title: Body mass index and survival after diagnosis of invasive breast cancer: a study based on the Japanese National Clinical Database-Breast Cancer Registry.
abstract: Few studies have reported the association between body mass index (BMI) and outcome among Asian breast cancer patients. We analyzed data for 20,090 female invasive breast cancer patients who had been followed-up for a median period of 6.7 years entered in the National Clinical Database-Breast Cancer Registry between 2004 and 2006. We used mainly the WHO criteria for BMI (kg/m(2) ) categories; <18.5 (underweight), ≥18.5-<21.8 (reference), ≥21.8-<25, ≥25-<30 (overweight), and ≥30 (obese). We divided normal weight patients into two subgroups because this category includes many patients compared to others. The timing of BMI measurement was not specified. The Cox proportional hazards model and cubic spline regression were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Smoking, alcohol, and physical activity were not controlled. A total of 1418 all-cause, 937 breast cancer-specific deaths, and 2433 recurrences were observed. Obesity was associated with an increased risk of all-cause (HR: 1.46; 95% CI: 1.16-1.83) and breast cancer-specific death (HR: 1.47; 95% CI: 1.11-1.93) for all patients, and with all-cause (HR: 1.47; 95% CI: 1.13-1.92) and breast cancer-specific death (HR: 1.58; 95% CI: 1.13-2.20) for postmenopausal patients. Being underweight was associated with an increased risk of all-cause death for all (HR: 1.41; 95% CI: 1.16-1.71) and for postmenopausal patients (HR: 1.45; 95% CI: 1.15-1.84). With regard to subtype and menopausal status, obesity was associated with an increased risk of breast cancer-specific death for all cases of luminal B tumor (HR: 2.59; 95% CI: 1.51-4.43; Pheterogeneity of Luminal B vs. Triple negative = 0.016) and for postmenopausal patients with luminal B tumor (HR: 3.24; 95% CI: 1.71-6.17). Being obese or underweight is associated with a higher risk of death among female breast cancer patients in Japan.
authors.affiliation: Department of Breast Oncology, Miyagi Cancer Center, Natori, Japan.
authors.forename: Masaaki
authors.identifier: 0000-0003-1383-0487
authors.initials: M
authors.lastname: Kawai
authors.affiliation: Department of Healthcare Quality Assessment, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Tomotaki
authors.affiliation: Department of Healthcare Quality Assessment, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Miyata
authors.affiliation: Departments of Breast and Endocrine Surgery, Okayama University Hospital, Okayama, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Iwamoto
authors.affiliation: Departments of Breast and Endocrine Surgery, Tokai University School of Medicine, Isehara, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Niikura
authors.affiliation: Department of Surgery, Kitakyushu Municipal Medical Center, Kitakyushu, Japan.
authors.forename: Keisei
authors.initials: K
authors.lastname: Anan
authors.affiliation: Department of Breast Surgery, St. Luke's International Hospital, Tokyo, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Hayashi
authors.affiliation: Department of Breast Surgery, Shikoku Cancer Center, Matsuyama, Japan.
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Aogi
authors.affiliation: Department of Surgical Oncology, Graduate School of Medicine, Tohoku University, Sendai, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Ishida
authors.affiliation: Sapporo-kotoni Breast Clinic, Sapporo, Japan.
authors.forename: Hideji
authors.initials: H
authors.lastname: Masuoka
authors.affiliation: Department of Breast Oncology, Cancer Institute Hospital, Tokyo, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Iijima
authors.affiliation: Department of Pathology, Nihon University School of Medicine, Tokyo, Japan.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Masuda
authors.affiliation: Division of Breast and Endocrine Surgery, Department of Surgery,  St. Marianna University School of Medicine, Kawasaki, Japan.
authors.forename: Koichiro
authors.initials: K
authors.lastname: Tsugawa
authors.affiliation: Department of Breast Surgery, National Cancer Center Hospital, Tokyo, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kinoshita
authors.affiliation: Division of Breast Surgical Oncology, Department of Surgery, Showa University, Tokyo, Japan.
authors.forename: Seigo
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Departments of Breast and Endocrine Surgery, Tokai University School of Medicine, Isehara, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tokuda
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000453:epidemiology / Q000401:mortality* / Q000473:pathology* / Q000628:therapy; D002423:Cause of Death; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D063868:Patient Outcome Assessment; D011159:Population Surveillance; D012042:Registries; D012307:Risk Factors
keywords: Body mass index; breast cancer; menopausal status; subtypes; survival