Daniel W. Golden

STAT1 Pathway Mediates Amplification of Metastatic Potential and Resistance to Therapy

Background Traditionally IFN/STAT1 signaling is connected with an anti-viral response and pro-apoptotic tumor-suppressor functions. Emerging functions of a constitutively activated IFN/STAT1 pathway suggest an association with an aggressive tumor phenotype. We hypothesized that tumor clones that constitutively overexpress this pathway are preferentially selected by the host microenvironment due to a resistance to STAT1-dependent cytotoxicity and demonstrate increased metastatic ability combined with increased resistance to genotoxic stress. Methodology/Principal Findings Here we report that clones of B16F1 tumors grown in the lungs of syngeneic C57BL/6 mice demonstrate variable transcriptional levels of IFN/STAT1 pathway expression. Tumor cells that constitutively overexpress the IFN/STAT1 pathway (STAT1H genotype) are selected by the lung microenvironment. STAT1H tumor cells also demonstrate resistance to IFN-gamma (IFNγ), ionizing radiation (IR), and doxorubicin relative to parental B16F1 and low expressors of the IFN/STAT1 pathway (STAT1L genotype). Stable knockdown of STAT1 reversed the aggressive phenotype and decreased both lung colonization and resistance to genotoxic stress. Conclusions Our results identify a pathway activated by tumor-stromal interactions thereby selecting for pro-metastatic and therapy-resistant tumor clones. New therapies targeted against the IFN/STAT1 signaling pathway may provide an effective strategy to treat or sensitize aggressive tumor clones to conventional cancer therapies and potentially prevent distant organ colonization.

Prognostic factors and grading systems for overall survival in patients treated with radiosurgery for brain metastases: variation by primary site

OBJECT The authors conducted a study to determine whether prognostic factors and the applicability of prognostic systems vary by primary tumor site in patients treated with radiosurgery for brain metastases. METHODS The authors evaluated data obtained in patients who underwent radiosurgery with or without whole-brain radiotherapy (WBRT) from 1991 to 2005 for newly diagnosed brain metastases. Four groups were analyzed: 1) all primary sites combined, 2) breast, 3) lung, and 4) melanoma primary sites. Kaplan-Meier, log-rank, Cox proportional hazard uni- and multivariate analysis, and recursive partitioning analysis (RPA) were used to assess prognostic factors and 4 prognostic systems: Radiation Therapy Oncology Group (RTOG) RPA, Graded Prognostic Assessment (GPA), basic score for brain metastases (BSBM), and the newly proposed Golden grading system (GGS). The GGS divides patients into 4 prognostic groups by age >or= 65 years, Karnofsky Performance Scale (KPS) score < 70, and known presence of extracranial metastases. RESULTS Data acquired in 479 newly diagnosed patients with 1664 lesions were analyzed. The median survival time from diagnosis of brain metastases was 12.1 months; the median follow-up was 25.4 months in 73 patients who were censored. Survival and prognostic factors were equivalent for 369 patients treated with radiosurgery compared with 110 patients treated with radiosurgery and WBRT, so these subsets were combined. Multivariate analysis of all primary sites combined demonstrated age < 65 years, KPS score >or= 70, no known extracranial metastases, and <or= 3 brain metastases were associated with longer survival, and primary tumor control was not. In subgroup multivariate analysis of patients with breast, lung, or melanoma primaries, favorable factors included only primary tumor control in 87 patients with breast primary; age < 65 years, no known extracranial metastases, and <or= 3 brain metastases in 169 patients with lung primary; and KPS >or= 70 years, primary tumor control, and <or= 3 brain metastases in 137 patients with melanoma primary. The median survival for <or= 3 versus > 3 metastases was 15.6 and 16.9 months, respectively, for breast, 16.5 and 11.3 months for lung, and 9.0 and 5.7 months for melanoma. Analysis of the 4 prognostic systems (RTOG RPA, BSBM, GPA, and GGS) showed that each prognostic systems clinical applicability varied depending on primary tumor site. The RPA confirmed that GGS and primary tumor site are significant variables for prognosis. CONCLUSIONS Favorable prognostic factors for patients with newly diagnosed brain metastases treated with radiosurgery vary by primary site. The 4 prognostic grading systems analyzed were applicable to different primary sites depending on which prognostic factors each individual system incorporated. Therefore, the authors recommend further development and use of primary-specific prognostic systems.

Poly(ADP-Ribose) Polymerase Inhibitor Induces Accelerated Senescence in Irradiated Breast Cancer Cells and Tumors

Persistent DNA double-strand breaks (DSB) may determine the antitumor effects of ionizing radiation (IR) by inducing apoptosis, necrosis, mitotic catastrophe, or permanent growth arrest. IR induces rapid modification of megabase chromatin domains surrounding DSBs via poly-ADP-ribosylation, phosphorylation, acetylation, and protein assembly. The dynamics of these IR-induced foci (IRIF) have been implicated in DNA damage signaling and DNA repair. As an IRIF reporter, we tracked the relocalization of green fluorescent protein fused to a chromatin binding domain of the checkpoint adapter protein 53BP1 after IR of breast cancer cells and tumors. To block DSB repair in breast cancer cells and tumors, we targeted poly(ADP-ribose) polymerase (PARP) with ABT-888 (veliparib), one of several PARP inhibitors currently in clinical trials. PARP inhibition markedly enhanced IRIF persistence and increased breast cancer cell senescence both in vitro and in vivo, arguing for targeting IRIF resolution as a novel therapeutic strategy.

Hypofractionated Image-Guided Radiation Therapy for Patients with Limited Volume Metastatic Non-small Cell Lung Cancer

Introduction: Outcomes data treating patients with oligometastatic (⩽5 metastases) non-small cell lung carcinoma (NSCLC) with hypofractionated image-guided radiotherapy (HIGRT) are limited. Methods: Consecutive oligometastatic NSCLC patients were reviewed from a prospective database. Patients were included if all active diseases were treated with HIGRT. Lesions that had received prior radiation or had radiographic/metabolic resolution after chemotherapy were not treated with HIGRT. Local control of all treated lesions, distant control, progression-free survival (PFS), overall survival (OS), and control of individual lesions (LeC) were calculated. Results: Twenty-five patients with median of 2 treated oligometastatic lesions were included. Median follow-up was 14 months. Median age was 66 years. Nineteen patients received systemic therapy before HIGRT and 11 had progressive disease after their most recent systemic therapy before HIGRT. Median OS and PFS were 22.7 and 7.6 months. The 18 months local control, distant control, OS, and PFS were 66.1%, 31.7%, 52.9%, and 28.0%. Greater than two sites treated with HIGRT, nonadenocarcinoma histology, prior systemic therapy, and progression after systemic therapy were associated with worse PFS. Sixty-two individual lesions of median size 2.7 cm were treated. For extracranial lesions, median total and fraction dose were 50 and 5 Gy. Median standard equivalent dose in 2 Gy fractions for extracranial lesions was 64.6 Gy yielding 18 months LeC of 70.7%. Standard equivalent dose ≥64.6 Gy increased LeC (p = 0.04). Two patients experienced grade 3 toxicity. Conclusions: HIGRT for oligometastatic NSCLC provides durable LeC and may provide long-term PFS in some patients. Future HIGRT studies should optimize patient selection and integration with systemic therapy.

Stereotactic body radiotherapy for the treatment of oligometastatic renal cell carcinoma.

Objectives:Renal cell carcinoma (RCC) is considered radioresistant, but stereotactic radiosurgery can control intracranial metastases. Advances in radiotherapy, such as stereotactic body radiotherapy (SBRT), allow high-dose radiation delivery to extracranial sites. Herein, we report our experience treating oligometastatic RCC with SBRT. Methods:Patients with RCC and limited metastases were treated on a 3-fraction dose-escalation protocol (8 to 14 Gy/fraction) or off protocol with 10 fractions (4 to 5 Gy/fraction). Disease control was evaluated with serial imaging, and the Kaplan-Meier method was used to estimate lesion control (LeC), distant control, and survival. Results:Eighteen consecutively treated patients with 39 metastases were treated using SBRT; 12 underwent treatment for all metastatic sites. Median follow-up was 16.2 months. Treatment was well tolerated; the most common acute toxicity was fatigue (61.1%) and late toxicity was limited. At 2 years, LeC was 91.4% and overall survival was 85%. Those who underwent treatment for all metastatic sites had a 2-year LeC of 100% and distant control of 35.7%. A shorter interval from diagnosis to SBRT predicted for distant progression. Freedom from any post-SBRT therapy was 64.2% at 1 year. Conclusions:In metastatic RCC, SBRT produces promising LeC with minimal toxicity. Further study should be expanded beyond that of managing intracranial disease. Its selected use may delay the requirement for systemic therapies.

Cytogenetic damage in blood lymphocytes and exfoliated epithelial cells of children with inflammatory bowel disease

This longitudinal, prospective study sought to establish whether pediatric Crohns disease (CD) and ulcerative colitis (UC) are associated with increased levels of cytogenetic damage and whether folate supplementation in combination with other treatments mitigates cytogenetic damage in children with inflammatory bowel disease (IBD). After a 1-mo treatment and folate supplementation, all clinical tests in CD (n = 24) and UC (n = 17) patients improved. Patients with CD were comparable in the cytogenetic response with controls (n = 28) assessed by micronucleus (MN) assay, but both groups differed from the UC group. While the MN frequency in epithelial cells slightly decreased from first to second observations in CD patients (p = 0.05) and controls (p = 0.11), an increase was observed in UC patients (p = 0.001). Similar changes were observed in blood lymphocytes resulting in significantly higher levels of the MNs and chromosome bridges in UC patients. These preliminary findings of a difference in chromosome damage between pediatric UC patients compared with CD patients and healthy controls warrant confirmation and expansion to determine (1) the role of cytogenetic damage in the pathogenesis of these diseases, (2) relative contribution of treatment and folate supplementation, and (3) potential links to the eventual development of cancer in some patients.

RIG-I–like receptor LGP2 protects tumor cells from ionizing radiation

Significance An undesirable outcome of radiotherapy (ionizing radiation, IR) of cancer is the emergence of radioresistant cells. We report that Laboratory of Genetics and Physiology 2 (LGP2), a resident RIG-I (retinoic acid inducible gene I)–like receptor protein, can induce radioresistance. IR induces interferon and stimulates accumulation of LGP2. In turn, LGP2 shuts off the synthesis of interferon and blocks its cytotoxic effects. Ectopic expression of LGP2 enhances resistance to IR, whereas depletion enhances cytotoxic effects of IR. Here we show that LGP2 is associated with radioresistance in numerous diverse cancer cell lines. Examination of available databases links expression of LGP2 with poor prognosis in cancer patients. An siRNA screen targeting 89 IFN stimulated genes in 14 different cancer cell lines pointed to the RIG-I (retinoic acid inducible gene I)–like receptor Laboratory of Genetics and Physiology 2 (LGP2) as playing a key role in conferring tumor cell survival following cytotoxic stress induced by ionizing radiation (IR). Studies on the role of LGP2 revealed the following: (i) Depletion of LGP2 in three cancer cell lines resulted in a significant increase in cell death following IR, (ii) ectopic expression of LGP2 in cells increased resistance to IR, and (iii) IR enhanced LGP2 expression in three cell lines tested. Studies designed to define the mechanism by which LGP2 acts point to its role in regulation of IFNβ. Specifically (i) suppression of LGP2 leads to enhanced IFNβ, (ii) cytotoxic effects following IR correlated with expression of IFNβ inasmuch as inhibition of IFNβ by neutralizing antibody conferred resistance to cell death, and (iii) mouse embryonic fibroblasts from IFN receptor 1 knockout mice are radioresistant compared with wild-type mouse embryonic fibroblasts. The role of LGP2 in cancer may be inferred from cumulative data showing elevated levels of LGP2 in cancer cells are associated with more adverse clinical outcomes. Our results indicate that cytotoxic stress exemplified by IR induces IFNβ and enhances the expression of LGP2. Enhanced expression of LGP2 suppresses the IFN stimulated genes associated with cytotoxic stress by turning off the expression of IFNβ.

Stereotactic Body Radiation Therapy for Curative Treatment of Adrenal Metastases

The detection of oligometastatic adrenal metastases is increasing and there are limited data supporting the use of curative intent stereotactic body radiation therapy (SBRT) to treat patients with limited metastatic disease with adrenal involvement. Therefore, we utilized a prospectively maintained database of consecutive patients treated with SBRT for limited metastatic disease (<5 sites) to identify patients with adrenal metastases. Patients were either treated on a three-fraction dose escalation protocol or a ten fraction off-protocol regimen. Outcomes including treated-metastasis control (TMC), distant control (DC), and overall survival (OS) were calculated by the Kaplan-Meier method. Ten patients with 13 adrenal metastases were identified for this case series. The median follow-up was 14.9 months. No patient experienced grade 3 toxicity. The most common grade 1–2 acute toxicities were fatigue (80%) and GI toxicity (40%). One patient experienced late grade 2 adrenal insufficiency. Overall, the 1-year TMC rate was 73%, DC was 30%, and OS was 90%. Three treated adrenal metastases progressed, all receiving the lowest BED10 (43.2 Gy), corresponding to 24 Gy in 3 fractions. After treatment of adrenal metastases with SBRT, the median time to salvage chemotherapy was 5.3 months (range 1.0–38.8 months) and 1-year freedom from salvage chemotherapy was 44%. These results suggest that SBRT to adrenal metastases was tolerated with low toxicity in limited metastatic patients and control rates are promising. This study supports the growing body of literature treating patients with adrenal metastases with SBRT.

A national radiation oncology medical student clerkship survey: didactic curricular components increase confidence in clinical competency.

PURPOSE Students applying to radiation oncology residency programs complete 1 or more radiation oncology clerkships. This study assesses student experiences and perspectives during radiation oncology clerkships. The impact of didactic components and number of clerkship experiences in relation to confidence in clinical competency and preparation to function as a first-year radiation oncology resident are evaluated. METHODS AND MATERIALS An anonymous, Internet-based survey was sent via direct e-mail to all applicants to a single radiation oncology residency program during the 2012-2013 academic year. The survey was composed of 3 main sections including questions regarding baseline demographic information and prior radiation oncology experience, rotation experiences, and ideal clerkship curriculum content. RESULTS The survey response rate was 37% (70 of 188). Respondents reported 191 unique clerkship experiences. Of the respondents, 27% (19 of 70) completed at least 1 clerkship with a didactic component geared towards their level of training. Completing a clerkship with a didactic component was significantly associated with a respondents confidence to function as a first-year radiation oncology resident (Wilcoxon rank-sum P=.03). However, the total number of clerkships completed did not correlate with confidence to pursue radiation oncology as a specialty (Spearman ρ P=.48) or confidence to function as a first year resident (Spearman ρ P=.43). CONCLUSIONS Based on responses to this survey, rotating students perceive that the majority of radiation oncology clerkships do not have formal didactic curricula. Survey respondents who completed a clerkship with a didactic curriculum reported feeling more prepared to function as a radiation oncology resident. However, completing an increasing number of clerkships does not appear to improve confidence in the decision to pursue radiation oncology as a career or to function as a radiation oncology resident. These results support further development of structured didactic curricula for the radiation oncology clerkship.

Feasibility and toxicity of hypofractionated image guided radiation therapy for large volume limited metastatic disease

PURPOSE Hypofractionated image guided radiation therapy (HIGRT) is increasingly used for limited metastases. Reported studies have mostly treated small volume tumors. Here, we report the toxicity and oncologic outcomes following treatment of large volume metastases. METHODS AND MATERIALS HIGRT patients treated from October 2005 to March 2010 were reviewed. Gross tumor volumes (GTV) and planning target volumes (PTV) were obtained from planning software. A metastasis was considered large volume if the treated PTV exceeded 50 cc. Patients were treated with either 10-fraction (4-5 Gy per fraction) or 3-5 fraction (8-14 Gy per fraction) regimens. Toxicity was obtained from both prospectively collected databases and retrospectively from patient charts. RESULTS Sixty-four patients with 93 treated lesions >50 cc were identified. The median GTV and PTV volumes were 41 and 119 cc, respectively. The median number of treated large volume lesions was 1, and a maximum of 3 large volume lesions were treated in a single patient. Primary malignancies included non-small cell lung cancer, renal cell, colorectal, breast, bladder, pituitary, small cell lung cancer, sarcoma, head-and-neck cancer, and hepatocellular cancer. Treated sites included lung (n = 33), regional lymph nodes (n = 20), bone (n = 17), adrenal (n = 9), and liver (n = 6). The most frequently used treatment regimen was 50 Gy in 5 Gy fractions. The median follow-up was 27 months for surviving patients. Treated lesion control was 78%. Low rates of acute and late grade 3 or higher toxicity were reported, with 3 and 5 patients experiencing each, respectively. CONCLUSIONS HIGRT to large volume oligometastatic disease is tolerable and feasible with promising tumor control. Local radiation therapy should be considered in patients with large volume, limited metastatic disease.