Keith A. Cengel

An evidence based review of proton beam therapy: The report of ASTRO’s emerging technology committee

Proton beam therapy (PBT) is a novel method for treating malignant disease with radiotherapy. The purpose of this work was to evaluate the state of the science of PBT and arrive at a recommendation for the use of PBT. The emerging technology committee of the American Society of Radiation Oncology (ASTRO) routinely evaluates new modalities in radiotherapy and assesses the published evidence to determine recommendations for the society as a whole. In 2007, a Proton Task Force was assembled to evaluate the state of the art of PBT. This report reflects evidence collected up to November 2009. Data was reviewed for PBT in central nervous system tumors, gastrointestinal malignancies, lung, head and neck, prostate, and pediatric tumors. Current data do not provide sufficient evidence to recommend PBT in lung cancer, head and neck cancer, GI malignancies, and pediatric non-CNS malignancies. In hepatocellular carcinoma and prostate cancer and there is evidence for the efficacy of PBT but no suggestion that it is superior to photon based approaches. In pediatric CNS malignancies PBT appears superior to photon approaches but more data is needed. In large ocular melanomas and chordomas, we believe that there is evidence for a benefit of PBT over photon approaches. PBT is an important new technology in radiotherapy. Current evidence provides a limited indication for PBT. More robust prospective clinical trials are needed to determine the appropriate clinical setting for PBT.

Class I PI3 Kinase Inhibition by the Pyridinylfuranopyrimidine Inhibitor PI-103 Enhances Tumor Radiosensitivity

Cell signaling initiated at the epidermal growth factor receptor (EGFR), RAS oncoproteins, or PI3K contributes to a common pathway that promotes tumor survival after radiation-induced DNA damage. Inhibition of signaling at the level of EGFR, RAS, and PI3K has been tested, but clinical applicability has been shown only at the level of the EGFR or by inhibiting RAS indirectly with prenyltransferase inhibitors. Inhibition of PI3K with LY294002 or wortmannin lacks specificity and has shown unacceptable toxicity in preclinical studies. We previously showed that inhibiting class I PI3K expression with siRNA resulted in enhanced radiation killing of tumor cells. Here, we tested the possibility of achieving specific tumor cell radiosensitization with a pharmacologic inhibitor of class I PI3K, the pyridinylfuranopyrimidine inhibitor PI-103. Our results show that inhibiting PI3K activity reduces phosphorylation of AKT at serine 473. Reduced survival is seen in cells with AKT activation and seems preferential for tumor cells over cells in which AKT activity is not elevated. Reduced survival is accompanied by persistence of DNA damage as evidenced by persistence of gamma H2AX and Rad 51 foci after irradiation in the presence of the inhibitor. Reduced survival does not result from cell cycle redistribution during the PI-103 treatment intervals tested, although combining PI-103 treatment with radiation enhances the G(2)-M delay observed after irradiation. These results indicate that pharmacologic inhibitors with enhanced specificity for class I PI3K may be of benefit when combined with radiotherapy.

Dietary Curcumin Increases Antioxidant Defenses in Lung, Ameliorates Radiation-Induced Pulmonary Fibrosis, and Improves Survival in Mice

Abstract The effectiveness of lung radiotherapy is limited by radiation tolerance of normal tissues and by the intrinsic radiosensitivity of lung cancer cells. The chemopreventive agent curcumin has known antioxidant and tumor cell radiosensitizing properties. Its usefulness in preventing radiation-induced pneumonopathy has not been tested previously. We evaluated dietary curcumin in radiation-induced pneumonopathy and lung tumor regression in a murine model. Mice were given 1% or 5% (w/w) dietary curcumin or control diet prior to irradiation and for the duration of the experiment. Lungs were evaluated at 3 weeks after irradiation for acute lung injury and inflammation by evaluating bronchoalveolar lavage (BAL) fluid content for proteins, neutrophils and at 4 months for pulmonary fibrosis. In a separate series of experiments, an orthotopic model of lung cancer using intravenously injected Lewis lung carcinoma (LLC) cells was used to exclude possible tumor radioprotection by dietary curcumin. In vitro, curcumin boosted antioxidant defenses by increasing heme oxygenase 1 (HO-1) levels in primary lung endothelial and fibroblast cells and blocked radiation-induced generation of reactive oxygen species (ROS). Dietary curcumin significantly increased HO-1 in lungs as early as after 1 week of feeding, coinciding with a steady-state level of curcumin in plasma. Although both 1% and 5% w/w dietary curcumin exerted physiological changes in lung tissues by significantly decreasing LPS-induced TNF-α production in lungs, only 5% dietary curcumin significantly improved survival of mice after irradiation and decreased radiation-induced lung fibrosis. Importantly, dietary curcumin did not protect LLC pulmonary metastases from radiation killing. Thus dietary curcumin ameliorates radiation-induced pulmonary fibrosis and increases mouse survival while not impairing tumor cell killing by radiation.

Radical pleurectomy and intraoperative photodynamic therapy for malignant pleural mesothelioma.

BACKGROUND Radical pleurectomy (RP) for mesothelioma is often considered either technically unfeasible or an operation limited to patients who would not tolerate a pneumonectomy. The purpose of this study was to review our experience using RP and intraoperative photodynamic therapy (PDT) for mesothelioma. METHODS Thirty-eight patients (42-81 years) underwent RP-PDT. Thirty five of 38 (92%) patients also received systemic therapy. Standard statistical techniques were used for analysis. RESULTS Thirty seven of 38 (97%) patients had stage III/IV cancer (according to the American Joint Committee on Cancer [AJCC manual 7th Edition, 2010]) and 7/38 (18%) patients had nonepithelial subtypes. Macroscopic complete resection was achieved in 37/38 (97%) patients. There was 1 postoperative mortality (stroke). At a median follow-up of 34.4 months, the median survival was 31.7 months for all 38 patients, 41.2 months for the 31/38 (82%) patients with epithelial subtypes, and 6.8 months for the 7/38 (18%) patients with nonepithelial subtypes. Median progression-free survival (PFS) was 9.6, 15.1, and 4.8 months, respectively. The median survival and PFS for the 20/31 (64%) patients with N2 epithelial disease were 31.7 and 15.1 months, respectively. CONCLUSIONS It was possible to achieve a macroscopic complete resection using lung-sparing surgery in 97% of these patients with stage III/IV disease. The survival we observed with this approach was unusually long for the patients with the epithelial subtype but, interestingly, the PFS was not. The reason for this prolonged survival despite recurrence is not clear but is potentially related to preservation of the lung or some PDT-induced effect, or both. We conclude that the results of this lung-sparing approach are safe, encouraging, and warrant further investigation.

Motexafin Lutetium-Photodynamic Therapy of Prostate Cancer: Short- and Long-Term Effects on Prostate-Specific Antigen

Purpose: The time course of serum prostate-specific antigen (PSA) response to photodynamic therapy (PDT) of prostate cancer was measured. Experimental Design: Seventeen patients were treated in a phase I trial of motexafin lutetium-PDT. PDT dose was calculated in each patient as the product of the ex vivo measured pre-PDT photosensitizer level and the in situ measured light dose. Serum PSA level was measured within 2 months before PDT (baseline), and at day 1; weeks 1 to 3; months 1, 2, and 3; months 4 to 6; and months 7 to 11 after PDT. Results: At 24 hours after PDT, serum PSA increased by 98% ± 36% (mean ± SE) relative to baseline levels (P = 0.007). When patients were dichotomized based on median PDT dose, those who received high PDT dose showed a 119% ± 52% increase in PSA compared with a 54% ± 27% increase in patients treated at low PDT dose. Patients treated with high versus low PDT dose showed a median biochemical delay of 82 versus 43 days (P = 0.024), with biochemical delay defined as the length of time between PDT and a nonreversible increase in PSA to a value greater than or equal to baseline. Conclusions: Results show PDT to induce large, transient increases in serum PSA levels. Patients who experienced high PDT dose showed greater short-term increase in PSA and a significantly more durable PSA response (biochemical delay). These data strongly promote the need for individualized delivery of PDT dose and assessment of treatment effect in PDT of prostate cancer. Information gained from such patient-specific measurements could facilitate the introduction of multiple PDT sessions in patients who would benefit.

Angiogenesis and tumor growth inhibition by a matrix metalloproteinase inhibitor targeting radiation-induced invasion

In this study, we have evaluated the interactions between ionizing radiation and a matrix metalloproteinase (MMP) inhibitor. Using Matrigel invasion assays, we show that ionizing radiation induced a dose-dependent increase in the invasive phenotype of cultured B16 melanoma cells and that conditioned medium from these irradiated B16 cells promoted endothelial cell [human microvascular endothelial cells (HMEC)] invasiveness. To determine whether the radiation-induced changes in invasive phenotype could be due to changes in MMP activation, we have tested the ability of the MMP inhibitor Metastat to modulate the ionizing radiation–induced invasive phenotype using both an in vitro melanoma model and a mouse s.c. tumor model. In these studies, Metastat inhibited the ionizing radiation–induced invasive phenotype in cultured B16 cells and similarly inhibited the increase in HMEC invasion induced by conditioned medium from irradiated B16 cells. Conversely, ionizing radiation increased B16 MMP-2 activity and the conditioned medium from irradiated B16 induced HMEC MMP-2 activity. To further investigate the interaction between ionizing radiation and MMP activation, we then studied the effects of ionizing radiation on downstream effectors of the MMP system. We found that ionizing radiation induced vascular endothelial growth factor (VEGF) secretion by B16 melanoma cells and that this secretion was inhibited by Metastat. Similarly, conditioned medium from irradiated B16 was also able to increase VEGF secretion in HMECs. Moreover, ionizing radiation–induced melanoma cell invasiveness was partially inhibited by an anti-VEGF monoclonal antibody. In vivo, ionizing radiation plus concomitant Metastat yielded the greatest growth inhibition of melanoma s.c. tumors and this effect correlated with inhibition of angiogenesis as measured by both Doppler ultrasonography and platelet/endothelial cell adhesion molecule-1 staining. Finally, ionizing radiation modulated MMP-2, VEGF, and VEGF receptor expression in these tumor samples using immunohistochemistry. Taken together, these results suggest that there is an ionizing radiation–induced tumor survival pathway and a possible paracrine ionizing radiation–induced stimulatory pathway emanating from tumor cells toward the endothelial bed that is impeded when Metastat is given simultaneously. This model could provide in vivo evidence of the antitumor efficacy of combining a MMP inhibitor with ionizing radiation to target radiation-induced invasion and angiogenesis.

Dietary flaxseed prevents radiation-induced oxidative lung damage, inflammation and fibrosis in a mouse model of thoracic radiation injury

Flaxseed (FS) has high contents of omega-3 fatty acids and lignans with antioxidant properties. Its use in preventing thoracic X-ray radiation therapy (XRT)-induced pneumonopathy has never been evaluated. We evaluated FS supplementation given to mice given before and post-XRT. FS-derived lignans, known for their direct antioxidant properties, were evaluated in abrogating ROS generation in cultured endothelial cells following gamma radiation exposure. Mice were fed 10% FS or isocaloric control diet for three weeks and given 13.5 Gy thoracic XRT. Lungs were evaluated at 24 hours for markers of radiation-induced injury, three weeks for acute lung damage (lipid peroxidation, lung edema and inflammation), and at four months for late lung damage (inflammation and fibrosis). FS-Lignans blunted ROS generation in vitro, resulting from radiation in a dose-dependent manner. FS-fed mice had reduced expression of lung injury biomarkers (Bax, p21, and TGF-beta1) at 24 hours following XRT and reduced oxidative lung damage as measured by malondialdehyde (MDA) levels at 3 weeks following XRT. In addition, FS-fed mice had decreased lung fibrosis as determined by hydroxyproline content and decreased inflammatory cell influx into lungs at 4 months post XRT. Importantly, when Lewis Lung carcinoma cells were injected systemically in mice, FS dietary supplementation did not appear to protect lung tumors from responding to thoracic XRT. Dietary FS is protective against pulmonary fibrosis, inflammation and oxidative lung damage in a murine model. Moreover, in this model, tumor radioprotection was not observed. FS lignans exhibited potent radiation-induced ROS scavenging action. Taken together, these data suggest that dietary flaxseed may be clinically useful as an agent to increase the therapeutic index of thoracic XRT by increasing the radiation tolerance of lung tissues.

Pancreatic Cancer Cell Radiation Survival and Prenyltransferase Inhibition: The Role of K-Ras

Activating K-ras mutations are found in approximately 90% of pancreatic carcinomas and may contribute to the poor prognosis of these tumors. Because radiotherapy is frequently used in pancreatic cancer treatment, we assessed the contribution of oncogenic K-ras signaling to pancreatic cancer radiosensitivity. Seven human pancreatic carcinoma lines with activated K-ras and two cell lines with wild-type ras were used to examine clonogenic cell survival after Ras inhibition. Ras inhibition was accomplished by small interfering RNA (siRNA) knockdown of K-ras expression and by blocking Ras processing using a panel of prenyltransferase inhibitors of differing specificity for the two prenyltransferases that modify K-Ras. K-ras knockdown by siRNA or inhibition of prenyltransferase activity resulted in radiation sensitization in vitro and in vivo in tumors with oncogenic K-ras mutations. Inhibition of farnesyltransferase alone was sufficient to radiosensitize most K-ras mutant tumors, although K-Ras prenylation was not blocked. These results show that inhibition of activated K-Ras can promote radiation killing of pancreatic carcinoma in a superadditive manner. The finding that farnesyltransferase inhibition alone radiosensitizes tumors with K-ras mutations implies that a farnesyltransferase inhibitor-sensitive protein other than K-Ras may contribute to survival in the context of mutant K-ras. Farnesyltransferase inhibitors could therefore be of use as sensitizers for pancreatic carcinoma radiotherapy.

Photodynamic therapy for the treatment of non-small cell lung cancer.

Photodynamic therapy is increasingly being utilized to treat thoracic malignancies. For patients with early-stage non-small cell lung cancer, photodynamic therapy is primarily employed as an endobronchial therapy to definitely treat endobronchial, roentgenographically occult, or synchronous primary carcinomas. As definitive monotherapy, photodynamic therapy is most effective in treating bronchoscopically visible lung cancers ≤1 cm with no extracartilaginous invasion. For patients with advanced-stage non-small cell lung cancer, photodynamic therapy can be used to palliate obstructing endobronchial lesions, as a component of definitive multi-modality therapy, or to increase operability or reduce the extent of operation required. A review of the available medical literature detailing all published studies utilizing photodynamic therapy to treat at least 10 patients with non-small cell lung cancer is performed, and treatment recommendations and summaries for photodynamic therapy applications are described.

Photodynamic Therapy and the Evolution of a Lung-Sparing Surgical Treatment for Mesothelioma

BACKGROUND Photodynamic therapy (PDT) is a light-based cancer treatment that acts to a depth of several millimeters into tissue. This study reviewed the results of patients who underwent a macroscopic complete resection, by two different surgical techniques, and intraoperative PDT as a treatment for malignant pleural mesothelioma. METHODS From 2004 to 2008, 28 patients with malignant pleural mesothelioma underwent macroscopic complete resection, 14 by modified extrapleural pneumonectomy (MEPP) and 14 by radical pleurectomy (RP) and intraoperative PDT. The surgical technique evolved over this period such that 13 of the last 16 patients underwent lung-sparing procedures, even in the setting of large-bulk tumors. RESULTS Demographics in the MEPP and RP cohorts were similar in age, sex, stage, nodal status, histology, and adjuvant treatments. Stage III/IV disease was present in 12 of 14 patients (86%), with 50% or more with +N2 disease. The median overall survival for the MEPP group was 8.4 months, but has not yet been reached for the RP group at a median follow-up of 2.1 years. CONCLUSIONS In addition to the inherent advantages of sparing the lung, RP plus PDT yielded a superior overall survival than MEPP plus PDT in this series. The overall survival for the RP plus PDT group was, for unclear reasons, superior to results reported in many surgical series, especially for a cohort with such advanced disease. Given these results, we believe RP plus PDT is a reasonable option for appropriate patients pursuing a surgical treatment for malignant pleural mesothelioma and that this procedure can serve as the backbone of surgically based multimodal treatments.