Does Occupational Pesticide Exposure Lead to Treatment Failure for DLBCL?

The treatment failure rate for immunotherapy with R-CHOP was almost twice as high in patients with diffuse large B-cell lymphoma (DLBCL) who were occupationally exposed to pesticides compared with patients with no exposure, a new study showed.

Additionally, patients with occupational pesticide exposure had significantly reduced event-free survival and worse overall survival.

“The results of this study suggest that the prognosis of DLBCL in terms of treatment failure and survival is statistically associated with a history of occupational exposure to pesticides, notably agricultural occupations,” wrote Sylvain Lamure, MD, of Montpellier University Hospital in Montpellier, France, and colleagues, in JAMA Network Open.

Lamure and colleagues conducted a retrospective study looking at patients with DLBCL from 2010 to 2015. The study included 404 patients with newly diagnosed disease treated with anthracycline-based immunochemotherapy.

The researchers hypothesized that “cellular adaptation to damage induced by long-term occupational pesticide exposure, promoting DNA repair pathways and antioxidant defenses, hinders chemotherapy efficiency.”

Occupational history was reconstructed and the researchers used the PESTIPOP French job-exposure matrix to determine the likelihood of each patient’s exposure to pesticides. Using the PESTIPOP matrix, occupational groups were classified as agriculture, green spaces, woodwork, and public hygiene, with the possibility for placement into more than one group. For the study, the researchers considered pesticide exposure in four ways:

• Categorization of all probabilities of exposure

• Only exposing agricultural occupations

• Only high probability of exposure (> 75%), as defined by the PESTIPOP matrix generation

• High probability of exposure (> 75%) and high reliability, as defined by the PESTIPOP matrix generation.

Complete occupational data were available for 244 of 404 patients. Patients occupationally exposed to pesticides had a treatment failure rate of 22.4% compared with 11.3% for patients without exposure (P = .03). Multivariate analysis showed that occupational exposure to pesticides was independently associated with treatment failure for all occupational exposure compared with none (adjusted odds ratio [OR], 3.0). An even greater difference in treatment failure rate was seen in patients exposed to agriculture pesticides (29.0% vs 11.7%), with a greater independent risk for treatment failure (OR, 5.1) for agriculture exposure compared with others.

Whereas the 2-year event-free survival rate in patients without occupational pesticide exposure was 82%, this decreased to 70% for those with pesticide exposure (adjusted hazard ratio [HR], 2.2; 95% CI, 1.3–3.9). There was also a large difference in overall survival between patients occupationally exposed to pesticides compared with those who were not (81% vs 92%; HR, 3.9; 95% CI, 1.5–10.0).

“This study suggests for the first time, to our knowledge, a poorer prognosis for patients with DLBCL exposed to pesticides, concerning the response to treatment, 2-year event-free survival, and overall survival,” the researchers wrote. “These findings must be confirmed in further prospective studies.”