Association between plasma angiotensin-converting enzyme level and radiation pneumonitis

Angiotensin-converting enzyme (ACE) plays an important role in pulmonary fibrosis and may be involved in the development of radiation-induced lung damage. The objective of this study was to evaluate the predictive value of plasma ACE in radiation pneumonitis (RP). Patients with stage I–III lung cancer were treated with radiotherapy with or without chemotherapy. ACE levels were measured using enzyme-linked immunosorbent assay before radiotherapy (pre-RT) and when a median dose of 45 Gy (Range: 40–48 Gy) was reached (during-RT). The primary end point was ⩾grade 2 RP. Statistic significances were evaluated with independent T-test and chi-square. Thirty-nine patients were enrolled in this study, among which 33.3% experienced ⩾grade 2 RP. ACE levels, either pre-RT or during-RT, were significantly lower in the RP group than in the non-RP group (P = 0.02 and 0.03, respectively). Nine out of the 19 patients (47.4%) with pre-RT ACE levels ⩽462 ng/mL experienced RP, versus 3 of 19 (15.8%) patients with ACE levels >462 ng/mL (P = 0.04). This study suggested that plasma ACE as a predictive factor for radiation pneumonitis deserves further study.