A randomized trial of armpit (axilla) treatment for women with early stage breast cancer. POSNOC - POsitive Sentinel NOde: adjuvant therapy alone versus adjuvant therapy plus Clearance or axillary radiotherapy.

During surgery for early-stage breast cancer, surgeons usually remove and test the first few lymph glands in the armpit (known as sentinel nodes). Lymph glands filter fluid and help fight infection, but they are also the first place breast cancer can spread. In the past, finding even a small amount of cancer in these glands meant a woman would need further surgery to clear out most armpit glands, or radiotherapy to the whole armpit area.

While extra armpit treatments help remove cancer cells, they can lead to uncomfortable, long-term problems. The most common is lymphoedema, an ongoing swelling in the arm and hand that can be painful and hard to manage. It can also cause numbness and restricted shoulder movement.

Most women with early breast cancer now receive modern drug therapies—such as hormone tablets, chemotherapy, or targeted drugs. These medicines travel throughout the entire body to seek out and destroy stray cancer cells. Specialists think these drugs may already deal with small amounts of cancer left in the armpit, making extra armpit surgery or radiotherapy unnecessary.

The POSNOC trial was designed to test this question safely. By comparing women who have drug treatment alone with women who have drug treatment plus armpit surgery or radiotherapy, researchers hope to confirm whether extra armpit treatment can be safely left out without increasing the chance of cancer returning.