Simultaneous use of an (125)I-seed to guide tumour excision and (99m)Tc-nanocolloid for sentinel node biopsy in non-palpable breast-conserving surgery.

PURPOSE: In the present study we describe patients with non-palpable breast lesions, in which an Iodine-125 ((125)I)-marker (or "seed") for excision of the primary tumour and Technetium-99m nanocolloid ((99m)Tc-nanocolloid) for sentinel node biopsy (SNB) are used simultaneously. The purpose was to investigate any interference between (125)I-seeds and (99m)Tc-nanocolloid by an in vitro and in vivo analysis.

METHODS: Contrast/interference-ratios between (125)I and (99m)Tc count-rates were determined in vitro using a realistic simulation model. Measurements were performed with 3 gamma-probes with different crystal materials. In 25 consecutive patients (99m)Tc-nanocolloid was intratumourally administered at the site of a previously implanted (125)I-seed. Respectively, the (125)I-setting and (99m)Tc-setting of the gamma-probe guided the wide local excision and SNB and maximum counts-per-second (cps) were measured.

RESULTS: In vitro the different probes varied in (125)I- and (99m)Tc-sensitivity. The contrast-ratio between (125)I and (99m)Tc in the (125)I-channel was 4.6 for a 3-month-old (125)I-seed using the most appropriate gamma-probe. In vivo the gamma-probe in the (125)I-setting measured a median of 16,300 cps at the tumour site compared to 4820 cps using the (99m)Tc-setting. The (125)I-seed could be well distinguished from the (99m)Tc-nanocolloid in 92% of the patients and 96% required a single operation. The SNB was successful in all patients.

CONCLUSIONS: Simultaneous use of (125)I-seeds and (99m)Tc-nanocolloid is possible under well-standardised conditions. Non-palpable breast lesions can be safely excised using the (125)I-seed in combination with a SN procedure. Use of (125)I-seeds is a next step within fine-tuning breast-conserving surgery that should lead to further investigation to confirm its value.