IMPORTANCEUntil now, most studies on cutaneous squamous cell carcinoma (cSCC) incidence rates concerned only the first cSCC per patient. Given the increase in incidence rates and the frequent occurrence of subsequent cSCCs per patient, population-based data on the incidence rates of both first and multiple cSCCs are needed.OBJECTIVES To calculate annual age-standardized incidence rates for histopathologically confirmed first and multiple cSCCs per patient and to estimate future cSCC incidence rates up to 2027. DESIGN, SETTING, AND PARTICIPANTS A nationwide population-based epidemiologic cohort study used cancer registry data on 145 618 patients with a first histopathologically confirmed cSCC diagnosed between January 1, 1989, and December 31, 2017, from the Netherlands Cancer Registry and all patients with multiple cSCCs diagnosed in 2017. MAIN OUTCOMES AND MEASURES Age-standardized incidence rates for cSCC-standardized to the European Standard Population 2013 and United States Standard Population 2000-were calculated per sex, age group, body site, and disease stage. A regression model with positive slope was fitted to estimate cSCC incidence rates up to 2027. RESULTS A total of 145 618 patients in the Dutch population (84 572 male patients [58.1%]; mean [SD] age, 74.5 [11.5] years) received a diagnosis of a first cSCC between 1989 and 2017.Based on incident data, European Standardized Rates (ESRs) increased substantially, with the highest increase found among female patients from 2002 to 2017, at 8.2% (95% CI, 7.6%-8.8%) per year. The ESRs for first cSCC per patient in 2017 were 107.6 per 100 000 person-years (PY) for male patients, an increase from 40.0 per 100 000 PY in 1989, and 68.7 per 100 000 PY for female patients, an increase from 13.9 per 100 000 PY in 1989, which corresponds with a US Standardized Rate of 71.4 per 100 000 PY in 2017 for men and 46.4 per 100 000 PY in 2017 for women. Considering multiple cSCCs per patient, ESRs increased by 58.4% for men (from 107.6 per 100 000 PY to 170.4 per 100 000 PY) and 34.8% for women (from 68.7 per 100 000 PY to 92.6 per 100 000 PY). Estimation of ESRs for the next decade show a further increase of 23.0% for male patients (ESR up to 132.4 per 100 000 PY [95% prediction interval, 125.8-139.0 per 100 000 PY]) and 29.4% for female patients (ESR up to 88.9 per 100 000 PY [95% prediction interval, 84.3-93.5 per 100 000 PY]).CONCLUSIONS AND RELEVANCE This nationwide epidemiologic cohort study suggests that incidence rates of cSCC keep increasing, especially among female patients, and that the occurrence of multiple cSCCs per patient significantly adds to the current and future burden on dermatologic health care. Revision of skin cancer policies are needed to halt this increasing trend.

Background The COVID-19 pandemic impacted Dutch society and the healthcare system. Focus switched to care for COVID-19 patients, thereby altering care for non-COVID patients. Non-urgent medical visits were cancelled or postponed and patients were reluctant to visit healthcare services.Objectives This study aimed to investigate the impact of the COVID-19 pandemic on trends in diagnoses of keratinocyte carcinoma (cutaneous squamous cell carcinoma (cSCC), basal cell carcinoma (BCC)) and to assess the magnitude of diagnostic delays. MethodsThe number of cSCC and BCC diagnoses in each month of 2020 was compared to the expected number of diagnoses for these months, using data from the Netherlands Cancer Registry. Expected diagnoses for 2020 were used as a reference to take the yearly increase in keratinocyte carcinoma incidence into account and were calculated by extrapolating the trends observed in 2017-2019. Comparisons were further stratified by age, sex and region. Estimates of diagnostic delays were calculated and corrected for the influence of excess mortality due to the pandemic on keratinocyte carcinoma incidence. ResultsThe number of cSCC and BCC diagnoses substantially decreased when compared to the number of diagnoses expected from March to May 2020 (cSCC À29%, BCC À50%). These decreases were observed across all age groups, both sexes, and all regions. From June to September the number of cSCC and BCC diagnoses was higher than expected, after which it slightly dropped below expected in October to December. In total, 2020 keratinocyte carcinoma diagnoses continued to trail those expected, with a backlog of around 1150 cSCCs and 11 767 BCCs remaining at the end of the year. ConclusionDiagnosis of keratinocyte carcinoma was suboptimal during the COVID-19 pandemic, due to diagnostic delays likely resulting from both patient and health system-related delay. Further studies will need to determine the effects of these diagnostic delays on outcomes.

Background: Cutaneous squamous cell carcinoma (cSCC) represents the most serious form of keratinocyte cancers because of its metastatic potential. Studies on nationwide incidence and diseasespecific survival rates of metastatic cSCC (mcSCC) are lacking.Objective: To investigate the cumulative incidence and disease-specific survival of patients with mcSCC in the Dutch population and assess patient-based risk factors.Methods: We conducted a nationwide cancer registry study including all patients with the first cSCC in 2007 or 2008, using data from the Netherlands Cancer Registry, the nationwide network and registry of histopathology and cytopathology, and Statistics Netherlands. Cumulative incidence and Kaplan-Meier curves were calculated, and time-dependent Cox proportional hazards regression analyses were used.Results: Of the 11,137 patients, metastases developed in 1.9% (n = 217). The median time to metastasis was 1.5 years (interquartile range 0.6-3.8 years). The risk factors were age (adjusted hazard ratio [aHR] 1.03, 95% CI 1.02-1.05), male sex (aHR 1.7, 95% CI 1.3-2.3), and immunosuppression (aHR [organ transplant recipient] 5.0, 95% CI 2.5-10.0; aHR [hematologic malignancy] 2.7, 95% CI 1.6-4.6). The 5-year diseasespecific survival for patients with mcSCC was 79.1%.Limitations: Only histopathologically confirmed mcSCCs were included.Conclusion: About 2% of cSCCs metastasize, with higher risk for men, increasing age, and immunocompromised patients. Disease-specific survival for patients with mcSCC is high.

The characteristics and disease patterns of primary stage I and II cutaneous melanomas that progress to stage III or IV disease were investigated based on data from the Netherlands Cancer Registry (NCR). Data on stage III or IV melanomas at first diagnosis or during follow-up between 2017 and 2019 were retrieved. Patient and primary tumour characteristics were investigated in relation to time to disease progression and the number of organ sites with metastatic disease using regression models. In total, 2763 patients were included, of whom 1613 were diagnosed with stage IV disease. Among the patients with stage IV disease, 60% (n = 963) were initially diagnosed with stage I or II disease. The proportion of patients who received a sentinel lymph node biopsy increased after the introduction of adjuvant therapy in 2019 from 61% to 87%. Among all patients with stage III disease who were eligible for adjuvant systemic therapy (n = 453) after 2019, 37% were not treated with this therapy. Among patients with stage IV disease, lung metastases were most often detected as the first metastatic site and females presented with more metastatic sites than males. Most patient and primary tumour characteristics were not associated with the distant metastatic organ site, except melanoma localisation in the lower extremities and the head or neck. Our observation that most stage IV patients were initially diagnosed with early-stage disease highlights the need for more accurate risk prediction models.

Background Cutaneous melanoma (CM) is a multifactorial disease, with both environmental and genetic factors involved. The incidence of CM has risen rapidly during the last decades, making it a growing public health problem. Objectives The purpose of this retrospective study was to compare incidence and survival data of CM between two neighbouring countries, Belgium (BE) and the Netherlands (NL). Methods Data were collected by the Belgian Cancer Registry (BCR) and the Netherlands Cancer Registry (NCR) from 1 January 2004 until 31 December 2016. Mucosal melanoma, in situ CM and melanoma in children from 0 to 14 years were excluded. Age‐standardized incidence rates were calculated using the World Standard Population (WSR) per 100 000 persons. Five‐year relative survival ratios were calculated using the Ederer II methodology. Results Total number of CM was higher in NL (63 789) compared with BE (27 679). The WSR was 1.5 times higher in NL compared with BE (27.7 vs. 18.6/100 000/year). The WSR of stage IV tumours was higher in BE than in NL (0.3 vs. 0.2/100 000/year). Five‐year relative survival of stage IV tumours was higher in BE compared with NL (27.2% vs. 13.7%). Conclusions Incidence of CM was higher in NL, indicating a higher risk of CM diagnosis. Stage IV tumours were relatively more frequent in BE for both sexes, while relative survival of stage IV tumours was higher in BE. As geographical location and latitude of both neighbouring countries are almost identical, other factors like differences in behaviour, follow‐up and/or treatment may explain these differences.