Editing Breast cancer (section)

=== Local tumors ===
[[File:Mastectomie 02.jpg|thumb|Chest after right breast [[mastectomy]]]]

Those whose tumors have not spread beyond the breast often undergo surgery to remove the tumor and some surrounding breast tissue.{{sfn|Hayes|Lippman|2022|loc="Local (Primary) Treatments"}} The surgery method is typically chosen to spare as much healthy breast tissue as possible, removing just the tumor ([[lumpectomy]]) or a larger part of the breast (partial [[mastectomy]]). Those with large or multiple tumors, high genetic risk of subsequent cancers, or who are unable to receive [[radiotherapy|radiation therapy]] may instead opt for full removal of the affected breast(s) (full mastectomy).{{sfn|Hayes|Lippman|2022|loc="Local (Primary) Treatments"}} To reduce the risk of cancer spreading, women will often have the nearest lymph node removed in a procedure called [[sentinel lymph node]] biopsy. Dye is injected near the tumor site, and several hours later the lymph node the dye accumulates in is removed.{{sfn|Hayes|Lippman|2022|loc="Evaluation and Treatment of the Axillary Lymph Nodes"}} 

After surgery, many undergo radiotherapy to decrease the chance of [[cancer recurrence]].{{sfn|Hayes|Lippman|2022|loc="Local (Primary) Treatments"}} Those who had lumpectomies receive radiation to the whole breast.<ref name=ACS-Radio>{{cite web|url=https://www.cancer.org/cancer/types/breast-cancer/treatment/radiation-for-breast-cancer.html |accessdate=12 April 2024 |title=Radiation for Breast Cancer |publisher=American Cancer Society |date=27 October 2021}}</ref> Those who had a mastectomy and are at elevated risk of tumor spread – tumor greater than five centimeters wide, or cancerous cells in nearby lymph nodes – receive radiation to the mastectomy scar and chest wall.<ref name=ACS-Radio/>{{sfn|Hayes|Lippman|2022|loc="Local (Primary) Treatments"}} If cancerous cells have spread to nearby lymph nodes, those lymph nodes will be irradiated as well.<ref name=ACS-Radio/> Radiation is typically given five days per week, for up to seven weeks.<ref name=ACS-Radio/> Radiotherapy for breast cancer is typically delivered via [[external beam radiotherapy]], where a device focuses radiation beams onto the targeted parts of the body. Instead, some undergo [[brachytherapy]], where radioactive material is placed into a device inserted at the surgical site the tumor was removed from. Fresh radioactive material is added twice a day for five days, then the device is removed.<ref name=ACS-Radio/> Surgery plus radiation typically eliminates a person's breast tumor. Less than 5% of those treated have their breast tumor grow back.{{sfn|Hayes|Lippman|2022|loc="Local (Primary) Treatments"}} After surgery and radiation, the breast can be [[breast reconstruction|surgically reconstructed]], either by adding a [[breast implant]] or transferring excess tissue from another part of the body.{{sfn|Hayes|Lippman|2022|loc="Local (Primary) Treatments"}} 

Chemotherapy reduces the chance of cancer recurring in the next ten years by around a third. However, 1-2% of those on chemotherapy experience life-threatening or permanent side effects. To balance these benefits and risks, chemotherapy is typically offered to those with a higher risk of cancer recurrence. There is no established risk cutoff for offering chemotherapy; determining who should receive chemotherapy is controversial.{{sfn|Hayes|Lippman|2022|loc="Prognostic and Predictive Variables"}} Chemotherapy drugs are typically given in two- to three-week cycles, with periods of drug treatment interspersed with rest periods to recover from the therapies' side effects.<ref>{{cite web|url=https://www.cancer.org/cancer/types/breast-cancer/treatment/chemotherapy-for-breast-cancer.html |accessdate=15 April 2024 |title=Chemotherapy for Breast Cancer |publisher=American Cancer Society |date=27 October 2021}}</ref> Four to six cycles are given in total.{{sfn|Hayes|Lippman|2022|loc="Chemotherapy"}} Many classes of chemotherapeutic agents are effective for breast cancer treatment, including the [[Alkylating antineoplastic agent|DNA alkylating]] drugs ([[cyclophosphamide]]), [[anthracycline]]s ([[doxorubicin]] and [[epirubicin]]), [[antimetabolite]]s ([[fluorouracil]], [[capecitabine]], and [[methotrexate]]), [[taxane]]s ([[docetaxel]] and [[paclitaxel]]), and [[platinum-based chemotherapy|platinum-based chemotherapies]] ([[cisplatin]] and [[carboplatin]]).
{{sfn|Hayes|Lippman|2022|loc="Chemotherapy"}} Chemotherapies from different classes are typically given in combination, with particular chemotherapy drugs selected based on the affected person's health and the different chemotherapeutics' side effects.{{sfn|Hayes|Lippman|2022|loc="Chemotherapy"}} Anthrocyclines and cyclophosphamide cause [[leukemia]] in up to 1% of those treated. Anthrocyclines also cause [[congestive heart failure]] in around 1% of people treated. [[Taxane]]s cause [[peripheral neuropathy]], which is permanent in up to 5% of those treated.{{sfn|Hayes|Lippman|2022|loc="Chemotherapy Toxicities"}} The same chemotherapy agents can be given before surgery – called [[neoadjuvant therapy]] – to shrink tumors, making them easier to safely remove.{{sfn|Hayes|Lippman|2022|loc="Neoadjuvant Chemotherapy"}}

For those whose tumors are HER2-positive, adding the [[HER2]]-targeted antibody [[trastuzumab]] to chemotherapy reduces the chance of cancer recurrence and death by at least a third.{{sfn|Hayes|Lippman|2022|loc="Predictive Factors"}}{{sfn|Hayes|Lippman|2022|loc="Anti-HER2 Therapy"}} Trastuzumab is given weekly or every three weeks for twelve months.{{sfn|Hayes|Lippman|2022|loc="Anti-HER2 Therapy"}} Adding a second HER2-targeted antibody, [[pertuzumab]] slightly enhances treatment efficacy.{{sfn|Hayes|Lippman|2022|loc="Anti-HER2 Therapy"}} In rare cases, trastuzumab can disrupt heart function, and so it is typically not given in conjunction with anthracyclines, which can also damage the heart.{{sfn|Hayes|Lippman|2022|loc="Anti-HER2 Therapy"}}

After their chemotherapy course, those whose tumors are ER-positive or PR-positive benefit from [[endocrine therapy]], which reduces the levels of [[estrogen]]s and [[progesterone]]s that hormone receptor-positive breast cancers require to survive.<ref name=ACS-Hormone>{{cite web|url=https://www.cancer.org/cancer/types/breast-cancer/treatment/hormone-therapy-for-breast-cancer.html |accessdate=16 April 2024 |title=Hormone Therapy for Breast Cancer |publisher=American Cancer Society |date=31 January 2024}}</ref> [[Tamoxifen]] treatment blocks the ER in the breast and some other tissues, and reduces the risk of breast cancer death by around 40% over the next ten years.{{sfn|Harbeck|Penault-Llorca|Cortes|Gnant|2019|loc="Systemic Therapy"}}{{sfn|Hayes|Lippman|2022|loc="Endocrine Therapy"}} Chemically blocking estrogen production with [[GnRH]]-targeted drugs ([[goserelin]], [[leuprolide]], or [[triptorelin]]) and [[aromatase inhibitors]] ([[anastrozole]], [[letrozole]], or [[exemestane]]) slightly improves survival, but has more severe side effects.{{sfn|Harbeck|Penault-Llorca|Cortes|Gnant|2019|loc="Systemic Therapy"}}{{sfn|Hayes|Lippman|2022|loc="Endocrine Therapy"}} Side effects of estrogen depletion include [[hot flash]]es, vaginal discomfort, and muscle and joint pain.{{sfn|Hayes|Lippman|2022|loc="Endocrine Therapy"}} Endocrine therapy is typically recommended for at least five years after surgery and chemotherapy, and is sometimes continued for 10 years or longer.{{sfn|Hayes|Lippman|2022|loc="Endocrine Therapy"}}{{sfn|Harbeck|Penault-Llorca|Cortes|Gnant|2019|loc="Systemic Therapy"}}

Women with breast cancer who had a [[lumpectomy]] or a [[mastectomy]] and kept their other breast have similar survival rates to those who had a double mastectomy.<ref>{{cite journal | vauthors = Giannakeas V, Lim DW, Narod SA | title = Bilateral Mastectomy and Breast Cancer Mortality | journal = JAMA Oncology | volume = 10 | issue = 9 | pages = 1228–1236 | date = September 2024 | pmid = 39052262 | pmc = 11273285 | doi = 10.1001/jamaoncol.2024.2212 | pmc-embargo-date = July 25, 2025 }}</ref> There seems to be no survival advantage to removing the other breast, with only a 7% chance of cancer occurring in the other breast over 20 years.<ref>{{Cite news | vauthors = Kolata G |date=2024-07-25 |title=Breast Cancer Survival Not Boosted by Double Mastectomy, Study Says |url=https://www.nytimes.com/2024/07/25/health/breast-cancer-double-mastectomy-study.html |access-date=2024-07-27 |work=The New York Times }}</ref>