Scientists hope that soon all they will need to detect cancer and its response to treatment is just a drop of blood or a chunk of very tiny tissue.
In a recently study, researchers at the Stanford University School of Medicine used a specialized machine that was capable of analysing whether individual cancer-associated proteins were present in the tiny samples, and even whether modifications of the proteins varied in response to cancer treatments.
The study focussed on blood cancers, but the research team is optimistic that their technique may some day provide a faster, less invasive way to track solid tumours.
"Currently we don't know what's going on in a patient's actual tumor cells when a treatment is given," Nature magazine quoted oncologist Dr. Alice Fan, a clinical instructor in the division of oncology at the medical school, as saying.
"The standard way we measure if a treatment is working is to wait several weeks to see if the tumor mass shrinks. It would really be a leap forward if we could detect what is happening at a cellular level," the researcher added.
Dr. Dean Felsher, a member of Stanford's Cancer Center in whose lab the research was performed, said: "This technology allows us to analyse cancer-associated proteins on a very small scale. Not only can we detect picogram levels - one-trillionth of a gram - of protein, but we can also see very subtle changes in the ways the protein is modified."
During the study, the researchers used the machine to separate cancer-associated proteins in narrow capillary tubes based on their charge, which varies according to modifications on the proteins' surface. Two versions of the same protein - one modified and one not - can be easily distinguished because they travel different distances in the tube.
The team then used antibodies to identify the relative amounts and positions of the various proteins.
The scientists found that not only was the technique able to identify oncogene activation in cultured tumour cells, but it also worked well in small lymphoma samples drawn from laboratory mice with small, hollow needles.
They were also able to detect varying levels of expression of two common oncogenes in 44 of 49 lymphoma samples from human patients as compared with normal controls, and even distinguish some types of lymphomas from others.
Fan and Felsher said that their study also detected subtle differences in modifications in several other cancer-associated proteins.
"Some of these proteins can exist as five or six phosphorylated variants. With this technology we can see changes that occur in as little as 10 percent of the total protein pool. Now we have a tool that will really help us look at what's happening in cells over time," said Felsher.
"Surgical biopsies usually require general anaesthesia and large amounts of tissue. If we can figure out how to go in with a needle and remove just a few cells for analysis, we could repeatedly assess how the tumour is responding to treatment," added Fan.
Though the research group focused on lymphoma and leukaemia during the study, Fan is expanding her investigations to include head and neck tumours, which tend to be relatively accessible for cell sampling.
Both Fan and Felsher caution that more research is needed before the technology is widely available clinically.
"This is really a complement to existing diagnostic and therapeutic methods," said Fan.
The study has been published in the online version of the journal Nature Medicine.