Data are n (%) unless otherwise noted.

NA, not applicable.

Four cases with breast cancer after HL had missing year of breast cancer diagnosis, which were imputed with the median year of breast cancer diagnosis among participants from the same country.

Four cases with breast cancer after HL and 6 HL controls had missing year of HL diagnosis. These missing years were imputed with the median year of HL diagnosis among participants in the same group (cases or controls) from the same country.

For the Dutch HL survivors, chest RT was defined as (in)complete mantle field or mediastinal RT, or RT to the lungs or axilla. Subjects with only infradiaphragmatic RT were excluded. For HL survivors from the United States, chest RT was defined as chest or total nodal RT (subjects with only brain, other head, neck, abdomen, spine, pelvis, and/or limb RT were excluded). For HL survivors from the United Kingdom, chest RT was defined as mantle field, chest, mediastinal, axillary, mini mantle field or partial chest RT (subjects with only neck, clavicular and/or head or other supradiaphragmatic RT or infradiaphragmatic RT, RT field unknown or chemotherapy only were excluded).

Information on the radiation fields was only available for HL survivors from the United Kingdom and The Netherlands.

Pelvic RT encompassed RT to the whole abdomen or iliac nodes on both sides, or RT with inverted Y field, in women with no (successful) oophoropexy.

Alkylating chemotherapy consists of combinations of cytostatic agents with at least 1 alkylating agent (ie, procarbazine, cyclophosphamide, ifosfamide, lomustine, melphalan, dacarbazine, cisplatin, mechlorethamine, chlorambucil, and carmustine).