Single-institutional outcome-analysis of low-dose stereotactic body radiation therapy (SBRT) of adrenal gland metastases

Multi-institutional experience of MR-guided stereotactic body radiation therapy for adrenal gland metastases

Purpose

While dose escalation is associated with improved local control (LC) for adrenal gland metastases (AGMs), the proximity of gastrointestinal (GI) organs-at-risk (OARs) limits the dose that can be safely prescribed via CT-based stereotactic body radiation therapy (SBRT). The advantages of magnetic resonance-guided SBRT (MRgSBRT), including tumor tracking and online plan adaptation, facilitate safe dose escalation.

Methods

This is a multi-institutional review of 57 consecutive patients who received MRgSBRT on a 0.35-T MR linac to 61 AGMs from 2019 to 2021. The Kaplan-Meier method was used to estimate overall survival (OS), progression-free survival (PFS), and LC, and the Cox proportional hazards model was utilized for univariate analysis (UVA).

Results

Median follow up from MRgSBRT was 16.4 months (range [R]: 1.1-39 months). Median age was 67 years (R: 28-84 years). Primary histologies included non-small cell lung cancer (N = 38), renal cell carcinoma (N = 6), and melanoma (N = 5), amongst others. The median maximum diameter was 2.7 cm (R: 0.6-7.6 cm), and most AGMs were left-sided (N = 32). The median dose was 50 Gy (R: 30-60 Gy) in 5-10 fractions with a median BED10 of 100 Gy (R: 48-132 Gy). 45 cases (74 %) required adaptation for at least 1 fraction (median: 4 fractions, R: 0-10). Left-sided AGMs required adaptation in at least 1 fraction more frequently than right-sided AGMs (88 % vs 59 %, p = 0.018). There were 3 cases of reirradiation, including 60 Gy in 10 fractions (N = 1) and 40 Gy in 5 fractions (N = 2). One-year LC, PFS, and OS were 92 %, 52 %, and 78 %, respectively. On UVA, melanoma histology predicted for inferior 1-year LC (80 % vs 93 %, p = 0.012). There were no instances of grade 3+ toxicity.

Conclusions

We demonstrate that MRgSBRT achieves favorable early LC and no grade 3 + toxicity despite prescribing a median BED10 of 100 Gy to targets near GI OARs.

Radiation of bilateral adrenal metastases is associated with a high risk of primary adrenal insufficiency

BACKGROUND

Adrenal metastasis is the most common adrenal malignancy and can be bilateral in up to 43% of patients. Radiotherapy (RT) is one option available to treat adrenal metastases. The risk of primary adrenal insufficiency (PAI) after adrenal RT is unclear.

OBJECTIVE

Determine the incidence and the timeline of PAI in patients undergoing adrenal RT.

DESIGN, SETTING AND PARTICIPANTS

Single-centre longitudinal retrospective cohort study of adult patients with adrenal metastases treated with RT between 2010 and 2021.

RESULTS

Of 56 patients with adrenal metastases treated with adrenal RT, eight (14.3%) patients developed PAI at a median of 6.1 months (interquartile range [IQR]: 3.9-13.8) after RT All patients developing PAI had either unilateral RT in the setting of contralateral adrenalectomy or bilateral adrenal RT. Patients who developed PAI received a median RT dose of 50 Gy (IQR: 44-50 Gy), administered in a median of five fractions (IQR: 5-6). Treated metastases decreased in size and/or metabolic activity on positron emission tomography in seven patients (87.5%). Patients were initiated on hydrocortisone (median daily dose of 20 mg, IQR: 18-40) and fludrocortisone (median daily dose of 0.05 mg, IQR: 0.05-0.05 mg). At the end of the study period, five patients died, all due to extra-adrenal malignancy, at a median time of 19.7 months (IQR: 16-21.1 months) since RT and median time of 7.7 months (IQR: 2.9-12.5 months) since the diagnosis of PAI.

CONCLUSION

Patients receiving unilateral adrenal RT with two intact adrenal glands have a low risk of PAI. Patients receiving bilateral adrenal RT have a high risk of PAI and require close monitoring.

Radiation Therapy in the Management of Adrenal Metastases

Adrenal glands represent a common site of metastases from several primary tumors, including lung cancer, breast cancer and melanoma. Surgical resection is considered the standard of care, but surgery is not always feasible given the challenges related to anatomical site and/or due to patient and/or disease characteristics. Stereotactic body radiation therapy (SBRT) represents a promising treatment for oligometastases, though the literature on its role for adrenal metastases is still heterogeneous. Herein are summarized the most relevant published studies on the efficacy and safety of SBRT for adrenal gland metastases. The preliminary data suggests that SBRT yields high local control rates and symptom relief with a mild pattern of toxicity. Advanced radiotherapy techniques including IMRT and VMAT, a BED10 > 72 Gy and the use of 4DCT for motion control should be considered for a high quality ablative treatment of adrenal gland metastases.

The efficacy and outcomes of stereotactic body radiotherapy in adrenal gland metastases

Aim

This retrospective study presents our single-institutional experience with stereotactic body radiotherapy for adrenal gland metastases.

Materials and Methods

We evaluated patients with adrenal metastases treated by stereotactic body radiotherapy (SBRT) from 2014 to 2020. We performed an analysis of 35 patients. The median age of the patients was 62.2. Dosimetric parameters and treatment outcomes were evaluated.

Results

The primary diagnosis of the majority of patients was non-small cell lung cancer (94.3%). Treatment was performed in a median of 3 fractions, and the median prescribed dose was 24 Gy (range 22,5-27). The median follow-up was 17 months. Treatment response according to Response Evaluation Criteria in Solid Tumours was categorized as complete response in 11 patients, partial response in nine patients, stable disease in 7, and progressive disease in eight patients. Twenty seven patients had oligometastatic disease and treatment response. Patients with oligometastatic disease had a significantly higher rate of complete response and partial response to treatment than patients with common disease (P = 0,011). The 6-month and 1-year local control rates were 68.4% and 43%, respectively. In general, SBRT was well tolerated and no acute toxicities were observed.

Conclusion

Our retrospective study shows that SBRT can be applied safely in adrenal metastases with good results especially in patients with oligometastatic disease.

Two-institution results of Stereotactic Body Radiation Therapy (SBRT) for treating adrenal gland metastases from liver cancer

OBJECTIVE

Stereotactic Body Radiation Therapy (SBRT) has been found beneficial for adrenal gland metastases (AGMs) with a high local control rate and low toxicity. The role of SBRT for AGMs in patients with liver cancer has not been well-discussed before. We, therefore, report our two-institution experience to further elaborate on the feasibility and effectiveness of SBRT in the treatment of AGMs from liver cancer.

METHODS

A total of 23 liver cancer patients (19 males, 4 females) with 24 AGMs treated by SBRT from July 2006 to April 2021 were retrospectively included in this study. Toxicity was assessed based on clinical adverse events using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. The effectiveness was assessed based on local control (LC), progression-free survival (PFS), and overall survival (OS), which were calculated using the Kaplan-Meier method. Univariate analyses were compared by log-rank test. The relevant covariates were evaluated using Cox proportional hazards models.

RESULTS

The median dose was 40 Gy in 5 fractions, with the corresponding median biological effective dose (BED10, α/β = 10 Gy) of 72 Gy. The median overall follow-up time was 15.4 months (range: 4.2-70.6 months). The complete response (CR), partial response (PR), stable disease (SD) and progressive disease (PD) rates were 25.0%, 20.8%, 33.3%, and 20.8%, respectively. All 6 patients with AGMs accompanying symptoms had varying degrees of alleviation after SBRT. The 0.5-, 1-year and 2-year LC rates were 87.5%, 77.8%, and 77.8%, respectively. The 0.5-, 1-year and 2-year OS rates were 95.5%, 66.8%, and 41.1%, respectively. The treatments were all tolerated with only one patient reporting a grade-3 hepatic injury. The univariate analysis concluded that only gross tumor volume (GTV) < 34.5 ml (p = 0.039) was associated with a favorable LC rate. After multivariate analysis, favorable predictors correlated with OS were GTV < 34.5 ml (p = 0.043), systemic therapy (p = 0.017), and without additional organ metastasis after SBRT (p = 0.009).

CONCLUSION

Our results suggest that SBRT is a safe and effective technique to treat AGM from liver cancer, especially for small GTV (< 34.5ml). Moreover, the small metastatic lesion volume, fewer metastatic lesions, and intervention of systemic therapy are more likely to improve OS.

Planning issues on linac-based stereotactic radiotherapy

This work aims to summarize and evaluate the current planning progress based on the linear accelerator in stereotactic radiotherapy (SRT). The specific techniques include 3-dimensional conformal radiotherapy, dynamic conformal arc therapy, intensity-modulated radiotherapy, and volumetric-modulated arc therapy (VMAT). They are all designed to deliver higher doses to the target volume while reducing damage to normal tissues; among them, VMAT shows better prospects for application. This paper reviews and summarizes several issues on the planning of SRT to provide a reference for clinical application.

Stereotactic radiotherapy for adrenal oligometastases

Approximately 50% of melanomas, 30–40% of lung and breast cancers and 10–20% of renal and gastrointestinal tumors metastasize to the adrenal gland.

Metastatic adrenal involvement is diagnosed by computed tomography (CT ) with contrast medium, ultrasound (which does not explore the left adrenal gland well), magnetic resonance imaging (MRI) with contrast medium and 18F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸FDGPET-CT ) which also evaluates lesion uptake. The simulation CT should be performed with contrast medium; an oral bolus of contrast medium is useful, given adrenal gland proximity to the duodenum. The simulation CT may be merged with PET-CT images with ¹⁸FDG in order to evaluate uptaking areas. In contouring, the radiologically visible and/or uptaking lesion provides the gross tumor volume (GTV ). Appropriate techniques are needed to overcome target motion. Single fraction stereotactic radiotherapy (SRT ) with median doses of 16–23 Gy is rarely used. More common are doses of 25–48 Gy in 3–10 fractions although 3 or 5 fractions are preferred. Local control at 1 and 2 years ranges from 44 to 100% and from 27 to 100%, respectively. The local control rate is as high as 90%, remaining stable during follow-up when BED_10Gy is equal to or greater than 100 Gy. SRT-related toxicity is mild, consisting mainly of gastrointestinal disorders, local pain and fatigue. Adrenal insufficiency is rare.

Dosimetric comparison of mDCAT and VMAT techniques according to 6MV-FFF and 10MV-FFF energies in patients with single adrenal metastasis

OBJECTIVE

To compare dosimetric and radiobiological terms of modified dynamic conformal arc therapy (mDCAT) and volumetric modulated arc therapy (VMAT) techniques using different flattening-filter free (FFF) energies in patients with single adrenal metastasis.

METHODS

In this study, plans were prepared for 10 patients drawing on the mDCAT and VMAT techniques with 6MV-FFF and 10MV-FFF energies. Target volume doses, biological effective doses (BED), quality indices, Monitor Unit (MU), number of segments, beam-on time and critical organ doses were compared in the plans.

RESULTS

Plans with the significantly lower gradient index (GI) and conformity index (CI) values were obtained with 6MV-FFF energy VMAT planning (p < 0.05). The higher values were obtained for dose to 95% of internal target volume (ITVD95), ITVD95-BED10 with 10MV-FFF energy VMAT planning, whereas lower results were obtained for high dose spillage (HDS%) values (p < 0,05). With 10MV-FFF energy, HDS% values were 21.1% lower in VMAT plans and 5.6% lower in mDCAT plans compared to 6MV-FFF energy. Plans with approximately 50% fewer segments were obtained in mDCAT plans than VMAT plans (p < 0,05). Beam-on time values with mDCAT was 1.84 times lower when 6MV-FFF energies were analyzed, and 2.11 times lower when 10MV-FFF was analyzed (p < 0,05). Additionally, when 6MV-FFF and 10MV-FFF energies were examined, MU values with mDCAT were 2.1 and 2.5 times lower (p < 0,05). In general, the smaller the target volume size, the greater the differences between MU and beam-on time values mDCAT and VMAT.

CONCLUSIONS

The study results implied that VMAT enabled to offer significantly more conformal SBRT plans with steeper dose fall-off beyond the target volume for single adrenal metastasis than the mDCAT, which attained at the cost of significantly higher MU and beam-on times. Especially with 10MV-FFF energy mDCAT plans, low-dose-bath zones can be reduced, and shorter-term treatments can be implemented with large segments. In adrenal gland SBRT, higher effective doses can be achieved with the right energy and technique, critical organ doses can be reduced, thus increasing the possibility of local control of the tumor with low toxicity.

Risk assessment, diagnosis, and treatment of cancer treatment-related adrenal insufficiency

INTRODUCTION

Adrenal insufficiency (AI) is an easily treatable, potentially life-threatening condition, which is increasingly recognized in malignancy. The recent introduction of immune checkpoint inhibitors, in particular, and increasing use of tyrosine kinase inhibitors have increased the frequency of AI in patients with malignancy. A review is therefore warranted to summarize current knowledge on the topic and guide safe clinical practices.

AREAS COVERED

Malignancy may directly impact the hypothalamic-pituitary-adrenal axis and cause AI, or their treatment including surgery, radiotherapy and medication. In this narrative review, we discuss new causes of AI, recognition of suggestive clinical features, diagnosis and subsequent treatment, aiming to avoid potentially fatal adrenal crisis (AC). Standard literature searching and authors assessment of clinical applicability were used.

EXPERT OPINION

Adrenal insufficiency can be easily treated once identified but life threatening if unrecognized. While use of new agents such as immune checkpoint inhibitors (ICIs) is increasing, greater understanding of the mechanism of AI is needed to target prediction tools and enhance risk stratification.

Stereotactic body radiation therapy (SBRT) for patients with oligometastatic/oligoprogressive adrenal metastases: Outcomes and toxicities profile in a monoinstitutional study

AIMS

To evaluate survival outcomes and toxicology profiles in oligometastatic/oligoprogressive patients treated with SBRT for adrenal metastases.

METHODS

We retrospectively analyzed 25 metastatic adrenal lesions in 24 oligometastatic/oligoprogressive patients undergoing ablative Stereotactic Body Radiation Therapy (SBRT) between February 2010 and November 2019 in our department. The primary endpoint was overall survival (OS). Secondary endpoints were local overall response rate (ORR), acute and late toxicities.

RESULTS

The most common primary tumor was non-small cell lung cancer (54%). Twenty-one patients received chemo or immuno-therapy. The median planning target volume (PTV) was 41.7 cm³. Median SBRT dose was 36 Gy. Median dose per fraction was 15 Gy. Median survival was 35-months with OS outcomes ranging from 6-months (100%), 1-year (87.5%) and 2-years (66.7%). ORR based on RECIST criteria was 66.5%. 12 patients experienced acute toxicities, mostly grade 1-2 (8 patients, 32%).

CONCLUSIONS

SBRT for oligometastatic/oligoprogressive patients with adrenal metastases showed acceptable survival outcomes and a safe toxicity profile.

How to handle oligometastatic disease in nonsmall cell lung cancer

Patients with nonsmall cell lung cancer and limited metastatic disease have been defined as oligometastatic if local ablative therapy of all lesions is amenable. Evidence from different clinical retrospective series suggests that this subgroup harbours better prognosis than other stage IV patients. However, most reports have included patients with inconsistent numbers of metastases in different locations treated by a variety of invasive and noninvasive therapies. As long as further results from randomised clinical trials are awaited, treatment decision follows an interdisciplinary debate in each individual case. Surgery and radiotherapy should capture a dominant role in the treatment course offering the option of a curative-intended local therapy in combination with a systemic therapy based on an interdisciplinary decision. This review summarises the current treatment standard in oligometastatic lung cancer with focus on an ablative therapy for both lung primary and distant metastases in prognostically favourable locations.