Background/Purpose: Differentiating between effects of drugs vs. disease activity on cancer risk in SLE is difficult. Because all renal transplant recipients are on similar immunomodulatory medications, we hypothesize that additional cancer risk due to SLE itself would manifest as a higher cancer risk in SLE vs. non-SLE transplant recipients.  

Methods: A cohort of 143,652 renal transplant recipients contributing 585,420 patient-years of follow-up were identified between 2001-2009 from the United States Renal Data System, USRDS.  Patients were stratified by primary cause of renal failure: SLE (n=4289 [3%], contributing 18,435 patient-years) and non-SLE (n=139,361 [97%], contributing 566,985 patient-years).  ICD 9 cancer codes were identified from Medicare physician claims. All cancers and individual cancer types were expressed as incidence per 100,000 patient-years.  The expected number of cancers was derived from SEER general population cancer data from 2000-2009, accounting for age and sex. Standardized incidence ratios, SIRs, were calculated by dividing the observed by the expected number of cancers and 95% confidence intervals were generated.

Results: We identified 10,160 cancers occurring 3 months post transplant in this cohort.  Tables 1 and 2, indicate a 3-4 fold increased cancer risk over-all in renal transplant recipients, vs. the general population. SIRs were similar in SLE vs. non-SLE transplant recipients  for many specific cancers, with increased risks (compared to the general population) for lip/oropharyngeal, Kaposi, renal, lymphoma, colorectal, breast, and decreased risk (compared to the general population) for prostate.  The SIRs for neuroendocrine and melanoma were increased in SLE vs. non-SLE transplant recipients.  In contrast, the SIR for lung was decreased in SLE vs. non-SLE transplant recipients. 

Conclusion: Cancer risk in transplant recipients is high and surveillance may need to be tailored to the indication for transplant. Different methods of cancer ascertainment using physician claims data vs. tumor registries and inclusion of different SLE patient populations, restriction to those with severe SLE renal disease vs. our multinational cohort, may explain higher SIRs for cancer seen in SLE renal transplant recipients than in our previous multinational SLE cohort study evaluating cancer risk.

Table 1. SIRs for Cancer in SLE Renal Transplant Recipients vs. General Population

Cancer	Observed Cases/100,000 person-years	Expected Cases/100,000 person-years	Standardized Incidence Ratio (SIR)	95% Confidence Interval (CI)
All Cancers	1622	466	3.5	2.1-5.7
Lip/Oropharyngeal	781	11	72.6	57.3-92.0
Kaposi	38	0.6	62.2	35.2-141.1
Neuroendocrine*	163	5	42.8	30.7-50.2
Renal	217	14	15.4	12.3-21.7
Lymphoma	293	22	13.1	9.0-14.6
Colorectal	222	49	4.5	3.2-6.1
Melanoma	27	20	2.1	1.6-2.8
Breast	255	127	2.0	1.1-3.1
Lung	43	65	0.7	0.6-1.0
Prostate	54	163	0.7	0.01-1.0

Table 2. SIRs for Cancer in Non-SLE Renal Transplant Recipients vs. General Population

Cancer	Observed Cases/100,000 person-years	Expected Cases/100,000 person-years	Standardized Incidence Ratio (SIR)	95% Confidence Interval (CI)
All Cancers	1739	469	4.0	2.4-5.7
Lip/Oropharyngeal	665	11	58.1	36.2-80.1
Kaposi	0.6	42	72.5	55.2-89.9
Neuroendocrine*	74	5	14.3	4.1-24.6
Renal	142	14	10.1	7.6-12.6
Lymphoma	194	22	9.0	7.4-10.5
Colorectal	150	50	2.8	2.2-3.4
Melanoma	22	20	1.0	0.7-1.25
Breast	280	127	2.1	1.3-2.8
Lung	90	64	1.4	1.0-1.7
Prostate	65	163	0.4	0.2-0.5

* Neuroendocrine tumors include carcinoid tumors, islet cell tumors, medullary thyroid carcinoma, Merkel cell, secondary neuroendocrine,pheochromocytoma

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/standardized-incidence-ratios-for-cancer-after-renal-transplant-in-systemic-lupus-erythematosus-and-non-systemic-lupus-erythematosus-recipients/