The potential cell population doubling time in neuroblastoma and nephroblastoma

Estimates are presented of the median potential cell population doubling time in five neuroblastomas and six nephroblastomas. The median time in the neuroblastomas was 4·2 days (101 hours) and in the nephroblastomas was 7·8 days (188 hours). Estimates of the duration of metaphase in the two kinds of tumour are also offered, based on the natural mitotic index in six neuroblastomas and five nephroblastomas. The findings are set in the context of a brief review of other studies on the cell population kinetics of human tumours. A more detailed but frankly speculative analysis is made of one nephroblastoma which suggests that cells are produced at the rate of at least 5 per 1000 tumour cells per hour, of which about 3 are lost.