Abstract
Aim
To estimate the risk of bone malignancy arising in premalignant conditions.
Methods
There are quite a number of possible premalignant conditions with considerable uncertainty about the actual risk of a bone sarcoma developing. The incidence of these malignant conditions was identified from a prospective database containing 3000 primary bone sarcomas.
Results
178 of the 3000 patients with newly diagnosed bone sarcomas had a pre-exiting condition which in all probability led to the sarcoma. These included 50 with previous radiotherapy treatment and 47 with Paget's disease. 31 patients developed malignancy in HME, 8 with neurofibromatosis and 7 each with Ollier's disease and retinoblastoma. There were 4 malignancies in patients with Mafucci's syndrome, 3 in patients with fibrous dysplasia, 3 in patients with synovial chondromatosis and 2 in patients with Rothmund-Thomson syndrome.
Given that the incidence of bone sarcomas is 9/million population per year, our 3000 patients represent 333 million population years. When the incidence of a condition is known in the population this allows an estimation of the risk of malignancy compared with the normal population. Retinoblastoma for instance is known to arise in 1 in 16000 births. The 7 malignancies we saw thus represents a risk to individuals with retinoblastoma of 336/million/yr - a figure 37 times the risk of the normal population. Approximate figures of risk have been calculated for other entities.
Conclusion
Data from a supra-regional register allows an approximate estimate of the increased risk of bone tumours in premalignant conditions.
