Merkel cell carcinoma – A population-based epidemiological study in Finland with a clinical series of 181 cases

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Abstract

Background

Merkel cell carcinoma (MCC) is a rare malignancy of the skin, and its incidence is reported to be rising. The purpose of this study was to calculate its incidence and survival ratios, and to describe the clinical characteristics of Merkel cell carcinoma patients in Finland.

Methods

We calculated the incidence of MCC based on data from the Finnish Cancer Registry. In addition, patient files from hospitals and primary health care centres were reviewed for detailed data on the treatment and disease recurrence of 181 patients diagnosed with MCC in Finland during 1983–2004, and relative survival ratios were calculated for them.

Results

The incidence (per 100,000) of MCC in Finland in 1989–2008 was 0.11 for men and 0.12 for women, adjusted for age to the world standard population. The mean age at diagnosis was 76 years (range 27–100), and 69% of the patients were women. The most common site of the primary tumour was the head and neck (53%). No extra benefit was gained from a wide surgical margin (⩾2 cm) compared to a margin of 0.1–0.19 cm, but an intralesional excision was more often associated with local recurrence. None of the patients with Stage I–II disease who had received postoperative radiotherapy to the tumour bed had a local recurrence. The 5-year relative survival ratio amongst men was 36% (95% confidence interval 20–54%), and amongst women 69% (56 to −82%).

Conclusions

MCC is a rare disease in Finland, with incidence rates similar to those in the other Nordic countries. Our results support the view that complete excision with clear margins and post operative radiotherapy decrease local recurrences.

Introduction

Merkel cell carcinoma (MCC) is a rare malignant neuroendocrine tumour of the skin. The incidence rates of MCC reported from different countries vary, but are not comparable because of differences in observation periods and in age-adjustment methods. In all studies, the incidence has been less than one per 100,000.1, 2, 3, 4, 5, 6

MCC affects mainly the white population with median age at presentation of approximately 70 years, and according to previous studies it is more common in men than in women.1, 2, 7, 8 The aetiology of MCC may be multifactorial. Exposure to ultraviolet radiation is associated with MCC.9, 10, 11 MCC also occurs more often in immuno-compromised individuals, such as those diagnosed with chronic lymphocytic leukaemia, lymphoma, or a human immunodeficiency virus infection, as well as amongst organ transplant recipients.12, 13, 14, 15, 16 Recently, a novel polyomavirus, named Merkel cell polyomavirus (MCPyV), was identified in MCC tumour tissue suggesting that a viral infection might also be an aetiological factor.17

Tumour size has been shown to be a strong prognostic factor,8, 18, 19, 20, 21 but the most consistent predictor of survival in MCC to date is the presence or absence of lymph node metastases at time of presentation.22 Sentinel node biopsy (SNB) is recommended for all patients with localised disease for the purpose of staging. The impact of SNB on survival is still unclear.7, 23 MCC has a high incidence of local recurrences and a propensity for regional and distant metastases. It is usually treated surgically, either with or without postoperative radiation therapy.

The aim of this study was to calculate the incidence and survival of MCC patients in Finland, and to present clinical characteristics of this large national patient series.

Section snippets

Material and methods

Individuals diagnosed in Finland with MCC or small cell carcinoma of the skin up until 2008 were identified from the Finnish Cancer Registry. The Registry was set up in 1953, and it maintains a nation-wide population-based database on all cancer cases in Finland (population 5.4 million in 2010). All physicians, hospitals and pathology and haematology laboratories are obligated to submit data to the Finnish Cancer Registry on all cancer cases that come to their attention. The Registry has a

Incidence

Since the early years of the recognition of MCC, the incidence estimates have become more reliable, and since 1989 they have been fairly stable. The age-adjusted (world standard) incidence of MCC (per 100,000) in 1989–2008 in Finland was 0.11 for men and 0.12 for women (Fig. 1). The corresponding rates adjusted to the European standard population are 0.19 and 0.20, and to the US 2000 population 0.24 and 0.25.

The incidence increases sharply with age and is similar in both sexes (Fig. 2). Because

Discussion

The age-adjusted (world standard) incidence rates of MCC based on a nationwide Finnish cancer registry are 0.11 and 0.12 per 100,000 person-years for men and women, respectively. The incidence increased during the early years (1979–1993), but thereafter the incidence has stabilised. The data before year 1989 are most likely incomplete due to diagnostic difficulties before immunohistochemical techniques, and, therefore, probably do not reflect the real incidence. Increased awareness of MCC

Conflict of interest statement

None declared.

Acknowledgment

This study was funded by Helsinki University Central Hospital Research Fund.

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