I read with great interest the recent article by Roberts and colleagues [1]. Of concern was the marked lymphocytosis present in lavage fluid before irradiation, as well as the slightly elevated cell count. The patients had an increased total cell count (22.4 x 10⁶ cells with 61% macrophages, 34.5% lymphocytes, and 4% neutrophils). Such an increase in cellularity and prominent lymphocytosis represents a markedly abnormal baseline. In studies reviewed by the Bronchoalveolar Lavage Cooperative Group Steering Committee, total cell counts were generally less than 16 x 10⁶ cells in nonsmoking patients when the lavage volume was 150 mL. The percentage of lymphocytes in bronchoalveolar lavage fluid in normal persons is universally less than 20% (10% on average). In normal smokers, the total cell count is generally increased on the order of 30 to 50 x 10⁶ cells, with lymphocytes not expected to exceed 8% [2].

This finding suggests a baseline lymphocytic alveolitis before any radiotherapy that was apparently exacerbated by a course of unilateral thoracic irradiation.

Determining the cause of this baseline abnormality in these patients is essential before concluding anything about the true effect of unilateral thoracic radiation. These findings could be associated with methotrexate pneumonitis [3] or toxicity from another chemotherapeutic agent, or they could be secondary to extrinsic allergic alveolitis [4] related to a humidifier system or related to another antigen in the local environment. Studying bronchoalveolar lavage fluid obtained before chemotherapy, as well as screening the patients for hypersensitivity pneumonitis, would be helpful to clarify the underlying disorder.