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Antimatter rays studied as medical treatment

Nov. 2, 2006
Courtesy CERN
and World Science staff

Sci­en­tists are stu­dy­ing what could ar­guably be the first ap­pli­ca­tion of an ex­ot­ic sub­stance known as an­ti­mat­ter in med­i­cal treat­ment.

An­ti­mat­ter con­sists of fun­da­men­tal par­ti­cles al­most iden­ti­cal to those that make up or­di­nary atoms, but with some prop­er­ties re­versed. For in­stance, “an­tipro­tons” are like pro­tons, com­po­nents of the atom­ic nu­cle­us, but have neg­a­tive in­stead of pos­i­tive charge.

A pa­tient is pre­pared for ra­di­a­tion ther­a­py. (Cour­te­sy NIH Sen­ior Health)

Sci­en­tists at CERN, the Eu­ro­pe­an Or­ga­n­i­sa­tion for Nu­c­le­ar Re­search, out­side Ge­ne­va, are test­ing the ef­fects of beams of an­ti­pro­tons fired at live cells. 

The work could por­tend a new form of ra­di­a­tion the­r­a­py, a can­cer treat­ment in which beams of par­t­i­cles are aimed at tu­mor cells to de­s­troy them.

In pre­li­m­i­nary re­sults an­nounced this week, the re­search­ers said an­ti­pro­tons have four times great­er cell-kil­ling pow­er than pro­tons, used in stand­ard ra­di­a­tion ther­a­py. 

“Although it still has to be com­pared with oth­er ex­ist­ing meth­ods, it is a break­through in this ar­ea,” said CERN’s Mi­chael Doser, one of an in­ter­na­tion­al team of physi­cists, doc­tors and bi­ol­o­gists col­lab­o­rat­ing on the pro­ject.

In tests, the re­search­ers filled tubes with ham­s­ter cells in a gel­a­tine to si­m­u­late hu­man tis­sue. 

“To achieve the same lev­el of dam­age to cells at the tar­get ar­ea one needs four times few­er an­ti­pro­tons than pro­tons,” said Mi­chael Holz­schei­ter, spokes­man for the proj­ect. This en­ables ex­per­i­ment­ers to li­m­it tis­sue dam­age in ar­e­as along the beam path where it is un­de­sir­a­ble, the re­search­ers said. This is key be­cause doc­tors wish to spare healthy tis­sue while de­stroying tu­mors.

An­ti­pro­tons can be pro­duced in small amounts in lab­o­ra­to­ries. But an­ti­mat­ter is rare as a rule be­cause when mat­ter and an­ti­mat­ter par­ti­cles meet, they an­ni­hi­late each oth­er. Since there is a pre­pon­der­ance of mat­ter in the known uni­verse, an­ti­mat­ter par­ti­cles, once cre­at­ed, usu­al­ly run in­to mat­ter par­ti­cles and van­ish in short or­der.

This would be a use­ful prop­er­ty for an­ti­pro­tons on ther­a­py, the re­search­ers ar­gued. An an­ti­pro­ton an­ni­hi­lates with pro­tons in atoms of the tar­get cell. The re­sult is a sort of ti­ny ex­plo­sion that spreads the dam­age to im­me­di­ate­ly neigh­bor­ing cells.

The re­search­ers are plan­ning fur­ther tests. “If all goes well, the first clin­i­cal ap­pli­ca­tion would still be a dec­ade or more” away, proj­ect mem­bers said in a state­ment re­leased this week.

An­ti­mat­ter is cur­rent­ly har­nessed in med­i­cine for a few lim­ited ap­pli­ca­tions, but not nor­mal­ly in ac­tu­al treat­ment, Doser said.

A di­ag­nos­tic tech­nique called Pos­i­tron Emis­sion To­mog­ra­phy uses positrons, an­ti­par­ti­cles of elec­trons, for scan­ning tis­sue. And an un­com­mon form of ra­di­a­tion ther­a­py uses pi­ons, “a hy­brid form of mat­ter and an­ti­mat­ter suba­tom­ic par­ti­cles called quark­s,” Doser added. “In that sense, one could per­haps talk of an­ti­mat­ter hav­ing been ap­plied in med­i­cal treat­ment, but it would be stretch­ing it a bit.” Oth­er than that, the CERN ex­per­i­ments would be the first ap­pli­ca­tion of an­ti­mat­ter in med­i­cal treat­ment, he said.

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Scientists are studying what could arguably be the first application of an exotic substance known as antimatter in medical treatment. Antimatter consists of fundamental particles almost identical to those that make up ordinary atoms, but with some properties reversed. For instance, “antiprotons” are like protons, components of the atomic nucleus, but have positive instead of negative charge. Scientists at CERN, the European Organisation for Nuclear Research, outside of Geneva, are testing the effects of beams of antiprotons fired at live cells. The work, they say, could portend a new form of radiation therapy, a cancer treatment in which beams of particles are aimed at tumor cells to destroy them. In preliminary results announced this week, they said antiprotons are four times more effective at killing cells than protons, used in standard radiation therapy. “Although it still has to be compared with other existing methods, it is a breakthrough in this area,” said CERN’s Michael Doser, one of an international team of physicists, doctors and biologists collaborating on the experiment. In tests, the researchers filled tubes with hamster cells suspended in gelatine to simulate a cross-section of human tissue. “To achieve the same level of damage to cells at the target area one needs four times fewer antiprotons than protons,” said Michael Holzscheiter, spokesman for the project. This enables experimenters to limit tissue damage in areas along the beam path where damage is undesirable, the researchers said. This is important because doctors wish to spare healthy tissue while destroying tumors. Antiprotons can be produced in small amounts in a laboratory. But antimatter is rare as a rule because matter and antimatter particles meet, they annihilate, or destroy each other. Since there is a preponderance of matter in the known universe, antimatter particles, once created, usually run into matter particles and vanish in short order. This would be a useful property for antiprotons on therapy, the researchers argued. An antiproton annihilates with protons in atoms of the target cell. The result is a sort of tiny explosion that spreads the damage to immediately neighboring cells. The researchers are planning further tests. “If all goes well, the first clinical application would still be a decade or more” away, project members said in a statement released this week. Antimatter is currently harnessed in medicine for a few limited applications, but not normally in actual treatment, Doser said. A diagnostic technique called Positron Emission Tomography uses positrons, antiparticles of electrons, for scanning tissue. And an uncommon form of radiation therapy uses pions, “a hybrid form of matter and antimatter subatomic particles called quarks,” Doser added. “In that sense, one could perhaps talk of antimatter having been applied in medical treatment, but it would be stretching it a bit.” Other than that example, the CERN experiments would be the first application of antimatter in medical treatment, he said.