Does lapatinib increase pulmonary toxicity when concurrently used with radiation therapy? An experimental study with Wistar albino rats.

e11136 Background: Lapatinib (L) is an receptor tyrosine kinase inhibitor which has shown activity in the treatment of metastatic breast cancer. Adjuvant usage of L is being investigated in phase III trials. There is no data regarding toxicity of RT and L combination which may be a problem when L is used in adjuvant setting. Lung is the most radiosensitive organ to observe late effects of RT. We evaluated if concurrent L administration has any impact for the development of radiation induced pulmonary fibrosis in rats (RIPF). Methods: 40 female Wistar albino rats (WAR) were divided into 4 groups (G). G1 (control) did not receive any treatment. G2 received RT to whole thoracic region, G3 L without RT and G4 L with RT. A total dose of 30 Gy in 10 fractions was given to lungs with an anterior field at 2 cm depth. L equivalent to 1500 mg/day, 60 kg adult dose, were calculated according to the mean weight of rats, orally administrated with a feeding tube twice daily including the week-ends until WAR were sacrif...