Published: 29.11.2017. Last updated: 30.11.2017
Project group. Photo: Inger M. Nergaard, Statens strålevern
Norway has one of the highest incidence and mortality rates of melanoma in Europe. The steep incidence increase during the last 60 years is largely caused by more intense exposure to ultraviolet radiation (UVR). Cutaneous Malignant Melanoma (CM) ranks third in Norway and eighth in Europe with respect to CM incidence and mortality, respectively, and they both continue to rise. Apart from UVR exposure, adiposity and both decreased serum levels of vitamin D have been suggested as CM risk factors. However, the interplay between vitamin D and adiposity and their relation to CM risk is scarcely described.Increased knowledge on these factors is warranted for better CM prevention and prognosis.
Obesity has been linked to cancer risk, cancer prognosis and to vitamin D. Body mass index (BMI) provides an indicator of body fatness, where a BMI in the range 25–29.9 and ≥30 classified as overweight and obesity, respectively.
BMI has been positively associated with CM risk in males and obesity is found to increase melanoma progression. Vitamin D deficiency is suggested to cause obesity and this raises the hypothesis that low vitamin D levels is a common cause for increased BMI and CM risk.
This project aims to examine CM risk, risk of second cancer after CM, and risk of death after CM according to BMI, and serum levels of vitamin D and leptin.
Methods and study design
The study population is based on the Janus Serum Bank Cohort, a population-based prospective cancer biobank containing blood serum samples and questionnaire data from 292,851 Norwegians participating in five regional health surveys 1972–2003.
The project is based on a comprehensive research file established through linkage of the Janus Cohort to several registries and data sources to acquire individual information on education, occupation, cancer diagnoses, vital status and cause of death, and to group level information on ambient UVR data and sun tanning behaviour:
Main findings in Stenehjem et al. BMJ Open (2017):
- Linkage of independent, national data sources by use of a unique personal identification number for a comprehensive research file and complete control of loss to follow-up.
- Prediagnostic serum samples assuring a true prospective relationship between exposures and cancer, limiting bias introduced by reverse causality.
- Lifetime ambient ultraviolet radiation (UVR) exposure data (UVA, UVB and erythemally weighted UV) and group-level data on sunburns, sunbathing vacations and solarium use capturing variations in age, time period and county of residence.
- Ambient UVR exposure and data on sunburns, sunbathing vacations and solarium use can only be linked to the Janus Cohort on a group level.
- Lack of data on pigmentary characteristics and naevi.
Main findings in Stenehjem et al. Int J Cancer (2017):
Anthropometric factors, such as height and weight, affect melanoma risk, according to new results. These authors looked at data from a large Norwegian cohort, including 3000 cases of cutaneous melanoma. They found that body mass index, body surface area, weight, and height all influence CM risk in males, with an exponential increase for all factors. In women, only height and body surface area correlated with cancer risk – possibly because women with higher weight and BMI sunbathe less. They further showed that men who reduced their weight by 2 kg or more also lowered their melanoma risk.
Appearances in news media
2017 (Oct.) Interview on national radio with the Norwegian Broadcasting Corporation (NRK)
2017 (Oct.) Interview on the Norwegian TV channel “TV2’s” website
2017 (Oct.) Interview on the Norwegian Broadcasting Corporation website
Stenehjem JS, Grimsrud TK, Rees J, Vos L, Babigumira R, Veierød MB, Robsahm TE. A protocol for prospective studies of 25-hydroxyvitamin D, leptin and body mass index in relation to cutaneous melanoma incidence and survival. BMJ Open (2017).