Tsukuba, Japan—Breast cancer survivors may face a substantially higher risk of herpes zoster than women without a history of breast cancer, with the greatest excess risk appearing during the first year after diagnosis, according to a nationwide analysis of medical claims data in Japan. The study, published in Breast Cancer Research, found that female breast cancer survivors were 1.57 times more likely to develop herpes zoster, commonly known as shingles, during up to ten years of follow-up. They were also 1.70 times more likely to develop postherpetic neuralgia, a chronic pain syndrome caused by damage to sensory nerves during or after a shingles episode.
The investigation was conducted by researchers at the University of Tsukuba using anonymized medical claims data collected by JMDC Co., Ltd. The analysis included 23,169 women diagnosed with breast cancer and 92,801 age-matched women from the general population. The median age in both groups was 49.4 years. By comparing diagnoses recorded over time, the researchers evaluated not only whether breast cancer survivors experienced more herpes zoster, but also when the risk was most pronounced and whether it differed according to the cancer treatments received. The study also examined postherpetic neuralgia, which can persist for months or years after the characteristic rash has disappeared.
Herpes zoster is caused by varicella-zoster virus, the same virus responsible for chickenpox. After the initial infection, the virus is not eliminated from the body. Instead, it remains latent in sensory nerve ganglia, clusters of nerve cells located near the spinal cord and cranial nerves. Years or decades later, weakening of virus-specific cellular immunity can allow the virus to reactivate and travel along a nerve toward the skin. This produces the painful, often one-sided rash associated with shingles. In some patients, inflammation and injury to the affected nerves continue after the rash resolves, resulting in postherpetic neuralgia. The condition can cause burning, stabbing, or electric-shock-like pain and may be particularly difficult to treat.
The Japanese analysis showed that breast cancer survivors experienced their highest relative risk of herpes zoster during the first year after their cancer diagnosis. At its peak, the risk was approximately twice that observed in women without breast cancer. Although the difference between the groups gradually narrowed over time, it did not disappear: breast cancer survivors continued to have an elevated risk throughout the ten-year observation period. The sustained pattern suggests that the relationship may involve more than the temporary effects of surgery or systemic treatment. The cancer itself, treatment-related immune changes, and the long-term physiological consequences of surviving breast cancer may all contribute to the observed vulnerability.
The timing of the association is biologically plausible because the period immediately after a cancer diagnosis often involves several processes capable of influencing antiviral immunity. Breast cancer treatment may include chemotherapy, radiation therapy, endocrine therapy, targeted medicines, or combinations of these approaches. Cytotoxic chemotherapy can reduce the number or function of immune cells involved in controlling latent viruses, including T lymphocytes that recognize virus-infected cells. Cancer-related inflammation, nutritional changes, psychological stress, and other illnesses may further affect immune surveillance. When cellular immunity is temporarily impaired, latent varicella-zoster virus may have a greater opportunity to reactivate in sensory ganglia.
Among the treatment categories assessed, anthracycline-based chemotherapy was associated with an increased risk of herpes zoster. Anthracyclines are widely used anticancer agents that interfere with DNA and generate cellular stress, helping to destroy rapidly dividing tumor cells. Their effects are not limited to malignant tissue, however, and treatment can produce transient reductions in circulating blood cells and broader changes in immune function. The association observed in this study does not establish that anthracyclines directly cause shingles, because patients receiving particular regimens may differ in cancer stage, treatment intensity, underlying health, or other factors. Nevertheless, the finding identifies a treatment group that may warrant closer attention to herpes zoster prevention and early recognition of symptoms.
The increased risk of postherpetic neuralgia is clinically important because shingles is not simply a short-lived skin disorder. Varicella-zoster virus reactivation can inflame and injure peripheral sensory nerves, and the resulting pain may remain after the virus has stopped replicating and the skin lesions have healed. Older age is one of the strongest known predictors of postherpetic neuralgia, but the complication can also occur in younger adults, particularly when immune function is altered. For breast cancer survivors, persistent neuropathic pain may compound other treatment-related symptoms, including fatigue, postoperative discomfort, or chemotherapy-induced peripheral neuropathy, making diagnosis and management more complex.
The findings support incorporating herpes zoster prevention into survivorship care, although the study did not directly test vaccination strategies. Vaccines can reduce the probability of varicella-zoster virus reactivation and lower the risk of complications. Current prevention decisions may depend on age, previous chickenpox or shingles, cancer treatment history, immune status, and national recommendations. The recombinant zoster vaccine uses a viral protein rather than live varicella-zoster virus and is designed to stimulate strong immune responses, including in older adults. For patients undergoing cancer treatment, the timing of vaccination is important because immune responses may be weaker during periods of intensive chemotherapy or other immunosuppressive therapy. Decisions should therefore be made with the patient’s oncology and primary-care teams.
Because the study relied on routine claims data, it provides a large-scale view of herpes zoster diagnoses but cannot capture every clinical detail. Claims records may not fully describe cancer stage, laboratory measurements of immune function, vaccination status, disease severity, or symptoms that were managed without a medical visit. Differences in healthcare-seeking behavior could also influence recorded incidence. In addition, the analysis was observational, so it cannot prove that breast cancer or a specific treatment caused herpes zoster. Even with these limitations, the size of the population, the age-matched comparison group, and the ten-year follow-up provide evidence that the elevated risk is consistent and persists well beyond the immediate treatment period. The results indicate that clinicians should remain alert for shingles in breast cancer survivors, particularly during the first year after diagnosis and among women treated with anthracycline-based chemotherapy.
Subject of Research: Herpes zoster and postherpetic neuralgia risk among female breast cancer survivors in Japan.
Article Title: Herpes zoster risk among female survivors of breast cancer in Japan
News Publication Date: 22-Jul-2026
Web References: University of Tsukuba Institute of Medicine: https://www.md.tsukuba.ac.jp/top/en/ ; Correspondence, Department of Digital Health/Department of Health Services Research, Institute of Medicine, University of Tsukuba: https://digitalhealth.md.tsukuba.ac.jp/
References: Breast Cancer Research. DOI: 10.1186/s13058-026-02345-1
Keywords: Breast cancer, breast cancer survivors, herpes zoster, shingles, varicella-zoster virus, postherpetic neuralgia, chemotherapy, anthracyclines, vaccination, cancer survivorship, viral reactivation, Japan.
