Addition of rituximab to cyclophosphamide, doxorubicin, vincristine, and prednisolone therapy has a high risk of developing interstitial pneumonia in patients with non-Hodgkin lymphoma.

There are a few reports suggesting that rituximab (RTX) might be a risk for interstitial pneumonitis (IP). We also experienced such patients in the era of RTX. Here, we reviewed all the patients with non-Hodgkin lymphoma who were treated with RTX-CHOP-like regimen (R-CHOP) to determine the risk of developing IP. One of 59 (1.7%) patients who received CHOP alone and 8 of 129 (6.2%) patients who were treated with R-CHOP experienced IP (p = 0.28). Furthermore, three of eight patients who have had IP during R-CHOP were confirmed having Pneumocystis jirovecii pneumonia (PCP). PCP occurred during the fourth, sixth, and seventh cycle of chemotherapy, respectively. Among the patients treated by R-CHOP, 3 of 32 (9%) patients whose lymphocyte counts were <1000/microL before chemotherapy developed PCP, while 70 patients whose lymphocyte counts were >1000/microL did not (p = 0.03). In four of eight patients, IP occurred during the administration of granulocyte-colony stimulating factor. RTX seems to have a certain risk to induce IP including PCP. Patients with lymphoma who were treated by R-CHOP regimen, might be considered as PCP prophylactic, especially if the number of lymphocytes is low at the beginning of chemotherapy.