- Design
- Prospective longitudinal cohort with confocal and electron microscopy
- Population
- 21 patients with HER2-positive breast cancer on HER2-targeted ADCs
- Primary outcome
- Incidence and features of ocular surface toxicity
- Effect
- 18/21 (85.7%) affected; mean onset 28 days
A prospective study followed 21 patients with HER2-positive breast cancer starting HER2-targeted antibody-drug conjugates, with full ocular surface assessment including in vivo confocal microscopy.
18 of 21 (85.7%) developed ocular surface toxicity, at a mean of 28 days. It began as inferior subepithelial microcysts and progressed to linear deposits and vortex keratopathy. Confocal imaging showed severe subepithelial nerve fragmentation and loss, with reduced corneal sensitivity. Changes were dose- and time-dependent and partly reversible, with corneal structure improving after 12 cycles.
With ADCs increasingly used in breast and other cancers, eye toxicity will present in general eye clinics. Recognising the pattern prevents misdiagnosis as infection or dry eye alone, and allows lubrication and liaison with oncology rather than stopping effective cancer treatment unnecessarily.
- Ask about ADC therapy in any patient with new vortex keratopathy or blurred vision.
- Offer a baseline eye examination before HER2-ADC therapy starts.
- Review within the first month, when toxicity typically appears.
- Use preservative-free lubricants and liaise with oncology on dose timing.
- Record corneal sensitivity; neurotrophic change raises the risk of epithelial breakdown.
Why it matters
Most patients on these drugs develop corneal toxicity, and eye clinics will see it before they are told to look for it.
Don't overread it
Twenty-one patients from one centre; the frequency may differ with other ADCs and doses.
The statistics, in plain English
18 of 21 is 86%, but with so few patients the true rate could plausibly be anywhere from about two-thirds to nearly all. The consistency of the pattern is more informative than the exact figure.
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