Clinical Proton Radiation Therapy Research at the Francis H. Burr Proton Therapy Center

Deep-Tissue Activation of Photonanomedicines: An Update and Clinical Perspectives

Simple Summary

Photodynamic therapy (PDT) is a light-activated treatment modality, which is being clinically used and further developed for a number of premalignancies, solid tumors, and disseminated cancers. Nanomedicines that facilitate PDT (photonanomedicines, PNMs) have transformed its safety, efficacy, and capacity for multifunctionality. This review focuses on the state of the art in deep-tissue activation technologies for PNMs and explores how their preclinical use can evolve towards clinical translation by harnessing current clinically available instrumentation.

Abstract

With the continued development of nanomaterials over the past two decades, specialized photonanomedicines (light-activable nanomedicines, PNMs) have evolved to become excitable by alternative energy sources that typically penetrate tissue deeper than visible light. These sources include electromagnetic radiation lying outside the visible near-infrared spectrum, high energy particles, and acoustic waves, amongst others. Various direct activation mechanisms have leveraged unique facets of specialized nanomaterials, such as upconversion, scintillation, and radiosensitization, as well as several others, in order to activate PNMs. Other indirect activation mechanisms have leveraged the effect of the interaction of deeply penetrating energy sources with tissue in order to activate proximal PNMs. These indirect mechanisms include sonoluminescence and Cerenkov radiation. Such direct and indirect deep-tissue activation has been explored extensively in the preclinical setting to facilitate deep-tissue anticancer photodynamic therapy (PDT); however, clinical translation of these approaches is yet to be explored. This review provides a summary of the state of the art in deep-tissue excitation of PNMs and explores the translatability of such excitation mechanisms towards their clinical adoption. A special emphasis is placed on how current clinical instrumentation can be repurposed to achieve deep-tissue PDT with the mechanisms discussed in this review, thereby further expediting the translation of these highly promising strategies.

Proton and Heavy Particle Intracranial Radiosurgery

Stereotactic radiosurgery (SRS) involves the delivery of a highly conformal ablative dose of radiation to both benign and malignant targets. This has traditionally been accomplished in a single fraction; however, fractionated approaches involving five or fewer treatments have been delivered for larger lesions, as well as lesions in close proximity to radiosensitive structures. The clinical utilization of SRS has overwhelmingly involved photon-based sources via dedicated radiosurgery platforms (e.g., Gamma Knife® and Cyberknife®) or specialized linear accelerators. While photon-based methods have been shown to be highly effective, advancements are sought for improved dose precision, treatment duration, and radiobiologic effect, among others, particularly in the setting of repeat irradiation. Particle-based techniques (e.g., protons and carbon ions) may improve many of these shortcomings. Specifically, the presence of a Bragg Peak with particle therapy at target depth allows for marked minimization of distal dose delivery, thus mitigating the risk of toxicity to organs at risk. Carbon ions also exhibit a higher linear energy transfer than photons and protons, allowing for greater relative biological effectiveness. While the data are limited, utilization of proton radiosurgery in the setting of brain metastases has been shown to demonstrate 1-year local control rates >90%, which are comparable to that of photon-based radiosurgery. Prospective studies are needed to further validate the safety and efficacy of this treatment modality. We aim to provide a comprehensive overview of clinical evidence in the use of particle therapy-based radiosurgery.

Radiotherapy of Parasellar Tumours

Parasellar tumours represent a wide group of intracranial lesions, both benign and malignant. They may arise from several structures located within the parasellar area or they may infiltrate or metastasize this region. The treatment of the tumours located in these areas is challenging because of their complex anatomical location and their heterogenous histology. It often requires a multimodal approach, including surgery, radiation therapy (RT), and medical therapy. Due to the proximity of critical structures and the risks of side effects related to the procedure, a successful surgical resection is often not achievable. Thus, RT plays a crucial role in the treatment of several parasellar tumours. Conventional fractionated RT and modern radiation techniques, like stereotactic radiosurgery and proton beam RT, have become a standard management option, in particular for cases with residual or recurrent tumours after surgery and for those cases where surgery is contraindicated. This review examines the role of RT in parasellar tumours analysing several techniques, outcomes and side effects.

Socio-economic factors affect the outcome of soft tissue sarcoma: an analysis of SEER data

BACKGROUND

This study analyzed whether socio-economic factors affect the cause specific survival of soft tissue sarcoma (STS).

METHODS

Surveillance, Epidemiology and End Results (SEER) soft tissue sarcoma (STS) data were used to identify potential socio-economic disparities in outcome. Time to cause specific death was computed with Kaplan-Meier analysis. Kolmogorov-Smirnov tests and Cox proportional hazard analysis were used for univariate and multivariate tests, respectively. The areas under the receiver operating curve were computed for predictors for comparison.

RESULTS

There were 42,016 patients diagnosed STS from 1973 to 2009. The mean follow up time (S.D.) was 66.6 (81.3) months. Stage, site, grade were significant predictors by univariate tests. Race and rural-urban residence were also important predictors of outcome. These five factors were all statistically significant with Cox analysis. Rural and African-American patients had a 3-4% disadvantage in cause specific survival.

CONCLUSIONS

Socio-economic factors influence cause specific survival of soft tissue sarcoma. Ensuring access to cancer care may eliminate the outcome disparities.

Underusage of radiotherapy and a lack of socio-economic disparity in treatment outcome: a population-based study on adenoid cystic carcinomas

This study used receiver operating characteristic curve to analyse a long list of biological, treatment and socio-economic predictors of adenoid cystic carcinoma treatment outcome. Anatomical staging was found to be the most predictive factor of outcome.

Purpose

This study used receiver operating characteristic curve (ROC) to analyse surveillance, epidemiology and end results (SEER) adenoid cystic carcinoma data to identify predictive models and potential disparity in outcome.

Materials and methods

For the risk modelling, each factor was fitted by a generalised linear model to predict the cause-specific survival. The area under the ROC was computed. Similar strata were combined to construct the most parsimonious models. A random sampling algorithm was used to estimate the modelling errors. Risk of adenoid cystic carcinoma death was computed for the predictors for comparison.

Results

There were 5,947 patients diagnosed from 1973 to 2009 included in this study. The mean follow-up time (SD) was 93·8 (90·6) months. Three out of five patients were women. The mean (SD) age was 58·55 (16·01) years. SEER stage was the most predictive factor of outcome (ROC area of 0·68). Sex, radiotherapy and surgery had ROC areas of about 0·57. None of the socio-economic disparities was found for treatment outcome. Radiotherapy was underused in localised and regional stages when the intent was curative, especially in older patients.

Conclusion

Anatomical staging was predictive and useful in treatment selection. Understaging and underuse of radiotherapy may have contributed to poor outcomes.

Surveying and optimizing the predictors for ependymoma specific survival using SEER data

PURPOSE

This study used receiver operating characteristic curve to analyze Surveillance, Epidemiology and End Results (SEER) ependymoma data to identify predictive models and potential disparity in outcome.

MATERIALS AND METHODS

This study analyzed socio-economic, staging and treatment factors available in the SEER database for ependymoma. For the risk modeling, each factor was fitted by a Generalized Linear Model to predict the outcome ('brain and other nervous systems' specific death in yes/no). The area under the receiver operating characteristic curve (ROC) was computed. Similar strata were combined to construct the most parsimonious models. A random sampling algorithm was used to estimate the modeling errors. Risk of ependymoma death was computed for the predictors for comparison.

RESULTS

A total of 3,500 patients diagnosed from 1973 to 2009 were included in this study. The mean follow up time (S.D.) was 79.8 (82.3) months. Some 46% of the patients were female. The mean (S.D.) age was 34.4 (22.8) years. Age was the most predictive factor of outcome. Unknown grade demonstrated a 15% risk of cause specific death compared to 9% for grades I and II, and 36% for grades III and IV. A 5-tiered grade model (with a ROC area 0.48) was optimized to a 3-tiered model (with ROC area of 0.53). This ROC area tied for the second with that for surgery. African-American patients had 21.5% risk of death compared with 16.6% for the others. Some 72.7% of patient who did not get RT had cerebellar or spinal ependymoma. Patients undergoing surgery had 16.3% risk of death, as compared to 23.7% among those who did not have surgery.

CONCLUSION

Grading ependymoma may dramatically improve modeling of data. RT is under used for cerebellum and spinal cord ependymoma and it may be a potential way to improve outcome.

New strategies in radiation therapy: exploiting the full potential of protons

Protons provide significant dosimetric advantages compared with photons because of their unique depth-dose distribution characteristics. However, they are more sensitive to the effects of intra- and intertreatment fraction anatomic variations and uncertainties in treatment setup. Furthermore, in the current practice of proton therapy, the biologic effectiveness of protons relative to photons is assumed to have a generic fixed value of 1.1. However, this is a simplification, and it is likely higher in different portions of the proton beam. Current clinical practice and trials have not fully exploited the unique physical and biologic properties of protons. Intensity-modulated proton therapy, with its ability to manipulate energies (in addition to intensities), provides an entirely new dimension, which, with ongoing research, has considerable potential to increase the therapeutic ratio.

Impact of socioeconomic disparities on cause-specific survival of retinoblastoma

Retinoblastoma (RB) is a rare disease of infancy and early childhood. This study investigated the effects of socioeconomic factors on the cause-specific survival of RB. Data from patients diagnosed with RB between 1973 and 2009 were obtained from the Surveillance, Epidemiology and End Results (SEER) database. The study included 1,456 patients with a the mean follow-up time (SD) of 128.75 (113.74) months and a mean age (SD) of 1.4 (2.6) years. This study analyzed socioeconomic, staging and treatment factors available in the SEER database for RB. Kaplan-Meier analysis was used to analyze time-to-failure data. The two-sample Kolmogorov-Smirnov test was used for univariate analysis and the Cox proportional hazards model was used for multivariate analysis. The area under the receiver operating characteristic (ROC) curve was computed for predictors. SEER stage was the most significant predictive pretreatment factor. The identified socioeconomic barriers included ethnicity and rural-urban residence status that led to a 3% decrease in RB cause-specific survival. Thus, eliminating barriers to treatment is crucial for reducing the outcome disparities.

Radiosurgery with photons or protons for benign and malignant tumours of the skull base: a review

Stereotactic radiosurgery (SRS) is an important treatment option for intracranial lesions. Many studies have shown the effectiveness of photon-SRS for the treatment of skull base (SB) tumours; however, limited data are available for proton-SRS.Several photon-SRS techniques, including Gamma Knife, modified linear accelerators (Linac) and CyberKnife, have been developed and several studies have compared treatment plan characteristics between protons and photons.The principles of classical radiobiology are similar for protons and photons even though they differ in terms of physical properties and interaction with matter resulting in different dose distributions.Protons have special characteristics that allow normal tissues to be spared better than with the use of photons, although their potential clinical superiority remains to be demonstrated.A critical analysis of the fundamental radiobiological principles, dosimetric characteristics, clinical results, and toxicity of proton- and photon-SRS for SB tumours is provided and discussed with an attempt of defining the advantages and limits of each radiosurgical technique.

A case of hemorrhagic gastroduodenitis after proton beam radiation for pancreatic cancer with multiple hemorrhagic risk factors: successful treatment with argon plasma coagulation

Radiation-induced gastroduodenitis is a well-known but rare disorder causing uncontrollable hemorrhage and has not been reported as a complication of proton beam therapy in radiation treatment. Argon plasma coagulation (APC) has been shown to be effective and safe in the management of radiation-induced hemorrhagic gastroduodenitis. We describe a case of hemorrhagic gastroduodenitis after proton beam radiation therapy for pancreatic cancer with multiple hemorrhagic risk factors, which was treated successfully with APC. A 62-year-old man was diagnosed as having early pancreatic cancer that was incidentally detected on computed tomography when screening for hepatocellular carcinoma. He opted to receive radical proton beam radiation for pancreatic cancer but not surgery because he had multiple risk factors such as liver cirrhosis due to hepatitis C virus and chronic renal failure that required hemodialysis. Three months later, however, he developed hemorrhagic gastroduodenitis induced by proton beam radiation although the cancer had been eradicated. Initially, he required frequent blood transfusions, but his disease condition improved dramatically after several endoscopic treatments using APC. The patient has been free of relapse after pancreatic cancer for >2 years.

Enhanced antitumor effect of combined gemcitabine and proton radiation in the treatment of pancreatic cancer

OBJECTIVES

This study evaluates the efficacy of combining proton irradiation with gemcitabine, and the role the inhibitor of apoptosis proteins survivin and X-linked inhibitor of apoptosis protein (XIAP) play in the radiosensitive versus radioresistant status of pancreatic cancer.

METHODS

The radioresistant (PANC-1) and radiosensitive (MIA PaCa-2) pancreatic carcinoma cells' response to combined gemcitabine and proton irradiation was compared. Cells were treated with 0.1 to 500 microM gemcitabine and 0- to 15-Gy proton irradiation after which trypan blue and flow cytometry were used to determine changes in the cell cycle and apoptosis. Expression levels of survivin and XIAP were measured using Western blotting. Combination therapy with gemcitabine for 24 hours followed by 10-Gy proton irradiation proved most effective.

RESULTS

Gemcitabine and proton irradiation resulted in increased survivin levels with little apoptosis. However, combination therapy resulted in robust apoptotic induction with a concomitant survivin and XIAP reduction in the MIA PaCa-2 cells with little effect in the PANC-1 cells. Small interfering RNA studies confirmed a role for XIAP in the radioresistance of PANC-1 cells.

CONCLUSIONS

Our data demonstrate that combining gemcitabine and proton irradiation enhances apoptosis in human pancreatic cancer cells when XIAP levels decrease. Therefore, XIAP may play an important role in human pancreatic cancer proton radioresistance.

Definitive radiotherapy for prostate cancer

The probability of extraprostatic disease may be estimated based on clinical T-stage, pretreatment prostatic-specific antigen, Gleason score, and percent positive core biopsies. Patients with disease confined to the prostate may be treated with either prostatectomy or radiotherapy (RT). Patients with extraprostatic disease without evidence of distant metastases are best managed with RT. RT consisting of either external beam and/or brachytherapy results in a relatively high likelihood of cure, particularly for those with low- and intermediate-risk disease. The impact of elective nodal RT on survival is unclear. Dose escalation results in improved biochemical relapse-free survival compared with standard dose RT. Androgen deprivation therapy likely improves the probability of disease control in patients with high-risk cancers.