# CyberKnife Staged Radiotherapy for Elderly Patients With Poorly Differentiated Lung Adenocarcinoma: A Case Report and Dosimetric Analysis

## TL;DR

An elderly patient with lung cancer and chronic health issues received staged CyberKnife radiotherapy, achieving significant tumor shrinkage with minimal side effects.

## Contribution

This case demonstrates the feasibility of staged CyberKnife SBRT for elderly patients with complex comorbidities.

## Key findings

- Staged radiotherapy reduced tumor volume by 79% with no severe toxicity.
- Dynamic dose optimization lowered ipsilateral lung V20 from 3.35% to 1.63%.
- The treatment achieved 120 Gy EQD2 while adhering to OAR constraints.

## Abstract

This case describes an 81-year-old male patient with poorly differentiated lung adenocarcinoma, complicated by severe chronic obstructive pulmonary disease (COPD) and a history of coronary stenting. The patient underwent CyberKnife (Accuray Inc., Madison, WI, United States) stereotactic body radiotherapy (SBRT) with synchrony respiratory tracking and staged radiotherapy. The patient received staged radiotherapy delivered in two sequential phases: phase I (30 Gy in three fractions) was administered from November 18 to 24, 2022, followed by phase II (30 Gy in three fractions) initiated on February 20, 2023, after a 12-week intermission for therapeutic response assessment and normal tissue recovery. The cumulative prescription totaled 60 Gy in six fractions (equivalent dose in 2-Gy fractions (EQD2) = 120 Gy, α/β = 10), with strict adherence to organ-at-risk (OAR) constraints. Through fiducial marker implantation and dynamic dose optimization, the ipsilateral lung V20 was reduced from 3.35% to 1.63%. No severe treatment-related toxicities (≥ grade 2) were observed during or after the treatment period. At a three-month follow-up, the tumor volume decreased by 79% (117.04 cm³ → 24.26 cm³), demonstrating significant local control. This case provides a practical reference for personalized radiotherapy in elderly patients with cardiopulmonary comorbidities.