Numbers of SMNs in these groups were small, but there was a highly significant trend ( P <0.001) in the risk of secondary myeloid leukaemia with a striking increase in the SIR from 2.7 in those treated pre-1970 to 69.9 in the group treated after 1979.
The SIR for all SMNs and specifically of the digestive tract and female breast demonstrated a significant trend of increasing excess risk with the more recent era of diagnosis ( Table 5 ), particularly for secondary myeloid leukaemia: ( P <0.001) across the diagnostic periods pre-1970, 1970–1979 and 1980 onwards, for which the SIRs were 2.7, 11.4 and 69.9, respectively.