Analysing a tu­mor's genes can pre­dict which prostate can­cers won't need ad­di­tion­al treat­ment and which cas­es re­quire more in­ten­sive ther­a­pies.

Watch­ful wait­ing is a com­mon strat­e­gy for treat­ing prostate can­cer, since in about 40 per cent of cas­es the tu­mors are so slow-grow­ing that they don't re­quire ad­di­tion­al, in­va­sive biop­sies or treat­ment and men with the can­cer are more like­ly to die of oth­er caus­es.

But based on analy­ses of tis­sue from men whose prostates were sur­gi­cal­ly re­moved as a pre­cau­tion even if they were deemed to be low-risk, any­where from 15 per cent to 20 per cent of these low-risk cas­es ac­tu­al­ly turn out to in­volve tu­mors that were more ag­gres­sive.

As a re­sult, the tu­mors were mis­char­ac­terised by avail­able pre­dic­tive meth­ods such as the blood-based prostate spe­cif­ic anti­gen (PSA) test and imag­ing to search for hid­den growths.

So re­searchers at Ge­nom­ic Health, the com­pa­ny that de­vel­oped a gene-based test for pre­dict­ing which breast can­cers might re­cur, turned their at­ten­tion to cre­at­ing a sim­i­lar as­say for prostate can­cer.

The breast can­cer as­say, On­co­type Dx, pro­vides women with a num­ber be­tween ze­ro and 100 that in­di­cates their risk of re­cur­rence and their re­sponse to chemother­a­py.

The prostate can­cer pan­el, known as On­co­type Dx Ge­nom­ic Prostate Score, is now avail­able fol­low­ing re­lease of the study re­sults. Dr Pe­ter Car­roll, di­rec­tor of the de­part­ment of urol­o­gy at the Uni­ver­si­ty of Cal­i­for­nia, San Fran­cis­co, led the in­de­pen­dent tri­al that val­i­dat­ed the new test.

"We want­ed to see if we could im­prove the is­sue of risk as­sess­ment for prostate can­cer pa­tients," said Car­roll.

Work­ing with biop­sy sam­ples from 400 pa­tients who had prostate surgery and were de­ter­mined to be at low risk of re­cur­ring tu­mors, Car­roll and his team found that the pan­el of 17 genes in the as­say could re­li­ably pre­dict how ag­gres­sive the can­cers were.

In some cas­es, the more ac­tive the genes were, the high­er the risk of re­cur­rence, while in oth­ers, less ac­tiv­i­ty con­ferred the greater risk. When the re­searchers matched the ac­tiv­i­ty of these genes to the men's prostate can­cer out­comes, they were en­cour­aged to see that in about half of the par­tic­i­pants, the ge­net­ic as­say proved to be an ef­fec­tive pre­dic­tor of the tu­mor's ag­gres­sive­ness; the ge­net­ic in­for­ma­tion moved the men's risk score (de­ter­mined by the ex­ist­ing PSA and imag­ing tests) for de­vel­op­ing ad­di­tion­al tu­mors high­er or low­er by about five points.

For about 23 per cent of the men, the pan­el of genes changed the scores by ten points of more. "You might say that for most pa­tients, the test pro­vides them with some in­for­ma­tion," said Campell. "We think the in­for­ma­tion is sig­nif­i­cant in about half of pa­tients and very sig­nif­i­cant in about a quar­ter."

The test in­clud­ed not just the pan­el of 17 can­cer-re­lat­ed genes but an ad­di­tion­al five con­trol genes to en­sure that re­searchers ac­cu­rate­ly mea­sured when the genes were more or less ac­tive.

The 17 genes ap­pear to be in­volved in cell growth, an­dro­gen hor­mone me­tab­o­lism (which in­flu­ences prostate func­tion) and oth­er tu­mor-re­lat­ed process­es.

Car­roll and his team pre­sent­ed the re­sults on the test at the an­nu­al meet­ing of the Amer­i­can Uro­log­i­cal As­so­ci­a­tion.

Car­roll is al­ready plan­ning a fol­low-up tri­al that will track 1,000 men pri­or to prostate can­cer treat­ment to see if the ge­net­ic pan­el can ac­cu­rate­ly pre­dict which men went on to de­vel­op ag­gres­sive dis­ease and which ones did not–and which men might avoid treat­ments al­to­geth­er.

The in­for­ma­tion could be help­ful in pro­vid­ing more con­fi­dence in physi­cians'–and pa­tients'–de­ci­sions to avoid treat­ments be­cause men aren't like­ly to need them.

A ge­net­ic test that could de­ter­mine men at the high­est risk of de­vel­op­ing ag­gres­sive dis­ease could change how prostate can­cer was treat­ed, Car­roll said, since doc­tors would be able to more ac­cu­rate­ly pre­dict which men would need more rig­or­ous fol­low-up and which men like­ly won't have to wor­ry about their prostate that much. (Time.com)

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