Recent Advances in Brachytherapy Using Radioactive Nanoparticles: An Alternative to Seed-Based Brachytherapy

Interstitial brachytherapy (BT) is generally used for the treatment of well-confined solid tumors. One example of this is in the treatment of prostate tumors by permanent placement of radioactive seeds within the prostate gland, where low doses of radiation are delivered for several months. However, successful implementation of this technique is hampered due to several posttreatment adverse effects or symptoms and operational and logistical complications associated with it. Recently, with the advancements in nanotechnology, radioactive nanoparticles (radio-NPs) functionalized with tumor-specific biomolecules, injected intratumorally, have been reported as an alternative to seed-based BT. Successful treatment of solid tumors using radio-NPs has been reported in several preclinical studies, on both mice and canine models. In this article, we review the recent advancements in the synthesis and use of radio-NPs as a substitute to seed-based BT. Here, we discuss the limitations of current seed-based BT and advantages of radio-NPs for BT applications. Recent progress on the types of radio-NPs, their features, synthesis methods, and delivery techniques are discussed. The last part of the review focuses on the currently used dosimetry protocols and studies on the dosimetry of nanobrachytherapy applications using radio-NPs. The current challenges and future research directions on the role of radio-NPs in BT treatments are also discussed.

Efficacy and prognosis of CT-guided of 125I radioactive seeds implantation brachytherapy as salvage treatment for recurrent nasopharyngeal carcinoma after external beam radiotherapy--A long-term experience at a single institution

Background: To assess the efficacy and prognosis of computed tomography (CT)-guided 125I radioactive seeds implantation brachytherapy (RSI-BT) for recurrent nasopharyngeal carcinoma (NPC) after external beam radiotherapy (EBRT). Methods: Thirty-one patients with recurrent NPC (forty-one lesions) after EBRT from February 2003 to January 2019 were enrolled in this retrospective study. The work-follow of CT-guidance RSI-BT was: indication selection, patient set-up and immobilization on CT couch, CT-simulation, preoperative planning, prescription doses (PD) definition of 110-160Gy, seed implantation, postoperative dosimetric evaluation and postoperative follow-up. Median radioactivity of RSI was 0.43 (range 0.22-0.79, average 0.61) mCi. Median actuarial number of 125I seeds was 24 (range 3-83, average 37). Median value of post-operative D90 was 118.5 (range 62.4-246, average 136.2) Gy. Local control (LC) and overall survival (OS) were investigated for their relationship with the prognosis. The adverse events were evaluated by the Radiation Therapy Oncology Group (RTOG) classification criteria. Results: Median follow-up was 41.9 (range 2.1-60.2, average 44.1) months. Median LC was 35.8 (range 2.1-60.2, average 34.9) months. LC at 1-, 3- and 5-year was 71.3%, 41.9% and 27.9%, respectively. Median OS was 22.6 (range 2.1~60.2, average 27.1) months. OS at 1-, 3- and 5-years was 57.7%, 23.8% and 11.9%, respectively. Univariate analysis suggested that sex (P=0.037) and frequency of previous EBRT (P=0.001) were prognostic factors influencing LC. Moreover, univariate analysis also suggested that frequency of previous EBRT (P=0.012) was prognostic factors influencing OS. Prevalence of side effects (≥grade 3) was 6.5%. Conclusion: 125I RSI-BT was a safe and feasible salvage treatment for recurrent NPC after EBRT. Key words: recurrent nasopharyngeal carcinoma; External beam radiotherapy; 125I seed implantation brachytherapy; overall survival; local control; side effects.

Radiotherapy and Its Impact on the Nervous System of Cancer Survivors

Radiotherapy is routinely used for the treatment of nearly all brain tumors, but it may lead to progressive and debilitating impairments of cognitive function. The growing evidence supports the fact that radiation exposure to CNS disrupts diverse cognitive functions including learning, memory, processing speed, attention and executive functions. The present review highlights the types of radiotherapy and the possible mechanisms of cognitive deficits and neurotoxicity following radiotherapy. The review summarizes the articles from Scopus, PubMed, and Web of science search engines. Radiation therapy uses high-powered x-rays, particles, or radioactive seeds to kill cancer cells, with minimal damage to healthy cells. While radiotherapy has yielded relative success in the treatment of cancer, patients are often plagued with unwanted and even debilitating side effects from the treatment, which can lead to dose reduction or even cessation of treatment. Little is known about the underlying mechanisms responsible for the development of these behavioral toxicities; however, neuroinflammation is widely considered as one of the major mechanisms responsible for radiotherapy-induced toxicities. The present study reviews the different types of radiotherapy available for the treatment of various types of cancers and their associated neurological complications. It also summarizes the doses of radiations used in the variety of radiotherapy, and their early and delayed side effects. Special emphasis is given to the effects of various types of radiations or late side effects on cognitive impairments.

Use of Intraoperative Radioguidance in Recurrent Merkel Carcinoma

Merkel cell carcinoma is a rapidly progressive nonmelanoma skin cancer with a high risk of recurrence. When recurrence occurs, it is associated with poor prognosis and there is a lack of guidelines for the management of such cases. This article describes a challenging case in which the innovative use of iodine-125 radioactive seeds permitted us to precisely identify and resect two nonpalpable recurrent nodules. The safety and accuracy of the surgical procedure were compromised by the presence of scar tissue following two past resections and two courses of radiotherapy. Radioactive seed localization is a well-known procedure in breast cancer, demonstrating potential for an extended application in other cancer types and in complex clinical situations.