Childhood cancer treatment exposures

Information on treatment received within 5 years of childhood cancer diagnosis, including radiation fields and doses and chemotherapy use, was abstracted from medical records using a standardised protocol.

We defined chest radiation field as a categorical variable ordered by size of the treatment field (TBI and whole lung, mantle, other fields). Participants treated with more than one field were included in the category for the widest field received.

The delivered dose of chest radiotherapy was taken as the sum of delivered doses (as abstracted from radiation therapy records or treatment summaries) for all chest fields. The only exception were patients treated with abdominal fields including breast tissue (including the diaphragm) and a non-overlapping chest field for whom only the dose for the superior field was included.

Cumulative doses of alkylators were determined using the Cyclophosphamide Equivalent Dose (CED) method (Green et al, 2014).