The safety and benefits of radio-guided localization (RGL) versus wire-guided localization (WGL) surgery in the treatment of non-palpable breast cancers have been confirmed through several meta-analyses. RGL has become the standard of care in several institutions, although overall uptake has been slow. In view of this evidence supporting RGL, we believe that the future discussion is not of RGL versus WGL, but rather of what form of RGL will constitute best practice of care going forward. We therefore discuss the case for radio-guided occult lesion localization versus radioactive seed localization in the treatment of non-palpable breast cancers, is it really a toss of a coin?Keywords Wire-guided localization Á Radio-guided occult lesion localization Á ROLL Á Radioactive seed localization Á RSL Á Radio-guided localization Á Non-palpable breast cancer Non-palpable breast cancers constitute approximately onethird of all diagnosed breast cancers, [1] therefore creating a heavy burden upon health care systems. The current accepted standard of treatment for non-palpable breast cancers of wire-guided localization (WGL) has been increasingly challenged by radio-guided localization (RGL) techniques in the form of radio-guided occult lesion localization (ROLL) and radio-guided seed localization (RSL). In the four meta-analyses of RGL versus WGL, [2][3][4][5] three have demonstrated the superiority of RGL [2,4,5] with the remaining study demonstrating shorter operating times but also greater volume excisions for RGL [3]. However, the clinical relevance of this greater volume of excision remains questionable [6]. The two largest cohort series [7-9] each composed of approximately 1,000 patients supports the excellent outcomes achievable with RGL. The economical assessment has also demonstrated no disadvantage for RGL [7,[9][10][11]. In view of the mounting evidence supporting RGL, the question no longer remains that of the previous decade in terms of deciding between RGL and WGL, but rather the clinically relevant issue has now progressed to deciding between ROLL and RSL in the treatment of non-palpable breast cancers.Both techniques depend upon the presence of a skilled radiologist to perform either ultrasound or stereotactically guided localization, with the administration of between 0.2 and 0.5 mL of 99m Tc-radiolabelled albumin-based colloid for ROLL or a single 8 9 0.4 mm titanium seed radiolabelled with 125 I in RSL. Great variation exists in the radiation dose administered for ROLL, with the literature quoting anywhere between 5 and 123 MBq, [12,13] whilst for RSL it is between 3.7 and 10.7 MBq [14,15]. ROLL requires localization to be performed within 24 h of surgery due to the short 6 h half-life of 99m Tc-labelled colloid and RSL typically is performed 0-5 days prior to surgery [7,[14][15][16][17]. In the primary systemic therapy (PST) setting RSL can be undertaken several months before surgery because the half-life of 125 I is 60 days [18]. This flexibility in the timing of seed insertion provides a clear ...