. Rising utilization — and substantial geographic variation in practice patterns — argue for further research to optimize IHC use in the diagnoses of melanoma, according to the authors.
But with sparse guidance regarding best practices for IHC in melanoma diagnosis, concerns for appropriate use are rising, they wrote in their report, recently published in JAMA Dermatology.
Kenechukwu Ojukwu, MD, MPP, of the department of pathology and laboratory medicine, University of California, Los Angeles, and coinvestigators, searched the Surveillance, Epidemiology, and End Results (SEER)–Medicare database for incident in situ or invasive cutaneous melanoma in patients 65 years and older and accompanying IHC claims made during the month of diagnosis through 14 days afterward.
Among 132,547 melanomas in 116,117 patients, 43,396 (33%) had accompanying IHC claims. Such claims were less common with increasing age, declining from 44% in patients aged 65-74 years to 18% in patients 85 aged years and older. Although melanoma incidence increased throughout the period studied, melanoma mortality rates remained relatively stable.
By summary stage at diagnosis, IHC utilization ranged from 29% of in situ cases to 75% of distant cases. After the researchers controlled for year of diagnosis, IHC use was statistically significantly associated with all demographic, tumor, and geographic characteristics examined, except race and ethnicity. Across all the years of the study, regional usage ranged from a low of 22% in Detroit to a high of 44% in both Louisiana and San Jose-Monterey, California. Figures for 2017 ranged from 39% of cases in Kentucky and Atlanta to 68% in New Mexico.
“Given the extensive use of IHC in clinical practice,” the authors concluded, “studies examining the resulting outcomes of IHC on different domains, such as symptom burden, quality of life, and mortality, are crucial.”
The “notable” regional variation in IHC utilization suggests uncertainty about its optimal employment in clinical practice, and, they wrote, “these findings highlight the need for research to identify where IHC provides the most value and to develop guidelines regarding the appropriate use of IHC.”
In an accompanying JAMA Dermatology editorial, Alexandra Flamm, MD, wrote, “now is an exciting time to practice dermatopathology, with an increased number of ancillary tests, such as IHC, that can be used to diagnose malignant neoplasms more precisely and to more accurately determine prognosis and therapeutic options in this age of precision medicine”.
However, added Dr. Flamm, a dermatologist and dermatopathologist at New York University, New York City, the increasing number of ancillary tests is fueling awareness of appropriate use and the importance of ensuring high-quality, value-based healthcare. “With this increased scrutiny on the appropriateness of ancillary histopathologic testing within dermatopathology,” she wrote, “the need is growing for parameters that can be used to guide when to use IHC testing and other ancillary testing.” And using dermatopathologist-developed tools such as American Society of Dermatopathology guidelines for 11 IHC tests can help ensure that appropriate medical decision-making is taken into account when creating these tools, she added.