Observation of de novo bladder dysfunction under treatment with Her2-neu antibodies

We diagnosed de novo bladder dysfunction in several breast cancer patients under cancer-specific therapy with trastuzumab. The goal of this retrospective analysis was to investigate whether bladder dysfunction is common in a larger population of breast cancer patients receiving trastuzumab therapy.

We identified 93 patients who received at least two doses of trastuzumab at our institution in the years 2003-2006. 57 of those patients were still alive at the time of this analysis. We mailed a validated global questionnaire for the assessment of incontinence (King's Health Questionnaire, KHQ) to them, additionally asking for bladder dysfunction observed under trastuzumab therapy.

43 (75%) of the patients returned the questionnaire, 11 (25%) of them reporting severe de novo bladder dysfunction under therapy. Significant differences between symptomatic and asymptomatic patients were detected in all KHQ subscales. Previous conditions and surgeries as well as medications, especially hormonal therapy, were excluded as underlying causes. However, there were more patients under taxane-based chemotherapy in the symptomatic group.

The epidermal growth factor receptor is involved in the cellular response to mechanical stretch in the urinary bladder. Based on our findings, we hypothesize that interfering with this pathway may well be the cause of symptomatic bladder dysfunction in patients under trastuzumab medication. A prospective study is required to further elucidate this hypothesis.