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.