The analytic cohort comprised 1,136 RCC subjects who consented to and completed both the epidemiological interview and medical record review (). The average age at diagnosis was younger for the analytic cohort compared with the 762 cases who did not consent to both interview and medical record review (58.6 vs 60.9 years, p < 0.001); otherwise, the two groups were similar with respect to race (29% vs 32% African-American), gender (41% vs 38% female), study site (84% vs 83% Detroit) and year of diagnosis (all p-values > 0.10). For Detroit cases, moreover, the distributions of tumor stage, size, and histology were similar between the analytic cohort and the complete sample of identified cases (p-values > 0.10, data not shown).
Demographic and clinical characteristics of patients with RCC
Among the analytic cohort, 951 (84%) and 185 (16%) cases accrued in the Detroit and Chicago study sites, respectively. A majority of KCS cases were white, married, insured, and younger than 65 years at the time of kidney cancer diagnosis (). In terms of clinical characteristics, most patients had localized or regional tumors, including more than 50% with tumor size ≤ 4 cm. Seventy four percent of patients had a classic clear cell RCC; patients with clear cell RCC (22%) were more likely than those with papillary (13%) or chromophobe (3%) tumors to have regional or distant disease at the time of diagnosis (p<0.01).
depicts the annual proportion of patients presenting with no, local, or systemic symptoms attributable to RCC. The proportion of cases with asymptomatic tumors increased progressively from 35% in 2002 to 50% in 2007 (, p-value for trend < 0.001). In terms of diagnostic studies, computed tomography, magnetic resonance imaging and ultrasonography were employed as the sole pre-treatment imaging modality for 42%, 2%, and 2% of cases, respectively; 39% of cases underwent more than one imaging evaluation from the time of diagnosis through receipt of initial therapy. Only 14% of KCS cases underwent diagnostic biopsy of either the primary tumor or a suspected metastasis.
Trends in the clinical presentation of patients with RCC by year of diagnosis *
Among the analytic cohort, 24% had ≥ 2 of the comorbid conditions comprising the Charlson Index at the time of diagnosis (). A history of hypertension (58%) or diabetes (17%) were commonly reported by the KCS cases during the epidemiological interview, and 23% of cases reported having at least 2 prevalent conditions that may threaten long-term renal function (e.g., diabetes, urolithiasis, nephrotic syndrome).
Medical comorbidities among patients with RCC
Ninety-six percent (n=1,093) of cases underwent surgical therapy for RCC. Nearly three in four patients underwent radical nephrectomy as primary surgical therapy; the proportion of radical nephrectomies performed laparoscopically increased significantly during the study interval (p<0.001), plateauing at approximately 40% of cases from 2004 through 2006 (). The proportion of patients treated with nephron-sparing surgery was 20% or lower for each year in the study interval except 2005 (29%) (). Among Detroit cases treated with a nephron-sparing surgical approach (n=185), the proportion of patients treated with laparoscopic partial nephrectomy increased from 21% in 2002 to 38% in 2006 (, p=0.005). Our principal findings did not change substantively in sensitivity analyses based only on Detroit cases.
Surgical treatments for patients with RCC by year of diagnosis *
Distribution of nephron-sparing surgical treatments for Detroit patients by year of diagnosis *