|
It is established that heat can enhance the effect of radiation cancer treatment. Due to the ability to localize
thermal energy using nanoparticle hyperthermia, as opposed to other, less targeted, hyperthermia
modalities, it appears such enhancement could be accomplished without complications normally associated
with systemic or regional hyperthermia. This study employs non-curative (suboptimal), doses of heat and
radiation, in an effort to determine the therapeutic enhancement potential for IONP hyperthermia and
radiation. Methods: MTG-B murine breast adenocarcinoma cell are inoculated into the right flanks of
female CH3/HEJ mice and grown to volumes of 150mm3+ /- 40 mm3. A single dose of 15 Gy (6 MeV)
radiation was uniformly delivered to the tumor. A pre-defined thermal dose is delivered by direct injection
of iron oxide nanoparticles into the tumor. By adjusting the field strength of the 160 KHz alternating
magnetic field (AMF) an intra-tumoral temperature between 41.5 and 43 degrees Celsius was maintained
for 10min. The alternating magnetic field was delivered by a water-cooled 36mm diameter square copper
tube induction coil operating at 160 kHz with variable magnet field strengths up to 450 Oe . The primary
endpoint of the study is the number of days required for the tumor to achieve a volume 3 fold greater than
the volume at the time of treatment (tumor regrowth delay). Results: Preliminary results suggest the
addition of a modest IONP hyperthermia to 15 Gy radiation achieved an approximate 50% increase in
tumor regrowth delay as compared to a 15 Gy radiation treatment alone. The therapeutic effects of IONP
heat and radiation combined were considered additive, however in mice that demonstrated complete
response (no tumor present after 30 days), the effect was considered superadditive or synergistic. Although
this data is very encouraging from a multimodality cancer therapy standpoint, additional temporal and dose
related information is clearly necessary to optimize the therapy.
|
