Officials said GPs’ failure to give patients sufficient consultation access and refer them for further investigation were among the reasons why cancers were often not diagnosed early enough.
They called for more GP training in the use of a computer tool that can improve the detection of symptoms suggestive of cancer.
Each year, 1,000 people in London die due to delays in cancer diagnosis.
The new Cancer Commissioning Strategy for London by NHS England sets out a five-year plan to boost survival rates and improve services for patients living with the disease in the capital.
The plan urges CCGs to pay for cover so that GPs can attend training in how to use the Cancer Decision Support Tool, a program developed by the charity Macmillan. The tool works with practices’ IT systems to flag combinations of symptoms that could be caused by cancer.
The strategy said: ‘Interventions tackling GP delay will improve the patient experience since patients will be referred more promptly, access diagnostics quickly and, where referred onto a diagnosis pathway, should reach that diagnosis more quickly.'
Dr Anne Rainsberry, London regional director for NHS England, said: 'More than a quarter of cancers are diagnosed in A&E or as an emergency referral. We need to change services so that London’s health services become better at preventing cancer and detecting it earlier.'