Optimal particle size of radiocolloid for sentinel node identification in breast cancer-electron microscopic study and clinical comparison.
BACKGROUND
Sentinel node (SN) biopsy using a radiotracer is easy to learn, reproducible, and performed by the majority of breast cancer surgeons. However, this technique raises the question: what is the optimal particle size of colloid?


METHODS
Patients were injected with conventional tin colloid (median particle diameter: 700 nm) and the predominant particle size of radiocolloid retained in the SN was measured using electron microscopy. This showed a narrow distribution of colloidal size (100-150 nm). Patients were then injected with modified tin colloid having a median particle size of 100 nm. A clinical comparison was performed between conventional particle size or reduced particle size tin colloid and the SN biopsy success rate, the number of SNs, and the colloidal uptake in SNs.


RESULTS
A total of 118 patients were injected with the conventional tin colloid (group I) and 124 patients with the smaller particle colloid (group II). The identification rate and the number of SN in both groups were almost equal, and the patients with low-uptake SNs were not significantly less in group I(p = 0.55). However, in the subgroup of patients 60 years of age or more, group II had significantly more SNs than group I(1.4 vs 1.9; p = 0.03) and low-uptake SNs were significantly less common than in group I(p = 0.02).


CONCLUSIONS
The improvement of colloidal uptake in SNs using the smaller particle size tin colloid was confirmed, and this impact was statistically significant in the older population.
Sato
Kazuhiko
K
Breast Oncology Center, Dana-Farber Cancer Institute 44 Binney Street, Boston, Massachusetts 02115, USA. sato-k-a@mtg.biglobe.ne.jp.
Krag
David
D
Tamaki
Kuniyoshi
K
Anzai
Mikio
M
Tsuda
Hitoshi
H
Kosuda
Shigeru
S
Kusano
Shoichi
S
Hiraide
Hoshio
H
Mochizuki
Hidetaka
H
D000328:Adult; D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D001940:Breast / Q000000981:diagnostic imaging / Q000473:pathology; D001943:Breast Neoplasms / Q000473:pathology*; D003102:Colloids; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000000981:diagnostic imaging* / Q000473:pathology / Q000648:ultrastructure; D008854:Microscopy, Electron; D008875:Middle Aged; D009367:Neoplasm Staging; D010316:Particle Size; D011877:Radionuclide Imaging; D013667:Technetium
D003102:Colloids; D013667:Technetium