Direct-to-unit, single-visit, curative-intent online adaptive stereotactic ablative radiotherapy for early-stage lung adenocarcinoma.

Background: Advancements in cone beam computed tomography (CBCT)-guided radiotherapy (RT) platforms have created new frontiers in adaptive radiotherapy (ART). This report describes the novel application of single-fraction adaptive stereotactic body radiotherapy (SBRT) for a 66-year-old woman with lung adenocarcinoma for whom a conventional RT workflow was impractical due to advanced Parkinson's disease with uncontrolled tremors.

Case presentation: The patient presented with a 2.4 cm spiculated nodule in the left upper lobe (LUL) diagnosed as stage 1A3 lung adenocarcinoma. She declined surgery, and local radiation oncologists deemed SBRT unsafe due to her tremors. Our team proposed a direct-to-unit, single-visit SBRT treatment utilizing anesthesia for immobilization and the Ethos platform for online adaptation to day-of-treatment positioning. An initial treatment plan was generated offline using a diagnostic CT acquired near the patient's home. On the treatment day the patient was anesthetized and a custom foam mold created using a diagnostic CT was used for setup. An internal gross tumor volume (iGTV) was adjusted based on the CBCT of the treatment day. An adaptive plan improved target coverage by 5% without violating organ-at-risk constraints. The entire procedure from initial CBCT to treatment completion took 63 min. Post-treatment recalculations on a CBCT confirmed dosimetric accuracy.

Conclusions: This case illustrates the feasibility of direct-to-unit single-fraction CT-guided ART with high-quality CBCT imaging and anesthesia-facilitated immobilization. Our successful completion of this treatment establishes a procedure for future direct-to-unit ART in lung cancer, enhancing accessibility and reducing treatment time for a patient population for whom conventional RT is impractical.