Effect of increased (99m)Tc/(99)Tc ratios on count rates in sentinel node procedures: a randomised study

Area of Science:

• Nuclear medicine
• Oncology
• Surgical oncology

Background:

• Sentinel lymph node (SLN) biopsy is crucial for breast cancer staging.
• Optimizing radiotracer preparation can enhance SLN detection rates.
• Technetium-99m (99mTc)-based radiocolloids are commonly used for SLN procedures.

Purpose of the Study:

• To evaluate the impact of different technetium-99m to technetium-99 ratios in (99m)Tc-Nanocoll on sentinel lymph node (SLN) count rates.
• To compare the efficacy of SLN procedures performed simultaneously with lumpectomy versus those performed after prior excision biopsy.

Main Methods:

• A double-blinded randomized study involving 161 breast cancer patients.
• Preparation of (99m)Tc-colloid albumin with varying elution times (2-hour vs. 24-hour).
• Ex vivo gamma probe measurements of excised SLNs to determine count rates (counts per second).

Main Results:

• A 2-hour elution yielded significantly higher SLN count rates compared to a 24-hour elution (P<0.004).
• No significant difference in SLN count rates was observed when comparing simultaneous procedures with those performed after prior excision biopsy within the same elution groups.
• SLN procedures demonstrated reliability regardless of timing relative to lumpectomy or prior excision biopsy.

Conclusions:

• A 2-hour elution of (99m)Tc-Nanocoll in vacuum maximizes specific activity, leading to higher SLN count rates.
• The timing of SLN procedures (simultaneous vs. delayed) does not significantly impact reliability.
• (99m)Tc-Nanocoll prepared with a 2-hour elution is an effective radiotracer for sentinel lymph node identification in breast cancer.