Inclusion Criteria:

          -  Histologically or cytologically confirmed non-small cell lung cancer (NSCLC) with any
             actionable mutation or translocation in EGFR, ALK, or ROS1

          -  Stage IV disease (AJCC Staging system 7th edition)

          -  Within 6 months of initiating their first TKI treatment regimen

          -  Stable or responding systemic disease to TKI (no evidence of progression) on the most
             recent staging studies. The complete extent of the current residual systemic disease
             must be deemed amenable to SBRT as per review of imaging studies by a radiation
             oncologist, based on the following criteria:

               -  Lung: 1-3 lesions (including the primary) of maximum size 5 cm in longest
                  diameter. A minimum size 1 cm in the longest diameter is recommended. (Patients
                  with a malignant pleural effusion prior to the start of TKI therapy will be
                  considered eligible for SBRT if there is complete radiographic resolution of the
                  effusion while on systemic therapy);

               -  Spine: Bone lesions must be limited to the spine. A maximum of 2 spinal
                  metastases will be considered for SBRT, with each site spanning 1-3 vertebral
                  bodies. A minimum size of 1 cm in longest diameter is recommended. SBRT may
                  target sclerotic lesions that persist following TKI therapy;

               -  GI: 1-4 liver metastases of maximum size 5 cm in longest diameter and/or 1-2
                  adrenal metastases of maximum 4 cm size in longest diameter. A minimum size of 1
                  cm in longest diameter is recommended.

        In addition:

          -  CNS: 1-4 brain metastases of maximum size 3cm in longest diameter. However, these
             should be treated with standard-of-care SRS and will not be defined as target lesions
             for purposes of this protocol.

          -  A maximum number of 5 target lesions outside the brain, excluding the lung primary, is
             recommended to ensure that enrollment is limited to patients with low-burden disease
             and that treatments can be delivered within the specified time frame.

               -  History of prior radiation therapy to brain or skeleton is allowed, but should
                  have occurred > 2 months from enrollment.

               -  Age at least 18 years.

               -  Life expectancy of greater than 6 months.

               -  ECOG performance status ≤ 2.

               -  Women of child-bearing potential and men must agree to use adequate contraception
                  (hormonal or barrier method of birth control; abstinence) prior to study entry
                  and for the duration of study participation. Should a woman become pregnant or
                  suspect she is pregnant while participating in this study, she should inform her
                  treating physician immediately. A negative serum or urine pregnancy test within 2
                  weeks of registration for women of childbearing potential is required.

               -  Ability to understand and the willingness to sign a written informed consent
                  document.

        Exclusion Criteria:

          -  Residual hilar or mediastinal lymph node disease (size > 1cm in short-axis diameter on
             CT). Non-malignant etiologies for enlarged lymph nodes may be evaluated per standard
             clinical practice.

          -  Participants who have received prior radiation therapy to anatomical sites other than
             brain or skeleton.

          -  Uncontrolled intercurrent illness including, but not limited to ongoing or active
             infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
             arrhythmia, or psychiatric illness/social situations that would limit compliance with
             study requirements.

          -  Patients who are pacemaker or defibrillator-dependent as these devices may not be
             operated concurrently with delivery of proton beam radiation.

          -  Pregnant or lactating women, as treatment involves unforeseeable risks to the embryo
             or fetus.