The addition of the anaesthetic lidocaine to radiocolloid injection for sentinel-lymph-node (SLN) mapping in patients with early breast cancer reduces injection pain and improves patient comfort without compromising SLN identification, and should be introduced as standard practice, based on research reported in the August edition of Lancet Oncology.

Although shown to be effective, a radiocolloid injection is a painful procedure for which there is currently no effective pain management, according to authors.

To investigate methods of pain control, Alexander Stojadinovic, MD, a surgeon from the U.S. Military Cancer Institute at Walter Reed Medical Center in Washington, D.C., and colleagues conducted the first randomised trial to assess whether pH modification of the radioisotope formulation with sodium bicarbonate or addition of the anaesthetic lidocaine could reduce injection pain in patients undergoing SLN mapping.

The researchers assessed 121 patients with early-stage breast cancer who were randomly assigned to receive either the standard topical 4-percent lidocaine cream and standard radiocolloid injection (28 patients) or topical placebo cream and radiocolloid injection containing either sodium bicarbonate (31), 1-percent lidocaine (32), or sodium bicarbonate and 1-percent lidocaine (30). Immediately after the injection, patients were asked to report the pain experienced at the time of injection using a pain-rating scale and a pain-intensity questionnaire.

Overall, Stojadinovic and colleagues found a significant reduction in pain reported in the two groups of patients whose injection contained 1-percent lidocaine, without significantly affecting the success of SLN identification. However, they noted that pH modification of the radioisotope solution showed no additional benefit compared with the standard preparation.

Investigators reporters the mean score on the pain rating scale (0=no pain and 10=most pain) was 6 for the standard care group, 4.7 for the sodium bicarbonate group, 1.6 for the 1-percent lidocaine group and 1.6 for the sodium bicarbonate plus 1-percent lidocaine group. Mean pain-rating intensity, based on questionnaire responses, was 17.5 for the standard care group, 15.4 for the sodium bicarbonate group, 4.6 for the 1-percent lidocaine group and 3.4 for the sodium bicarbonate plus 1-percent lidocaine group.

"For centers that use standard radiocolloid injections for SLN mapping in patients with early breast cancer...adding 1-percent lidocaine can significantly improve patient comfort...and should be considered a new standard of practice," the authors concluded.

In an accompanying commentary, Hiram S. Cody, MD, a surgeon from the Memorial Sloan-Kettering Cancer Center in New York City, praised the authors for addressing a problem which has been widely ignored by the surgical community.

"All of us who use [radiocolloid injections]...are well advised to add lidocaine to our injection protocols; many patients will benefit," he wrote.