Risk of hematological malignancies among Chernobyl liquidators

Abstract

A case-control study of hematological malignancies was conducted among Chernobyl liquidators (accident recovery workers) from Belarus, Russia and Baltic countries to assess the effect of low- to medium-dose protracted radiation exposures on the relative risk of these diseases. The study was nested within cohorts of liquidators who had worked around the Chernobyl plant in 1986-1987. A total of 117 cases [69 leukemia, 34 non-Hodgkin lymphoma (NHL) and 14 other malignancies of lymphoid and hematopoietic tissue] and 481 matched controls were included in the study. Individual dose to the bone marrow and uncertainties were estimated for each subject. The main analyses were restricted to 70 cases (40 leukemia, 20 NHL and 10 other) and their 287 matched controls with reliable information on work in the Chernobyl area. Most subjects received very low doses (median 13 mGy). For all diagnoses combined, a significantly elevated OR was seen at doses of 200 mGy and above. The excess relative risk (ERR) per 100 mGy was 0.60 [90% confidence interval (CI) -0.02, 2.35]. The corresponding estimate for leukemia excluding chronic lymphoid leukemia (CLL) was 0.50 (90% CI -0.38, 5.7). It is slightly higher than but statistically compatible with those estimated from A-bomb survivors and recent low-dose-rate studies. Although sensitivity analyses showed generally similar results, we cannot rule out the possibility that biases and uncertainties could have led to over- or underestimation of the risk in this study.

Figure 1

Distribution of total RBM dose among study subjects (overall, by country, and by case-control status) (results based on the main data set 2)

Figure 2

. Comparison of odds ratios (ORs) predicted by different risk models with categorical odds ratios estimated in 6 dose categories (results based on the main data set 4) ◆ OR and 95% CI Log-linear model – linear dose-response Log-linear model – linear-quadratic dose-response ERR model – linear dose-response ERR model – linear-quadratic dose-response

Figure 3

Profile likelihood, MLE and 90% CI for β from both the unsimulated data and the 10,000 simulations, using the log-linear model - All hematological malignancies combined (results based on the main data set 5)

Figure 4

Profile likelihood, MLE and 90% CI for β from both the unsimulated data and the 10,000 simulations, using the linear ERR model - All hematological malignancies combined (results based on the main data set 6)