Stereotactic body proton therapy for non-small cell lung cancer: Clinical indications and recommendations

Stereotactic body radiation therapy (SBRT) has emerged as a standard treatment approach for early-stage lung cancer and intrathoracic oligometastatic or oligoprogressive disease. While local control is often excellent with this modality when delivered with photon therapy, toxicities for select patients can be significant. Proton therapy offers a unique opportunity to widen the therapeutic window when treating patients with thoracic malignancies requiring or benefitting from ultra-high doses per fraction. Thoracic proton SBRT may be particularly beneficial in cases requiring dose escalation, for tumors >5 cm, for central or ultra-central tumors, for reirradiation, in patients with interstitial lung diseases, and when combining radiation with immunotherapy. These clinical indications are detailed, along with supporting literature and clinical recommendations. Other considerations, future directions and potential benefits of proton SBRT, including sparing lymphocytes, when delivered as intensity-modulated proton therapy or as FLASH, and for the treatment of locally advanced non-small cell lung cancer or in patients with homologous recombination repair deficiencies, are also discussed.