Clonal Hematopoiesis Increases Risk of Therapy-Related Myeloid Neoplasms

Introduction

Therapy-related myeloid neoplasms (t-MNs) are often fatal secondary malignancies. There is no predictive biomarker for t-MNs. Recent studies suggested that individuals with clonal hematopoiesis have higher risk of developing leukemia. We hypothesized that cancer patients with clonal hematopoiesis have increased risk of developing t-MNs.

Methods

We studied 14 patients with t-MNs who had paired samples of t-MN bone marrow (BM) and peripheral blood (PB) that were previously obtained at the time of primary cancer diagnosis and before therapy. We performed targeted capture sequencing (median depth 245x) on t-MN BM and detected driver mutations. Then we performed molecular barcode deep sequencing (median 1,606x) on the prior PB samples to detect pre-leukemic driver mutations. Using the same method, we detected clonal hematopoiesis in the pre-treatment PB samples from 54 patients with lymphoma who did not develop t-MNs (control cohort). We further validated association between clonal hematopoiesis and t-MNs in a separate cohort of 74 patients with lymphoma.

Results

Targeted capture sequencing of the 14 t-MN BM samples revealed 29 driver mutations in 16 genes. TP53 mutations were detected in 5 patients (36%). The median variant allele frequency (VAF) of the mutations was 26.2% (range: 8.8% - 97.2%). Among the 29 driver mutations detected in t-MN BM samples, 21 mutations (72%) were detectable as pre-leukemic clonal hematopoiesis in 10 patients' prior PB samples (71%). The median VAF of the clonal hematopoiesis was 8.5% (range: 0.7-36.9%). There were also 12 mutations in prior PB samples that did not become drivers in t-MN BM. The VAF was significantly higher in the mutations that became drivers than in the mutations that did not become drivers (8.5% [range: 0.7-36.9%] vs. 1.2% [range: 0.1-7.6%], P < 0.001).

The control cohort included 54 patients with lymphoma who did not develop t-MNs after therapy. Using the same molecular barcode sequencing, we detected 22 mutations in 17 (31%) patients' pre-treatment PB samples. Compared to the 14 t-MN cases, patients who developed t-MNs had significantly higher incidence of clonal hematopoiesis at the time of cancer diagnosis (71% vs. 31%, P = 0.008). The rate of t-MN development at 5 years was significantly higher in patients with clonal hematopoiesis than in patients without (30% [95% CI: 16-51%] vs. 7% [95% CI: 2-21%], P = 0.015). The median VAF of the mutations detected as clonal hematopoiesis was significantly higher in the t-MN cases than in the control (2.4% [range: 0.1-37%] vs. 0.8% [range: 0.3-1.8%], P = 0.001).

The validation cohort included 74 patients with lymphoma who received frontline CHOP-based regimen. Median age was 56 years (range: 17-83 years) and 35 (47%) and 16 (22%) patients received radiation therapy and autologous stem cell transplant (auto-SCT), respectively. During the median follow up duration of 14.8 years (95% CI: 14.5-15.1 years), 5 patients (7%) developed t-MNs with the median 5.4 years latency (range: 1.5-12.8 years). Molecular barcode sequencing of pre-treatment PB samples detected total 17 mutations as clonal hematopoiesis in 15 patients (23%). Clonal hematopoiesis was detected in 4 of 5 patients (80%) who developed t-MNs, while it was detected in 11 of 69 patients (16%) who did not develop t-MNs (P = 0.005). The positive predictive value and negative predictive value of clonal hematopoiesis were 26.7% (95% CI: 7.8-55.1%) and 98.3% (95% CI: 90.9-99.9%), respectively. The rate of t-MN development at 10 years was significantly higher in patients with clonal hematopoiesis than in patients without (29% [95% CI: 12-59%] vs. 0% [95% CI: 0-0%], P = 0.001). Multivariate Cox model revealed that clonal hematopoiesis and auto-SCT significantly increased the risk of t-MNs (clonal hematopoiesis: HR 12.0 [95% CI: 1.3-108.7], P = 0.027 and auto-SCT: HR 10.5 [95% CI: 1.2-95.1], P = 0.037).

Conclusion

Pre-leukemic clonal hematopoiesis was frequently detected in patients with t-MNs at the time of primary cancer diagnosis and before exposure to therapy. Detection of clonal hematopoiesis significantly increased the risk of t-MN development in both case-control and validation study. These data suggest potential approaches of screening clonal hematopoiesis in cancer patients to identify patients at risk of t-MN development and warrants a validation in prospective trial investigating a role of clonal hematopoiesis as a predictive marker for t-MNs.