Photon activation therapy and brachytherapy.
OBJECTIVE
In photon activation therapy (PAT), energy deposition at critical sites within a tumor can be increased by complexing the DNA with higher Z atoms, and provoking the emission of Auger electrons after inducing a photoelectric effect. This in vivo study evaluates the hypothesis using X-rays from palladium-103 seeds to excite the L-edge of platinum (Pt) atoms bound to the DNA of cancerous cells.


METHODS
Pt (II) tetrakis(N-methyl-4-pyridyl) porphyrin chloride was used to locate Pt atoms adjacent to the DNA of the KHJJ murine mammary carcinoma; a 2.3-mCi palladium-103 seed was implanted in the tumor.


RESULTS
The tumor periphery received subtherapeutic doses. The rate of tumor growth in mice treated with PAT was slower than in mice treated with brachytherapy only.


CONCLUSIONS
The tumor growth delay for PAT-treated mice is attributed to Auger emission from Pt atoms that produced substantial local damage. However, other co-existing mechanisms cannot be ruled out.
Laster
Brenda H
BH
Department of Nuclear Engineering, Ben Gurion University of the Negev, Beer Sheva, Israel. blaster@bgumail.bgu.ac.il
Dixon
Dabney W
DW
Novick
Sara
S
Feldman
Jon P
JP
Seror
Veronique
V
Goldbart
Zvi I
ZI
Kalef-Ezra
John A
JA
D000818:Animals; D001918:Brachytherapy / Q000379:methods*; D004273:DNA, Neoplasm / Q000378:metabolism; D005260:Female; D007364:Intercalating Agents / Q000627:therapeutic use; D008325:Mammary Neoplasms, Experimental / Q000532:radiotherapy*; D008665:Metalloporphyrins / Q000627:therapeutic use; D051379:Mice; D008807:Mice, Inbred BALB C; D009944:Organoplatinum Compounds / Q000627:therapeutic use; D010165:Palladium; D017785:Photons; D011868:Radioisotopes
D004273:DNA, Neoplasm; D007364:Intercalating Agents; D008665:Metalloporphyrins; D009944:Organoplatinum Compounds; D011868:Radioisotopes; C544926:platinum(II) tetrakis(N-methyl-4-pyridyl)porphyrin; D010165:Palladium