for at least a part of the familial clustering for skin SCC.

Familial risk of cancer by site and histopathology

Familial risks for histopathology-specific cancers have not been determined. We used the nationwide Swedish Family-Cancer Database on 10.2 million individuals and 1 million tumors to calculate standardized incidence ratios (SIRs) for familial cancers of specific histology and morphology among 0- to 66-year-old offspring. We used histology codes for both offspring and parents, but because of the limited number of cases, the morphology-specific classification could be used only for offspring by all site-specific cancers in parents, resulting in inflated risk estimates. A number of novel findings emerged in the histopathology-specific analysis of familial risks, in addition to some known associations. Overall, specific histology showed an SIR of 2.07 for all cancers compared to an SIR of 2.00 for any histology. However, the small effect was due to breast and prostate cancers, which showed a negligible effect of specific histology. Familial risks of over 4.0 were found for serous papillary cystadenocarcinoma of the ovary, papillary thyroid cancer and low-grade astrocytoma. Familial risks of over 3.0 were found for signet-ring gastric cancer, various forms of ovarian cancer and squamous cell skin cancer. Also noteworthy were familial risks of hepatocellular carcinoma (2.48), pancreatic adenocarcinoma (1.92), large cell carcinoma and adenocarcinoma of the lung (2.29 and 2.18, respectively) and clear cell carcinoma of the kidney (2.73). Many of the findings were novel and could be revealed only by applying codes for specific histopathology. These data call for a closer description of familial aggregations and probing for the underlying genetic mechanisms.

Human papillomaviruses and non-melanoma skin cancer

Epidemiological and experimental studies have overwhelmingly confirmed human papillomaviruses as important causal agents in anogenital carcinogenesis. A role for human papillomaviruses has also been proposed in a diverse range of other malignancies, and particular interest has focused on non-melanoma skin cancer, the commonest malignancy in fair-skinned populations worldwide. Although the evidence for this is considerably less convincing than for anogenital cancer, important epidemiological and functional data have emerged over the past year that have furthered our understanding of the possible contribution of human papillomaviruses to skin cancer. Epidemiological human papillomavirus DNA detection studies have shown associations with non-melanoma skin cancer, but have also emphasized the ubiquity of epidermodysplasia verruciformis human papillomavirus types in normal skin, hair follicles and benign hyperproliferative disorders, as have seroepidemiological approaches. Functional investigations have demonstrated mechanistically relevant interactions between the virus and ultraviolet radiation, host cytokines and cellular proteins including p53 and the pro-apoptotic protein Bak. Taken together, these data have advanced our understanding of the contribution of human papillomaviruses to malignant transformation in cutaneous keratinocytes, but further research is required before a causal association between human papillomaviruses and skin cancer is reliably confirmed.

Familial testicular cancer and second primary cancers in testicular cancer patients by histological type

The Swedish Family-Cancer Database was used to assess familial cancer risks in first-degree relatives and the risks of second primary cancers in testicular cancer patients by the histological type of their testicular cancers. Standardised incidence ratios (SIRs) were employed to estimate cancer risks. Among 4650 patients, 1.3% were familial testicular cancer. Seminomas showed a 10 years later median age of onset than teratomas (30 versus 40 years). The familial risks of testicular cancer were 3.8 for fathers, 8.3 for brothers and 3.9 for sons; they were similar for the two histologies. The fraternal risks were elevated 2- to 2.8-fold for pure histologies compared with the mixed histologies. Significantly increased risks for subsequent cancers were observed in the stomach, pancreas, testis, kidney, bladder, thyroid and connective and lymphatic tissues in the patients. Our data support the contention that genetic predisposition is one of the major contributors to familial and multiple testicular cancers.

Genetic Epidemiology--science and ethics on familial cancers

Genetic epidemiology provides data on cancer etiology, familial risks and genotype-specific risks. These data are useful for clinical counselling and gene identification. The studies require large, unbiased sample sizes and collaboration between research teams, nationally and internationally. A recent study on Nordic twins suggests that in colorectal, breast and prostate cancer, the inherited component ranges between 27 and 42%, far in excess of the known susceptibility genes. The data from the Swedish Family-Cancer Database, particularly on second cancers, also suggest that a main genetic component in cancer is polygenic. The results have implications for design of genetic studies and for clinical counselling.

Second primary neoplasms among 53 159 haematolymphoproliferative malignancy patients in Sweden, 1958-1996: a search for common mechanisms

The Swedish Family-Cancer Database was used to analyse site-specific risk of second primary malignancies following 53 159 haematolymphoproliferative disorders (HLPD) diagnosed between 1958 and 1996. Standardized incidence ratio (SIR) of a second malignancy was calculated as the ratio of observed to expected numbers of second malignancies by applying site-, sex-, age-, period-, residence- and occupation-specific rates in the corresponding population in the Database to the appropriate person-years at risk. Among 18 960 patients with non-Hodgkin's lymphoma (NHL), there was over a 3-fold significant increase in cancer of the tongue, small intestine, nose, kidney and nervous system, squamous cell carcinoma (SCC) of the skin, NHL, Hodgkin's disease (HD) and lymphoid and myeloid leukaemia. Among 5353 patients with HD, there was over a 4-fold significant increase in cancer of the salivary glands, nasopharynx and thyroid, NHL and myeloid leukaemia, and over a 1.6-fold increase in cancer of the stomach, colon, lung, breast, skin (melanoma and SCC), nervous system and soft tissues and lymphoid leukaemia. Among 28 846 patients with myeloma and leukaemia, there was a significant increase in cancer of the skin, nervous system and non-thyroid endocrine glands and all HLPD except for myeloma. Our findings showed some clustering between first and second primaries among Epstein-Barr virus-, ultraviolet radiation- and immunosuppression-related cancers.

Second primary cancers after anogenital, skin, oral, esophageal and rectal cancers: etiological links?

The Swedish Family-Cancer Database was used to analyze second cancers after oral, esophageal, rectal, cervical, genital and skin (squamous cell carcinoma) cancers. A strong and consistent association of second cancers was observed at all these sites, in men and women. As a novel finding, an association of rectal cancer with the human papillomavirus (HVP)-related cancers was shown. New evidence on an excess of skin cancer with the HPV-related cancers was also provided. As an epidemiological study, the associations were strong and often supported by a number of comparisons. These could not be explained by bias or long-term treatment related effects. However, whether the findings on rectal and skin cancer are due to HPV or other infections, transient or inherited depressed immune function or other constitutional factors remains to be established.

Second primary neoplasms in 633,964 cancer patients in Sweden, 1958-1996

The Swedish Family-Cancer Database was used to analyze concordant (same site) and discordant (different site) second primary neoplasms in 633,964 cancer patients diagnosed from 1958 to 1996. Cases of second malignant neoplasms were extracted from the Database if the diagnosis date of the first and second cancer differed by at least 1 month. The expected numbers of cancers were obtained by applying site-, sex-, age-, period-, residence- and socioeconomic level-specific rates in the corresponding population in the Database to the appropriate person-years at risk. The standardized incidence ratio (SIRs) of a second cancer was taken to be the ratio of observed to expected numbers of second cancers. Of all cancers, 8.5% were subsequent neoplasms (8.4% for males and 8.7% for females). SIRs for both concordant and discordant subsequent cancer were elevated in patients with cancer of the upper aerodigestive tract, colon, nose, breast, other female genitals, testis, kidney, urinary, bladder, skin, nervous system, endocrine, bone, connective tissue, melanoma, lymphoma and leukemia. The risks at some concordant sites, such as nose, squamous cell skin, bone and connective tissue in both sexes, breast in males and upper aerodigestive tract and leukemia in females, were very high (>10). At discordant sites, SIRs were less than 2 but significantly increased after all but gastric and prostatic cancer. Compared with the general population, cancer patients were at a modestly increased risk for new primary cancer after cancers at many sites, calling for attention in treatment, management and prevention.

A population-based study of familial cutaneous melanoma

We studied familial risks in cutaneous melanoma by comparing the occurrence of melanoma, or discordant cancer, in two generations, based on the Swedish Family-Cancer Database of 9.6 million individuals. Offspring were from 0 to 61 years of age. Cancers were obtained from the Swedish Cancer Registry for the years 1958 to 1996. The study was based on 30,170 cases of melanoma. Among these, 196 offspring came from families where a parent also presented with melanoma. The overall familial hazard ratio (FHR) was 2.47 when a parent had melanoma; an early age of onset increased the risk. Multiple primary melanomas in parents increased the FHR in offspring, being 2.23 for one, 9.10 for two and up to 83 for more than two melanomas in the parent. The number of affected offspring increased the risk of melanoma in the parents, from 3.05 when one was affected to 5.12 and 151 when two or three offspring were affected, respectively. Melanoma risk to a sibling with an affected proband was 3.56. Melanoma in one generation was associated with an increased occurrence of squamous cell carcinoma of the skin in the other generation. Other weaker associations were found to pancreatic, breast, testicular and nervous system cancers and non-Hodgkin lymphomas.

Cancer risks to spouses and offspring in the Family-Cancer Database

It is generally accepted that cancer is caused by environmental and inherited factors but these are only partially identified. Family studies can be informative but they do not separate shared lifestyles and genes. We estimate familial risks for concordant cancers between spouses in common cancers of both sexes in order to quantify cancer risks from the shared environment. The risks are compared to those seen between parents and offspring in order to estimate the inherited component. The nation-wide Family-Cancer Database was used as the source of family and cancer data. Standardized incidence ratios (SIRs) were calculated for concordant cancer in offspring by parental cancer and in spouses. Among the 23 cancer sites considered, all but two showed an increased SIR for offspring by father or mother. Only two sites, stomach and lung, showed an increase in SIR of concordant cancer among spouses. Additionally, pancreatic cancer and melanoma were increased in couples where at least one spouse was diagnosed before age 50. If both spouses presented melanoma before age 40, SIR was 3.82 for husbands. SIRs of colon, renal, and skin (squamous cell) cancers were unchanged by spouses' concordant cancer. Shared lifestyle among spouses seems to explain only a small proportion of cancer susceptibility. Because lifestyles are likely to differ more between parents and offspring than between spouses, familial cancer risks between parents and offspring are likely to be more due to heritable rather than environmental effects.

Genetic epidemiology of multistage carcinogenesis

It is commonly believed that cancer is a multistage, polygenic disease. Even though conceptually appealing, the evidence supporting the multistage theory remains limited. Most known tumor suppresser genes are associated with monogenic dominant cancers following a two-hit pathway. We review results from a recent twin study on 90000 individuals that give support to the multistage theory. Statistically significant heritability estimates were shown for cancers of the colorectum (35%), breast (27%), and prostate (42%). These estimates are much higher than those obtained from family studies in which parents and offspring, or sibs are compared. The difference can be accounted for by the involvement of many genes. A polygenic cancer would show small effects in family studies but large effects in twin studies. We present calculations on the decrease in familial risks when the number of genes involved increases or when the penetrance decreases. We test the apparent number of stages involved in the main cancers from the Swedish Family-Cancer Database. The logarithms of the slopes suggest large differences in the apparent numbers of mutations involved in different cancers. The number of mutations required appears to be less in familial breast cancer compared to sporadic breast cancer. Study designs for gene identification should be revised to accommodate polygenic cancers.

Familial cancer risks to offspring from mothers with 2 primary breast cancers: leads to cancer syndromes

The nationwide Swedish Family-Cancer Database was used to analyse the risk of cancer among the offspring of bilateral breast cancer patients. We studied 4,734 such mothers who had 9,391 offspring, of whom 328 presented with a primary cancer in the years 1958-1996. Standardised incidence ratios (SIRs) were increased for breast [SIR 3.05, 95% confidence interval (CI) 2.57-3.59], ovarian (SIR 1.84, 95% CI 1.03-3.05) and anogenital (SIR 1.75, 95% CI 1.11-2.63) cancers and childhood sarcomas (SIR 9.39, 95% CI 1.93-29.13). Additionally, squamous-cell skin cancer was increased among sons and all childhood cancers among daughters. When analysed by histological type, adenocarcinomas of the breast and ovary, all squamous-cell carcinomas and tumours at glandular epithelium (seminomas and intestinal carcinoids) were increased. Mothers with bilateral breast cancer had an excess of 2 or more children with cancer. The increased risk of ovarian cancer is consistent with germline mutations in the BRCA1 and BRCA2 genes, while the risk of soft tissue and bone sarcomas may reflect the association of these tumours with Li-Fraumeni syndrome. The increases in squamous-cell carcinomas at many sites may reflect a new susceptibility syndrome.