International Journal of Radiation Oncology*Biology*Physics
3D-CRTEffects of radiotherapy and chemotherapy on lung function in patients with non–small-cell lung cancer☆
Introduction
Thoracic radiotherapy (RT) is associated with significant alterations in lung function as assessed by objective pulmonary function tests (PFTs) 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. The extent of residual lung function is a major determinant of a patient’s functional status after treatment. This is particularly true of patients with lung cancer who frequently have pretreatment pulmonary compromise secondary to both malignancy and coexisting lung disease. It is increasingly important to understand the relationship between thoracic RT and the decline in lung function in the setting of aggressive concurrent chemoradiation regimens. After RT alone, the decline in diffusion capacity has been reported to range from 10% to 34% (1). Greater declines in PFTs have been reported after combined therapy with chemotherapy and RT compared with RT alone 2, 6, 11, 12. Among combined modality regimens, concurrent chemoradiation is expected to be more toxic than sequential treatment.
Patients treated with thoracic RT are usually a heterogeneous group that has received different combinations of RT and chemotherapy. However, all the patients in our study were treated in one of five multi-institutional or in-house protocols. All treatments, therefore, fell into a small number of well-defined groups, with all patients within a group receiving the same treatment. This allowed a meaningful comparison of the effects of different combinations of RT and chemotherapy on indexes of lung function.
Section snippets
Patients
One hundred patients with non–small-cell lung cancer were treated in five protocols between 1992 and 2000 with combinations of thoracic RT and chemotherapy and had pre- and posttreatment PFTs. Four of the protocols were the multi-institutional Radiation Therapy Oncology Group (RTOG) 91-06 (7 patients), RTOG 92-04 (23 patients), RTOG 93-11 (19 patients), and RTOG 94-10 (28 patients) trials that evaluated different combinations of chemotherapy and RT and the effects of radiation dose escalation.
Obstruction
Great variation in FEV1/VC after treatment was observed. FEV1/VC decreased in 45 of 93 patients, increased in 46 patients, and was unchanged in 2 patients. The time after treatment had no significant effect on FEV1/VC. Table 3 shows the posttreatment FEV1/VC as a percentage of the pretreatment value in each treatment group. The differences were not statistically significant. No treatment, patient, or tumor factors were significantly associated with FEV1/VC changes. The significance of the
Changes in FEV1
Most previous studies have evaluated the effects of RT on FEV1. FEV1 is highly dependent on the VC. Hence, a low VC can result in a low FEV1 without any airway obstruction. The American Thoracic Society recommends using FEV1/VC as a measure of airway obstruction to account for abnormal VC (16). This is particularly important in evaluating lung function after RT. Lung volumes change after treatment, both because of fibrosis associated with radiation damage and because of reexpansion of a
Conclusion
Thoracic RT is associated with a significant reduction in DLCO. The addition of chemotherapy and, particularly, concurrent chemotherapy to RT exacerbates the decline in diffusion capacity 13, 14, 15, 33, 34, 35, 36.
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Presented at the 3rd Annual Meeting of the American Society for Therapeutic Radiology and Oncology, San Francisco, CA, November 4–7, 2001.