Abnormalities by pulmonary regions studied with computer tomography and clinical correlation following local-regional radiotherapy for breast cancer

BACKGROUND: Adjuvant local-regional radiotherapy (RT) is commonly recommended for breast cancer patients. Postoperative adjuvant RT for breast cancer is associated with pulmonary side effects. This study was undertaken to measure the RT-induced pulmonary radiological changes with computer tomography (CT) scan using a CT-adapted modification of the Arriagada classification system, and to correlate these changes to RT techniques, pulmonary complications, and pulmonary function. The aim of the study is to study pulmonary radiological abnormalities with CT following different RT techniques for breast cancer, and their correlation to pulmonary complications and reduction in forced vital capacity (FVC). MATERIALS AND METHODS: CT scans of the lungs were performed prior to and 4 months following RT in 53 breast cancer patients treated with local-regional RT. The radiological abnormalities were analyzed with a CT-adapted modification of a classification system originally proposed by Arriagada. The patients were monitored for RT-induced pulmonary complications. FVC was measured prior to and 6 months following RT. Statistical analysis used were that increasing CT scores were correlated with pulmonary complications (P < 0.001). The correlation between density grade (0-3, 4-9) and pulmonary complications (no complication vs slight/severe) was tested using Chi-square exact test for trend (2-sided). In addition, correlation between CT scores and FVC was done. RESULTS: Increasing CT scores were correlated with pulmonary complications (P < 0.001). The mean reduction of FVC for patients scoring 4-9 (-220 ml) was larger than for patients scoring 0-3 (-15 ml) (Spearson correlation coefficient significant at 0.01 level 2 tailed). But the mean reduction of FVC with greater volume of lung irradiated was not statistically different than lesser volume of lung irradiated (P > 0.05). CONCLUSIONS: Radiological abnormalities detected on CT images and scored with a modification of Arriagada's classification system can be used as an objective endpoint for pulmonary side effects in postmastectomy RT.