Is Season of Diagnosis a Predictor of Cancer Survival? Results from the Zurich Cancer Registry

Abstract

In Switzerland, there is a large seasonal variation in sunlight, and vitamin D deficiency is relatively common during winter. The season of diagnosis may be linked to cancer survival via vitamin D status. Using data from the Cancer Registry of Zurich, Zug, Schaffhausen, and Schwyz with more than 171,000 cancer cases registered since 1980, we examined the association of the season of diagnosis with survival for cancers including prostate (ICD10 code C61; International Categorization of Diseases, version 10), breast (C50), colorectal (C18-21), lung (C34), melanoma (C43), and all sites combined. Cox proportional hazards regression models were used to assess the differences in the all-cause mortality by the season of the diagnosis. Winter was used as the reference season. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated for all the cancers combined (excluding nonmelanoma skin cancer) and for prostate (in men), breast (in women), colorectal, lung cancer, and melanomas, separately. A diagnosis in summer and/or autumn was associated with improved survival in all the sites combined for both sexes (men: HR 0.97 [95% CI 0.96–0.99]; women: HR 0.97 [95% CI 0.94–0.99]) and in colorectal (HR 0.91 [95% CI 0.84–0.99]), melanoma (HR 0.81 [95% CI 0.65–1.00]), and breast cancer (HR 0.91 [95% CI 0.94–0.99]) in women. Our study results suggest that a cancer diagnosis in summer and/or autumn is associated with a better prognosis. The improved seasonal survival coincides with the seasonal variation of sun-induced vitamin D, and vitamin D may play a protective and beneficial role in cancer survival.

The Impact of Vitamin D and Its Dietary Supplementation in Breast Cancer Prevention: An Integrative Review

“…Increased exposure time to sunlight may reduce the risk of BC, and this could be explained by increased vitamin D production in the body [ 91 , 129 , 130 ]. This factor, in turn, can be influenced by factors such as latitude [ 131 , 132 , 133 ] or the season of the year [ 134 ].…”

The Contrasting Seasonality Patterns of Some Cancer-Types and Herpes Zoster Can Be Explained by a Binary Classification of Immunological Reactions

“… 13 In a recent analysis of breast, prostate, colorectal and lung cancer data from the Cancer Registry of Zurich (Switzerland), a diagnosis in summer and/or autumn was associated with improved survival in all the sites combined for both sexes, and in colorectal and breast cancers, in women. 14 An exception to these results was reported in one Swedish study of breast and prostate cancers. 15 The lower incidence and better survival of patients diagnosed in summer are commonly explained by the higher production rate of vitamin D during summer, due to the higher exposure to UV radiation.…”

“… 15 The lower incidence and better survival of patients diagnosed in summer are commonly explained by the higher production rate of vitamin D during summer, due to the higher exposure to UV radiation. 14 , 16 …”

Potential tactics with vitamin D and certain phytochemicals for enhancing the effectiveness of immune-checkpoint blockade therapies

“…Levels of active vitamin D have been downregulated in the serum of patients with colorectal cancer, which might be correlated with increased Th17 lymphocytes [16]. Accordingly, vitamin D might play a protective and beneficial role in cancer survival [17]. In fact, vitamin D supplementation has been associated with a reduction in lung cancer mortality [18].…”