Risk of Rare Cancers Among Solid Organ Transplant Recipients

BACKGROUND

Immunosuppressed solid organ transplant recipients (SOTRs) have elevated rates of certain rare cancers caused by viruses. Evaluating risk of rare cancers among SOTRs may provide etiological clues for additional cancers linked to poor immunity and viral infections.

METHODS

We performed a cohort study of 262 455 SOTRs (1987-2014) from the US SOTR registry linked to 17 population-based cancer registries. First cancers in SOTRs were categorized using an established classification scheme based on site and histology. Standardized incidence ratios (SIRs) compared risk in SOTRs with the general population. We used Poisson regression to calculate incidence rate ratios according to immune-related SOTR characteristics, including time since transplant (ie, duration of immunosuppression). All statistical tests were 2-sided.

RESULTS

We examined 694 distinct cancer subtypes, with 33 manifesting statistically significantly elevated SIRs (Bonferroni P < 7.2 × 10-5). All 33 are rare (incidence <6 per 100 000 person-years) and several have known viral etiology (eg, Merkel cell carcinoma: SIR = 24.7, 95% confidence interval [CI] = 20.8 to 29.1). Additional cancers that were increased include squamous cell carcinomas of the lip (SIR range = 18.3-19.8), eye and adnexa (SIR = 13.8, 95% CI = 7.9 to 22.3), salivary gland (SIR = 9.3, 95% CI = 6.1 to 13.5), and nasal cavity and sinuses (SIR = 4.5, 95% CI = 2.8 to 6.8); sebaceous adenocarcinoma (SIR = 34.3, 95% CI = 26.3 to 44.0); malignant fibrous histiocytoma (15.4); and subtypes of bladder, kidney, lung, and colon cancer (SIR range = 3.2-13.3). Incidence of several cancers increased over time since transplant (Ptrend < .05), including squamous cell carcinomas of the lip, salivary gland, and anogenital sites.

CONCLUSIONS

SOTRs experience elevated rates of several rare cancers. Because some of these cancers exhibit aggressive behavior with poor outcomes, it is important to further characterize the role of immunity and the potential involvement of oncogenic viruses to improve prevention and treatment.

Survival after a cancer diagnosis among solid organ transplant recipients in the United States

BACKGROUND

Transplant recipients have an elevated risk of cancer because of immunosuppressive medications used to prevent organ rejection, but to the authors' knowledge no study to date has comprehensively examined associations between transplantation status and mortality after a cancer diagnosis.

METHODS

The authors assessed cases in the US general population (N=7,147,476) for 16 different cancer types as ascertained from 11 cancer registries. The presence of a solid organ transplant prior to diagnosis (N=11,416 cancer cases) was identified through linkage with the national transplantation registry (1987-2014). Cox models were used to examine the association between transplantation status and cancer-specific mortality, adjusting for demographic characteristics and cancer stage.

RESULTS

For the majority of cancers, cancer-specific mortality was higher in transplant recipients compared with other patients with cancer. The increase was particularly pronounced for melanoma (adjusted hazard ratio [aHR], 2.59; 95% confidence interval [95% CI], 2.18-3.00) and cancers of the breast (aHR, 1.88; 95% CI, 1.61-2.19), bladder (aHR, 1.85; 95% CI, 1.58-2.17), and colorectum (aHR, 1.77; 95% CI, 1.60-1.96), but it also was increased for cancers of the oral cavity/pharynx, stomach, pancreas, kidney, and lung as well as diffuse large B-cell lymphoma (aHR range, 1.21-1.47). Associations remained significant after adjustment for first-course cancer treatment and generally were stronger among patients with local-stage cancers for whom potentially curative treatment was provided, including patients with melanoma (aHR, 3.82; 95% CI, 2.94-4.97) and cancers of the colorectum (aHR, 2.77; 95% CI, 2.07-3.70), breast (aHR, 2.08; 95% CI, 1.50-2.88), and prostate (aHR, 1.60; 95% CI, 1.12-2.29), despite the lack of an association for prostate cancer overall.

CONCLUSIONS

For multiple cancer types, transplant recipients with cancer appear to have an elevated risk of dying of their cancer, even after adjustment for stage and treatment, which may be due to impaired immunity.