Undifferentiated Pruritus Associated with Increased Risk of Hematologic Cancer

Junwen Deng, BA

A new cohort study determined that the risk ratio for hematologic cancer in patients with undifferentiated pruritus was highest in the first 12 months, which prompted investigators to suggest that clinicians consider the symptoms and risk of cancer in patients who present with the disease.

Previous research has shown that pruritus, when approaching a prevalence of 30%, can be an early symptoms in patients with hematologic cancers. Yet the risk of future cancer in patients with pruritus has not been thoroughly researched.

However, previous evaluations of cancer in patients with pruritus have involved measuring of serum lactate dehydrogenase (LDH).

For this study, an investigative team led by Junwen Deng, BA, from the Department of Dermatology at Johns Hopkins University School of Medicine, sought to assess the risk of hematologic cancer in pruritus patients though the utilization of serum LDH level as a prognostic marker.

The team utilized the global health research network TriNetX, which is comprised of deidentified electronic medical records from more than 69 million patients from the US and Europe.

Patients from 2002-2020 were identified using the International statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) code for unspecified pruritus. Patients with existing chronic pruritus dermatoses or systemic diseases associated with pruritus were excluded.

After careful selection, patients with pruritus and controls were 1:1 propensity score matched by age, sex, race and ethnicity, smoking status, alcohol use, and BMI.

Investigators then assessed the risk of developing Hodgkin lymphoma, non-Hodgkin lymphoma, lymphocytic leukemia, myeloid leukemia, myelodysplastic syndrome, multiple myeloma, Waldenström macroglobulinemia, monoclonal gammopathy, and polycythemia vera.

In total, 327,502 patients with undifferentiated pruritus were matched with 327,502 controls. A sensitivity analysis showed that both groups had a comparable mean number of ambulatory visits and the same frequency of emergency visits, which were 3 and 1, respectively.

At 1 year, investigators observed that undifferentiated pruritus was associated with an increased risk of Hodgkin lymphoma (RR, 4.42, 95% CI, 2.83-6.88), myeloid leukemia (RR, 2.56, 95% CI, 1.79-3.67), multiple myeloma (RR, 2.38, 95% CI, 1.66-3.41), non-Hodgkin lymphoma (RR, 2.35, 95% CI, 1.96-2.82), monoclonal gammopathy (RR, 1.90, 95% CI, 1.55-2.32), myelodysplastic syndrome (RR, 1.74, 95% CI, 1.14-2.64), and lymphocytic leukemia (RR, 1.47, 95% CI, 1.07-2.02).

Patients with pruritus were at a similar increased risk for these cancers at 5 and 10 years as well.

Notably, patients with pruritus had the highest absolute risk of diagnosis with non-Hodgkin lymphoma in 1 year (0.117% vs 0.050%) (P < .001) and 5 years (0.222% vs 0.134%) (P < .001), in addition to monoclonal gammopathy in 5 years (0.196% vs 0.145%) (P < .001) and 10 years (0.235% vs 0.176%) (P < .001).

Though patients with undifferentiated pruritus had higher serum LDH levels, these levels were not associated with an increased risk of hematologic cancer.

“Future studies should examine covariates, such as age or patient-specific risk factors, for the development of specific hematologic cancers in patients with pruritus, as well as the optimal diagnostic and prognostic hematologic workup,” the team wrote.

The study, "Risk of Hematologic Cancer in Patients With Undifferentiated Pruritus," was published online in JAMA Dermatology.