La cancer-associated retinopathy (CAR) is a rare retinal disease of paraneoplastic and tumour-associated origin that can cause blindness. Tumour-associated retinopathy was first described in lung carcinoma patients in 1976. CAR is a remote effect of carcinomas, which, however, is not metastatic in nature, is not related to tumour invasiveness, and is characterised by a rapid deterioration of vision. Loss of visual acuity from CAR can occur in many patients even before cancer diagnosis (up to 50% of cases).Â
Causes and epidemiology
Cancer-associated retinopathy is caused by circulating antibodies attacking retinal cells in the presence of a systemic carcinoma, which does not directly affect the retina but other organs. In essence, it is a retinopathy autoimmune disease associated with a neoplasm in the body. In autoimmune diseases, antibodies that should protect the body against pathogens start reacting against our own body.
Small cell lung cancer (SCLC) is the condition most often associated with CAR. Other associated cancers include breast cancer, lymphoma, cervical cancer, myeloma, colon cancer, leukaemia and others.Â
Although its incidence is not fully known, cancer-associated retinopathy is considered a rare disease, in fact, about 100 cases have been described to date and it appears to be more common in females than males. The average age of onset of CAR ranges from 55 to 65 years.
Symptoms of cancer-associated retinopathy
CAR leads to progressive and rapid vision loss caused by dysfunction of the cones and rods, i.e. the receptors that receive light stimuli in the eye, with retinal degeneration. Visual deterioration can be sudden and may affect only one eye or both.
Symptoms can be very non-specific and this makes diagnosis complex, so a differential diagnosis is often necessary to rule out other diseases. For example, compared to autoimmune retinopathy, tumour-associated retinopathy usually occurs in older patients. Among the non-specific complaints of CAR, photosensitivity, reduced vision, and apparent greying or darkening of the surroundings are not uncommon. Clinical features of cone dysfunction are, for example, decreased visual acuity and abnormal colour vision. In contrast, rod dysfunction leads, among other symptoms, to a prolonged time for adaptation to darkness and restricted visual fields. Both receptor types can also be affected at the same time, depending on the type of circulating antibodies present and in, this case, a mixture of symptoms will be present.Â
As mentioned, the visual symptoms of CAR can occur even months or years before the diagnosis of the malignancy and occur as a consequence of the remote effect of the tumour. This interval can last up to 11 years.
Prognosis and management
Early diagnosis by an ophthalmologist and timely treatment are a prerequisite for vision preservation. According to scientific studies, early diagnosis in patients at risk of developing CAR can be aided by the search for anti-retinal autoantibodies. In addition, the ophthalmologist may also find fundus examination of the eye, visual field testing, optical coherence tomography and electrophysiological tests useful. The visual prognosis is not affected by the treatment of the underlying cancer, however the disease causes severe loss of photoreceptors so, despite immunomodulatory therapy, the visual prognosis remains bleak.
Management options for cancer-associated retinopathy include the administration of systemic steroids, intravenous immunoglobulins and the administration of monoclonal antibodies to act on modulation of the immune system and reduction of the autoimmune response. A multidisciplinary approach, involving several specialists, is very important for the management of patients with cancer-associated retinopathy. In particular, the oncologist, ophthalmologist and radiologist must be involved. This unified inter-professional approach is crucial for better management of patients and to support the possibility of favourable disease outcomes.
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