Testing the Safety of M6620 (VX-970) When Given With Standard Whole Brain Radiation Therapy for the Treatment of Brain Metastases From Non-small Cell Lung Cancer, Small Cell Lung Cancer, or Neuroendocrine Tumors

This phase I trial studies the side effects and best dose of berzosertib (M6620 \[VX-970\]) when given together with whole brain radiation therapy in treating patients with non-small cell lung cancer, small cell lung cancer, or neuroendocrine tumors that have spread from the original (primary) tumor to the brain (brain metastases). Berzosertib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Radiation therapy uses high energy x-rays to kill tumor cells and shrink tumors. Giving berzosertib together with radiation therapy may work better compared to standard of care treatment, including brain surgery and radiation therapy, in treating patients with non-small cell lung cancer, small cell lung cancer, or neuroendocrine tumors.