Julia Rogers, from Newton Abbot in Devon, made about 20 visits to GPs and hospitals with stomach and back pain.
She was only diagnosed with advanced and inoperable cancer of the pancreas after paying for a private scan.
An NHS England report said "better continuity of care" needed to be ensured.
NHS England launched a review of the case when Mrs Rogers' concerns were investigated by BBC Spotlight in July 2014.
The report, published by NHS England, details how:
Dr Graham Lockerbie, medical director for NHS England covering Devon, Cornwall and the Isles of Scilly, said: "All the organisations involved recognise the need to think deeply about cases like this, where different actions or tighter systems might have led to the earlier diagnosis of such a serious condition.
"We are only too aware that such hindsight is of limited use to Mrs Rogers, but we hope the changes that result will reduce the chances of similar occurrences in the future."
The report made a number of recommendations including a new protocol to ensure the pancreas is seen in ultrasound examinations.
Mrs Rogers is now having regular chemotherapy. She said she was aware of the very low survival rate for patients with cancer of the pancreas.
"It's an awful lot of suffering on this journey so if I can help any other person - if they can be prevented from suffering like I have - then it's something worthwhile," she said.
The Kingskerswell and Ipplepen Medical Practice said it would be introducing a named GP for every patient.
A woman's terminal cancer was not diagnosed because of delays, missed opportunities and poor continuity of care, an NHS report has found.