The season in which a man is diagnosed with prostate cancer has been shown to affect his survivability. Men diagnosed in the summer and autumn months have a better chance of survival than if they were diagnosed in the spring and winter, according to Tomasz Beer, M.D., Oregon Health & Science University Cancer Institute, and a team of Norwegian researchers led by Johan Moan, Ph.D., University of Oslo. The study recently was published in the journal The Prostate.
“Summer and autumn months correspond to times when vitamin D is highest. Although the study does not prove vitamin D is the determining factor, it does suggest that this possibility should be studied further,” said Beer, Grover C. Bagby Endowed Chair for Cancer Research, the director of the OHSU Cancer Institute Prostate Cancer Program, and associate professor of medicine (hematology/medical oncology), OHSU School of Medicine.
Vitamin D is a fat soluble vitamin that is found in food and can also be made in your body after exposure to ultraviolet rays. Sunshine is a significant source of vitamin D because UV rays trigger vitamin D synthesis in the skin. Vitamin D has been shown to inhibit cancer growth.
Although the study was conducted in Norway, Oregonians are also susceptible to vitamin D deficiency in the winter, said Beer. “Even without cancer considerations, vitamin D is important for general health,” he said. Research also suggests that vitamin D may help maintain a healthy immune system and help regulate cell growth and differentiation.
Prostate cancer is the most common type of cancer found in American men, other than skin cancer. The American Cancer Society estimates that there will be about 218,890 new cases of prostate cancer in the United States in 2007. About 27,050 men will die of this disease this year. In Oregon, approximately 2,600 men are diagnosed each year, and more than 400 will die of the cancer, according to Oregon Health Services.
The researchers used data on prostate cancer incidence provided by the Cancer Registry of Norway, which records all cancer diagnosis since 1953. During the observation period, 1964 to 1992, 46,205 men were diagnosed with prostate cancer. They were then divided into four groups: winter, (Dec. 1 - Feb. 28); spring, (March 1 - May 31); summer, (June 1 to Aug. 31); and autumn (Sept. 1 to Nov. 30). Compared with men diagnosed in the winter and spring, men diagnosed in the summer and fall had a 20 percent lower risk of dying from prostate cancer within three years from diagnosis.
The researchers also looked at whether foods high in vitamin D, such as fatty fish, vacations to southern latitudes, age, and latitude of residence in Norway affected survivability. None of these factors proved predictive of risk of death except for the modest effect of age. Younger men were found to have a slightly better survivability rate. It is known that the photosynthesis of vitamin D decreases with age. The capacity of the skin to produce vitamin D is about 40 percent lower in men 75 and older than in men 60 and younger.
Beer’s other research on a high-dose activated vitamin D pill called Calcitriol when combined with chemotherapy has been shown to increase survivability in men with prostate cancer.
“Considering my previous research and this, it does suggest that vitamin D activity during cancer therapy may be important. But more research is needed,” Beer said.
Beer cautions that too much vitamin D can be toxic. He suggests people talk with their physicians about taking vitamin D. And, although sunshine may be good for you, too much sun may cause skin cancer. Moderation is the key, he said.
The research was carried out by investigators at the University of Oslo and the Institute of Cancer Research, Oslo. Beer was the only U.S. collaborator.
Particulars: The Norwegian investigators include: Zoya Lagunova, Alina Carmen Porojnicu, both from the Department of Radiation Biology, Institute for Cancer Research; Arne Dahlback, Department of Physics, University of Oslo; Jens Petter Berg, Hormone Laboratory, Aker University Hospital, faculty division Aker University Hospital and Johan Moan, Department of Radiation Biology, Institute for Cancer Research and Department of Physics, University of Oslo.
Calcitrol is produced by Novacea Inc. OHSU and Beer have significant financial interest in Novacea, Inc., a company that has a commercial interest in the results of this research and technology. This potential conflict was reviewed and a management plan approved by the OHSU Conflict of Interest in Research Committee and the Integrity Program Oversight Council was implemented.
The OHSU Cancer Institute is the only National Cancer Institute-designated center between Sacramento and Seattle. It comprises some 120 clinical researchers, basic scientists and population scientists who work together to translate scientific discoveries into longer and better lives for Oregon's cancer patients. In the lab, basic scientists examine cancer cells and normal cells to uncover molecular abnormalities that cause the disease. This basic science informs more than 200 clinical trials conducted at the OHSU Cancer Institute.