REB is leading a multicenter international study of second primary gastrointestional (GI) cancers among survivors of Hodgkin lymphoma and cancers of the testis, breast and cervix. This series of seven nested case-control studies, with detailed radiotherapy and chemotherapy treatment data, represents the first comprehensive effort outside of the studies of atomic bomb survivors to quantify the radiation dose-response relationship for upper-GI cancers. Additionally, the study provides novel information about solid tumor risks in relation to type and dose of chemotherapy agents. Findings to date include a demonstrated increased stomach cancer risk after Hodgkin lymphoma with increasing radiation dose to the stomach and with increasing number of alkylating agent-containing chemotherapy cycles. Patients who received both 25+ Gy radiation to the stomach and high-dose (5600+ mg/m2) procarbazine had multiplicatively increased stomach cancer risk (OR=77.5). Additional findings from the series of studies included radiation-related increased stomach cancer risk after testicular and cervical cancers, radiation-related increased esophageal cancer risk after Hodgkin lymphoma, and radiation- and chemotherapy-related increased pancreatic cancer risk after Hodgkin lymphoma. REB dosimetrists described the patterns of radiation dose to the esophagus from breast cancer radiotherapy over the last several decades, and derived a method to better characterize the variability in the stomach size, shape, and location for radiation dose.