An increased relative frequency of retinoblastoma at a rural regional referral hospital in Miraj, Maharashtra, India

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Abstract
Background. Retinoblastoma is a relatively uncommon childhood malignant neoplasm. It has been suggested previously that there is an increased incidence of retinoblastoma in India, but this has been reported primarily from urban cancer centers and may have been confounded by a referral bias. Methods. The authors have evaluated the relative frequency of tumors in children younger than 15 years of age from 1987 to 1990 at Wanless Hospital, a rural regional referral hospital in India. Results. Of 158 children with malignant neoplasms, 13% (20) had the histologically confirmed diagnosis of retinoblastoma. Assuming that these 158 children represent a nonbiased reflection of childhood cancer incidence in this region, these 20 cases of retinoblastoma represent a 3.3-fold increase over the expected number estimated with worldwide relative frequencies and a 4.4-fold increase over the relative frequency expected among a similar group of children as estimated with United States rates. The proportion of children with bilateral disease was 15%, which is less than expected (20–30%). The mean age at presentation was 41 ± 14 months (mean ± standard deviation) compared with 26 months in Western centers. In addition, 50% had metastases at the time of diagnosis compared with 5–10% at Western centers. The increased rate of metastases and late age at diagnosis suggest of a diagnostic delay. Conclusions. These results, in combination with previously reported increased relative frequencies from urban cancer centers in India, suggest that there may be a true increase in the incidence of retinoblastoma in India. The increase in unilateral retinoblastoma indicates that environmental factors may contribute to an increase of the nonheritable form in India. Cancer 1993; 72:282–6.