Invasive and in situ squamous cell carcinoma of the skin: a nationwide study in Iceland

BACKGROUND

The worldwide incidence of cutaneous squamous cell carcinoma (cSCC) is increasing.

OBJECTIVES

To evaluate the tumour burden of in situ and invasive cSCC in Iceland, where the population is exposed to limited ultraviolet radiation.

METHODS

This whole-population study used the Icelandic Cancer Registry, which contains records of all in situ and invasive cSCC cases from 1981 to 2017. Incidence of cSCC was evaluated according to age, anatomical location, residence and multiplicity, and trends were assessed using joinpoint analysis. Age-standardized rates (WSR) and age-specific incidence rates per 100 000 person-years were calculated, along with cumulative and lifetime risks.

RESULTS

Between 1981 and 2017, in situ cSCC WSR increased from 1·2 to 19·1 for men and from 2·0 to 22·3 for women. Invasive cSCC WSR rose from 4·6 to 14 for men and from 0·3 to 13·2 for women. The average number of in situ cSCC lesions was 1·71 per woman and 1·39 per man. Women developed more in situ cSCCs than invasive cSCCs in almost all anatomical locations, whereas men developed more invasive cSCCs, mostly on the head and neck. The rates of in situ cSCC were higher in Reykjavik compared with rural areas. Furthermore, women more commonly developed multiple in situ lesions. For lip cSCCs, invasive lesions occurred more frequently than in situ lesions among both sexes. Joinpoint analysis showed that in situ cSCC in women exhibited the most rapid incidence increase.

CONCLUSIONS

cSCC has become an increasingly significant public health problem in Iceland. Tanning bed use and travelling abroad may contribute to skin cancer development. Public health efforts are needed to stem the behaviours leading to this rapid rise in cSCC.

Metformin is associated with decreased risk of basal cell carcinoma: A whole-population case-control study from Iceland

BACKGROUND

Metformin has anticarcinogenic properties and is also known to inhibit the sonic hedgehog pathway, but population-based studies analyzing the potential protective effect for basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are needed.

OBJECTIVES

To delineate the association between metformin use and invasive SCC, SCC in situ (SCCis), and BCC.

METHODS

A population-based case-control study design was employed using all 6880 patients diagnosed in Iceland between 2003-2017 with first-time BCC, SCCis, or invasive SCC, and 69,620 population controls. Multivariate odds ratios (ORs) were calculated using conditional logistic regression.

RESULTS

Metformin was associated with a lower risk of developing BCC (OR, 0.71; 95% confidence interval [CI], 0.61-0.83), even at low doses. No increased risk of developing SCC was observed. SCCis risk was mildly elevated in the 501-1500 daily dose unit category (OR, 1.40; 95% CI, 1.00-1.96).

LIMITATIONS

This study was retrospective in nature with the inability to adjust for ultraviolet exposure, Fitzpatrick skin type, and comorbidities.

CONCLUSION

Metformin is associated with decreased risk of BCC development, even at low doses. Metformin might have potential as a chemoprotective agent for patients at high risk of BCC, although this will need confirmation in future studies.

Loss-of-Function Variants in the Tumor-Suppressor Gene PTPN14 Confer Increased Cancer Risk

The success of genome-wide association studies (GWAS) in identifying common, low-penetrance variant-cancer associations for the past decade is undisputed. However, discovering additional high-penetrance cancer mutations in unknown cancer predisposing genes requires detection of variant-cancer association of ultra-rare coding variants. Consequently, large-scale next-generation sequence data with associated phenotype information are needed. Here, we used genotype data on 166,281 Icelanders, of which, 49,708 were whole-genome sequenced and 408,595 individuals from the UK Biobank, of which, 41,147 were whole-exome sequenced, to test for association between loss-of-function burden in autosomal genes and basal cell carcinoma (BCC), the most common cancer in Caucasians. A total of 25,205 BCC cases and 683,058 controls were tested. Rare germline loss-of-function variants in PTPN14 conferred substantial risks of BCC (OR, 8.0; P = 1.9 × 10^-12), with a quarter of carriers getting BCC before age 70 and over half in their lifetime. Furthermore, common variants at the PTPN14 locus were associated with BCC, suggesting PTPN14 as a new, high-impact BCC predisposition gene. A follow-up investigation of 24 cancers and three benign tumor types showed that PTPN14 loss-of-function variants are associated with high risk of cervical cancer (OR, 12.7, P = 1.6 × 10^-4) and low age at diagnosis. Our findings, using power-increasing methods with high-quality rare variant genotypes, highlight future prospects for new discoveries on carcinogenesis. SIGNIFICANCE: This study identifies the tumor-suppressor gene PTPN14 as a high-impact BCC predisposition gene and indicates that inactivation of PTPN14 by germline sequence variants may also lead to increased risk of cervical cancer.

Association between hydrochlorothiazide and the risk of in situ and invasive squamous cell skin carcinoma and basal cell carcinoma: A population-based case-control study

BACKGROUND

Population-based studies analyzing hydrochlorothiazide's (HCTZ's) effect on keratinocyte carcinoma, and particularly invasive squamous cell carcinoma (SCC), are lacking.

OBJECTIVES

To characterize the association between HCTZ use and invasive SCC, SCC in situ (SCCis), and basal cell carcinoma (BCC).

METHODS

This population-based case-control study included all 6880 patients diagnosed with first-time BCC, SCCis, and invasive SCC between 2003 and 2017 in Iceland and 69,620 population controls. Conditional logistic regression analyses were used to calculate multivariate odds ratios (ORs) for keratinocyte carcinoma associated with HCTZ use.

RESULTS

A cumulative HCTZ dose above 37,500 mg was associated with increased risk of invasive SCC (OR, 1.69; 95% confidence interval [CI], 1.04-2.74). Users of HCTZ also had an increased risk of SCCis (OR, 1.24; 95% CI, 1.01-1.52) and BCC (OR, 1.14; 95% CI, 1.02-1.29).

LIMITATIONS

Limitations include this study's retrospective nature with the resulting inability to adjust for ultraviolet exposure, Fitzpatrick skin type, and comorbidities.

CONCLUSIONS

High cumulative exposure to HCTZ is associated with the development of keratinocyte carcinoma and, most importantly, invasive SCC. Sun protective behaviors alone may not eliminate the carcinogenic potential of HCTZ.

Basal cell carcinoma: an emerging epidemic in women in Iceland

BACKGROUND

An epidemic of basal cell carcinoma (BCC) has led to a significant healthcare burden in white populations.

OBJECTIVES

To provide an update on incidence rates and tumour burden in an unselected, geographically isolated population that is exposed to a low level of ultraviolet radiation.

METHODS

This was a whole-population study using a cancer registry containing records of all cases of BCC in 1981-2017. We assessed BCC incidence according to age, residence and multiplicity and assessed trends using join-point analysis. Age-standardized and age-specific incidence rates were calculated along with cumulative and lifetime risks.

RESULTS

During the study period, the age-standardized incidence rates increased from 25·7 to 59·9 for men, and from 22·2 to 83·1 for women (per 100 000). Compared with the single-tumour burden, the total tumour burden in the population was 1·72 times higher when accounting for multiplicity. At the beginning of the study period, the world-standardized rates in men and women were similar, but by the end of the study period the rates were 39% higher in women (83·1 per 100 000, 95% confidence interval 77·9-88·3) than in men (59·9 per 100 000, 95% confidence interval 55·6-64·2). This increase was most prominent in women on sites that are normally not exposed to ultraviolet radiation in Iceland: the trunk and legs.

CONCLUSIONS

This is the only reported population in which the incidence of BCC is significantly higher in women than in men. The period of notable increase in BCC lesions correlates with the period of an increase in tanning beds and travel popularity. The high multiplicity rates suggest that the total tumour burden worldwide might be higher than previously thought. What is already known about this topic? Basal cell carcinoma (BCC) is becoming an increasing healthcare burden worldwide, especially in white populations. Recent population studies have reported a rapid increase in incidence among younger individuals, especially women. What does this study add? Iceland is the only reported population in which the incidence of BCC is significantly higher in women than in men, and there does not seem to be a clear relationship between latitude and BCC incidence in Europe. Men might be comparatively protected in the northern low-ultraviolet environment, with tanning beds and travel abroad likely playing important roles in the observed incidence increase, especially in women. The high multiplicity rates suggest that the total tumour burden worldwide might be higher than previously thought. Linked Comment: Pandeya. Br J Dermatol 2020; 183:799-800.

Replication error in colorectal carcinoma: association with loss of heterozygosity at mismatch repair loci and clinicopathological variables

Instability of microsatellite DNA or replication error (RER) is characteristic of tumours caused by mismatch repair (MMR) deficiency. Germline mutations in MMR genes are associated with Hereditary non-polyposis colorectal carcinoma (HNPCC) and somatic mutations in these genes are also found in a substantial fraction of colorectal cancers (CRC). In this study we concurrently screened colorectal tumours for the RER phenotype and loss of heterozygosity (LOH) at MMR gene loci. The RER phenotype was evident in 47/197 (24%) tumours. RER was more commonly detected in young patients (< 50 years) and in tumours located in the proximal colon. RER was positively associated with LOH at the hMSH2/hMSH6 loci on chromosome 2p, where LOH was observed in 46% of the RER+ tumours. LOH at hMLH1 and hPMS1 loci was more frequent in the younger patients (< 50 years). RER was not associated with clinicopathological parameters, such as Duke's stage and tumour differentiation (grade). The RER phenotype was associated with better overall survival, but there was a trend towards significance when multivariate analysis was used. This indicates that loss of MMR genes generate a less aggressive phenotype, and raises the question about RER being a useful indicator of prognosis for CRC patients.

Loss of heterozygosity at chromosome 7q in human breast cancer: association with clinical variables

In this study 238 human primary breast cancers were analysed with 9 polymorphic microsatellite markers specific to region 7q21-q35 on chromosome 7. LOH was observed at one or more marker in 82 cases or (34%). The deletions were evenly distributed throughout the region. Patients were divided into two groups according to whether LOH was observed in their tumours or not, and tested for association with overall survival, the clinicopathological features: steroid receptor content, tumour size, node status, DNA ploidy and S-phase fraction, and LOH at other chromosomal regions. An association was found between 7q LOH and high S-phase fraction. An association was found between LOH at 7q and LOH at 1p, 3p, 9p, 13q and 17q. These results suggest the location of a putative tumour suppressor gene at chromosome 7q21-q35 that, in combination with other deletions, might enhance tumour growth.