e11599 Background: Although the efficacy of both radiation and tamoxifen (TAM) in early-stage breast cancer is well established, data are lacking about the impact of this sequence on outcomes, including local recurrence and complications of therapy. These are questions of practical importance in the treatment of breast cancer patients, many of whom require both radiation (RT) and adjuvant TAM. Methods: 160 eligible patients were prospectively randomized 1:1 into two groups: The control group (80 patients) , containing one arm (C) received sequential TAM and RT and the intervention group which was further subdivided into arm (A) (40 patients), received concurrent TAM 20 mg/day with RT, arm( B) (40 patients), received concurrent TAM + Pentoxifylline (PTX) ( 800 mg/day )+ Alpha-Tocopherol (AT) (1000 U/day) and RT. The primary endpoint was to compare the radiation induced pulmonary fibrosis using serial high resolution computed tomography (HRCT) and the role of the PTX and AT combination in reduction of pulmonary fibrosis, the secondary endpoint was to evaluate loco-regional control in the three arms usingChi-Square test, Fisher’s exact test, Log rank test andAnova test. Results: Analysis of the incidence of clinical pneumonitis was 25% in arm A ( TAM) , 12.5% in arm B (TAM+PTX+AT) and 18.8% in arm C (control) with p=.110. The incidence of lung fibrosis was 26.5% in arm A( TAM) , 12.9% in arm B (TAM+VIT.E) and 23.4% in arm C (Control) with p=.608. As regard loco-regional relapse, the preliminary result, revealed no significant difference in the 3 arms (1.3% in control arm, 5 % in TAM, 2.5% in TAM+VIT) (p=.827). Conclusions: It seems that the interaction between tamoxifen and radiotherapy could affect the tissue remodeling rather than the damage induction step of the radiation pathogenesis. In this case, temporal separation of the two modalities (Concurrent Versus Sequential) may not make much difference in the incidence of radiation induced lung fibrosis.

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