To the Editor:

I respectfully differ with several points made in a recent Eye editorial by Dunavoelgyi et al. entitled ‘Minimal residual disease—a novel concept in uveal melanoma’ [1].

In oncological parlance, ‘residual disease’ is the term widely used to mean viable tumour cells persisting after treatment, with the adjective ‘minimal’ indicating that this disease is undetectable by clinical examination or imaging. For example, minimal residual disease after inadequate plaque radiotherapy of choroidal melanoma is what gives rise to local tumour re-growth. With generalised neoplastic disease, such as leukaemia, minimal residual disease indicates surviving neoplastic cells that are undetectable following systemic therapy.

I do not consider it appropriate to refer to hepatic metastases from uveal melanoma as ‘minimal residual disease’ unless these tumours have survived hepatic treatment aimed at eradicating such disease. It is conventional to refer to clinically undetectable metastases as ‘micrometastases’. Genetic analysis of uveal melanoma and survival prognostication in patients with this malignancy essentially indicate the likelihood of sub-clinical tumour cells being present in the liver and other organs.

The concept of minimal residual disease in ocular oncology is not as novel as claimed by Dunavoelgyi et al. As long ago as 1918, this concept led to Treacher Collins administering adjunctive brachytherapy after excision of conjunctival melanoma [2]. Similarly, concern about the risk of minimal residual disease is the reason why my colleagues and I have administered adjunctive plaque radiotherapy after local excision of uveal and conjunctival melanomas in the absence of any visible residual tumour [3, 4]. This concept is also the reason why my colleagues and I have for several years administered long-term systemic maintenance immunotherapy for patients with vitreoretinal lymphoma [5]. There are many other examples of adjunctive treatment for minimal residual disease in the ocular oncology literature.