A phase I/II trial of 125I methylene blue for one-stage sentinel lymph node biopsy.

BACKGROUND

Sentinel lymph node biopsy can be associated with delays in operating room schedule and with significant pain during the preoperative Tc colloid injection. To avoid these problems, we developed a novel radiolabeled blue dye that can be injected intraoperatively.

METHODS

We performed a phase I/II trial (IND#70627) of sterile pyrogen-free I-methylene blue to identify sentinel nodes in patients with breast cancer. Twelve women were studied. Two women each were given peritumoral or circumareolar injections of 100, 200, 300, 400, 500, or 1000 microCi of I methylene blue.

RESULTS

Sentinel nodes were detected in 11 of 12 patients, with a low-dose 200 microCi patient being the single exception. The number of sentinel nodes detected per patient ranged from 0 to 3 (mean = 1.66 nodes/case). Radioactivity at the tumor injection site [counts per second (cps) averaged over 10 seconds] ranged from 3346 to 47,300 cps and was highly dose-dependent (r = 0.90, P = 0.0002). In contrast, the in vivo node counts ranged from 0 to 1228 cps, while ex vivo counts ranged from 0 to 1516 cps. The in vivo nodal counts were dose-dependent (r = 0.67, and P = 0.0231). Radiation was carefully monitored inside the operating room and in pathology. Even with the 1-mCi dose, the radioactive blue dye produced significantly lower personnel exposure than historically seen with Tc.

CONCLUSIONS

This method eliminates the painful preoperative injections of Tc colloid, is performed by the surgeon in the operating room, is associated with lower radiation exposures for personnel, and avoids the delays caused by nonoperating room personnel. These observations warrant a more extensive trial of this method using the 1000-microCi dose of I methylene blue dye for sentinel lymph node biopsies.