1. ¹Department of Radiation Biology, Institute for Cancer Research, Montebello, 0310 Oslo, Norway
2. ²Department of Biophysics and Cell Biotechnology, Carol Davila University of Medicine and Pharmacy, 15-205 Bucharest, Romania
3. ³The Cancer Registry of Norway, Institute of Population-based Cancer Research, Montebello, 0310 Oslo, Norway
4. ⁴Departments of Tumour Biology and Oncology, The Norwegian Radium Hospital, Montebello 0310 Oslo, Norway
5. ⁵Department of Physics, University of Oslo, 0316 Oslo, Norway

Correspondence: Dr AC Porojnicu, Department of Radiation Biology, Institute for Cancer Research, Montebello, 0310 Oslo, Norway. E-mail: a.c.porojnicu@usit.uio.no

Received 6 April 2005; Revised 25 May 2005; Accepted 20 June 2005; Published online 2 August 2005.

Abstract

Experimental studies show that vitamin D derivatives are potent anticarcinogenic factors. Epidemiological observations support this, and vitamin D sufficiency has been hypothesised to be an important risk-reducing factor in several forms of cancer. Vitamin D level exhibits seasonal variations. In the present work, we have investigated the effect of the season of diagnosis on the risk of death among Hodgkin's lymphoma patients diagnosed in Norway between 1964 and 2000. Risk estimates were calculated as relative risk (RR), with 95% confidence intervals (95% CI), using Cox regression model. Epidemiological data for this period indicate that season of diagnosis is a strong prognostic factor for Hodgkin's lymphoma, with 20% lower case fatality for patients diagnosed during autumn vs winter diagnosis (RR=0.783, 95% CI,-0.62 to 0.99; P=0.041). Notably, the improved autumnal survival rate was higher than 60% (RR=0.364, 95% CI, -0.15 to 0.87; P=0.025) for patients younger than 30 years. This finding may be related to higher endogenous levels of vitamin D in autumn, with a favourable influence on the conventional therapy.