Trastuzumab, a humanized monoclonal antibody, is used in the treatment of metastatic breast cancer overexpressing human epidermal growth factor receptor 2 (HER2). Trastuzumab-related cardiotoxicity can usually be reversed by interrupting the use of the drug. We present a 78-year-old woman with metastatic HER2-positive breast cancer whose left ventricular ejection fraction (LVEF) decreased from 56％ to 37％ within 3 months after starting trastuzumab treatment prior to surgery. She complained of shortness of breath on exertion. Trastuzumab was stopped immediately, and an angiotensin-converting enzyme inhibitor and a beta blocker were started. Her LVEF did not increase 6 months after the cessation of trastuzumab use. Low-dose digoxin (0.0625 mg daily) was added, and the patient's LVEF increased from 35％ to 44％ one month later. The next month, she was able to undergo mastectomy with axillary lymph node dissection followed by radiation and tamoxifen as adjuvant therapy. She was followed up for 3 years after surgery and experienced no recurrence of breast cancer.

Trastuzumab-related cardiotoxicity can usually be reversed by interrupting the use of the drug. Patients with inadequate or nonexistent recovery of LVEF despite cardioprotective therapy cannot undergo standard cancer treatment; this restriction leads to a worsened prognosis. Low-dose digoxin in addition to cardioprotective therapy increased our patient's LVEF to over 40％, allowing her to undergo surgery.

Informed consent for clinical trials is often difficult for patients. In particular, placebo-controlled randomized double-blind trials are poorly understood. While many studies have measured patients' understanding, there is no validated scale used in Japan. The “Quality of Informed Consent Scale” (QuIC) is a validated scale used to assess patients' objective and subjective understanding of cancer clinical trials. Therefore, we have translated the QuIC into Japanese and created a modified version for general use in placebo-controlled, randomized, double-blind trials; we subsequently examined the linguistic validity of the modified version of the QuIC. This study was conducted in accordance with the guidelines of the International Society for Pharmacoeconomics and Outcomes Research.

First, three translators put forward translations from English to Japanese, which were synthesized into a Japanese version and modified through discussions with our research team. The original author confirmed the back-translated Japanese versions, which were refined via feedback from the original author. Furthermore, cognitive debriefing of the modified version was conducted on patients who had undergone a clinical trial.

Through the procedures outlined by the scale translation guidelines, consultations with the original authors, and cognitive debriefings with actual patients, a Japanese translation consistent with the original version was developed, and the linguistic validity of the modified version was confirmed. Although the reliability and validity of these scales for Japanese patients in clinical trials are yet to examined, this modified QuIC may be useful for measuring understanding in placebo-controlled, randomized, double-blind trials.

In the risk management of drugs by regulatory authorities, efforts to utilize information directly from patients and their families have been progressing globally. As one of these efforts, in the adverse drug reaction (ADR) reporting system where the ADR information is reported to regulatory authorities, patients and their families have been newly added as reporters, in addition to pharmaceutical companies and healthcare professionals, who have been the main reporters. In Japan, although the direct reporting system from patients has been launched since 2019 based on the pilot scheme, the number of reports remain low.

In this study, we analyzed and compared the literature available on the European and Japanese direct reporting systems of ADRs from patients to regulatory authorities. Here, we have summarized the current status and challenges of the ADR reporting system from patients in Europe, which precedes Japan's system, and discussed the points of reference and issues specific for Japan. The ADR reporting system needs to be promoted comprehensively in cooperation with patient groups and healthcare professionals. However, some issues need to be addressed while promoting the system, such as lack of active recognition of the risks of drugs, confirmation of the basic principles of reporting and sharing experiences of ADRs, and diversification of the methods of consumer participation and involvement in public risk management schemes. As the importance of collecting information on ADRs after product approval increases, it is necessary to reconsider the functioning of the ADR reporting system and the way of collection and utilization of the information from patients.