Burton and Swadlincote women left waiting for potentially-lifesaving breast cancer screening after an IT blunder are urged to call their GP if they spot any signs.
It is believed 450,000 women aged between 68 and 71 were not invited to the vital appointments after a "computer algorithm failure" dating back to 2009 was spotted.
Health Secretary Jeremy Hunt told the House of Commons up to 270 patients may have died as a result.
The error emerged when the system was upgraded in 2016 - and women across East Staffordshire and South Derbyshire are among those affected.
A spokesman for Burton's Queen's Hospital reassured them the incident was being handled nationally.
Breast Cancer Care chief executive Samia al Qadhi told the Mirror some women had their lives shortened as a result of the error - and was shocked that it has now been discovered after almost a decade.
She said affected women and their families "will be left reeling, scared and confused" and it was her priority to ensure they get all the support and information they need.
It is not known whether any delay in diagnosis of women resulted in avoidable deaths.
But Mr Hunt said computer modelling suggested between 135 and 270 women may have had their "lives shortened".
He launched an independent review into Public Health England's national breast screening invitation system.
The NHS screens all women between the ages of 50 and 70 for breast cancer every three years.
Women normally get a letter from their GP about the test, which aims to catch the disease early, when it is easier to treat with better survival rates.
According to Cancer Research UK, there were 11,563 breast tumour deaths in 2016.
One in eight women and one in 870 men will be diagnosed with the disease during their lifetime. About 55,000 people are diagnosed each year with the disease.
All women affected will now be contacted by letter by the end of May and those under 72 will receive an appointment for a catch-up mammogram.
There is also a breast screening helpline number on 0800 169 2692.
Those with concerns are urged to call the helpline or contact their GP.
The signs and symptoms of breast cancer, according to nhs.uk, are:
◾A new lump or area of thickened tissue in either breast that was not there before
◾A change in the size or shape of one or both breasts
◾Bloodstained discharge from either of the nipples
◾A lump or swelling in either of your armpits
◾Dimpling on the skin of the breasts
◾A rash on or around the nipple
◾A change in the appearance of the nipple, such as becoming sunken into the breast
What you need to know about breast cancer
Breast cancer is the most common type of cancer in the UK. Most women diagnosed with breast cancer are over 50, but younger women can also get breast cancer so should be aware of the signs and check themselves regularly, according to the NHS wesbsite.
About one in eight women are diagnosed with breast cancer during their lifetime but there is a good chance of recovery if it is detected in its early stages.
Mammograms involve x-ray images being taken of the breasts and is the most commonly available method of detecting an early breast lesion.
However, women should be aware that a mammogram might fail to detect some breast cancers.
As the risk of breast cancer increases with age, all women who are 50 to 70 years old are invited for breast cancer screening every three years.
Women over the age of 70 are also entitled to screening and can arrange an appointment through their GP or local screening unit.
Breast cancer can be treated using a combination of surgery, chemotherapy and radiotherapy.
