Materials and Methods
This study, conducted in Australia, New Zealand and the United States, enrolled patients who developed NMSC (i.e. SCC or BCC) within 3 years and who underwent kidney transplant at least 1 year before enrollment. Patients were 18 years or older, on CNI-based regimens with cyclosporine or tacrolimus for at least 1 year prior, and on consistent immunosuppressive regimens for at least 1 month, with calculated Nankivell glomerular filtration rate (GFR) of at least 40 mL/min and proteinuria 500 mg or less per day. Patients with malignancies other than NMSC within 3 years of enrollment, history of NMSC with metastatic disease or excessive number of lesions (>20 in previous year) were ineligible. Patients receiving systemic retinoid therapy, field treatment with topical agents, photodynamic therapy, medium-depth chemical peels or laser resurfacing within 12 months before enrollment were excluded.
Study follow-up was to comprise a 2-year treatment phase plus a 1-month follow-up for adverse events. A blinded review of the data was performed 7 months after the last patient was randomized, because of low enrollment and a high early discontinuation rate. It was determined that there was minimal added power to detect a difference with continuing follow-up through 2 years versus limiting follow-up to 1 year, assuming that the rate of NMSC would continue as had been observed to that point. As a result, the study duration was amended to at least 1 year of treatment plus 1-month follow-up, with last-patient visit in January 2009.
The trial was sponsored by Wyeth Pharmaceuticals, which was acquired by Pfizer Inc. in October 2009. The authors and Wyeth representatives designed the study. Drs. Campbell, Walker, Russ and other study investigators collected data. Wyeth monitored the conduct of the study, performed statistical analyses, and held the data. The authors interpreted the data and collaborated in the preparation of the manuscript, supported by a professional medical writer provided by Pfizer Inc. All authors had access to the data, approved the article for submission, and assume responsibility for completeness and accuracy of the data and data analyses.
Institutional review boards at participating centers approved the study protocol, and the study was conducted in accordance with international standards of good clinical practice. All patients provided written informed consent before enrollment.
Screening and baseline evaluations were performed within 4 weeks prior to randomization using a computer-generated schedule. Patients were stratified by the number of new NMSC lesions in the previous 12 months (0–5 or 6–20) and randomly assigned (1:1) to CNI continuation or conversion to sirolimus. Patients were allocated to treatment according to a computer-generated Clinical Operation Randomization Environment (CORE) schedule. When the first site accessed the system, the first block of randomization codes were allocated to that site. The clinical enrollment system then assigned blocks of randomization codes in ascending sequential order each time a new site was activated or as an active site required an additional block. The block size was not revealed to investigators.
The CNI continuation group maintained their baseline therapy postrandomization, and doses of CNIs were adjusted or switched at the investigator's discretion. The sirolimus conversion group discontinued CNIs and started sirolimus on the same day with a single 6- to 12-mg loading dose, followed by 2–4 mg daily. Sirolimus dosing was adjusted to maintain whole-blood trough concentrations of 5–15 ng/mL, as measured by high-performance liquid chromatography (6–18 ng/mL as measured by immunoassay). Once sirolimus was at least 5 ng/mL, mycophenolate mofetil was decreased to 1.5 g/day or less, mycophenolate sodium to 1080 mg/day or less and azathioprine to 75 mg/day or less.
For both groups, mycophenolate mofetil, mycophenolate sodium or azathioprine were switched, decreased, temporarily withheld or discontinued as needed, based on clinical circumstances. Patients receiving corticosteroids at randomization were maintained on a minimum dose of 2.5 mg/day of prednisone (or equivalent). Corticosteroid withdrawal was prohibited. In patients not receiving corticosteroids at baseline, initiation of corticosteroids was permissible.
At baseline and at regular intervals, medical staff performed complete physical examinations and assessments of serum chemistries, lipids, liver function tests and blood counts. Study dermatologists examined patients at least every 3 months. All suspected NMSC lesions were to be biopsied and/or excised, with lesions reported at time of biopsy or treatment. Dermatologists were not blinded to treatment, as patients could be evaluated by both a dermatologist and transplant health care provider within a single clinical setting. Because the primary end point was limited to biopsy-confirmed NMSC lesions, pathologists, who were responsible for determining the nature of each lesion examined, were blinded to the immunosuppression treatment to maintain unbiased evaluation of the primary end point.
Patients who discontinued protocol-assigned treatment early, yet continued study participation, were evaluated at: (1) the time of treatment discontinuation; (2) 4 weeks postdiscontinuation and (3) at weeks 24, 52, 76 and 104 following randomization. These visits included examination by the study dermatologist.
The study was designed to have approximately 90% power to detect a mean difference of 1 new lesion, with two-sided alpha of 5%. Assuming a standard deviation of 2 lesions per year, a sample size of 90 patients per group was needed. These assumptions were based on previously published data that reported a mean accrual of NMSC to be 1.85 ± 3.84 tumors/person/year.
The primary end point, the number of new biopsy-confirmed NMSC lesions per patient per year, was calculated by summarizing the total number of new lesions reported over the observation period and standardizing it to an annual rate. The between-group difference in standardized rates was compared using a Poisson regression model adjusted by baseline NMSC stratum.
Primary efficacy analysis was based on the intent-to-treat population, comprising all randomly assigned patients receiving at least one dose of study medication for the duration of study follow-up, whether or not they remained on assigned therapy. As prespecified in the protocol, some analyses were performed on the on-therapy population, comprising all patients remaining on assigned therapy up to discontinuation of that therapy.
Secondary efficacy end points included time to first new biopsy-confirmed NMSC lesion and number of lesions recurring at the site of a previously treated lesion. Time to first new biopsy-confirmed NMSC lesion was graphically displayed with Kaplan-Meier curves and compared using the Cox proportional hazards method adjusted for baseline NMSC stratum.
In addition, calculated creatinine clearance (Nankivell method), serum creatinine, and urine protein:creatinine ratios were assessed. Analysis of covariance (ANCOVA) was used to compare GFR and serum creatinine change from baseline, with baseline as the covariate. Patients' protein:creatinine ratios were summarized by each scheduled visit, and the nonparametric Wilcoxon rank sum test was used to compare between-group differences. Graft loss, death and biopsy-confirmed acute rejection were summarized. Safety end points included the incidence of infection, wound healing complications and other malignancies.