Each year the Danish mammography-screening programme identifies a large number of patients with small non-palpable breast cancers or precancerous lesions. The majority of these patients are suitable for breast conserving surgery (BCS). The object of BCS is to remove the suspicious lesion completely without removing excess healthy breast tissue. To obtain this accurate lesion localization is essential.

Until today the standard procedure in Denmark has been wire guided localization (WGL). Although the method has been utilized for a number of years it has several disadvantages. Often inaccurate lesion localization leads to incomplete lesion removal (positive margin) and subsequently reoperation. It can postpone the additional systemic treatment, offered after the operation. Other disadvantages are poor cosmetic outcome and inconvenient planning for the patient and the departments involved. The wire needs to be placed on the day of the operation, which decreases the flexibility of the procedure.

The purpose of this study is to test a new method named radioactive seed localization (RSL). The method uses a small titanium seed containing radioactive iodine. It will be placed in the centre of the lesion, and during the operation, the surgeon can locate it with a handheld gamma probe. The seed can be placed a few days in advance, which means a more flexible course of treatment. The method seems promising with regards to reoperation rates, but it needs further testing.

Hypothesis:

RSL is a more accurate method, for localization of nonpalpable breast lesions, than WGL. Using RSL obtains, to a great extent, adequate negative margins, resulting in a reduced number of re-operations.

The study will be performed as a randomised clinical trial, where the two methods will be compared to each other. The trial will be performed at the department of breast surgery at Rigshospitalet and include patients with nonpalpable breast lesions. Besides reoperation rates, duration of the surgical procedure and the amount of removed breast tissue will be compared.

Inclusion Criteria:

• Patients with nonpalpable breast lesions, carcinoma in situ or invasive carcinoma, where preoperative lesion localization is necessary.
• All age groups, minimum 18 years

Exclusion criteria:

• Patients with benign nonpalpable breast lesions.
• Patients who are unable to comprehend the information.
• Patients who are pregnant, breastfeeding or have children < 3 years.
• Patients who have lesions, which requires more than two wires or seeds for localization.

Data will be presented in a international peer review article.