Kenneth R. Olivier

PD-1 Restrains Radiotherapy-Induced Abscopal Effect

Park, Dong, and colleagues show in mouse models of melanoma and renal cell carcinoma that stereotactic ablative radiotherapy synergized with PD-1 blockade to induce near-complete regression of the irradiated tumors, and a tumor-specific 66% reduction in the nonirradiated tumors outside the radiation field. We investigated the influence of PD-1 expression on the systemic antitumor response (abscopal effect) induced by stereotactic ablative radiotherapy (SABR) in preclinical melanoma and renal cell carcinoma models. We compared the SABR-induced antitumor response in PD-1–expressing wild-type (WT) and PD-1–deficient knockout (KO) mice and found that PD-1 expression compromises the survival of tumor-bearing mice treated with SABR. None of the PD-1 WT mice survived beyond 25 days, whereas 20% of the PD-1 KO mice survived beyond 40 days. Similarly, PD-1–blocking antibody in WT mice was able to recapitulate SABR-induced antitumor responses observed in PD-1 KO mice and led to increased survival. The combination of SABR plus PD-1 blockade induced near complete regression of the irradiated primary tumor (synergistic effect), as opposed to SABR alone or SABR plus control antibody. The combination of SABR plus PD-1 blockade therapy elicited a 66% reduction in size of nonirradiated, secondary tumors outside the SABR radiation field (abscopal effect). The observed abscopal effect was tumor specific and was not dependent on tumor histology or host genetic background. The CD11ahigh CD8+ T-cell phenotype identifies a tumor-reactive population, which was associated in frequency and function with a SABR-induced antitumor immune response in PD-1 KO mice. We conclude that SABR induces an abscopal tumor-specific immune response in both the irradiated and nonirradiated tumors, which is potentiated by PD-1 blockade. The combination of SABR and PD-1 blockade has the potential to translate into a potent immunotherapy strategy in the management of patients with metastatic cancer. Cancer Immunol Res; 3(6); 610–9. ©2015 AACR.

Progression-free Survival Following Stereotactic Body Radiotherapy for Oligometastatic Prostate Cancer Treatment-naive Recurrence: A Multi-institutional Analysis

UNLABELLED The literature on metastasis-directed therapy for oligometastatic prostate cancer (PCa) recurrence consists of small heterogeneous studies. This study aimed to reduce the heterogeneity by pooling individual patient data from different institutions treating oligometastatic PCa recurrence with stereotactic body radiotherapy (SBRT). We focussed on patients who were treatment naive, with the aim of determining if SBRT could delay disease progression. We included patients with three or fewer metastases. The Kaplan-Meier method was used to estimate distant progression-free survival (DPFS) and local progression-free survival (LPFS). Toxicity was scored using the Common Terminology Criteria for Adverse Events. In total, 163 metastases were treated in 119 patients. The median DPFS was 21 mo (95% confidence interval, 15-26 mo). A lower radiotherapy dose predicted a higher local recurrence rate with a 3-yr LPFS of 79% for patients treated with a biologically effective dose ≤100Gy versus 99% for patients treated with >100Gy (p=0.01). Seventeen patients (14%) developed toxicity classified as grade 1, and three patients (3%) developed grade 2 toxicity. No grade ≥3 toxicity occurred. These results should serve as a benchmark for future prospective trials. PATIENT SUMMARY This multi-institutional study pools all of the available data on the use of stereotactic body radiotherapy for limited prostate cancer metastases. We concluded that this approach is safe and associated with a prolonged treatment progression-free survival.

Tumor Localization Using Cone-Beam CT Reduces Setup Margins in Conventionally Fractionated Radiotherapy for Lung Tumors

PURPOSE To determine whether setup margins can be reduced using cone-beam computed tomography (CBCT) to localize tumor in conventionally fractionated radiotherapy for lung tumors. METHODS AND MATERIALS A total of 22 lung cancer patients were treated with curative intent with conventionally fractionated radiotherapy using daily image guidance with CBCT. Of these, 13 lung cancer patients had sufficient CBCT scans for analysis (389 CBCT scans). The patients underwent treatment simulation in the BodyFix immobilization system using four-dimensional CT to account for respiratory motion. Daily alignment was first done according to skin tattoos, followed by CBCT. All 389 CBCT scans were retrospectively registered to the planning CT scans using automated soft-tissue and bony registration; the resulting couch shifts in three dimensions were recorded. RESULTS The daily alignment to skin tattoos with no image guidance resulted in systematic (Sigma) and random (sigma) errors of 3.2-5.6 mm and 2.0-3.5 mm, respectively. The margin required to account for the setup error introduced by aligning to skin tattoos with no image guidance was approximately 1-1.6 cm. The difference in the couch shifts obtained from the bone and soft-tissue registration resulted in systematic (Sigma) and random (sigma) errors of 1.5-4.1 mm and 1.8-5.3 mm, respectively. The margin required to account for the setup error introduced using bony anatomy as a surrogate for the target, instead of localizing the target itself, was 0.5-1.4 cm. CONCLUSION Using daily CBCT soft-tissue registration to localize the tumor in conventionally fractionated radiotherapy reduced the required setup margin by up to approximately 1.5 cm compared with both no image guidance and image guidance using bony anatomy as a surrogate for the target.

A Randomized Phase 2 Study Comparing 2 Stereotactic Body Radiation Therapy Schedules for Medically Inoperable Patients With Stage I Peripheral Non-Small Cell Lung Cancer: NRG Oncology RTOG 0915 (NCCTG N0927)

PURPOSE To compare 2 stereotactic body radiation therapy (SBRT) schedules for medically inoperable early-stage lung cancer to determine which produces the lowest rate of grade ≥3 protocol-specified adverse events (psAEs) at 1 year. METHODS AND MATERIALS Patients with biopsy-proven peripheral (≥2 cm from the central bronchial tree) T1 or T2, N0 (clinically node negative by positron emission tomography), M0 tumors were eligible. Patients were randomized to receive either 34 Gy in 1 fraction (arm 1) or 48 Gy in 4 consecutive daily fractions (arm 2). Rigorous central accreditation and quality assurance confirmed treatment per protocol guidelines. This study was designed to detect a psAEs rate >17% at a 10% significance level (1-sided) and 90% power. Secondary endpoints included rates of primary tumor control (PC), overall survival (OS), and disease-free survival (DFS) at 1 year. Designating the better of the 2 regimens was based on prespecified rules of psAEs and PC for each arm. RESULTS Ninety-four patients were accrued between September 2009 and March 2011. The median follow-up time was 30.2 months. Of 84 analyzable patients, 39 were in arm 1 and 45 in arm 2. Patient and tumor characteristics were balanced between arms. Four (10.3%) patients on arm 1 (95% confidence interval [CI] 2.9%-24.2%) and 6 (13.3%) patients on arm 2 (95% CI 5.1%-26.8%) experienced psAEs. The 2-year OS rate was 61.3% (95% CI 44.2%-74.6%) for arm 1 patients and 77.7% (95% CI 62.5%-87.3%) for arm 2. The 2-year DFS was 56.4% (95% CI 39.6%-70.2%) for arm 1 and 71.1% (95% CI 55.5%-82.1%) for arm 2. The 1-year PC rate was 97.0% (95% CI 84.2%-99.9%) for arm 1 and 92.7% (95% CI 80.1%-98.5%) for arm 2. CONCLUSIONS 34 Gy in 1 fraction met the prespecified criteria and, of the 2 schedules, warrants further clinical research.

Stereotactic Body Radiation Therapy in Spinal Metastases

PURPOSE Based on reports of safety and efficacy, stereotactic body radiotherapy (SBRT) for treatment of malignant spinal tumors was initiated at our institution. We report prospective results of this population at Mayo Clinic. MATERIALS AND METHODS Between April 2008 and December 2010, 85 lesions in 66 patients were treated with SBRT for spinal metastases. Twenty-two lesions (25.8%) were treated for recurrence after prior radiotherapy (RT). The mean age of patients was 56.8 ± 13.4 years. Patients were treated to a median dose of 24 Gy (range, 10-40 Gy) in a median of three fractions (range, 1-5). Radiation was delivered with intensity-modulated radiotherapy (IMRT) and prescribed to cover 80% of the planning target volume (PTV) with organs at risk such as the spinal cord taking priority over PTV coverage. RESULTS Tumor sites included 48, 22, 12, and 3 in the thoracic, lumbar, cervical, and sacral spine, respectively. The mean actuarial survival at 12 months was 52.2%. A total of 7 patients had both local and marginal failure, 1 patient experienced marginal but not local failure, and 1 patient had local failure only. Actuarial local control at 1 year was 83.3% and 91.2% in patients with and without prior RT. The median dose delivered to patients who experienced local/marginal failure was 24 Gy (range, 18-30 Gy) in a median of three fractions (range, 1-5). No cases of Grade 4 toxicity were reported. In 1 of 2 patients experiencing Grade 3 toxicity, SBRT was given after previous radiation. CONCLUSION The results indicate SBRT to be an effective measure to achieve local control in spinal metastases. Toxicity of treatment was rare, including those previously irradiated. Our results appear comparable to previous reports analyzing spine SBRT. Further research is needed to determine optimum dose and fractionation to further improve local control and prevent toxicity.

Stereotactic body radiation therapy in the treatment of oligometastatic prostate cancer

Purpose/objective(s): To report outcomes and toxicity for patients with oligometastatic (≤5 lesions) prostate cancer (PCa) treated with stereotactic body radiation therapy (SBRT). Materials/methods: Seventeen men with 21 PCa lesions were treated with SBRT between February 2009 and November 2011. All patients had a detectable prostate-specific antigen (PSA) at the time of SBRT, and 11 patients (65%) had hormone-refractory (HR) disease. Treatment sites included bone (n = 19), lymph nodes (n = 1), and liver (n = 1). For patients with bone lesions, the median dose was 20 Gy (range, 8–24 Gy) in a single fraction (range, 1–3). All but two patients received some form of anti-androgen therapy after completing SBRT. Results: Local control (LC) was 100%, and the PSA nadir was undetectable in nine patients (53%). The first post-SBRT PSA was lower than pre-treatment levels in 15 patients (88%), and continued to decline or remain undetectable in 12 patients (71%) at a median follow-up of 6 months (range, 2–24 months). Median PSA measurements before SBRT and at last follow-up were 2.1 ng/dl (range, 0.13–36.4) and 0.17 ng/dl (range, <0.1–140), respectively. Six (55%) of the 11 patients with HR PCa achieved either undetectable or declining PSA at a median follow-up of 4.8 months (range, 2.2–6.0 months). Reported toxicities included one case each of grade 2 dyspnea and back pain, there were no cases of grade ≥3 toxicity following treatment. Conclusion: We report excellent LC with SBRT in oligometastatic PCa. More importantly, over half the patients achieved an undetectable PSA after SBRT. Further follow-up is necessary to assess the long-term impact of SBRT on LC, toxicity, PSA response, and clinical outcomes.

A Prospective, Phase II Study Demonstrating the Potential Value and Limitation of Radiosurgery for Spine Metastases

Purpose:To evaluate toxicity, efficacy, feasibility, and target volume dosimetry of single-fraction stereotactic body radiotherapy or radiosurgery for spine tumors. Methods:Twenty-five patients were treated on a prospective phase II protocol of single-fraction stereotactic body radiotherapy or radiosurgery for tumors near the spinal cord (N = 21). Patients received 15 Gy, given a spinal cord limit of 12 Gy to 0.1 mL for patients with no prior spine radiotherapy (N = 9), and 5 Gy to 0.5 mL for patients with prior spine radiotherapy (N = 12). The primary endpoint was toxicity. The secondary endpoint was efficacy measured with a pain scale, 2 neurologic function scales, and magnetic resonance scans. Minor endpoints were feasibility and dose coverage. Results:Acute toxicity was grade 1 to 2 dysphagia or nausea. There were no late toxicities. Three patients experienced radiographic evidence of vertebral body compression in field; 2 were asymptomatic and 1 was managed with vertebroplasty. One patient progressed at the radiosurgery site (local control, 95%); 43% experienced pain relief. Most patients died or developed progressive systemic disease soon after radiosurgery. One-year progression-free survival was 5% with 60% of patients dead by 1 year. Patients with the site of radiosurgery as their only site of disease also did poorly: 2-year progression-free survival ∼10% with half dead of cancer within 2 years. There were no problems planning and delivering spine radiosurgery with a 60-minute treatment slot. In patients with and without prior radiotherapy, we achieved our target-coverage goal in 91% and 95%, respectively. Conclusion:Radiosurgery is an excellent option for patients with symptomatic spine metastases in previously irradiated areas. In patients without previous irradiation, the biology of metastatic cancer limits spine radiosurgerys ability to improve outcome.

A higher radiotherapy dose is associated with more durable palliation and longer survival in patients with metastatic melanoma

Oncologists are often reluctant to recommend radiotherapy (RT) to palliate metastatic melanoma due to a perception that this tumor is “radioresistant.” The Mayo Clinic experience was analyzed to determine the efficacy of palliative RT.

Increased Bowel Toxicity in Patients Treated With a Vascular Endothelial Growth Factor Inhibitor (VEGFI) After Stereotactic Body Radiation Therapy (SBRT)

PURPOSE Gastrointestinal injury occurs rarely with agents that affect the vascular endothelial growth factor receptor and with abdominal stereotactic body radiation therapy (SBRT). We explored the incidence of serious bowel injury (SBI) in patients treated with SBRT with or without vascular endothelial growth factor inhibitor (VEGFI) therapy. METHODS AND MATERIALS Seventy-six patients with 84 primary or metastatic intra-abdominal lesions underwent SBRT (median dose, 50 Gy in 5 fractions). Of the patients, 20 (26%) received VEGFI within 2 years after SBRT (bevacizumab, n=14; sorafenib, n=4; pazopanib, n=1; sunitinib, n=1). The incidence of SBI (Common Terminology Criteria for Adverse Events, version 4.0, grade 3-5 ulceration or perforation) after SBRT was obtained, and the relationship between SBI and VEGFI was examined. RESULTS In the combined population, 7 patients (9%) had SBI at a median of 4.6 months (range, 3-17 months) from SBRT. All 7 had received VEGFI before SBI and within 13 months of completing SBRT, and 5 received VEGFI within 3 months of SBRT. The 6-month estimate of SBI in the 26 patients receiving VEGFI within 3 months of SBRT was 38%. No SBIs were noted in the 63 patients not receiving VEGFI. The log-rank test showed a significant correlation between SBI and VEGFI within 3 months of SBRT (P=.0006) but not between SBI and radiation therapy bowel dose (P=.20). CONCLUSIONS The combination of SBRT and VEGFI results in a higher risk of SBI than would be expected with either treatment independently. Local therapies other than SBRT may be considered if a patient is likely to receive a VEGFI in the near future.

Early pulmonary toxicity following lung stereotactic body radiation therapy delivered in consecutive daily fractions

BACKGROUND AND PURPOSE Identify the incidence of early pulmonary toxicity in a cohort of patients treated with lung stereotactic body radiation therapy (SBRT) on consecutive treatment days. MATERIAL AND METHODS A total of 88 lesions in 84 patients were treated with SBRT in consecutive daily fractions (Fx) for medically inoperable non-small cell lung cancer or metastasis. The incidence of pneumonitis was evaluated and graded according to the NCI CTCAE v3.0. RESULTS With a median follow-up of 15.8 months (range 2.5-28.6), the median age at SBRT was 71.8 years (range 23.8-87.8). 47 lesions were centrally located and 41 were peripheral. Most central lesions were treated with 48Gy in 4 Fx, and most peripheral lesions with 54Gy in 3 Fx. The incidence of grade ≥ 2 pneumonitis was 12.5% in all patients treated, and 14.3% among the subset of patients treated with 54Gy in 3 Fx. A total of two grade 3 toxicities were seen as one grade 5 toxicity in a patient treated for recurrence after pneumonectomy. CONCLUSIONS Treating both central and peripheral lung lesions with SBRT in consecutive daily fractions in this cohort was well tolerated and did not cause excessive early pulmonary toxicity.