Fanconi Anemia |
1 Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, MD, USA;
2 Clinical Genetics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Rockville, MD, USA and
3 Department of Pediatrics, Charité Medical School Berlin, Germany
Correspondence: Philip S. Rosenberg, Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 6120 Executive Blvd, Executive Plaza South, Room 8022, Rockville MD 20852-7244 USA. E-mail:rosenbep{at}mail.nih.gov
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Design and Methods: We assembled a cohort of 181 patients with Fanconi anemia mostly from Germany. We calculated the ratio of observed to expected cancers, and the risks of bone marrow failure, acute myeloid leukemia, and solid tumors by age.
Results: The first adverse event was bone marrow failure in 66 patients, acute meyloid leukemia in 14 patients and solid tumors in 10 patients. The ratio of observed to expected cancers was 44 for all cancers, 26 for all solid tumors, and 868 for acute myeloid leukemia; these increased risks were statistically significant. Significantly elevated ratios of observed to expected cancers were observed for esophageal (6281), vulvar (2411), head and neck (240), breast (34) and brain (23) tumors. Absent or abnormal radii, and a five-item congenital abnormality score, were significant risk factors for bone marrow failure. The cumulative incidence of bone marrow failure by the age of 10 years varied from 12.6% in the lowest bone marrow failure risk group to 84% in the highest. The relative hazard of bone marrow failure was significantly higher in complementation group G versus A (relative hazard=2.2) and in C versus A (relative hazard=5.4).
Conclusions: Findings from the German Fanconi Anemia Registry cohort validate prior risk estimates, and strongly support the concept that Fanconi anemia is a highly penetrant cancer susceptibility syndrome with early onset of acute myeloid leukemia and slightly later onset of specific solid tumors.
Key words: acute myeloid leukemia, neoplasms, bone marrow failure, Fanconi anemia, bone marrow transplantation, epidemiology.
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Previously, we used data from the North American Survey (NAS), a retrospective cohort of patients with Fanconi anemia from the United States and Canada, to develop estimates of cancer risks in Fanconi anemia, and to identify specific types of solid tumors occurring in excess.6 These estimates are strikingly high, similar in magnitude to those for the classical cancer susceptibility syndrome of Li-Fraumeni.7 We also developed a statistical model to predict the cumulative incidence of each adverse event type by age depending on the presence or absence of specific congenital abnormalities.8
Given the recent emphasis on cancer studies by the Fanconi anemia research community, and the needs of patients who require reliable risk estimates to inform medical decision-making, it is highly desirable to replicate these findings. Until now, it has not been possible to do so. Fanconi anemia is a rare disease, and for this reason, comparatively few epidemiological studies have been feasible. In this study, we use data from an independent cohort of patients with Fanconi anemia, the German Fanconi Anemia (GEFA) Registry, to assess the replication validity of our previous risk estimates.
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Signed informed consent was obtained from patients, parents or legal guardians, according to the Helsinki convention. This study was conducted in accordance with the ethical standards of the Federal Ministry of Education and Research of Germany. All analyses were conducted under the auspices of the Institutional Review Board of the Inherited Bone Marrow Failure Syndrome Program of the National Cancer Institute.
Some earlier patients were also reported to the International Fanconi Anemia Registry (IFAR) and the European Concerted Action on Fanconi Anemia Research (EUFAR). Eighteen patients were from outside of Germany.
Statistical methods
We used a competing risks approach to estimate cause-specific hazard functions and cumulative incidence curves for bone marrow failure, acute myeloid leukemia and solid tumors, as previously described for the NAS.6 For each specific type of cancer, we compared the observed number of cancers occurring prior to transplant to the expected number (O/E ratio) based on the experience of the Connecticut Tumor Registry.10 We studied the association between the risk of bone marrow failure and two previously identified predictors of bone marrow failure.8
The first predictor was the presence of radial ray abnormalities (patients with absent or abnormal radii were scored as 1, and patients with normal radii were scored as 0). The second predictor was a five-item congenital abnormality score with possible values from 0 through 5, inclusive. The value of the congenital abnormality score equals the number of abnormalities in the set: developmental delay, cardiopulmonary abnormality, abnormal kidney, abnormal hearing or deafness, and abnormal head size. We obtained individualized estimates of the relative hazard of bone marrow failure for each combination of radial ray abnormalities and congenital abnormality score, and incorporated these estimates in an absolute risk model.8 We also modeled the joint effects of complementation group, radial ray abnormalities, and congenital abnormality score. For patients who received transplants, we evaluated the mortality rate during the high-risk period from 0 to 6 months following the transplant, and the subsequent rate of squamous cell cancers of the head and neck.11 All statistical tests were two-sided. p-values less than or equal to 0.05 were considered statistically significant.
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View this table: [in a new window] [Download PPT slide] |
Table 1. Demographic data and outcomes for patients in the German Fanconi Anemia Registry.
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Figure 1. Annual hazard rates and cumulative incidence by age in GEFA and NAS. (A) For GEFA, annual hazard rates (incidence rate per year among subjects who are still at risk) of bone marrow failure (BMF), acute myeloid leukemia (AML), and solid tumors (ST), and 95% point-wise confidence envelopes (shaded regions). (B) Annual hazard rates of BMF (black), AML (red), and ST (blue) by age in GEFA (solid curves), compared to NAS (corresponding dashed, dotted, and dot-dashed curves). (C) For GEFA, cumulative incidence of BMF, AML, and ST by age (cumulative percent experiencing each endpoint as initial adverse event type), and 95% point-wise confidence envelopes (shaded regions). (D) Cumulative incidence of BMF (black), AML (red), and ST (blue) by age in GEFA (solid curves) compared to NAS (corresponding dashed, dotted, and dot-dashed curves).
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Table 2. Observed cancers, and ratio of observed to expected cancers, among patients in the German Fanconi Anemia Registry (GEFA) and the North American Survey (NAS).
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Together, radial ray abnormalities and congenital abnormality score separated GEFA patients into distinct bone marrow failure prognostic groups (Figure 2, Panels C and D). This model was compared to the same model previously developed in the NAS (Figure 2, Panels A and B). For each combination of radial ray abnormalities and congenital abnormality score values, the relative hazards (RH) of bone marrow failure were not significantly different from prior estimates obtained in NAS. In GEFA, after adjusting for radial ray abnormalities, the RH increased by a net of 1.38-fold for each unit increase in the congenital abnormality score value (95% confidence interval [CI]=1.07–1.75-fold, p=0.011). Hence, compared to people with a congenital abnormality score of 0, those with a score of 5 were at 1.385=5.0-fold higher risk of bone marrow failure. In NAS, the corresponding RH value per unit increase in congenital abnormality score was 1.23-fold (95% CI=1.0–1.49-fold). In GEFA patients with absent or abnormal radii and a congenital abnormality score of 5, the RH was 11.5-fold higher (95% CI=2.9–46.4-fold higher) compared to GEFA patients with normal radii and a congenital abnormality score of 0. The corresponding and comparable RH value in NAS was 10.6 (95% CI=4.2–26.8).
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Figure 2. Relative hazard of bone marrow failure (BMF) in GEFA and NAS according to Fanconi anemia phenotype. In each cohort, an absolute risk model was fitted for the rate of BMF by age. Models were fitted to 127 GEFA patients (see Table 1) and 144 NAS patients. BMF predictors were absent or abnormal radii versus normal radii (RAD), and a five-item congenital abnormality score (CABS). The referent group for each cohort comprises patients with normal radii and a CABS value of 0. (A) Relative hazards in GEFA (solid squares) and NAS (open circles) for each CABS value from 0 through 5, for patients with normal radii, with 95% point-wise confidence intervals (solid and dashed error-bars, respectively). (B) Relative hazards in GEFA (solid squares) and NAS (open circles) for each CABS value from 0 through 5, for patients with absent or abnormal radii, relative to patients with normal radii and a CABS value of 0. (C) Frequency of CABS values in GEFA (solid bars) and NAS (open bars), in patients with normal radii. (D) Frequency of CABS values in GEFA (solid bars) and NAS (open bars), in patients with absent or abnormal radii.
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Figure 3. Cumulative incidence of bone marrow failure (BMF), acute myeloid leukemia (AML), and solid tumors (ST) by age, in GEFA. Shaded regions show 95% point-wise confidence limits. CABS values are the congenital abnormality score. (A) Patients with CABS=0 and normal radii are at relatively low risk of BMF compared to patients with more congenital abnormalities. (B) Patients with CABS=5 and absent or abnormal radii are at relatively high risk of BMF compared to patients with fewer congenital abnormalities. By competing risks, patients in (A) are more likely to experience AML or ST as the initial adverse event, while patients in (B) are less likely.
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Figure 4. Proportional hazards model for the rate of bone marrow failure (BMF) in GEFA. Model fitted to data for 84 GEFA patients known to belong to Fanconi anemia complementation groups A (61 patients), G (17 patients), or C (6 patients). (A) Baseline hazard function describing BMF rate by age (solid curve), and 95% point-wise confidence limits (shaded regions). (B) Relative hazard of BMF for increasing CABS values (solid curve), and 95% point-wise confidence limits (shaded regions), compared to CABS=0. (C) RH for patients with absent or abnormal radii (5 patients), and 95% point-wise confidence interval (error bar), versus normal radii (79 patients). (D) Relative hazard values and 95% point-wise confidence limits for patients in complementation groups G or C versus A.
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The age-specific hazard of solid tumors was 3.8-fold higher in transplanted patients than in untransplanted ones. This increased risk did not attain statistical significance (p= 0.11), but was similar in magnitude to the elevated risk (4.4-fold) observed in the Hôpital Saint Louis (SLH) transplant cohort.11 During 2000–2004, none of five patients with matched donors and three of 18 patients with mismatched donors died in the period from 0–6 months after transplantation. In patients with matched donors, acute and chronic graft-versus-host diseases were statistically significant risk factors for death beyond 6 months, as was also the case in the SLH cohort.
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In the GEFA, the cause-specific hazards of bone marrow failure, acute myeloid leukemia, and solid tumors, and the corresponding cumulative incidence curves, were qualitatively and quantitatively similar to previously reported estimates from the NAS.6 Furthermore, there was good agreement with regard to the specific types of solid tumors occurring in excess.
There was also good agreement between the ratios of observed to expected numbers of cancers, when GEFA and NAS patients were compared to demographically matched cohorts from the general North American population. We used referent rates from the Connecticut Tumor Registry, a widely-used North American registry that was established prior to the birth of the oldest GEFA patient,10 because referent cancer rates from Germany that are contemporaneous with the GEFA cohort are not available.12 In recent years, however, variation in cancer incidence between Germany (Saarland) and the United States (Connecticut) has been minor compared to the striking relative risks we observed. Hence, O/E ratios for GEFA would likely have been very similar had a suitable German registry been available. Thus, regarding the risk of solid tumors in Fanconi anemia, reports from the NAS, the IFAR,13 a systematic synthesis of literature cases,14 and this report from the GEFA, are consistent: patients with Fanconi anemia are at extraordinary risk of specific solid tumors, notably, squamous cell cancers of the head and neck (risk elevated by several hundred fold), squamous cell cancers of the esophagus (risk elevated by several thousand fold), and vulvar cancers in women (risk elevated by several thousand fold). In addition, the risk of breast and brain tumors was elevated in the GEFA cohort and that of cervical and liver cancers and osteosarcoma in the NAS.
We also replicated the previous finding from the NAS that abnormal radii, and a five-item congenital abnormality score, separate Fanconi anemia patients into distinct bone marrow failure risk groups. In GEFA, the estimated cumulative incidence of bone marrow failure by the age of 10 years varied from 12.6% in the lowest bone marrow failure risk group to 84% in the highest, very similar to the range of 18% to 83% previously estimated from the NAS.8 These estimates can be useful for clinical decision making.15 In this study, we also found that the congenital abnormality score and being in complementation group G or C were significant and independent risk factors for bone marrow failure. This finding is consistent with reports from the EUFAR16 and the IFAR.17
Finally, we evaluated the outcome of 48 GEFA patients who received a transplant prior to any malignancy, under protocols similar to those in use at the SLH during the same period.11 Mortality rates were similar, as was the elevated incidence of post-transplant malignancies.
Fanconi anemia was first recognized 80 years ago by the astute clinician Guido Fanconi.18 Progress in understanding the molecular basis of Fanconi anemia has been remarkable over the last 15 years. At the clinical level, the GEFA experience validates previous epidemiological studies. It is now clear that Fanconi anemia is both a major bone marrow failure syndrome, and also a highly penetrant cancer susceptibility syndrome. For patients, quantitative estimates of risk derived from the NAS or GEFA cohorts appear to be valid, at least for patients of predominantly European ancestry. These findings, together with major advances in the treatment of bone marrow failure,19,20 strongly suggest that solid tumors will become the predominant clinical problem of patients with Fanconi anemia.
PSR, BPA and WE designed the study; WE set up the database and was involved in the care of patients; PSR analyzed the data and wrote the paper; all authors participated in writing the paper. The authors reported no potential conflicts of interest.
Received for publication September 13, 2007. Revision received November 9, 2007. Accepted for publication December 6, 2007.
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