The UK NHS is set to review around 4,500 more breast cancer cases dating back to 2015 after a review found delayed diagnoses and 20 cases involving unnecessary breast removal surgery.Hundreds of patients suffered harm under County Durham and Darlington NHS Foundation Trust in north-east England., according to the review.The Trust has apologized and is using specialists from other hospitals to determine whether more women underwent unnecessary operations or received poor care."The trust will complete the reviews already under way covering care between January 2023 and February 2025. It will then look back one year at a time, starting with patients treated in 2022 and working backwards towards 2015," it said in a statement.Review Could Cover 4,500 CasesAlso read: Alcohol-Linked Cancer Deaths Doubled In US: Colorectal Leads In Men, Breast Leads In WomenBoard chair Alison Marshall apologized to women and families affected by the failings."I would like to offer a sincere apology to all the women and their families who have been affected by the failings in our breast services," she said, according to the BBC."I can't imagine the impact that has had."She said the Trust could "not turn back the clock" but would be "open, honest and transparent" about the failings.Chief nurse Gill Hunt said concerns were first raised in 2015 following a "service reconfiguration" and the loss of breast surgical trainee posts.Till September 2, 2026, a total of 539 cases had been reviewed, and is expected to examine around 4,500 cases if it extends back to 2015.The Trust said each year's findings will be "carefully considered" before it moves to the next earlier year. As per the report, the review could take five years, with women treated in 2015 potentially having their cases reviewed as late as 2031. The admission came after the BBC reported last year that more than 200 patients were found to have suffered harm at the CDDFT."We have heard again today about the profound and lasting impact that failings in our breast services have had on women and their families," said Chief executive Steve Russell."We remain deeply sorry for the harm and distress caused, and for the times when, as a Trust, we should have listened more carefully, asked more questions and acted sooner," Russell added.About 640 patients have contacted a special helpline seeking a review of their cases. The current review cost about £523,000 in its first year and involved nine reviewers examining around 80 cases a month.20 Women Had Unnecessary MastectomiesRead More: FDA Approves New Breast Cancer Treatment That Targets Resistance Before Cancer ProgressesAbout 514 cases reviewed by the trust so far, between January 2023 and February 2025, alongside the cases of 640 former patients who contacted a dedicated helpline.Of the 514 cases, 315 patients have been found to have suffered harm, including 77 who were significantly harmed. One patient is known to have died. The Trust was found to have a high number of mastectomies compared with other NHS trusts, with operations carried out "too quickly". Breast Cancer Burden In UKBreast cancer is the most common cancer in the UK, accounting for roughly 15% of all new cancer cases.Around 60,763 new cases are diagnosed each year, according to Breast Cancer UK. An estimated 14,000-15,000 mastectomies are performed annually in the UK.What Is A Mastectomy?A mastectomy is surgery to remove the whole breast. Depending on the cancer, nearby lymph nodes and surrounding tissue may also be removed. It may be performed on one or both breasts depending on the type of cancer and individual risk factors.Some patients may undergo breast reconstruction after a mastectomy to restore breast shape and symmetry.