Abstract P6-08-21: Low body mass index (BMI) is associated with poor survival in Japanese patients with early breast cancer; an exploratory analysis of prospective randomized phase III trials N-SAS BC02 and 03
Authors: Naito Yoichi , Ohashi Yasuo , Yokota Isao , Watanabe Toru , Iwata Hiroji , Ohsumi Shozo , Ohno Shinji , Hozumi Yasuo , Yamamoto Seiichiro , Takahashi Masato , Aihara Tomohiko , Mukai Hirofumi 
Published: May 2015

Background: Obesity is reported to be associated with worse prognosis in early breast cancer. However, there is little data regarding the impact of low BMI on survival in patients with breast cancer. As obesity is rare and low BMI is relatively common in Japanese population compared to Caucasians, Japanese cohort is suitable to assess the impact of low BMI on survival in patients with early breast cancer. Recently an exploratory analysis of a small Japanese randomized phase II trial (JFMC 34-0601) suggested that low BMI was associated with a decreased overall response rate to neoadjuvant endocrine therapy with exemestane. We further explored the impact of low BMI on survival in patients with early breast cancer using a dataset of randomized phase III trials in Japan.

Methods: Patients included in prospective randomized phase III trial N-SAS BC02 and BC03 were retrospectively analyzed. N-SAS BC02 investigated four arms of adjuvant chemotherapy consisted of taxane alone or in combination with anthracycline-containing regimen (median follow up of 6.1 years). NSAS BC03 compared anastorozole with tamoxifen as adjuvant endocrine therapy (median follow up of 6.4 years). The correlation of BMI and overall survival was exploratory analyzed. This study was supported by the Public Health Research Center Foundation CSPOR.

Results: A total of 1726 patients were included in our study. Median age was 56 (24 – 82) years, 71.2% of tumors were ER positive, and 9.7% were HER2 overexpressed. Lymph node metastases were observed in 76% of patients. Mean value of BMI was 23.3 and only 4.6% of patients had BMI over 30. 33.1% of patients had BMI under 22 and 4.8% had BMI under 18.5. In the univariate Cox proportional hazard model, lower BMI was significantly associated with worse prognosis (BMI&lt;27 vs &gt;27, HR 0.55, 95% CI 0.32 – 0.93, p = 0.025). The same trend was observed in multivariate analysis (HR 0.61, p = 0.064).

Conclusion: We confirmed that obese patients were relatively rare in Japanese patients with early breast cancer. In this non-obese population, lower BMI was correlated with worse prognosis. However these results should be cautiously interpreted. Our findings suggest that there may be an optimal BMI in patients with early breast cancer and it should be confirmed by another cohort.

Citation Format: Yoichi Naito, Yasuo Ohashi, Isao Yokota, Toru Watanabe, Hiroji Iwata, Shozo Ohsumi, Shinji Ohno, Yasuo Hozumi, Seiichiro Yamamoto, Masato Takahashi, Tomohiko Aihara, Hirofumi Mukai. Low body mass index (BMI) is associated with poor survival in Japanese patients with early breast cancer; an exploratory analysis of prospective randomized phase III trials N-SAS BC02 and 03 [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-08-21.