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There have been a number of stories about cancer screening recently, not least with the reams of coverage of Jade Goody’s death and now her funeral.

Her tragic case seems to have increased the number of young women going for cervical cancer screening, but there has also been criticism of the information given to women undergoing breast cancer screening. What are we to make of all this? Thankfully, Jane Green of the Cancer Epidemiology Unit at the University of Oxford can act as our guide.

OxSciBlog: What differences have screening for breast cancer and cervical cancer made?
Jane Green: Breast screening is thought to save 1,400 lives a year in the UK, a reduction in mortality of about 25% in screened women. UK cervical cancer death rates have fallen by half since screening was introduced in 1988, with an estimated three-quarters of cancers that would otherwise occur (as many as 4,500 a year) being prevented by screening.

OSB: How can research determine when screening is effective, improves outcomes, and is cost-effective?
JG: This kind of research can be difficult, very time-consuming and expensive. But it is necessary if a screening programme is to be based on good evidence and to do more good than harm.

We need to make sure the screening test used is the most reliable test. Then we need to try out the test in a pilot programme to make sure that it works in practice, that the programme is feasible from a staffing, infrastructure and financial point of view; and that it is effective in reducing later serious disease or death.

The research also has to take into account coincidental changes in the underlying rates of the disease, and changes in survival because of new treatments.

The best way to test a screening programme is to do a randomised trial and the results between screened and unscreened groups compared over many years. Financial costs of screening have to be compared with the cost of not screening (where more people may go on to develop serious illness later) and with other health care priorities. Finally, when the programme is set up it is crucial to evaluate its performance at every level. 

OSB: Are there problems with false positives and worrying people unnecessarily?
JG: Yes. This is an inevitable part of screening. In an ideal world we would have a perfect screening test – one which picked up every person with early disease which we could usefully treat, but no-one who did not have the disease.

In practice there will be both 'false positives', people who test positive, but who do not have the disease; and 'false negatives', people who do not test positive when screened but who do in fact have the disease.

False positive tests cause, at the very least, anxiety and the need to have further tests; and, at the worst, unnecessary and often unpleasant treatment, because screening will detect some early stage disease which would not go on to cause problems later.

For the individual with a positive screening test, there is therefore always a chance that they are one of the 'false positives'. Some people will find this out when they are called back for further tests and find they do not after all have cancer. Some people with early disease detected by screening will never know whether their cancer treatment was necessary. What they do know is that overall, screening and subsequent treatment saves lives and that theirs may be one of these.

OSB: Should younger women be screened for cervical cancer than currently?
JG: This is not an easy question to answer. Cervical cancer is extremely rare in very young women (there are about 50 cases a year in the UK in under-25 year olds, and about 5 deaths) and abnormal cell changes on the cervix are quite common, but often resolve themselves without treatment.

For women under 25, the experience from the English screening programme has been that on balance, the harm caused by detecting and treating cell abnormalities in many screened women (some of whom may have later problems with pre-term birth because of damage to the cervix from treatment) outweighs the benefit of picking up the very rare cases where treatment is necessary. This is why it was decided to raise the lower age limit for routine screening from 20 to 25 in 2003.

The difficulty is of course that this decision is based on the balance of risks and benefits for the population as a whole. For the individual it is different. Some young women will benefit from not being screened, and some young women would benefit from screening.

Cervical screening is designed for women with no symptoms. A woman of any age who is concerned she may have a problem can of course ask for a test through her GP, family planning clinic or a genitourinary medicine or sexual health clinic.

OSB: What should women do in the face of the mixed messages they hear?
JG: It is important to remember that the cancer screening programmes in the UK are based on good scientific evidence. There is no serious argument about the overall effectiveness in terms of lives saved.

The debate is about the difficult issue of balancing the benefits and harms of screening: and screening always has both. Some women will have cancer that is missed, and some will be diagnosed with cancer that might not have progressed if left untreated.

Assessing the numbers involved is extremely difficult and involves making assumptions: we cannot know for certain how many cancers would not have progressed, or how many cancers would have been detected without screening.  Estimates of the numbers of cancers 'over diagnosed' vary widely and some of the recent debate has been based on extreme values.  

As part of the 100 Hours of Astronomy event which begins today Galaxy Zoo 2 are asking volunteers to do one million galaxy classifications in the next 100 hours.

You can see from our (now out of date!) image that GZ2 volunteers marshalled by a team here at Oxford have already topped 300,000 classifications but they need more people to join in and take them surging passed that one million mark.

It's a fun idea but with serious intent, Oxford's Chris Lintott tells us:

'To keep track, we've added the world's first Zoonometer to the front page of the Galaxy Zoo site at www.galaxyzoo.org, so people can stop by and watch the classifications roll in.'

'Completing this challenge will not only be another significant step towards our goal of producing the world's largest and most detailed catalogue of classified galaxies, it's also a good chance to demonstrate just how effective all of our volunteers' efforts are when taken together.'

100 Hours of Astronomy runs until 5 April and is a key part of celebrations for the International Year of Astronomy.

Dr Chris Lintott, one of the founders of Galaxy Zoo, is based at Oxford's Department of Physics. 

I couldn't pass up the opportunity to plug tonight's Horizon [BBC Two 9pm] featuring Oxford mathematician Marcus du Sautoy and everyone's favourite QI fall guy, comedian Alan Davies.

Alan hates maths - but is that just because he doesn't understand it? Enter Marcus with some explanations of how maths can help in all kinds of situations; from correctly sizing up probabilities to playing beautiful passing football.

The BBC tell us: 'Together they visit the fourth dimension, cross the universe and explore the concept of infinity. Along the way, Alan does battle with some of the toughest maths questions of our age. But did his abilities peak 25 years ago when he got his grade C O-Level? Or will Alan be able to master the most complex maths concept there is?'

You can whet your appetite with some great probability and football related video clips on the BBC website. So will Marcus change Alan's mind about maths by the end of the show? You'll just have to watch and find out...

'Horizon: Alan and Marcus Go Forth and Multiply' airs tonight on BBC Two at 9pm.

UPDATE: You can watch the programme on iPlayer (next 20 days).

Are there spiders in the store room? How about woodlice in the hall? And did anyone see beetles in the headteacher's office?

Pupils around Oxfordshire are looking into these and other questions as part of Bug Quest 2009, a six-month research project to survey invertebrate biodiversity across the county.

It's the the third time that the Oxford University Museum of Natural History (OUMNH) has staged a Bug Quest event and this time the emphasis is on pupils doing more of the research themselves: placing insect traps in locations around their schools, uploading data on the types of insects captured to the Bug Quest website as well as photos of any puzzling or unusual invertebrates.

The project began in January and at the latest count around half of the 42 schools taking part have entered their first batch of results with Sunningwell Cof E Primary School and Checkendon Cof E Primary School achieving the coveted accolade of buggiest schools in January!

Those taking part receive regular updates from Colin A Cricket with information on the Bug of the Month: March is officially Beetle Month [Colin tell us that the UK's largest insect is the Stag Beetle].

Bug Quest runs until June with bug identication sessions for teachers and a special morning reception on 14 July where pupils can bring along homemade bug models and the prize for this year's buggiest school will be awarded.

Next month Oxford engineers will start investigating what kind of composite materials would make for stronger, stealthier and more durable submarines.

Composites are already being used in warships because they can be made stronger and lighter than metal parts and are less susceptible to corrosion. They have also been shown to resist the forces unleashed in an explosion better than metal.

The Oxford team will begin their EPSRC-funded project by testing how composites submerged in water respond to a shockwave generated by a metal projectile. High-speed cameras will capture how the materials deform under the pressure.

Testing and modelling is vital to determine what the best structure for a submarine composite would be – many composites, for instance, are made out of a ‘sandwich’ of different materials – as well as how composites fare after being submerged in water for a long time.

Vito Tagarielli, one of the Oxford team led by Nik Petrinic, told The Engineer: ‘We hope to reduce the weight of the submarine so there is less inertia and it can have higher acceleration and easier manoeuvrability.’

‘[Also] If a submarine is made of composite it makes it invisible to modern sea mines that detonate when they recognise a specific magnetic or acoustic signature.’

The project runs for five years and involves a host of industrial partners alongside the Ministry of Defence.