The 32P test and other methods in the diagnosis of intraocular tumours

Abstract

Chapter 1 explains why the 32P test was reintroduced into The Netherlands for the diagnosis of intraocular tumours and how the present study was started. In Chapter 2 the physical features of 32P and the biochemical behaviour of radioactive phosphate in healthy and neoplastic tissue are described. The complications, which can be encountered after the administration of 32P, are mentioned. Chapter 3 gives a review of the 32P test in ophthalmology, with special attention to the methods used and the development of instruments for the measurements. The 32P test results published in the literature show when correct c.q. inaccurate results were obtained. In Chapter 4 the way in which the 32P test was performed in this study is described. The different counting techniques used according to the localization of the tumour under study, are given. The apparatus used to localize the lesions and to measure the radioactivity are described. Finally, features of the 211 patients in this series are given. Characteristics of the melanomas of 124 patients are compared with data in the literature. In Chapter 5 the 32P test results obtained in the patients of this study are described. A good diagnostic accuracy of the 32P test was present in the 192 lesions located in the posterior segment, with a correct result obtained in 186 patients. Only three malignant and three benign lesions showed an incorrect test result. The inaccuracy of the 32P test in the 19 anterior segment lesions is in accordance with published data. A study was performed to investigate the presence of correlations between histologie features of melanomas and the 32P test results. The small correlations found, mainly a positive with the tumour-mass (r = 0.4) and a negative with the thickness of the sclera overlying the tumour (r = − 0.3), are compared with literature data. The influence of the threshold-value on the number of positive and negative 32P test results and the influence of differences in the control sites on the value of the test result are mentioned briefly. Finally, the few complications encountered with the use of the 32P test are discussed. In Chapter 6 the results obtained with scintigraphy, fluorescein angiography, perimetry, transillumination, and ultrasonography are given and compared with data in the literature. In contrast with scintigraphy and transillumination, fluorescein angiography and to a lesser extent perimetry proved to be valuable methods for the diagnosis of intraocular tumours. Ultrasonography was not used systematically for each tumour of this study. In addition, the occurrence and significance of orange areas overlying the tumours under study are discussed. The results of the general examination and the occurrence of melanuria in the patients of this series are given. In Chapter 7 the value of fluorescein angiography, perimetry, and the 32P test for the diagnosis of various lesions, with relevance to the differential diagnosis of a choroidal tumour, is described. These three methods provide information about different aspects of the tumour under study which, in combination with the ophthalmoscopic features, permit good evaluation of the nature of the lesion. Three groups of small choroidal tumours are compared. Both melanomas and naevi showed specific characteristics and examination results. There remained, however, a small group of 5 lesions for which the results of the different examinations did not give clear diagnoses. This might justify observation in which tumour-growth can be established before enucleation is elected. The literature indicates that there is a tendency to use observation for every small tumour with ophthalmoscopic features suggesting melanoma. A review of the literature on the survival rate of melanomapatients is given. The existing difference in prognosis between small and large tumours is mentioned. On this basis and on the basis of the histologic features of the smallest melanomas in our series, a proposal is put forward for the investigation and treatment of small choroidal tumours. If the results of fluorescein angiography, perimetry and the 32P test point towards melanoma, enucleation should elected immediately. Observation should be restricted to those lesions which show an examination result inconsistent with malignancy. In Chapter 8 the 32P tests performed in 12 patients with an extraocular lesion are mentioned. The results, in every case correct, are compared with data in the literature. In Chapter 9 the indications for the 32P test are summarized. In hoofdstuk 9 worden de indicaties voor een 32P test aangegeven.