CHICAGO – The 10-year incidence rates for both squamous cell carcinoma and basal cell carcinoma arising after hematopoietic cell transplantation are impressively high at 17%-plus for each, but the malignancies occur on two very different timelines, according to Jeffrey F. Scott, MD, a fellow in micrographic surgery and dermatologic oncology at Case Western Reserve University in Cleveland.
Most of the squamous cell carcinomas (SCCs) in a large multicenter retrospective study developed within the first 5 years following hematopoietic cell transplantation (HCT), while the majority of the basal cell carcinomas (BCCs) occurred after that point, Dr. Scott reported at the annual meeting of the American College of Mohs Surgery.
He presented the results of the study, which included 876 HCT recipients followed for a mean of 6.1 years. The study objective was to pin down the risk factors for skin cancer after HCT, especially the patient-specific ones. This has become a pressing issue because the use of HCT is steadily growing, and the 5-year survival rate now exceeds 50%.
The transplant-specific risk factors have previously been fairly well described by others. They include the donor source, type of disease, the conditioning regimen, whether whole body irradiation was used, immunosuppression, graft versus host disease (GVHD), and others.
The patient-centric risk factors, in contrast, have not been well characterized. And it’s critical to thoroughly understand these risk factors in order to develop targeted prevention and surveillance strategies, Dr. Scott said.
“There remains a significant knowledge gap within our field. I would venture that the majority of this audience has treated a patient with skin cancer who has had a transplant,” he said. “Yet when a patient asks us, ‘Doc, what is my risk for skin cancer after my HCT?’ we’re really unable to give them an accurate and complete assessment of that risk. That’s because we’re missing the second major category of risk factors: the patient-specific risk factors.”
The reason for that, he added, is that the major population-based studies and national HCT registries are run by hematologists and oncologists, and they haven’t adequately captured the patient-specific skin cancer risk factors. But these are variables very familiar to dermatologists. They include skin phenotype, history of UV radiation exposure, and history of pre-HCT skin cancer.
Dr. Scott said the multicenter study he presented has two major advantages over prior studies: its large size and thorough followup. Nearly all 876 patients were followed by both an oncologist and a dermatologist at the same institution.
During followup, the HCT recipients collectively developed 63 SCCs, 55 BCCs, and 16 malignant melanomas. The 5- and 10-year incidence rates for SCC were 10.6% and 17.2%. For BCC, the 5- and 10-year rates were 5.7% and 17.6%. All 16 cases of melanoma occurred within 5 years after HCT.
In multivariate Cox proportional hazard analyses, photodamage documented on examination was independently associated with a 3.2-fold increased risk of post-HCT SCC and a 3.5-fold increased risk of BCC.
A pre-transplant history of BCC was associated with a 3.9-fold increased likelihood of developing a BCC afterwards. Similarly, a pre-HCT history of SCC conferred a 4.2-fold increased risk of post-transplant SCC and was also independently associated with a 6.6-fold increased risk of developing melanoma post-HCT.
Fitzpatrick skin types I and II were respectively associated with 9.3- and 7.2-fold increased risks of post-HCT nonmelanoma skin cancer, compared with skin types III-VI.
Acute GVHD wasn’t associated with an increased risk of nonmelanoma skin cancer after HCT. However, in an observation that hasn’t previously been reported by others, chronic GVHD with skin involvement was associated with a 2.7-fold increased likelihood of SCC post-HCT, Dr. Scott noted.
What’s next for Dr. Scott and his coinvestigators? “Our ultimate goal with this project is to develop an interactive risk assessment tool like the National Cancer Institute’s Breast Cancer Risk Assessment Tool that can be online and used by patients and providers to estimate their individualized risk of basal cell carcinoma, squamous cell carcinoma, and melanoma after HCT,” he said.
Dr. Scott reported having no financial conflicts related to the study.