title: Is season a prognostic factor in breast cancer?
abstract: BACKGROUND
  Some studies have indicated an inverse relationship between cancer risk and sunlight exposure. Others have reported that the prognosis of some cancers such as prostate, colon, ovarian and non melanoma skin cancer, were affected by the season in which the cancer was diagnosed. In our study, we evaluated whether season is prognostic in Turkish patients with breast cancer.
  
  
  METHODS
  A total of 517 patients from Kayseri Training and Research Hospital were analysed retrospectively. Patients were divided into 4 groups according to season of cancer diagnosis: winter, spring, summer and autumn. The prognostic factors for disease free survival and overall survival were investigated.
  
  
  RESULTS
  No significant differences were found among groups regarding prognostic factors overall. Only estrogen receptor status and lymphovascular invasion were independent prognostic factors (p=0.001 and p=0.001 respectively). We found significantly differences for mean disease free survival among groups (p=0.019). Winter group had better mean DFS while summer group had worse DFS. Mean overall survival was similar in the four groups (p=0.637).
  
  
  CONCLUSIONS
  The season is not an independent predictive factor. However, due to interaction with other factors, we think that the season of cancer diagnosis is important for cancer prognosis.
authors.affiliation: Department of Medical Oncology, Acibadem Kayseri Hospital, Kayseri, Turkey. doktorhasanmutlu@gmail.com
authors.forename: Hasan
authors.initials: H
authors.lastname: Mutlu
authors.forename: Zeki
authors.initials: Z
authors.lastname: Akca
authors.forename: Yasemin Benderli
authors.initials: YB
authors.lastname: Cihan
authors.forename: Fatih
authors.initials: F
authors.lastname: Kurnaz
authors.forename: Tuncay
authors.initials: T
authors.lastname: Aslan
authors.forename: Abdulsamet
authors.initials: A
authors.lastname: Erden
authors.forename: Hediye
authors.initials: H
authors.lastname: Ugur
authors.forename: Arzu
authors.initials: A
authors.lastname: Aksahin
authors.forename: Abdullah
authors.initials: A
authors.lastname: Buyukcelik
mesh_terms: D001943:Breast Neoplasms / Q000175:diagnosis* / Q000401:mortality*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008875:Middle Aged; D011960:Receptors, Estrogen / Q000378:metabolism; D012189:Retrospective Studies; D012306:Risk; D012621:Seasons; D013472:Sunlight; D013534:Survival; D014421:Turkey
chemical_list: D011960:Receptors, Estrogen