is pulmonary function test insensitive to possible pulmonary complications after tangential radiotherapy of breast cancer?

background: pulmonary complications of radiation to breast are inevitable, while its incidence and severity are not clear. one of the methods to assess pulmonary complications is spirometry. the influence of radiotherapy on pulmonary function test and the factors affecting it have been assessed in this study. methods: breast cancer patients with stage ii and iii (based on tnm staging), underwent six courses of chemotherapy, and the total mastectomy was included in this study. smokers, chronic pulmonary patients, cardiac patients, and those who suffered from anatomic chest malformations were excluded. sample size was 75 and data collection was conducted by the spirometer device. the total tumor dose varied between 4800 to 5040 cgy with fraction of 180 or 200 cgy. spirometry was performed before and 3 months after radiotherapy; the patients were examined at the same time by a specialist for respiratory complications. the measured parameters were fev 1(forced expiratory volume in 1 second) and fvc (forced vital capacity) which were normalized by age and sex. results: the average age of the patients was 45.6±7.92 .average length and widths of tangential fields were determined 18.2±1.8 and 6.7±1.37 respectively. average central lung distance was measured 2 ±1.07 cm. the mean of fev1% prior to and following radiotherapy was measured 74.9 ±15.59 and 78.86±12.55 respectively (p=0.09).the mean of fvc% before and after radiation treatment was measured 72.17±14.26 and 74.6±11.36 (p=0.07).  no abnormal signs were observed in the patients after radiotherapy. conclusion: it seems that three months is a short period for appearance of pulmonary changes after radiotherapy with cobalt machine. moreover, minimizing cld through planning might lower the probability of pneumonitis due to radiation. keywords: tangential radiotherapy; 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