Adrenal metastasis is a common site of metastasis in small cell lung cancers. CyberKnife robotic stereotactic radiosurgery is a minimally invasive tumor treatment modality that can deliver high precision radiotherapy to the adrenals with minimal exposure of surrounding vital organs. Appropriate motion management technique using implanted gold fiducial as a surrogate tracking marker for respiratory movements should be incorporated to target the adrenal lesions. The Objective of this study was to investigate the accuracy and efficacy of CyberKnife in the treatment of adrenal metastasis from small cell lung tumors with usage of body-compatible gold seed fiducial tracking.
21 patients with adrenal metastasis from small cell lung cancers who were treated with CyberKnife at Healthcare global hospital, India, between March 2010 and March 2017 were considered. Average tumor volume was 68.8 cm3 and total number of lesions were 35 with 3 patients having bilateral adrenal metastasis. Prescribed radiation dosage ranged from 30-45 Gy over of 3 to 7 fractions with a prescription isodose of 70% to 87%. There were a minimum of three gold fiducials implanted under ultrasound guidance around the adrenals for tumor tracking. PET-CT Scan was performed at 3 monthly intervals to evaluate response to therapy.
Median follow-up time was 27 months. No patient experienced local relapse during the evaluation period but there were 4 patients who progressed in other sites (3 patients in brain,1 patient with bone and liver). The actuarial local adrenal metastasis control rate was 100% after one year and two years. Dynamic fiducial based tumor tracking enabled accurate treatment with correlation errors less than 3 mm, despite extensive respiration-induced target motion of an average of up to 35 mm. Apart from nausea directly after treatment in 6 patients, there were no early or late side effects.
In the era of precision medicine, motion management is absolutely necessary to target the lesions accurately, tracking with tumor implanted gold fiducials using CyberKnife is highly effective with excellent local control for adrenal metastasis orginating from small cell lung cancers.
Clinical trial identification
Legal entity responsible for the study
Dr. G. Lohith.
Has not received any funding.
All authors have declared no conflicts of interest.