Response:Malignant mesothelioma after irradiation: consistency and synergy

Response

We thank Drs Teta and Wagner for their comments. We agree with their remark that the relative risk for mesothelioma differs between different cohorts and with different inclusion criteria. Within our own population, we noted that all mesothelioma cases were from the 2 hospitals from the highly industrialized ares, whereas no mesothelioma cases were observed in the populations from the other hospitals.¹ 

This heterogeneity, in combination with the unexpectedly high proportion of patients who had been exposed to asbestos, prompted us to state that a potential synergy might exist between radiation and asbestos.

Precisely because we had no data on asbestos exposure in Hodgkin lymphoma patients who did not develop mesothelioma, we very carefully worded our suggestion on the potential interaction between asbestos and irradiation. Similarly, we suggested a potential synergy between chemotherapy and radiotherapy, because the standardized incidence ratio (SIR) for patients treated with both chemo- and radiotherapy was considerably higher that for those who had been treated with chemotherapy alone.

In conclusion, we think our data might add to the scarce preclinical evidence for the synergistic action of asbestos and radiation in the pathogenesis of mesotheliomas, but our data certainly do not prove such synergy. Hardly any clinical, or even preclinical, data have been published on this topic. Determining whether or not an interaction exists between radiation and asbestos requires data from larger studies examining the etiology of mesothelioma as a second malignancy. The collection of valid exposure data on asbestos will not be a trivial task in such research.