The report, which analyses the effect of the 2007 Cancer Reform Strategy on care, estimates the NHS spends £6.3bn on cancer services each year.
Services have improved since 2007, although many hundreds of millions of pounds could be further saved if efficiency was improved.
But data collection about spending and outcomes is so poor many PCTs have little idea whether their commissioning benefits patients, it says.
Despite the issues, cancer care has improved since 2007, the report concludes.
Cancer patients spent 281,000 fewer days in hospital between 2006/07 and 2008/09. The average length of stay fell from 8.2 days to 7.7 days.
But emergency admissions continue to rise by 2% per year, despite pledges in the strategy to reduce them. Since 2000/01, emergency admissions have doubled.
The report found PCTs spend on cancer care varies from £55 to £154 per head.
But most PCTs have not recorded sufficient data to analyse performance and value for money, the NAO warns. Just 22% of PCTs attempted to assess value for money delivered by cancer service providers.
The NAO report concludes that although progress has been made, 'commissioners' poor understanding of costs and outcomes mean that they do not know whether they are commissioning services which optimise outcomes for patients'.
It adds: 'Furthermore, the department has limited assurance as to whether implementation of the strategy is achieving value for money.'
Karen Taylor, director of health value for money studies at the NAO, said: ‘There is a lack of high quality information on spending costs and outcomes. That lack of information is inhibiting further improvement.’
David Stout, director of the NHS Confederation’s PCT Network, said it was important to acknowledge the role PCTs have played in improving care.
"However, we fully recognise that further progress is required in a number of areas,' he said.
Mr Stoute said PCTs had been 'hampered' in achieving good value for money by inconsistent national data sets, the quality of coding and 'cumbersome' payment systems.
'It is vital that these national problems are recognised by the DoH. The government needs to understand and act on what is holding back local organisations.'