Abstract
ObjectiveTo evaluate the influence of target dose heterogeneity on normal tissue dose sparing for peripheral lung tumor stereotactic body radiation therapy (SBRT).MethodsBased on the volumetric-modulated arc therapy (VMAT) technique, three SBRT plans with homogeneous, moderate heterogeneous, and heterogeneous (HO, MHE, and HE) target doses were compared in 30 peripheral lung tumor patients. The prescription dose was 48 Gy in 4 fractions. Ten rings outside the PTV were created to limit normal tissue dosage and evaluate dose falloff.ResultsWhen MHE and HE plans were compared to HO plans, the conformity index of the PTV was increased by approximately 0.08. The median mean lung dose (MLD), V5, V10, V20 of whole lung, D2%, D1cc, D2cc of the rib, V30 of the rib, D2% and the maximum dose (Dmax) of the skin, and D2% and Dmax of most mediastinal organs at risk (OARs) and spinal cord were reduced by up to 4.51 Gy or 2.8%. Analogously, the median Dmax, D2% and mean dose of rings were reduced by 0.71 to 8.46 Gy; and the median R50% and D2cm were reduced by 2.1 to 2.3 and 7.4% to 8.0%, respectively. Between MHE and HE plans there was little to no difference in OARs dose and dose falloff beyond the target. Furthermore, the dose sparing of rib V30 and the mean dose of rings were negatively correlated with the rib and rings distance from tumor, respectively.ConclusionsFor peripheral lung tumor SBRT, target conformity, normal tissue dose, and dose falloff around the target could be improved by loosening or abandoning homogeneity. While there was negligible further dose benefit for the maximum target dose above 125% of the prescription, dose sparing of normal tissue derived from a heterogeneous target decreased as the distance from the tumor increased.
Highlights
IntroductionLung cancer remains the leading cause of cancer incidence and mortality [1]
Worldwide, lung cancer remains the leading cause of cancer incidence and mortality [1]
Patient eligibility A total of 30 patients, who were treated with stereotactic body radiation therapy (SBRT) at West China Hospital between April 2011 and March 2017 for peripheral lung cancer or pulmonary oligometastases, were enrolled
Summary
Lung cancer remains the leading cause of cancer incidence and mortality [1]. The lung is a common site of metastases for various other cancers. Radiotherapy is an alternative treatment method for inoperable patients. Local control of conventional fraction radiotherapy has historically been poor due to insufficient total radiation doses [2]. Wei et al Radiat Oncol (2021) 16:167 radiation therapy (SBRT) can very precisely deliver a high dose of radiation to an extracranial target, using either a single dose or a small number of fractions [3]. The clinical benefits of SBRT have been demonstrated by several prospective studies for both early-stage, non-small cell lung cancer (NSCLC) and pulmonary oligo-metastases [4,5,6]
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