Scans reveal cancer defences

Drugs may find it difficult to penetrate a large tumour

Scientists have found a new way to examine the structure of tumours and find out whether anti-cancer drugs are reaching all the cells inside.

High-resolution scans developed at the Massachusetts General Hospital could improve the way that chemotherapy is targeted in future.

A tumour is not simply a mass of cancer cells - if that were the case, conventional anti-cancer drugs would be far more effective.

However, in many cases the tumour also includes blood vessels and connective tissues.

The tough connective tissues can reduce the "permeability" of the tumour to drugs, often forming a tough "matrix" outside the target cell which chemicals find it hard to get through.

The scans were developed to help doctors work out the nature of the tumour they are trying to treat.

Breakdown

It can distinguish between various different types of connective tissue molecules, and display the structure and density of the fibres.

This could help doctors work out whether treatments to break down these structures are having any effect.

One such drug, relaxin, is also under trial at Massachusetts General Hospital.

It is a hormone which is released in women who are in the later stages of pregnancy in order to help dilate the cervix and prepare the body for birth.

It has the ability to trigger the breakdown of collagen.

Mice with implanted human tumours were injected with the hormone, then scanned over two days to see if the structure of the tumour had changed.

The relaxin treated connective tissue within the tumours was far looser - hopefully making it easier for the cell-killing chemotherapy drugs to enter.

Dr Rakesh Jain, who lead the research - which is detailed in the journal Nature Medicine - said: "We have found that a significant portion of a tumour is made up of an extracellular matrix that acts as a barrier, keeping drugs away from tumour cells.

"We have already started animal studies to measure whether relaxin can improve actual response to chemotherapy drugs."