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Biomedical subjects

J W Koten

Publications and source records attributed to J W Koten.

At least 19 recordsLinked to original sources
PubMed1990

Parental age in sporadic hereditary retinoblastoma.

Of 104 children with sporadic hereditary retinoblastoma born between 1945 and 1970, we studied the age of their parents at the birth and compared this age with the mean age of parents at the birth of their children during the same period in The Netherlands. The mean age of fathers at the birth of their children with sporadic hereditary retinoblastoma (33.7 years) was significantly higher than the mean age of fathers at the birth of their children in the general population (32.5 years) (P less than .05, one sided). Similarly, the mean age of mothers at the birth of their children with sporadic hereditary retinoblastoma (31.2 years) was significantly higher than the mean age of mothers at the birth of their children in the general population (29.5 years) (P less than .05, one sided). We further analyzed this parental age factor by measuring the relative risk of age groups and comparing the incidence of sporadic hereditary retinoblastoma in the various parental age groups with the incidence of sporadic hereditary retinoblastoma in the total population. Mothers 35 years of age or older had a relative risk of 1.7 to have a child with sporadic hereditary retinoblastoma compared with mothers in the population in general (P = .006, one sided). Similarly, fathers 50 years of age or older had a relative risk of 5.0 to have a child with sporadic hereditary retinoblastoma compared with fathers in the population in general (P = .04, one sided). No parental age effect was found in children with nonhereditary retinoblastoma. We conclude that a high paternal and a high maternal age are significant risk factors for sporadic hereditary retinoblastoma.

Adult↗
PubMed1989

Early diagnosis of bilateral retinoblastoma reduces death and blindness.

The influence of early diagnosis on sight and survival was studied in 130 patients with bilateral retinoblastoma. Nineteen patients died of this condition. Statistical analysis predicted that 12 of these 19 early deaths could have been prevented if doctors' delay had been less than 1 week. Consequently, a reduction of 65% in mortality is possible. Similarly, statistical analysis also predicted that the number of patients with resulting blindness could be reduced by 40%. Central registration and monitoring of retinoblastoma families would greatly improve early diagnosis.

Adolescent↗
PubMed1989

Heritability of breast cancer and its role in pre-menopausal cases.

The causes for the pre-menopausal incidence peak in breast cancer are still controversial. Other cancers also show an early incidence peak. Since the mammary tissue only starts to develop in puberty, the pre-menopausal incidence peak for breast cancer is comparable to the 'juvenile' peak in other cancers (retina, kidney). The four-mutation model for oncogenesis can explain pre-menopausal breast cancer. The model suggests that malignant transformation of a cell is due to four specific oncogenic mutations. These specific mutations accumulate during the proliferation of somatic cells. According to the model, one inherited oncogenic mutation can cause hereditary cancer. In this case only three additional specific mutations have to be accumulated during somatic cell proliferation. Epidemiological data and mathematical calculations indicate that in this case tumors occur early in life. Thus, the four-mutation model for oncogenesis predicts that the impact of heritability in pre-menopausal breast cancer is more significant than is generally believed. At this point, molecular biological studies are needed, to identify the involved specific mutations. Other implications of the model are an increased incidence of second primary tumors and an increased sensitivity for mutagenic factors in these patients.

Adult↗
PubMed1988

Non-ocular cancer in patients with hereditary retinoblastoma and their relatives.

In The Netherlands, retinoblastoma patients have been registered in the Utrecht national retinoblastoma registry since 1862. This register is virtually complete from 1945 onwards. We describe a unique epidemiological survey of the occurrence of non-ocular cancer in all patients registered during the period 1945-1970. The occurrence of non-ocular cancer in relatives of patients with hereditary retinoblastoma is also reported. One hundred and forty-one patients with hereditary retinoblastoma were studied for non-ocular second primary cancer. Nineteen patients died of retinoblastoma. The median follow-up of the surviving 122 patients was 25 years. Seventeen of these patients developed a second primary cancer, most frequently soft-tissue sarcoma. The cumulative incidence of non-ocular cancer was 19% at the age of 35, i.e., a 14-fold increase as compared to the general population. Twelve patients with hereditary retinoblastoma died of non-ocular cancer whereas none of 252 patients with non-hereditary retinoblastoma died of non-ocular cancer. Furthermore, among the parents of our hereditary retinoblastoma patients, 24 (born before 1945) had also been affected by retinoblastoma or had affected sibs. In the parents, 4 tumors occurred, of which 2 were rhabdomyosarcomas and 2 were urinary bladder cancers. Both types of non-ocular cancer were also encountered among the 122 patients with hereditary retinoblastoma. In 103 fathers and 103 mothers of patients with hereditary retinoblastoma who did not have retinoblastoma themselves, there was no previous family history of retinoblastoma. The fathers had a relative risk of 8.3 for pancreatic cancer compared to the general population. There was no significant increase in the number of non-ocular tumors in 332 sibs of patients with hereditary retinoblastoma.

Adolescent↗
PubMed1987

Carcinogenesis revisited.

The importance of mutations in carcinogenesis is still unclear. Assuming that mutations of the genetic material are central to this problem, the number needed to give rise to a cancer cell must be established. A one-mutation theory is unsatisfactory for a number of reasons. A four-mutation model fits better and can be calculated in humans assuming that the observed endogenous tumors in 2% of the population equals the frequency of spontaneous carcinogenesis, accepting a mean mutation rate of 2 X 10(-5) mutations per gene per generation, and a production of about 7 X 10(15) cells during our whole lifetime. This model is also consistent with the observed peak incidence of cancer in children, with the hereditary aspects of some pediatric tumors, and with the usually nonhereditary mechanisms of cancer in adults.

Humans↗
PubMed1987

Non-ocular cancer in hereditary retinoblastoma survivors and relatives.

An epidemiological survey has been carried out to establish the incidence of second malignant neoplasms in hereditary retinoblastoma survivors in The Netherlands and the relative risk of cancer in non-affected relatives. The cumulative incidence of second neoplasms was 19% at the age of 35 years. Fathers, unaffected by retinoblastoma, were at risk for pancreatic cancer, the relative risk being 8.3.

Eye Neoplasms↗
PubMed1979

Lichenoid melanodermatitis. A clinicopathological study of fifty-one Kenyan patients with so-called tropical lichen planus.

Fifty-one Kenyan patients with variable round plaques on the exposed parts, predominantly on the face, and characterized by central hyperpigmentation with annular hypopigmented borders, are described. The clinical and histological picture showed transitions, which ranged from lichen planus and lichenoid poikilodermatous syndromes to dermatitis. This syndrome corresponds largely with (sub-)tropical or actinic lichen planus as reported from the Middle East, where emphasis has been given mainly to a part of the described spectrum of transitions. We suggest that this syndrome should be considered as one of Pinkus' regional lichenoid syndromes which represent hybrids between lichen planus and other conditions rather than as a mere variant of lichen planus.

Adolescent↗