Japanese translation of the Functional Assessment of Cancer Therapy-Breast + 4 (FACT-B + 4) following international guidelines: a verification of linguistic validity.

Background: For breast cancer patients, postoperative lymphedema and upper limb movement disorders are serious complications that absolutely reduce their quality of life (QOL). To evaluate this serious complication, we used "Quick Dash" or "FACT-B", which can assess a patient's physical, social, emotional, and functional health status. To evaluate their breast cancer surgery-related dysfunction correctly, "FACT-B + 4" was created by adding four questions about "arm swelling'' and "tenderness". We have translated it into Japanese according to international translation guidelines.

Methods: At the beginning, we contacted FACT headquarters that we would like to create a Japanese version of FACT-B + 4. They formed the FACIT Trans Team (FACIT) following international translation procedures, and then, we began translating according to them. The steps are 1: perform "Forward and Reverse translations" to create a "Preliminary Japanese version", 2: request the cooperation of 5 breast cancer patients and "conduct a pilot study" and "questionnaire survey", and 3: amendments and final approval based on pilot study results and clinical perspectives.

Result: In Step1, FACIT requested faithful translation of the words, verbs, and nouns from the original text. In Step2, patients reported that they felt uncomfortable with the Japanese version words such as "numb'' and "stiffness'' and felt that it might be difficult to describe their symptoms accurately. In Step3, we readjusted the translation to be more concise and closer to common Japanese language, and performed "Step1" again to ensure that the translation definitely retained the meaning of the original.

Conclusion: A Japanese version of FACT has existed until now, but there was no Japanese version of FACT-B + 4, which adds four additional items to evaluate swelling and pain in the upper limbs. This time, we have created a Japanese version that has been approved by FACT.