Background and purpose: This study was performed to investigate whether the tamoxifen (TAM) induced the development of pulmonary fibrosis after post-mastectomy cobalt-60 (Co-60) irradiation of chest wall and regional lymphatics in patients with breast cancer along with patient age, menopausal status, body weight, observation time and adjuvant chemotherapy regimens.
Materials and methods: In this prospective study, 74 patients treated with post-mastectomy adjuvant radiotherapy (RT) and TAM and 37 patients treated with RT were evaluated by axial computerized tomography (CT). CT was first performed before initiation of radiotherapy and TAM treatment. A total of 824 thorax CT sections were evaluated by a radiologist blindly. Comparison of pre-treatment and post-treatment CT sections was used to monitor the development of pulmonary fibrosis.
Results: Pulmonary fibrosis developed in 26 of 74 patients who were treated with RT and TAM combination. It was found in five of 37 women treated only with RT. The difference was statistically significant (P<0.01). The median time for the development of pulmonary fibrosis was 8 months in TAM-treated patients whereas it was 10 months in non-TAM-treated patients. Among 111 patients who participated in that study, 65 were in the post-menopausal state and 46 in pre-menopausal state. In the multivariate analysis, the independent prognostic factors were age (P=0.010) and menopausal status (P=0.019). Advanced age and post-menopausal status predisposed to pulmonary fibrosis. The time interval in the development of lung fibrosis and body weight did not significantly influence the results. The time interval which is one independent prognostic factor was found to be associated with lung fibrosis under only-RT group in multivariate analysis (P<0.01).
Conclusion: TAM treatment during post-mastectomy RT in breast cancer patients significantly increases the risk of the development of lung fibrosis along with the patient age and menopausal status.