Characterization of participants
In Figure 2 the recruitment process is summarized. For the LATER 2 study, we started with 5,139 potentially eligible survivors alive October 10, 2016. After careful tracing and assessment, we excluded 418 individuals for the following reasons: 99 survivors died between the recruitment periods of the LATER 1 and LATER 2 study, 55 survivors were lost to follow-up, 179 survivors were living abroad, 47 survivors were considered ineligible for participation in the LATER 2 study by their physician, and 38 individuals were not invited due to other reasons constituting exclusion criteria (e.g. not proficient in Dutch language). In all, 4,735 survivors were invited for the LATER 2 study. In total, 2,519 (53.2%) of eligible survivors participated in the study, 744 survivors declined participation, 1,472 survivors did not respond to the invitation and the reminders. Of the participating survivors, 127 signed the informed consent, but eventually did not participate in additional data collection for the study. For this group, we were able to extract data from the medical records from their regular late effects outpatient clinic visit and use this for some of the research questions in the study.
In Figure 3 the planned and realized trend-lines of invitation and out-patient clinic visit are shown. Although the participation rate was initially lower than expected, we eventually included our intended number of 2,500 survivors. In addition, 541 (36.1%) of 1,499 invited siblings and 661 (66.4%) of 996 invited parents participated in the LATER 2 study.
Table 1 presents demographic information, tumor characteristics, treatment and follow-up information of the survivors who participated in the LATER 2 study. Of the 2,519 participating survivors, 49.3% was female (n=1,242). Median follow-up time since childhood cancer diagnosis was 26.9 years (range 14.8 to 54.7) and median attained age was 34.4 years (range 15.4 to 66.6 years). The majority of the participating survivors had been diagnosed with leukemia, myeloproliferative disease and myelodysplastic disease (35.6%), lymphoma and/ or reticuloendothelial neoplasm (18.9%) and renal tumor (11.3%). For treatment of primary cancer or recurrences, 13 (0.5%) survivors did not have any recorded surgery, chemotherapy or radiotherapy (mainly neuroblastoma stage IV’s and low grade CNS tumors, which sometimes have a wait and see policy), 163 (6.5%) survivors received surgery only, 1,375 (54.6%) survivors received chemotherapy only (with or without surgery), 133 (5.3%) survivors received radiotherapy only (with or without surgery) and 834 (33.1%) survivors received both chemotherapy and radiotherapy (with or without surgery). Of participating survivors, 166 (6.6%) had received a bone marrow transplant, of which 57 (2.3%) were autologous and 109 (4.3%) were allogenic. When comparing participants with non-participants (Table 1) in univariate analyses, we observed that females were more likely to participate than males (p<0.00001), CNS survivors were less likely to participate compared to other cancer types (p <0.00001), and survivors treated with chemotherapy and radiotherapy were more likely to participate compared to other survivors.