Treatment of advanced gastrointestinal stromal tumors in patients over 75 years old: clinical and pharmacological implications.

Data about the patterns of care and the specific outcome of elderly patients with advanced gastrointestinal stromal tumors (GISTs) are almost nonexistent. Between 2001 and 2009, 44 patients ≥75 years old with advanced GISTs started first-line imatinib (400 mg/day) in seven participating institutions. Clinical data were collected by reviewing medical records and were entered in a comprehensive database. During the same period, 160 patients with advanced GIST (136 patients <75 years old, 24 patients ≥75 years old) had access to an imatinib blood level testing program. Imatinib plasma concentration (patient dose 400 mg/day) tests were centralized in a single laboratory. Median age was 78 years old (range 75-86). Thirty-six patients (82 %) experienced at least one adverse event (Table 2). Drug-related adverse events were mainly of grades 1 and 2 and were medically manageable. Permanent dose reduction (200-300 mg/day) was required for 20 patients (45.5 %) and was significantly more frequent for patients with performance status (PS) ≥2: 33.5 versus 8.5 %, p = 0.04. Eight patients (18 %) required imatinib interruption for intolerance. Median PFS was 34.4 months (95 % CI 11.5-57.4) (Fig. 1). Median overall survival (OS) was 50.3 months (95 % CI 37-63.5). Performance status <2 was the sole pre-therapeutic factor associated with improved OS. No correlation was found between comorbidities and tolerance or outcome. Imatinib trough plasma concentrations increase with age, although this correlation did not reach statistical significance. First-line imatinib is a feasible and effective treatment in patients with advanced GISTs ≥75 years. Aging seems to have only a moderate impact on imatinib pharmacokinetics. Overall survival is similar to that of younger patients. Comorbidities did not result in increased incidence of toxicity. Careful follow-up regarding tolerance issues should be considered in elderly patients with poor PS.

Characterization and coupling of angiotensin-II receptor subtypes in cultured bovine adrenal fasciculata cells.

Angiotensin-II (A-II) receptor subtypes and their potential coupling mechanisms were investigated in bovine adrenal fasciculata cells (BAC) in culture, by the use of selective antagonists for AT1 (DUP 753 or Losartan) and AT2 (PD 123177 and CGP 42112A) sites. Competition for [125I]A-II specific binding with AT1 or AT2 selective ligands produced a biphasic displacement curve, suggesting two distinct A-II binding sites. In the presence of PD 123177 (10(-5) M), a concentration at which most of the AT2 sites were saturated, DUP 753 displaced [125I]A-II specific binding in a monophasic manner with an IC50 of 6.2 +/- 1.4 x 10(-7) M. In the presence of DUP 753 (10(-5) M), the displacement produced by CGP 42112A and PD 123177 was also monophasic, with IC50s of 8 +/- 3 x 10(-10) and 4.6 +/- 2.1 x 10(-7) M, respectively. The reducing agent dithio-1,4-erythritol inhibited the binding of [125I]A-II to AT1 (DUP 753 sensitive) sites, but increased its binding to AT2 sites 2-fold. The IC50 values for these two effects were about 0.5 and 3 mM, respectively. The biological effects of A-II in BAC, phosphoinositide hydrolysis and cortisol production, were inhibited in a dose-dependent manner by DUP 753, but not by AT2 antagonists. Similarly, the potentiating action of A-II on corticotropin-induced cAMP production was blocked by DUP 753, but not by AT2 antagonists. These data indicate that BAC contain both receptor subtypes, but that all the known effects of A-II in BAC were induced via the AT1 receptor subtype.