, results from a dual cohort study demonstrated.
The findings build on previous research and underscore the need for early diagnosis and aggressive surveillance in this patient population, corresponding author Adele C. Green, MBBS, PhD, professor and senior scientist at the QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia, and colleagues wrote in the study, which was published online in JAMA Dermatology. “Squamous cell carcinomas (SCCs) of the skin develop up to 77 times more frequently in immunosuppressed organ transplant recipients (OTRs) than the general population,” they wrote. “Because SCCs cause substantially more morbidity and death in the former, they are postulated to be innately more aggressive than in immunocompetent patients, but OTRs’ higher SCC mortality may simply reflect greater SCC tumor burdens per patient.”
In what is believed to be the first study of its kind, Dr. Green and colleagues drew data from two cohort studies to evaluate five key clinicopathologic indicators of poor SCC outcomes in organ transplant recipients, and in those from the general population in Queensland, Australia: cephalic location, perineural invasion, invasion to/beyond subcutaneous fat, poor differentiation, and tumor size greater than 20 mm. The study population included organ transplant recipients at high risk of skin cancer, who were enrolled in the Skin Tumours in Allograft Recipients (STAR) study, and those from a population-based cohort, the QSkin Sun and Health Study. STAR consisted of lung transplant recipients and kidney and liver transplant recipients at high risk of skin cancer who were recruited from tertiary centers and diagnosed with histopathologically confirmed SCC from 2012 to 2015. QSkin consisted of individuals from Queensland’s general adult population diagnosed with SCCs from 2012 to 2015.
SCC cases in QSkin were ascertained through Australia’s universal health insurance agency and linked with histopathology records. Next, the researchers performed data analysis from both cohort studies to determine the prevalence ratio (PR) of head/neck location, perineural invasion, tumor invasion to/beyond subcutaneous fat, poor cellular differentiation, and tumor diameter greater than 20 mm among SCCs among organ transplant recipients compared with the general population.
After combining the two studies, the researchers compared 741 SCCs excised from 191 organ transplant recipients and 2,558 SCCs excised from 1,507 individuals in the general population. Their median ages were similar (62.7 and 63.7 years, respectively) and most were male (78% and 63.4%, respectively).
As for site of involvement, SCCs developed most often on the head and neck in the transplant recipients (38.6%) and on the arms and hands in the general population (35.2%). After adjustment for age and sex, perineural invasion of SCCs was more than twice as common in transplant recipients than among cases in the general population, as was invasion to/beyond subcutaneous fat (PR of 2.37 for both associations).
In other findings, compared with SCCs in the general population, poorly vs. well-differentiated SCCs were more than threefold more common in transplant recipients (PR, 3.45), while the prevalence of tumors greater than 20 mm vs. 20 mm or smaller was moderately higher in transplant recipients (PR, 1.52).
“These findings are considered generalizable, confirming that OTRs’ poorer SCC outcomes are associated with not only their sheer numbers of SCC tumors, but also with a strong shift toward more invasive, less differentiated, and larger SCC tumors, in agreement with previous findings,” the researchers wrote. “This shift is likely associated with decreased immunosurveillance resulting from immunosuppressive therapy (since carcinogenesis decelerates with therapy cessation) interacting with effects of high UV radiation exposure.”
They acknowledged certain limitations of their analysis, chiefly the lack of central review of SCCs to ensure standard assessment of histopathologic features “including caliber of nerves with perineural invasion and cell differentiation; such a review would not have been feasible logistically.”
The study was supported by grants from the National Health and Medical Research Council of Australia. The researchers reported having no disclosures related to the submitted work.