Diagnosis and treatment options including stereotactic body radiation therapy (SBRT) for adrenal metastases

Abstract

Adrenal metastasis is common in oncology but patients with this diagnosis are usually asymptomatic. The diagnosis can be challenging and delayed. Incidence, presenting symptoms and diagnostic modalities are reviewed. Various treatment options are also discussed, including open and laparoscopic surgery, local ablation (radiofrequency ablation, cryoablation, microwave thermal ablation, and chemical ablation) as well as radiation therapy. These treatment modalities were compared and contrasted in regards to their invasiveness, risks, side effects, outcomes, and patients' tolerance. Radiotherapy including stereotactic body radiation therapy (SBRT) is the only non-invasive approach, which is important as majority of the patients with adrenal metastases also receive systemic therapy, e.g., chemotherapy. The initial goal of conventional radiotherapy for metastatic adrenal lesion is for palliation which has been shown to be effective. With the advent of technological advances in radiation oncology, e.g., imageguidance during radiation delivery, patient immobilization and patient re-positioning, tumor motion management, sophisticated treatment planning allowing rapid dose fall-off, accurate QA, etc., the clinical implementation of SBRT has been very successful. SBRT is defined as a "treatment method to deliver high dose of radiation to the target, utilizing either a single dose or a small number of fractions with a high degree of precision within the body". Adrenal metastasis, an example of oligometastases even from radioresistant primary, could be successfully treated with SBRT without significant toxicity as evidenced by various recently reported clinical trials. An additional advantage could be adrenal function preservation when compared to surgical intervention. The optimal total dose and fractionation scheme are yet to be determined. SBRT is an emerging non-invasive, safe, and effective treatment modality, and further research is warranted to define its role in the management of adrenal metastasis.

Motion Management in Stereotactic Body Radiotherapy

“…Stereotactic body radiation therapy (SBRT), however, is much more complicated due to motion of targets and normal tissues. SBRT is used in the treatment of a wide range of tumor sites, including lung [1], liver [2], pancreas [3], prostate [4], spine [5], head-and-neck [6] and some other sites [7][8][9][10][11][12]. A variety of techniques have been reported to address this issue; these techniques for improvement of accuracy and precision can be classified into two broad categories: immobilization and motion reduction techniques, and image guidance.…”