Comparison of the Effects of Aromatase Inhibitors and Tamoxifen on Radiation-induced Lung Toxicity: Results of an Experimental Study

Purpose: The purpose of this study is to compare the effects of anastrozole, letrozole and tamoxifen on radiation-induced pulmonary fibrosis.

Methods: Eighty female Wistar albino rats were divided into eight groups. Group (G) 1 was defined as control group. G2 was radiation therapy (RT) only group. Groups 3, 4 and 5 were tamoxifen, anastrozole and letrozole control groups respectively. Groups 6, 7 and 8 were RT plus tamoxifen, anastrozole and letrozole groups, respectively. A single dose of 12 Gy RT was given to both lungs. Tamoxifen, anastrozole and letrozole were started 1 week before the RT and continued until the animals were sacrificed 16 weeks after the RT. As an end point, the extent of pulmonary fibrosis for each rat was quantified with image analysis of histological sections of the lung. Kruskal-Wallis and Mann-Whitney U tests were used for statistical analyses.

Results: The congestion, inflammation and pulmonary fibrosis scores were significantly different between all the study groups (p values were <0.001 for each). When compared with RT only group, concomitant RT and tamoxifen group increased the radiation-induced pulmonary fibrosis (p = 0.005). However, using either anastrozole or letrozole with RT did not increase the radiation-induced pulmonary fibrosis (p values were 0.768 and 0.752, respectively).

Conclusion: Concomitant use of tamoxifen with RT seems to increase radiation-induced pulmonary toxicity. However, the use of both anastrozole and letrozole appears to be safe with concomitant RT, without increasing the risk of pulmonary fibrosis. This finding should be clarified with further clinical studies.