Priority symptoms in advanced breast cancer: development and initial validation of the National Comprehensive Cancer Network-Functional Assessment of Cancer Therapy-Breast Cancer Symptom Index (NFBSI-16)

Objectives: By using methods consistent with recent regulatory guidance on patient-reported outcomes as endpoints in clinical trials, we created a new version of the Functional Assessment of Cancer Therapy-Breast Cancer Symptom Index (FBSI), with emphasis on patient input during the development process.

Methods: We obtained input on the most important symptoms to monitor during treatment for stage III or IV breast cancer from 52 patients recruited from National Comprehensive Cancer Network institutions as well as support service organizations. Participating patients shared their top-priority symptoms/concerns through open-ended interviews and symptom checklists. To ensure adequate content coverage, we evaluated results alongside the original version of the FBSI, which was created on the basis of a survey of oncology clinicians at National Comprehensive Cancer Network institutions and items in the Functional Assessment of Chronic Illness Therapy measurement system. We also obtained input from 10 National Comprehensive Cancer Network oncologists regarding whether symptoms were primarily related to disease or treatment.

Results: We selected breast cancer-related symptoms and concerns endorsed as high priority by both oncology patients and clinicians for inclusion in the new National Comprehensive Cancer Network-Functional Assessment of Cancer Therapy-Breast Cancer Symptom Index-16 (NFBSI-16), which includes all eight items from the original FBSI and eight additional items from Functional Assessment of Chronic Illness Therapy measures. The NFBSI-16 is formatted by subscale: Disease-Related Symptom, Treatment Side-Effect, and General Function and Well-Being. Results provide preliminary support for NFBSI-16's internal consistency reliability (α = 0.87) and validity as evidenced by moderate-to-strong relationships with expected criteria.

Conclusions: Reflecting the priority symptoms of breast cancer patients and clinicians, the NFBSI-16 can be used to help evaluate the effectiveness of treatments for advanced breast cancer in clinical practice and research.