Yan Liu’s research while affiliated with Fred Hutch Cancer Center and other places

The ability to predict adverse-event occurrences accurately in long-term survivors of childhood cancer is of high importance in late effects research, both clinically and methodologically. This article considers a statistical prediction of future events in a cohort, taking second malignant neoplasm (SMN) incidence in a large cohort of long-term childhood cancer survivors as an example. The method consists of dividing the follow-up period of the cohort into two non-overlapping periods, using the first period as "training data," with which we model the patterns of SMN occurrences in the cohort, and the subsequent period as "testing data," with which we validate the model based on the training data. Future predictions are also applied beyond the testing-data period to calculate the SMN incidence of the cohort in the next five years for overall and specific types of SMNs. The proposed statistical prediction is shown empirically to perform well with respect to the prediction accuracy. Overall, the models were able to predict the future second cancers rates very well, with exceptions of a few cancer types that had very small observed counts in the testing period. Our proposed statistical method predicts future events in a cohort of long-term childhood cancer survivors and, as such, is a useful tool for late effects research on childhood cancer survivors.

Despite interest in the well-being of adult survivors of childhood rhabdomyosarcoma (RMS), few studies have examined their health-related quality of life (HRQOL). This study evaluated physical and social aspects of HRQOL among long-term childhood RMS survivors relative to a sibling comparison group, and assessed whether physical impairment among RMS survivors adversely affected their ability to achieve adult life goals. Using baseline data from the Childhood Cancer Survivor Study, we evaluated self-reported physical impairment and social adaptation among 417 survivors of childhood RMS and 2685 siblings > or =18 years of age at survey completion. Survivors were more likely than siblings to report physical impairment, characterized by: at least one medically diagnosed condition, limitations in the performance of routine activities, a health-related inability to work or attend school, cancer-related pain. Survivors were less likely than siblings to have completed high school, ever worked a job, or ever been married. The odds of completing high school were lower among survivors with performance limitations, a health-related inability to work or attend school, or moderate to high levels of cancer-related pain. Survivors who reported cancer-related pain had an increased likelihood of ever being married. The majority of adult survivors of pediatric RMS are successful in attaining adult life goals despite higher reported occurrence of physical impairment than their sibling counterparts. Additional studies are needed to advance our understanding of other aspects of HRQOL in this population of pediatric cancer survivors.

Subsequent primary neoplasms of the central nervous system (CNS) have frequently been described as late events following childhood leukemia and brain tumors. However, the details of the dose-response relationships, the expression of excess risk over time, and the modifying effects of other host and treatment factors have not been well defined. Subsequent primary neoplasms of the CNS occurring within a cohort of 14,361 5-year survivors of childhood cancers were ascertained. Each patient was matched with four control subjects by age, sex, and time since original cancer diagnosis. Tumor site-specific radiation dosimetry was performed, and chemotherapy information was abstracted from medical records. Conditional logistic regression was used to estimate odds ratios (ORs), to calculate 95% confidence intervals (CIs), and to model the excess relative risk (ERR) as a function of radiation dose and host factors. For subsequent gliomas, standardized incidence ratios (SIRs) and excess absolute risks (EARs) were calculated based on Surveillance, Epidemiology, and End Results data. Subsequent CNS primary neoplasms were identified in 116 individuals. Gliomas (n = 40) occurred a median of 9 years from original diagnosis; for meningiomas (n = 66), it was 17 years. Radiation exposure was associated with increased risk of subsequent glioma (OR = 6.78, 95% CI = 1.54 to 29.7) and meningioma (OR = 9.94, 95% CI = 2.17 to 45.6). The dose response for the excess relative risk was linear (for glioma, slope = 0.33 [95% CI = 0.07 to 1.71] per Gy, and for meningioma, slope = 1.06 [95% CI = 0.21 to 8.15] per Gy). For glioma, the ERR/Gy was highest among children exposed at less than 5 years of age. After adjustment for radiation dose, neither original cancer diagnosis nor chemotherapy was associated with risk. The overall SIR for glioma was 8.7, and the EAR was 19.3 per 10,000 person-years. Exposure to radiation therapy is the most important risk factor for the development of a new CNS tumor in survivors of childhood cancers. The higher risk of subsequent glioma in children irradiated at a very young age may reflect greater susceptibility of the developing brain to radiation.

This report examines the incidence of and risk factors for strokes that occur in > or = 5-year survivors of childhood leukemia and brain tumors. The rate of first occurrence of self-reported late-occurring strokes was determined for leukemia survivors (n = 4,828), brain tumor survivors (n = 1,871), and a comparison group of a random sample of cancer survivor siblings (n = 3,846). Relative risks (RRs) and 95% confidence intervals (CIs) of stroke by treatment exposures were examined by multivariate analyses. Thirty-seven leukemia survivors and 63 brain tumor survivors reported a late-occurring stroke. The rate of late-occurring stroke for leukemia survivors was 57.9 per 100,000 person-years (95% CI, 41.2 to 78.7). The RR of stroke for leukemia survivors compared with the sibling comparison group was 6.4 (95% CI, 3.0 to 13.8; P < .0001). The rate of late-occurring stroke for brain tumor survivors was 267.6 per 100,000 person-years (95% CI, 206.8 to 339.2). The RR of stroke for brain tumor survivors compared with the sibling comparison group was 29.0 (95% CI, 13.8 to 60.6; P < .0001). Mean cranial radiation therapy (CRT) dose of > or = 30 Gy was associated with an increased risk in both leukemia and brain tumor survivors in a dose-dependent fashion, with the highest risk after doses of > or = 50 Gy CRT. Survivors of childhood leukemia and brain tumors, particularly those with brain tumors treated with CRT at doses of greater than 30 Gy, are at an increased risk of stroke.

Radiation exposure at a young age is a strong risk factor for thyroid cancer. We conducted a nested case-control study of 69 thyroid cancer cases and 265 controls from a cohort of 14,054 childhood cancer survivors to evaluate the shape of the radiation dose-response relationship, in particular at high doses, and to assess modification of the radiation effects by patient and treatment characteristics. We considered several types of statistical models to estimate the excess relative risk (ERR), mainly guided by radiobiological models. A two-parameter model with a term linear in dose and a negative exponential in dose squared provided the best parsimonious description with an ERR of 1.3 per gray (95% confidence interval 0.4-4.1) at doses below 6 Gy and a relative decrease in ERR of 0.2% per unit dose squared with increasing dose, that is, decreases in the ERR/Gy of 53% at 20 Gy and 95% at 40 Gy. Further analyses using spline models suggested that the significant nonlinearity at high doses was characterized most appropriately as a true downturn rather than a flattening of the dose-response curve. We found no statistically significant modification of the dose-response relationship by patient characteristics; however, the linear parameter (i.e., the ERR/ Gy at doses less than 6 Gy) did decrease consistently and linearly with increasing age at childhood cancer diagnosis, from 4.45 for 0-1-year-olds to 0.48 for 15-20-year-olds. In summary, we applied models derived from radiobiology to describe the radiation dose-response curve for thyroid cancer in an epidemiological study and found convincing evidence for a downturn in risk at high doses.

To examine the prevalence and predictors of health insurance coverage and the difficulties obtaining coverage in a large cohort of childhood cancer survivors. This study included 12,358 5-year survivors of childhood cancer and 3,553 sibling controls participating in the Childhood Cancer Survivor Study. Data were collected by surveys distributed in 1994 (baseline) and 2000 (follow-up). At baseline, 83.9% of adult survivors, compared with 88.3% of siblings, had health insurance coverage (P < .01); 6 years later, small but significant survivor-sibling differences remained (88% v 91%; P < .01). Twenty-nine percent of survivors reported having had difficulties obtaining coverage, compared with only 3% of siblings (P < .01). In multivariate analysis of survivors 18 years of age or older, factors associated with being uninsured included younger age at diagnosis (diagnosis age of 0 to 4 years; odds ratio [OR] = 1.7; 95% CI, 1.3 to 2.2), male sex (OR = 1.3; 95% CI, 1.2 to 1.5), age at baseline survey (age 22 to 24 years; OR = 1.6; 95% CI, 1.2 to 2.1), lower level of attained education (less than high school, OR = 2.6, 95% CI, 2.1 to 3.3; high school graduate, OR = 2.1, 95% CI, 1.8 to 2.5), income less than 20,000 dollars (OR = 5.6, 95% CI, 4.5 to 7.1), marital status (widowed/divorced/separated; OR = 1.3; 95% CI, 1.1 to 1.6), smoking status (current smoker, OR = 2.0, 95% CI, 1.7 to 2.3; former smoker, OR = 1.4, 95% CI, 1.2 to 1.8), and treatment that included cranial radiation (OR = 1.3, 95% CI, 1.0 to 1.6). Compared with siblings, adult survivors of childhood cancer had significantly lower rates of health insurance coverage and more difficulties obtaining coverage. Since lack of coverage likely has serious health and financial implications for this at-risk population, any disparity in availability and quality of coverage is of great concern.

We determined risk of cancer among first-degree relatives of 5-year survivors of childhood leukemia, lymphoma, central nervous system tumors, sarcomas, Wilms' tumor, and neuroblastoma. Subjects were 13,703 participants in the Childhood Cancer Survivor Study. Family history was collected on 56,759 first-degree relatives using a self-reported questionnaire. Incidence was compared with age- and sex-specific rates using the U.S. Surveillance, Epidemiology and End Results program. Siblings of the survivors had an increased risk of cancer [standardized incidence ratio (SIR), 1.5; 95% confidence interval (95% CI), 1.35-1.7]. Risk was elevated for siblings of probands of leukemia (SIR, 1.3; 95% CI, 1.0-1.6), Hodgkin's disease (SIR, 1.5; 95% CI, 1.2-1.9), non-Hodgkin's lymphoma (SIR, 1.8; 95% CI, 1.3-2.5), Wilms' tumor (SIR, 1.9; 95% CI, 1.2-3.2), soft tissue sarcoma (SIR, 1.5; 95% CI, 1.0-2.2), and bone tumors (SIR, 1.6; 95% CI, 1.2-2.2). Cancer risk was elevated in siblings (SIR, 2.4; 95% CI, 1.5-3.7) and offspring (SIR, 15.0; 95% CI, 5.3-42.9) of probands with second malignant neoplasms (SMN) compared with relatives of probands without SMNs. Siblings of probands with leukemia, Hodgkin's disease, neuroblastoma, and Wilms' tumor had elevated risks for the same malignancies. Parents had no increased risk (fathers' SIR, 0.7; 95% CI, 0.7-0.8; mothers' SIR, 0.9; 95% CI, 0.9-1.0). Seventy percent of siblings' cancers developed in adulthood. These findings suggest that familial cancer syndromes may be revealed as this cohort and family members age and with accrual of more offspring and subjects with SMNs.

The objectives of this report are to examine the incidence of and risk factors for stroke among childhood Hodgkin's disease (HD) survivors. The Childhood Cancer Survivor Study is a multi-institutional cohort study of more than 5-year cancer survivors diagnosed between 1970 and 1986 and a sibling comparison group. Incidence rates of stroke among HD survivors (n = 1,926) and siblings (n = 3,846) were calculated and compared. Cox proportional hazards models were used to estimate the hazard ratios, reported as relative risks (RR), of developing stroke between HD survivors and siblings. Nine siblings reported a stroke, for an incidence of 8.00 per 100,000 person-years (95% CI, 3.85 to 14.43 per 100,000 person-years). Twenty-four HD survivors reported a stroke. The incidence of late-occurring stroke among HD survivors was 83.6 per 100,000 person-years (95% CI, 54.5 to 121.7 per 100,000 person-years). The RR of stroke among HD survivors was 4.32 (95% CI, 2.01 to 9.29; P = .0002). All 24 survivors received mantle radiation exposure (median dose, 40 Gy). The incidence of late-occurring stroke among HD survivors treated with mantle radiation was 109.8 per 100,000 person-years (95% CI, 70.8 to 161.1 per 100,000 person-years). The RR of late-occurring stroke among HD survivors treated with mantle radiation was 5.62 (95% CI, 2.59 to 12.25; P < .0001). Survivors of childhood HD are at increased risk of stroke. Mantle radiation exposure is strongly associated with subsequent stroke. Potential mechanisms may include carotid artery disease or cardiac valvular disease.

Nonmelanoma skin cancer (NMSC) has become the most common type of cancer in many populations throughout the world. Ultraviolet and ionizing radiation are known risk factors. Because NMSCs are rarely lethal and most cancer registries do not routinely report data regarding these cancers, they have received little attention in studies evaluating long-term effects of cancer therapy. This article reports on the occurrence of secondary NMSC as a long-term effect of cancer therapy in survivors of childhood cancer. The Childhood Cancer Survivor Study (CCSS) is a cohort study of 5-year survivors of childhood and adolescent cancer from 25 participating institutions in North America. NMSC patients were defined by a history of basal cell or squamous cell carcinoma of the skin after primary malignancy treatment. Demographic and treatment data were collected and analyzed. Among the 13,132 eligible CCSS participants, 213 have reported NMSC; 99 patients (46%) have had multiple occurrences. Median age of occurrence was 31 years (range, 7 to 46 years). Location of NMSC included head and neck (43%), back (24%), chest (22%), abdomen and pelvis (5%), extremity (3%), and unknown (4%). Ninety percent of patients had previously received radiation therapy (RT); 90% of tumors occurred within the RT field. RT was associated with a 6.3-fold increase in risk (95% CI, 3.5- to 11.3-fold). Long-term survivors of childhood and adolescent cancer who were treated with RT are at highest risk for developing NMSC. Educational efforts need to be directed to this population to facilitate early diagnosis of NMSC and reduction in sun exposure.

We assessed late mortality in 854 individuals who had survived 2 or more years after autologous hematopoietic cell transplantation (HCT) for hematologic malignancies. Median age at HCT was 36.5 years, and median length of follow-up was 7.6 years. Overall survival was 68.8% +/- 1.8% at 10 years, and the cohort was at a 13-fold increased risk for late death (standardized mortality ratio [SMR] = 13.0) when compared with the general population. Mortality rates approached those of the general population after 10 years among patients at standard risk for relapse at HCT (SMR = 1.1) and in patients undergoing transplantation for acute myeloid leukemia (AML; SMR = 0.9). Relapse of primary disease (56%) and subsequent malignancies (25%) were leading causes of late death. Relapse-related mortality was increased among patients with Hodgkin disease (HD; relative risk [RR] = 3.6), non-Hodgkin lymphoma (NHL; RR = 2.1), and acute lymphoblastic leukemia (ALL; RR = 6.5). Total body irradiation (RR = 0.6) provided a protective effect. Nonrelapse-related mortality was increased after carmustine (RR = 2.3) and with use of peripheral blood stem cells (RR = 2.4). Survivors were more likely to report difficulty in holding jobs (RR = 9.4) and in obtaining health (RR = 7.7) or life insurance (RR = 8.4) when compared with siblings. Although mortality rates approach that of the general population after 10 years in certain subgroups, long-term survivors of autologous HCT continue to face challenges affecting their health and well-being.