Stealth Nanoparticles Boost Radiotherapy

I hope, dear readers, that you all have been regularly browsing through http://medicalphysicsweb.org, the website from the Institute of Physics dedicated to medical physics news. I was particularly taken by the article published there this week titled “Stealth Nanoparticles Boost Radiotherapy.” Russ Hobbie and I don’t talk about nanoparticles in the 4th edition of Intermediate Physics for Medicine and Biology, but they are a hot topic in biomedical research these days. The article by freelance journalist Cynthia Keen begins

Imagine a microscopic bomb precisely positioned inside a cancer tumour cell that explodes when ignited by a dose of precision-targeted radiotherapy. The cancerous tumour is destroyed. The healthy tissue surrounding it survives.

This scenario may become reality within a decade if research by Massachusetts scientists on using nanoparticles to deliver cancer-fighting drugs proceeds smoothly. Wilfred F Ngwa, a medical physicist in the department of radiation oncology at Brigham and Women's Hospital and Dana Farber Cancer Institute in Boston, described the latest initiative at the AAPM annual meeting, held earlier this month in Indianapolis, IN. 

We discuss radiation therapy in Chapter 16 of IPMB. The trick of radiotherapy is to selectively kill cancer cells while sparing normal tissue. The nanoparticles are designed to target tumors

by applying tumour vasculature-targeted cisplatin, Oxaliplatin or carboplatin [three widely used, platinum-based chemotherapy drugs] nanoparticles during external-beam radiotherapy, a substantial photon-induced boost to tumour endothelial cells can be achieved. This would substantially increase damage to the tumour’s blood vessels, as well as cells that cause cancer to recur, while also delivering chemotherapy with fewer toxicities.

In general, nanoparticles typically have a size on the order of 10 to 100 nm. This size passes easily through the smallest blood vessels, but is too big to pass through ion channels in the cell membrane. It is about the size of a large biomolecule or a small virus. Nanoparticles are used in imaging and therapy. For an overview, see the review by Shashi Murthy (International Journal of Nanomedicine, Volume 2, Pages 129–141, 2007).

The medicalphysicsweb article concludes

“The promising result of using approved platinum-based nanoparticles combined with experimental results of the past two years convince us that our new RAID [radiotherapy application with in situ dose-painting] approach to cancer provides a number of possibilities for customizing and significantly improving radiotherapy,” Ngwa said at the press conference. This research is still in its early stages, with laboratory testing of the new approach in mice ongoing. If tests continue to prove successful, and a grant or private funding is available, it will lead to clinical trials in humans. The researchers are hopeful that they will be able to continue their work without any disruption and to move their novel treatment from laboratory to clinical use. 

Another news story about this research can be found here.