SEATTLE--A mixture of neutron radiation with conventional photon
radiation, using a custom tailored pelvic template for each patient,
appears to provide more effective therapy for prostate cancer
than photon radiation alone (eg, external beam or I-125), while
reducing the complications caused by neutron radiation alone,
said Jeffrey Forman, MD, of Wayne State University, Detroit.
Dr. Forman discussed the technique, called three-dimensional conformal
fast neutron irradiation, at the Pacific Northwest Cancer Foundation
Meeting on Transperineal Brachytherapy for Early Stage Prostate
He has been studying neutron radiation for prostate cancer treatment
because, he said, "radiobiologic principles would suggest
that a slowly proliferating tumor, like prostate cancer, would
be advantageously treated by high LET (linear energy transfer)
This has indeed proved to be the case, with 70% vs 58% local control
of the tumor, and 53% vs 29% 10-year survival in favor of neutron/photon
irradiation vs conventional external photon beam therapy alone
However, pelvic neutron irradiation has a high rate of complications,
including rectal toxicity, bladder complications, and hip stiffness,
progressing to pelvic bone necrosis in some patients. To address
this problem, researchers have applied 3D conformal irradiation
techniques to neutron therapy (see below).
In this technique, the neutron beams are directed more precisely
to the confined area of the tumor, thus sparing adjacent radiosensitive
structures such as the bladder and rectal tissue.