Principles and applications of radiation therapy

Inorganic Nanoparticles as Radiosensitizers for Cancer Treatment

Nanotechnology has expanded what can be achieved in our approach to cancer treatment. The ability to produce and engineer functional nanoparticle formulations to elicit higher incidences of tumor cell radiolysis has resulted in substantial improvements in cancer cell eradication while also permitting multi-modal biomedical functionalities. These radiosensitive nanomaterials utilize material characteristics, such as radio-blocking/absorbing high-Z atomic number elements, to mediate localized effects from therapeutic irradiation. These materials thereby allow subsequent scattered or emitted radiation to produce direct (e.g., damage to genetic materials) or indirect (e.g., protein oxidation, reactive oxygen species formation) damage to tumor cells. Using nanomaterials that activate under certain physiologic conditions, such as the tumor microenvironment, can selectively target tumor cells. These characteristics, combined with biological interactions that can target the tumor environment, allow for localized radio-sensitization while mitigating damage to healthy cells. This review explores the various nanomaterial formulations utilized in cancer radiosensitivity research. Emphasis on inorganic nanomaterials showcases the specific material characteristics that enable higher incidences of radiation while ensuring localized cancer targeting based on tumor microenvironment activation. The aim of this review is to guide future research in cancer radiosensitization using nanomaterial formulations and to detail common approaches to its treatment, as well as their relations to commonly implemented radiotherapy techniques.

Outcome of external beam radiotherapy for treatment of noncutaneous tumors of the head in horses: 32 cases (1999-2015)

Background

The long‐term outcomes of external beam radiotherapy for treatment of noncutaneous tumors of the head in horses is unknown.

Objective

To report the long‐term outcomes for treatment of noncutaneous tumors of the head of horses, and report short and long‐term clinical adverse effects.

Animals

Thirty‐two horses treated in 2 referral hospitals.

Methods

In this retrospective study, medical records of horses receiving radiation therapy for noncutaneous tumors between 1999 and 2015 were reviewed. Signalment, tumor type, treatment protocol, tumor control duration, and survival were recorded. Kaplan‐Meier survival curves were generated for overall survival (OS), by tumor type and location, and compared using Log‐rank tests, and treatment protocol adherence.

Results

Follow‐up ranged from 2 to 145 months (median 14 months). Of 32 horses, 16 (50%) were alive at the time of reporting, with complete tumor response occurring in 12 (38%). Horses with tumors of the maxilla/nasal cavity had significantly shorter median OS compared to horses with tumors in other locations (21 months vs 145 months) (P = .06). Adverse effects resulting from the tumor or the therapy occurred in 20/32 (63%). The occurrence of major adverse effects and delays in treatment protocol were not significantly associated with median survival estimates.

Conclusions and Clinical Importance

External beam radiotherapy can be used to treat a variety of noncutaneous tumors of the head of horses. Adverse effects related to radiotherapy or the tumor are common.

An observational study on the clinical features of esophageal cancer followed by multiple primary cancers

AIM

To investigate the nature of multiple primary cancers initiated by esophageal cancer-multiple primary cancers (EC-MPC).

PATIENTS & METHODS

SEER data about patients'/tumor characteristics, and survival were analyzed and compared.

RESULTS & CONCLUSION

1727 of 29,733 registered EC patients have EC-MPC. Individuals diagnosed at 60-79 years old, earlier stage and/or moderately differentiated EC were more likely to get EC-MPC. Fewer patients in the EC-MPC group suffered from metastases. Patients in the EC-MPC group showed a longer survival rate and lower EC-specific deaths. Other factors like age, sex, race, tumor differentiation and Tumor, Node, Metastasis stage also affected survival. Radiation can improve survival. EC-MPC patients have some distinct features compared with solitary EC.

Use of an orthovoltage X-ray treatment unit as a radiation research system in a small-animal cancer model

Background

We explore the use of a clinical orthovoltage X-ray treatment unit as a small-animal radiation therapy system in a tumoral model of cervical cancer.

Methods

Nude mice were subcutaneously inoculated with 5 × 10⁶ HeLa cells in both lower limbs. When tumor volume approximated 200 mm³ treatment was initiated. Animals received four 2 mg/kg intraperitoneal cycles (1/week) of cisplatin and/or 6.25 mg/kg of gemcitabine, concomitant with radiotherapy. Tumors were exposed to 2.5 Gy/day nominal surface doses (20 days) of 150 kV X-rays. Lead collimators with circular apertures (0.5 to 1.5 cm diameter) were manufactured and mounted on the applicator cone to restrict the X-ray beam onto tumors. X-ray penetration and conformality were evaluated by measuring dose at the surface and behind the tumor lobe by using HS GafChromic film. Relative changes in tumor volume (RTV) and a clonogenic assay were used to evaluate the therapeutic response of the tumor, and relative weight loss was used to assess toxicity of the treatments.

Results

No measurable dose was delivered outside of the collimator apertures. The analysis suggests that dose inhomogeneities in the tumor reach up to ± 11.5% around the mean tumor dose value, which was estimated as 2.2 Gy/day. Evaluation of the RTV showed a significant reduction of the tumor volume as consequence of the chemoradiotherapy treatment; results also show that toxicity was well tolerated by the animals.

Conclusion

Results and procedures described in the present work have shown the usefulness and convenience of the orthovoltage X-ray system for animal model radiotherapy protocols.