ESTRO 2021 Abstract Book

S1242

ESTRO 2021

Figure 2. Forest plot of the pooled analysis of the prognostic value of grade 4 RIL on OS.

Conclusion This meta-analysis of 21 cohorts demonstrated a significant detrimental prognostic association between radiation-induced lymphopenia and overall survival in patients who undergo radiotherapy for solid tumors, with an increase of 65% in the risk of death over time in patients who experience grade ≥3 lymphopenia and of 50% in patients with grade 4 lymphopenia. These HR estimates were adjusted for other prognostic factors in the individual studies. The association appears consistent for tumors of the brain, thorax and upper abdomen, and provides an imperative to further elucidate the potential survival benefit of lymphopenia mitigating strategies. PO-1516 Prospective evaluation of robotic radiosurgery in Indian patients with oligo-metastases R. Kamath 1 , S. K 1 , A. Gupte 1 , Y. Sreenija 1 , P. K U 1 , A. R 1 , A. Sasidharan 2 , H. Nair 1 , A. E H 3 , D. Dutta 1 1 Amrita Institute of Medical Sciences, Radiation Oncology, Kochi, India; 2 Amrita Institute of Medical Sciences, Radiation oncology, Kochi, India; 3 Amrita Institute of Medical Sciences, Medical Physics, Kochi, India Purpose or Objective SRS in Brain Metastases and Stereotactic radiotherapy (SBRT) in extracranial oligomets is at present considered as a treatment option. Recent prospective studies in western patient population showed the improved local control & survival function with SRS and SBRT. The present prospective study is to evaluate the impact of SRS and SBRT in Indian oligo-metastasis patients. Materials and Methods Between May 2017 and February 2021, 179 patients with 167 brain metastases and 109 extra-cranial oligometastases were accrued prospectively and treated with robotic radiosurgery (CK) (M6, Multiplan, VOLO). Patients with small volume oligomets (<3 sites) with good PS (0-1) and controlled primary were accrued. Frameless sterotactic based immobilization was ensured with thermoplastic masks. Contrast CT simulation was done with 0.625 mm slices and fused with T1 contrast/T2 Flair MRI images for contouring done for brain mets. PTV margin of 2-3 mm and a dose of 20-30Gy in 1-5 fractions was decided based on the treatment volume. In extra-cranial mets, immobilization with vacloc used and CT scan with contrast done as per protocol. Response to treatment, new lesion free survival, overall survival and toxicity profile after CK was evaluated. Results Between 2017 - 2020, 179 patients with 276 oligomets (167 brain lesion, 109 extra-cranial site) were treated with CK. In extra-cranial mets, 15 were bone mets, 13 lymphnode mets, 11 liver mets, 3 choroidal mets and 1