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MMC undetectable in plasma of PRK patients
Findings enable patient counseling regarding the low risk of absorption.
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Patients who underwent excimer laser PRK with mitomycin C showed no systemic absorption in plasma samples taken after application of the drug, according to a study.
The potential risk of systemic toxicity with MMC exists, but it is the least invasive method available to reduce scarring and prevent haze in PRK. MMC has been widely used with the assumption that small concentrations of the drug are benign.
Systemic absorption of MMC has been noted when used in comparatively massive concentrations, such as abdominal and vesicular carcinoma; however, there was no quantifiable evidence of systemic absorption for refractive surgery.
“Patients can now know that they are not at risk from this medication given intraoperatively,” study author Courtney M. Crawford, MD, told Ocular Surgery News.
The study was published in Journal of Cataract and Refractive Surgery.
Study methods
The unmasked, prospective study comprised 30 active-duty soldiers who underwent bilateral excimer laser PRK with MMC 0.2 mg/mL corneal application for 30 seconds by the same surgeon. Mean patient age was 23 years.
Blood plasma samples were drawn 30 minutes after MMC application to allow sufficient serum absorption. Liquid chromatography mass spectrometry was used to detect any signs of MMC.
Crawford and colleagues compensated for the rapid half-life of MMC in plasma by collecting the specimens within 30 minutes of procedure completion and maintaining all specimens at –80°C before analysis.
“There should be studies that look for more standardization in terms of time duration for MMC application,” Crawford said. “We used 30 seconds for our study, but others may use a minute, some 2 minutes and some 15 seconds.”
Outcomes and observations
The study results showed no MMC was detected among the submitted plasma samples. All 30 samples were below the quantifiable limit, which was greater than 10 ng/mL. There were no reported serious complications or side effects.
“The potential risk for systemic toxicity is a key aspect surgeons must consider to counsel patients regarding an agent such as topical MMC,” the authors said.
Furthermore, Crawford said that systemic problems were not seen with the chemotherapeutic medication.
“Previously we thought that there was no systemic absorption and that MMC used in refractive surgery was negligible systemically, but now we have proof that indeed this chemotherapeutic medication does not cause any systemic absorption and, therefore, any systemic problems,” Crawford said.
The study demonstrated that no levels of MMC were detectable before elimination, given adequate absorption time.
“Clinicians can better counsel and inform their patients about the negative systemic absorption [of MMC for refractive surgery],” Crawford said. – by Christi Fox