Considerations in Identifying Optimal Particles for Radiation Medicine

Nanoparticles for radiooncology: Mission, vision, challenges

Cancer is one of the leading non-communicable diseases with highest mortality rates worldwide. About half of all cancer patients receive radiation treatment in the course of their disease. However, treatment outcome and curative potential of radiotherapy is often impeded by genetically and/or environmentally driven mechanisms of tumor radioresistance and normal tissue radiotoxicity. While nanomedicine-based tools for imaging, dosimetry and treatment are potential keys to the improvement of therapeutic efficacy and reducing side effects, radiotherapy is an established technique to eradicate the tumor cells. In order to progress the introduction of nanoparticles in radiooncology, due to the highly interdisciplinary nature, expertise in chemistry, radiobiology and translational research is needed. In this report recent insights and promising policies to design nanotechnology-based therapeutics for tumor radiosensitization will be discussed. An attempt is made to cover the entire field from preclinical development to clinical studies. Hence, this report illustrates (1) the radio- and tumor-biological rationales for combining nanostructures with radiotherapy, (2) tumor-site targeting strategies and mechanisms of cellular uptake, (3) biological response hypotheses for new nanomaterials of interest, and (4) challenges to translate the research findings into clinical trials.

Proton-beam therapy for tumors of the CNS

The focus of this review is proton radiotherapy for primary neoplasms of the brain. Although glial cells are among the most radioresistant in the body, the presence of sensitive critical structures and the high doses needed to control CNS tumors present a formidable challenge to the treating radiation oncologist. Treatment with conventional photon radiation at doses required to control disease progression all too often results in unacceptable toxicity. Protons have intrinsic properties that often allow radiation oncologists to deliver a higher dose to the tumor compared with photons, while at the same time offering better sparing of normal tissues. Recognition of these advantages has resulted in development of many new proton treatment facilities worldwide.

Surgery and radiotherapy: complementary tools in the management of benign intracranial tumors

Historically, radiation therapy has been used extensively in the treatment of malignant and aggressive intracranial tumors, and the importance of its role has been repeatedly verified by prolonged patient survival rates and increased tumor control. As more modern capabilities are employed in surgery and radiotherapy, attention is being directed to the utility of radiation as either primary or secondary treatment of benign tumors. Specifically, primary treatment encompasses irradiation of small benign tumors without biopsy confirmation of tumor type; secondary treatment involves postoperative radiation therapy, with the possibility that less-aggressive tumor resection may be performed in areas that have a higher probability of resultant neurological deficit. Current literature suggests that this is not only a possible treatment strategy, but that it may be superior to more radical resection in some cases, for example, in vestibular schwannomas and meningiomas. This article provides an overview of factors to consider in the use of radiation therapy and reviews the relationships between radiation and surgery, notably the unique complementary role each plays in the treatment of benign intracranial tumors.

Improving outcomes in difficult bone cancers using multimodality therapy, including radiation: Physician and nursing perspectives

Principles of therapy are similar for Ewing's sarcoma and osteosarcoma. Chemotherapy or surgery alone cures few patients. Multimodality measures are needed for durable response. Quality of life and function are very important short- and long-term considerations. The spine, sacrum, pelvis, ankle, hand, mediastinum, pulmonary hilum, and chest wall are examples of bone cancer locations for which surgery is difficult. Patients with positive margins may need radiation and may experience systemic therapy delay, recurrence, loss of function, or any combination of these. When radiation is used as a means of local control, concomitant chemotherapy can increase its effectiveness. Options for difficult Ewing's sarcoma and osteosarcoma situations and multimodality solutions, including 1 mCi/kg of samarium and proton therapy, are discussed. Combination radiation and chemotherapy regimens are summarized, and organization of patients, caregivers, and medical teams for multimodality therapy is described, along with tools used in our institution that aid in this process.

The biological effectiveness of antiproton irradiation

BACKGROUND AND PURPOSE

Antiprotons travel through tissue in a manner similar to that for protons until they reach the end of their range where they annihilate and deposit additional energy. This makes them potentially interesting for radiotherapy. The aim of this study was to conduct the first ever measurements of the biological effectiveness of antiprotons.

MATERIALS AND METHODS

V79 cells were suspended in a semi-solid matrix and irradiated with 46.7MeV antiprotons, 48MeV protons, or (60)Co gamma-rays. Clonogenic survival was determined as a function of depth along the particle beams. Dose and particle fluence response relationships were constructed from data in the plateau and Bragg peak regions of the beams and used to assess the biological effectiveness.

RESULTS

Due to uncertainties in antiproton dosimetry we defined a new term, called the biologically effective dose ratio (BEDR), which compares the response in a minimally spread out Bragg peak (SOBP) to that in the plateau as a function of particle fluence. This value was approximately 3.75 times larger for antiprotons than for protons. This increase arises due to the increased dose deposited in the Bragg peak by annihilation and because this dose has a higher relative biological effectiveness (RBE).

CONCLUSION

We have produced the first measurements of the biological consequences of antiproton irradiation. These data substantiate theoretical predictions of the biological effects of antiproton annihilation within the Bragg peak, and suggest antiprotons warrant further investigation.