Emphasis on Repair, Not Just Avoidance of Injury, Facilitates Prudent Stereotactic Ablative Radiotherapy

Radiotherapy in the management of lung oligometastases

In recent years, the development of both medical imaging and new systemic agents (targeted therapy and immunotherapy) have revolutionized the field of oncology, leading to a new entity: oligometastatic disease. Adding local treatment of oligometastases to systemic treatment could lead to prolonged survival with no significant impact on quality of life. Given the high prevalence of lung oligometastases and the new systemic agents coming with increased pulmonary toxicity, this article provides a comprehensive review of the current state-of-art for radiotherapy of lung oligometastases. After reviewing pretreatment workup, the authors define several radiotherapy regimen based on the localization and size of the oligometastases. A comment on the synergistic combination of medical treatment and radiotherapy is also made, projecting on future steps in this specific clinical setting.

Obtaining organ-specific radiobiological parameters from clinical data for radiation therapy planning of head and neck cancers

Objective.Different radiation therapy (RT) strategies, e.g. conventional fractionation RT (CFRT), hypofractionation RT (HFRT), stereotactic body RT (SBRT), adaptive RT, and re-irradiation are often used to treat head and neck (HN) cancers. Combining and/or comparing these strategies requires calculating biological effective dose (BED). The purpose of this study is to develop a practical process to estimate organ-specific radiobiologic model parameters that may be used for BED calculations in individualized RT planning for HN cancers.Approach.Clinical dose constraint data for CFRT, HFRT and SBRT for 5 organs at risk (OARs) namely spinal cord, brainstem, brachial plexus, optic pathway, and esophagus obtained from literature were analyzed. These clinical data correspond to a particular endpoint. The linear-quadratic (LQ) and linear-quadratic-linear (LQ-L) models were used to fit these clinical data and extract relevant model parameters (alpha/beta ratio, gamma/alpha,dTand BED) from the iso-effective curve. The dose constraints in terms of equivalent physical dose in 2 Gy-fraction (EQD2) were calculated using the obtained parameters.Main results.The LQ-L and LQ models fitted clinical data well from the CFRT to SBRT with the LQ-L representing a better fit for most of the OARs. The alpha/beta values for LQ-L (LQ) were found to be 2.72 (2.11) Gy, 0.55 (0.30) Gy, 2.82 (2.90) Gy, 6.57 (3.86) Gy, 5.38 (4.71) Gy, and the dose constraint EQD2 were 55.91 (54.90) Gy, 57.35 (56.79) Gy, 57.54 (56.35) Gy, 60.13 (59.72) Gy and 65.66 (64.50) Gy for spinal cord, optic pathway, brainstem, brachial plexus, and esophagus, respectively. Additional two LQ-L parametersdTwere 5.24 Gy, 5.09 Gy, 7.00 Gy, 5.23 Gy, and 6.16 Gy, and gamma/alpha were 7.91, 34.02, 8.67, 5.62 and 4.95.Significance.A practical process was developed to extract organ-specific radiobiological model parameters from clinical data. The obtained parameters can be used for biologically based radiation planning such as calculating dose constraints of different fractionation regimens.

Risk of Myelopathy Following Second Local Treatment after Initial Irradiation of Spine Metastasis

Metastatic lesions of the spine occur in up to 40% of cancer patients and are a frequent source of pain and neurologic deficit due to cord compression. Palliative radiotherapy is the main first-intent local treatment in the form of single-fraction radiotherapy or fractionated courses. Reirradiation is a viable option for inoperable patients where spinal decompression is needed but with an increased risk of radiation-induced myelopathy (RM) and subsequent neurologic damage. This review summarizes reported data on local treatment options after initial irradiation in patients with relapsed spine metastasis and key dosimetric correlations between the risk of spinal cord injury and reirradiation technique, total dose, and time between treatments. The Linear Quadratic (LQ) model was used to convert all the published doses into biologically effective doses and normalize them to EQD2. For 3D radiotherapy, authors used cumulative doses from 55.2 Gy2/2 to 65.5 Gy2/2 EQD2 with no cases of RM mentioned. We found little evidence of RM after SBRT in the papers that met our criteria of inclusion, usually at the median reported dose to critical neural tissue around 93.5 Gy2/2. There is a lack of consistency in reporting the spinal cord dose, which leads to difficulty in pooling data.

Single and multi-fraction spine stereotactic body radiation therapy and the risk of radiation induced myelopathy

Purpose

This study reports on the risk of radiation-induced myelitis (RM) of the spinal cord from a large single-institutional experience with 1 to 5 fraction stereotactic body radiation therapy (SBRT) to the spine.

Methods and Materials

A retrospective review of patients who received spine SBRT to a radiation naïve level at or above the conus medullaris between 2007 and 2019 was performed. Local failure determination was based on SPIne response assessment in Neuro-Oncology criteria. RM was defined as neurologic symptoms consistent with the segment of cord irradiated in the absence of neoplastic disease recurrence and graded by Common Toxicity Criteria for Adverse Events, version 4.0. Rates of adverse events were estimated and dose-volume statistics from delivered treatment plans were extracted for the planning target volumes and spinal cord.

Results

A total of 353 lesions in 277 patients were identified that met the specified criteria, for which 270, 70, and 13 lesions received 1-, 3-, and 5-fraction treatments, respectively, with a median follow-up of 46 months (95% confidence interval [CI], 41-52 months) for all surviving patients. The median overall survival was 33.0 months (95% CI, 29-43). The median D0.03cc to the spinal cord was 11.7 Gy (interquartile range [IQR], 10.5-12.4), 16.7 Gy (IQR, 12.8-20.6), and 26.0 Gy (IQR, 24.1-28.1), for 1-, 3-, 5-fractions. Using an a/b = 2Gy for the spinal cord, the median single-fraction equivalent-dose (SFED₂) was 11.7 Gy (IQR, 10.2-12.5 Gy) and the normalized biological equivalent dose (nBED_2/2) was 19.9 Gy (IQR, 15.4-22.8 Gy). One patient experienced grade 2 RM after a single-fraction treatment. The cumulative probability of RM was 0.3% (95% CI, 0%-2%).

Conclusions

Spine SBRT is safe while limiting the spinal cord (as defined on treatment planning magnetic resonance imaging or computed tomography myelogram) D0.03cc to less than 14 Gy, 21.9 Gy, and 30 Gy, for 1, 3, and 5-fractions, consistent with standard guidelines.

Phase II Trial of Sipuleucel-T and Stereotactic Ablative Body Radiation for Patients with Metastatic Castrate-Resistant Prostate Cancer

(1) We hypothesized that adding concurrent stereotactic ablative radiotherapy (SAbR) would increase the time to progression in patients with metastatic castrate-resistant prostate cancer (mCRPCA) treated with sipuleucel-T. (2) Patients with a history of prostate cancer (PC), radiographic evidence of metastatic disease, and rising prostate-specific antigen (PSA) > 0.2 ng/dL on castrate testosterone levels were enrolled in this single-arm phase II clinical trial and treated with sipuleucel-T and SAbR. The primary endpoint was time to progression (TTP). Cellular and humoral responses were measured using ELISpot and Luminex multiplex assays, respectively. (3) Twenty patients with mCRPC were enrolled and treated with SAbR to 1−3 sites. Treatment was well tolerated with 51, 8, and 4 treatment-related grade 1, 2, and 3 toxicities, respectively, and no grade 4 or 5 adverse events. At a median follow-up of 15.5 months, the median TTP was 11.2 weeks (95% CI; 6.8−14.0 weeks). Median OS was 76.8 weeks (95% CI; 41.6−130.8 weeks). This regimen induced both humoral and cellular immune responses. Baseline M-MDSC levels were elevated in mCRPC patients compared to healthy donors (p = 0.004) and a decline in M-MDSC was associated with biochemical response (p = 0.044). Responders had lower baseline uric acid levels (p = 0.05). No clear correlation with radiographic response was observed. (4) While the regimen was safe, the PC-antigen-specific immune response induced by SAbR did not yield a synergistic clinical benefit for patients treated with sipuleucel-T compared to the historically reported outcomes.

Stereotactic body radiotherapy for spinal oligometastases: a review on patient selection and the optimal methodology

Stereotactic body radiotherapy (SBRT) has excellent local control and low toxicity for spinal metastases and is widely performed for spinal oligometastases. However, its additional survival benefit to standard of care, including systemic therapy, is unknown because the results of large-scale randomized controlled trials regarding SBRT for oligometastases have not been reported. Consequently, the optimal patient population among those with spinal oligometastases and the optimal methodology for spine SBRT remain unclear. The present review article discusses two topics: evidence-based optimal patient selection and methodology. The following have been reported to be good prognostic factors: young age, good performance status, slow-growing disease with a long disease-free interval, minimal disease burden, and mild fluorodeoxyglucose accumulation in positron emission tomography. In addition, we proposed four measures as the optimal SBRT method for achieving excellent local control: (i) required target delineation; (ii) recommended dose fraction schedule (20 or 24 Gy in a single fraction for spinal oligometastases and 35 Gy in five fractions for lesions located near the spinal cord); (iii) optimizing dose distribution for the target; (iv) dose constraint options for the spinal cord.

Prediction of chronic kidney disease in abdominal cancers radiation therapy using the functional assays of normal tissue complication probability models

Aim

The purpose of this study is to predict chronic kidney disease (CKD) in the radiotherapy of abdominal cancers by evaluating clinical and functional assays of normal tissue complication probability (NTCP) models.

Materials and Methods

Radiation renal damage was analyzed in 50 patients with abdominal cancers 12 months after radiotherapy through a clinical estimated glomerular filtration rate (eGFR). According to the common terminology criteria for the scoring system of adverse events, Grade 2 CKD (eGFR ≤30-59 ml/min/1.73 m²) was considered as the radiation therapy endpoint. Modeling and parameter estimation of NTCP models were performed for the Lyman-equivalent uniform dose (EUD), the logit-EUD critical volume (CV), the relative seriality, and the mean dose model.

Results

The confidence interval of the fitted parameters was 95%. The parameter value of D₅₀ was obtained 22-38 Gy, and the n and s parameters were equivalent to 0.006 -3 and 1, respectively. According to the Akaike's information criterion, the mean dose model predicts radiation-induced CKD more accurately than the other models.

Conclusion

Although the renal medulla consists of many nephrons arranged in parallel, each nephron has a seriality architecture as renal functional subunits. Therefore, based on this principle and modeling results in this study, the whole kidney organs may have a serial-parallel combination or a secret architecture.

Organs at risk radiation dose constraints

Dose constraints are essential for performing dosimetry, especially for intensity modulation and for radiotherapy under stereotaxic conditions. We present the update of the recommendations of the French society of oncological radiotherapy for the use of these doses in classical current practice but also for reirradiation.

Outcome and Immune Correlates of a Phase II Trial of High-Dose Interleukin-2 and Stereotactic Ablative Radiotherapy for Metastatic Renal Cell Carcinoma

PURPOSE

This phase II clinical trial evaluated whether the addition of stereotactic ablative radiotherapy (SAbR), which may promote tumor antigen presentation, improves the overall response rate (ORR) to high-dose IL2 (HD IL2) in metastatic renal cell carcinoma (mRCC).

PATIENTS AND METHODS

Patients with pathologic evidence of clear cell renal cell carcinoma (RCC) and radiographic evidence of metastasis were enrolled in this single-arm trial and were treated with SAbR, followed by HD IL2. ORR was assessed based on nonirradiated metastases. Secondary endpoints included overall survival (OS), progression-free survival (PFS), toxicity, and treatment-related tumor-specific immune response. Correlative studies involved whole-exome and transcriptome sequencing, T-cell receptor sequencing, cytokine analysis, and mass cytometry on patient samples.

RESULTS

Thirty ethnically diverse mRCC patients were enrolled. A median of two metastases were treated with SAbR. Among 25 patients evaluable by RECIST v1.1, ORR was 16% with 8% complete responses. Median OS was 37 months. Treatment-related adverse events (AE) included 22 grade ≥3 events that were not dissimilar from HD IL2 alone. There were no grade 5 AEs. A correlation was observed between SAbR to lung metastases and improved PFS (P = 0.0165). Clinical benefit correlated with frameshift mutational load, mast cell tumor infiltration, decreased circulating tumor-associated T-cell clones, and T-cell clonal expansion. Higher regulatory/CD8+ T-cell ratios at baseline in the tumor and periphery correlated with no clinical benefit.

CONCLUSIONS

Adding SAbR did not improve the response rate to HD IL2 in patients with mRCC in this study. Tissue analyses suggest a possible correlation between frameshift mutation load as well as tumor immune infiltrates and clinical outcomes.

Efficacy and Safety of a Second Course of Stereotactic Radiation Therapy for Locally Recurrent Brain Metastases: A Systematic Review

Simple Summary

Approximately 30% of patients diagnosed with cancer will ultimately develop brain metastases. Many improvements have been made in systemic and local cancer treatments, which have increased overall survival but also, as a consequence, the number of patients who present with local recurrence following intracranial stereotactic radiotherapy. The management of these recurrences remains controversial. The aim of our review is to evaluate the efficacy and tolerance of a second course of stereotactic radiotherapy.

Abstract

Recent advances in cancer treatments have increased overall survival and consequently, local failures (LFs) after stereotactic radiotherapy/radiosurgery (SRS/SRT) have become more frequent. LF following SRS or SRT may be treated with a second course of SRS (SRS2) or SRT (SRT2). However, there is no consensus on whenever to consider reirradiation. A literature search was conducted according to PRISMA guidelines. Analysis included 13 studies: 329 patients (388 metastases) with a SRS2 and 135 patients (161 metastases) with a SRT2. The 1-year local control rate ranged from 46.5% to 88.3%. Factors leading to poorer LC were histology (melanoma) and lack of prior whole-brain radiation therapy, large tumor size and lower dose at SRS2/SRT2, poorer response at first SRS/SRT, poorer performance status, and no controlled extracranial disease. The rate of radionecrosis (RN) ranged from 2% to 36%. Patients who had a large tumor volume, higher dose and higher value of prescription isodose line at SRS2/SRT2, and large overlap between brain volume irradiated at SRS1/SRT1 and SRS2/SRT2 at doses of 18 and 12 Gy had a higher risk of developing RN. Prospective studies involving a larger number of patients are still needed to determine the best management of patients with local recurrence of brain metastases

Brachial Plexus Tolerance to Single-Session SAbR in a Pig Model

PURPOSE

The single-session dose tolerance of the spinal nerves has been observed to be similar to that of the spinal cord in pigs, counter to the perception that peripheral nerves are more tolerant to radiation. This pilot study aims to obtain a first impression of the single-session dose-response of the brachial plexus using pigs as a model.

METHODS AND MATERIALS

Ten Yucatan minipigs underwent computed tomography and magnetic resonance imaging for treatment planning, followed by single-session stereotactic ablative radiotherapy. A 2.5-cm length of the left-sided brachial plexus cords was irradiated. Pigs were distributed in 3 groups with prescription doses of 16 (n = 3), 19 (n = 4), and 22 Gy (n = 3). Neurologic status was assessed by observation for changes in gait and electrodiagnostic examination. Histopathologic examination was performed with light microscopy of paraffin-embedded sections stained with Luxol fast blue/periodic acid-Schiff and Masson's trichrome.

RESULTS

Seven of the 10 pigs developed motor deficit to the front limb of the irradiated side, with a latency from 5 to 8 weeks after irradiation. Probit analysis of the maximum nerve dose yields an estimated ED₅₀ of 19.3 Gy for neurologic deficit, but the number of animals was insufficient to estimate 95% confidence intervals. No motor deficits were observed at a maximum dose of 17.6 Gy for any pig. Nerve conduction studies showed an absence of sensory response in all responders and absent or low motor response in most of the responders (71%). All symptomatic pigs showed histologic lesions to the left-sided plexus consistent with radiation-induced neuropathy.

CONCLUSIONS

The single-session ED₅₀ for symptomatic plexopathy in Yucatan minipigs after irradiation of a 2.5-cm length of the brachial plexus cords was determined to be 19.3 Gy. The dose-response curve overlaps that of the spinal nerves and the spinal cord in the same animal model. The relationship between the brachial plexus tolerance in pigs and humans is unknown, and caution is warranted when extrapolating for clinical use.

Stereotactic Ablative Radiation Therapy for Oligoprogressive Renal Cell Carcinoma

PURPOSE

Oligoprogression, defined as limited sites of progression on systemic therapy, in patients with metastatic renal cell carcinoma (mRCC) is not uncommon, possibly because of inter- and intratumoral heterogeneity. We evaluated the effect of stereotactic ablative radiation therapy (SAbR) for longitudinal control of oligoprogressive mRCC.

METHODS AND MATERIALS

Patients with extracranial mRCC were included in this retrospective analysis if they progressed in ≤3 sites on systemic therapy while demonstrating response/stability at other sites and received SAbR to all progressing sites without switching systemic therapy. Our primary endpoint was modified progression-free survival (mPFS), which we calculated from the start of SAbR to the start of a subsequent systemic therapy, death, or loss to follow-up.

RESULTS

We identified 36 patients with a median follow-up of 20.4 months (interquartile range, 10.9-29.4). Forty-three sites were treated with SAbR with a median dose of 36 Gy (range, 18-50) in 3 fractions (range, 1-5). Median time to SAbR from the start of systemic therapy was 11.4 months (interquartile range, 6.1-17.1). Median mPFS was 9.2 months (95% confidence interval [CI], 5.9-13.2). Patients receiving SAbR while on immunotherapy exhibited a longer median mPFS (>28.4 months, log-rank P = .0001) than patients not on immunotherapy (9.2 months). Median overall survival from SAbR administration was 43.4 months (95% CI, 21.5-not Reached). The 1-year local control rate was 93% (95% CI, 78.7-97.5). Most SAbR-related toxicities were grade 1 to 2 (33% of patients), with one grade 5 hemoptysis event possibly related to SAbR or disease progression.

CONCLUSIONS

SAbR has the potential to extend the the duration of current systemic therapy for selected patients with mRCC, preserving subsequent therapies for later administration possibly enabling longer treatment duration.

Organ at Risk Dose Constraints in SABR: A Systematic Review of Active Clinical Trials

PURPOSE

Organ at risk (OAR) dose constraints are a critical aspect of SABR treatment planning. There is limited evidence supporting preferred dose constraints for many OARs. We sought to evaluate OAR dose constraints used in ongoing clinical trials of SABR for oligometastatic disease.

METHODS AND MATERIALS

Clinicaltrials.gov was searched from inception to February 2020 to capture actively accruing clinical trials using SABR in oligometastatic disease. Dose constraints were obtained by contacting principal investigators and abstracted by 2 authors. Variability of constraints was assessed by comparing the width of the interquartile range and difference between the maximum and minimum dose to a volume.

RESULTS

Fifty-three of 85 eligible clinical trials contributed OAR constraints used in analysis. Dose constraints for 1 to 8 fractions of SABR were collected for 33 OARs. Variability was found in the absolute allowable OAR doses, use of planning OAR volumes, and whether constraints were optional versus mandatory. For many OARs, modal dose constraints often matched a pre-existing publication, but no single pre-existing publication matched the modes of all OAR dose constraints. Organs displaying the most variability were the rectum, penile bulb, and chest wall and ribs. The esophagus, stomach, duodenum, and small bowel also indicated high variability for at least 1 constraint. OARs previously evaluated by HyTEC appeared to have less variability among study protocols.

CONCLUSIONS

We found substantial variability in OAR dose constraints used in current clinical trials evaluating SABR in oligometastatic disease. We are unable to comment on toxicity rates or acceptability of dose constraints used. Future research and recommendations for standardized OAR dose constraints, as well as consistency in implementing planning OAR volume margins, should be priorities for the field of radiation oncology.

Dosimetric comparison of computed tomography-guided iodine-125 seed implantation assisted with and without three-dimensional printing non-coplanar template in locally recurrent rectal cancer: a propensity score matching study

Purpose

To compare post-implant dosimetric parameters of computed tomography (CT)-guided radioactive iodine-125 (¹²⁵I) seed (RIS) implantation assisted with and without three-dimensional printing non-coplanar template (3D-PNCT) in locally recurrent rectal cancer (LRRC).

Material and methods

One hundred and fifty-five LRRC patients treated by CT-guided RIS implantation assisted with or without 3D-PNCT from October 2003 to May 2019 were included in this study. Propensity score matching (PSM) method (1 : 1) was used to adjust for differences between the 3D-group (with 3D-PNCT) and the CT-group (without 3D-PNCT). After PSM, dosimetric parameters [D₉₀ (dose that covered 90% of target volume), D₁₀₀ (dose that covered 100% of target volume), V₁₀₀ (percentage of gross tumor volume (GTV) receiving 100% of prescription dose), V₁₅₀ (percentage of GTV receiving 150% of prescription dose), HI (homogeneity index), CI (conformity index), and EI (external index)] of the two groups were compared.

Results

After PSM, 45 pairs of matched cases were selected for analysis and differences in variables between the two groups were balanced. For the 3D-group, median values of D₉₀, D₁₀₀, V₁₀₀, V₁₅₀, EI, and HI were 142.6 Gy (73.7-218.2 Gy), 73.7 Gy (26.2-169.3 Gy), 94.1% (74.3-100%), 71.8% (35.4-98.3%), 0.7 (0.1-30.7), and 0.20 (0-0.60), respectively, and corresponding values were 119.9 Gy (39.8-159.3 Gy), 47.0 Gy (13.0-200.9 Gy), 89.9% (38.6-100%), 62.8% (14.8-100%), 0.39 (0-11.01), and 0.30 (0-0.95), respectively, for the CT-group. Parameters including D₉₀, D₁₀₀, V₁₀₀, V₁₅₀, and EI in the 3D-group were significantly higher than those in the CT-group (p < 0.001, p < 0.001, p < 0.001, p < 0.001, and p = 0.006, respectively).

Conclusions

3D-PNCT can improve the accuracy of radioactive seed implantation by increasing the dose delivered to the tumor and reducing the number of “cold” spots of dose.

Potential Clinical Significance of Overall Targeting Accuracy and Motion Management in the Treatment of Tumors That Move With Respiration: Lessons Learnt From a Quarter Century of Stereotactic Body Radiotherapy From Dose Response Models

OBJECTIVE

To determine the long-term normal tissue complication probability with stereotactic body radiation therapy (SBRT) treatments for targets that move with respiration and its relation with the type of respiratory motion management (tracking vs. compression or gating).

METHODS

A PubMed search was performed for identifying literature regarding dose, volume, fractionation, and toxicity (grade 3 or higher) for SBRT treatments for tumors which move with respiration. From the identified papers logistic or probit dose-response models were fitted to the data using the maximum-likelihood technique and confidence intervals were based on the profile-likelihood method in the dose-volume histogram (DVH) Evaluator.

RESULTS

Pooled logistic and probit models for grade 3 or higher toxicity for aorta, chest wall, duodenum, and small bowel suggest a significant difference when live motion tracking was used for targeting tumors with move with respiration which was on the average 10 times lower, in the high dose range.

CONCLUSION

Live respiratory motion management appears to have a better toxicity outcome when treating targets which move with respiration with very steep peripheral dose gradients. This analysis is however limited by sparsity of rigorous data due to poor reporting in the literature.

Hypofractionated spinal stereotactic body radiation therapy for high-grade epidural disease

OBJECTIVE

To characterize the clinical outcomes when stereotactic body radiation therapy (SBRT) alone is used to treat high-grade epidural disease without prior surgical decompression, the authors conducted a retrospective cohort study of patients treated at the Memorial Sloan Kettering Cancer Center between 2014 and 2018. The authors report locoregional failure (LRF) for a cohort of 31 cases treated with hypofractionated SBRT alone for grade 2 epidural spinal cord compression (ESCC) with radioresistant primary cancer histology.

METHODS

High-grade epidural disease was defined as grade 2 ESCC, which is notable for radiographic deformation of the spinal cord by metastatic disease. Kaplan-Meier survival curves and cumulative incidence functions were generated to examine the survival and incidence experiences of the sample level with respect to overall survival, LRF, and subsequent requirement of vertebral same-level surgery (SLS) due to tumor progression or fracture. Associations with dosimetric analysis were also examined.

RESULTS

Twenty-nine patients undergoing 31 episodes of hypofractionated SBRT alone for grade 2 ESCC between 2014 and 2018 were identified. The 1-year and 2-year cumulative incidences of LRF were 10.4% (95% CI 0-21.9) and 22.0% (95% CI 5.5-38.4), respectively. The median survival was 9.81 months (95% CI 8.12-18.54). The 1-year cumulative incidence of SLS was 6.8% (95% CI 0-16.0) and the 2-year incidence of SLS was 14.5% (95% CI 0.6-28.4). All patients who progressed to requiring surgery had index lesions at the thoracic apex (T5-7).

CONCLUSIONS

In carefully selected patients, treatment of grade 2 ESCC disease with hypofractionated SBRT alone offers a 1-year cumulative incidence of LRF similar to that in low-grade ESCC and postseparation surgery adjuvant hypofractionated SBRT. Use of SBRT alone has a favorable safety profile and a low cumulative incidence of progressive disease requiring open surgical intervention (14.5%).

Nephron-Sparing Robotic Radiosurgical Therapy for Primary Renal Cell Carcinoma: Single-Institution Experience and Review of the Literature

PURPOSE

We report our single-institution stereotactic body radiation therapy (SBRT) experience on stage I renal cancer with prospectively collected toxicity and efficacy data.

METHODS AND MATERIALS

A total of 21 patients with solitary renal tumors, including 14 surgical candidates who refused surgery (66%), were treated with SBRT. Histologic confirmation was obtained on all patients before treatment; 2 had transitional cell carcinoma and 19 had renal cell carcinoma. The median age was 71 years (range, 58-88). Nearly all patients received 48 Gy in 3 fractions.

RESULTS

The median follow-up was 78 months (range, 5-107). At 5 years post treatment, the local tumor control rate was 100%. Tumor size decreased by a median value of 5.3% at 1 year post treatment, 15.6% at 2 years post treatment, and 15.4% at 5 years post treatment. Glomerular filtration rate had decreased by a median value of 1.5% at 1 year post treatment, 7.0% at 2 years post treatment, and 14.2% at 5 years post treatment. Three patients experienced grade 1 toxicity; no other treatment-related adverse effects were reported.

CONCLUSIONS

SBRT is a promising noninvasive treatment in the management of primary renal cell carcinoma, with evolving clinical evidence demonstrating encouraging results with respect to local control and toxicity.

Safety and efficacy of concurrent immune checkpoint inhibitors and hypofractionated body radiotherapy

Integration of hypofractionated body radiotherapy (H-RT) into immune checkpoint inhibitor (ICI) therapy may be a promising strategy to improve the outcomes of ICIs, although sufficient data is lacking regarding the safety and efficacy of this regimen. We, hereby, reviewed the safety and efficacy of this combination in 59 patients treated with H-RT during or within 8 weeks of ICI infusion and compared results with historical reports of ICI treatment alone. Most patients had RCC or melanoma. Median follow-up was 11 months. Most patients received either Nivolumab alone or with Ipilimumab; 83% received stereotactic RT and 17% received conformal H-RT. Any grade adverse events (AEs) were reported in 46 patients, and grade 3-4 in 12 patients without any treatment-related grade 5 toxicity. The most common grade 3 AEs were fatigue and pneumonitis. Grade 3-4 toxicities were higher with ICI combination and with simultaneous ICIs. Overall, most any-grade or grade ≥3 AE rates did not differ significantly from historically reported rates with single-agent or multi-agent ICIs. Toxicity did not correlate with H-RT site, dose, fraction number, tumor type, or ICI and H-RT sequencing. Median progression-free survival was 6.5 months. Objective response rate (ORR) was 26%; 10% had complete response (CR). Median duration of response was 9.4 ± 4.6 months. H-RT of lung lesions was more likely to achieve CR than other sites. H-RT of bone lesions had a lower ORR than non-bone H-RT. In conclusion, combining body H-RT with ICIs is safe and promising. Prospective validation is warranted.

Robust optimization in lung treatment plans accounting for geometric uncertainty

Robust optimization generates scenario‐based plans by a minimax optimization method to find optimal scenario for the trade‐off between target coverage robustness and organ‐at‐risk (OAR) sparing. In this study, 20 lung cancer patients with tumors located at various anatomical regions within the lungs were selected and robust optimization photon treatment plans including intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were generated. The plan robustness was analyzed using perturbed doses with setup error boundary of ±3 mm in anterior/posterior (AP), ±3 mm in left/right (LR), and ±5 mm in inferior/superior (IS) directions from isocenter. Perturbed doses for D₉₉, D₉₈, and D₉₅ were computed from six shifted isocenter plans to evaluate plan robustness. Dosimetric study was performed to compare the internal target volume‐based robust optimization plans (ITV‐IMRT and ITV‐VMAT) and conventional PTV margin‐based plans (PTV‐IMRT and PTV‐VMAT). The dosimetric comparison parameters were: ITV target mean dose (D_mean), R₉₅(D₉₅/D_prescription), Paddick's conformity index (CI), homogeneity index (HI), monitor unit (MU), and OAR doses including lung (D_mean, V_{20 Gy} and V_{15 Gy}), chest wall, heart, esophagus, and maximum cord doses. A comparison of optimization results showed the robust optimization plan had better ITV dose coverage, better CI, worse HI, and lower OAR doses than conventional PTV margin‐based plans. Plan robustness evaluation showed that the perturbed doses of D₉₉, D₉₈, and D₉₅ were all satisfied at least 99% of the ITV to received 95% of prescription doses. It was also observed that PTV margin‐based plans had higher MU than robust optimization plans. The results also showed robust optimization can generate plans that offer increased OAR sparing, especially for normal lungs and OARs near or abutting the target. Weak correlation was found between normal lung dose and target size, and no other correlation was observed in this study.