Incidence of squamous cell carcinomas of the head and neck following prolonged pegylated liposomal doxorubicin.

Despite numerous case reports, the incidence of a secondary diagnosis of head and neck squamous cell carcinoma (HNC) following pegylated liposomal doxorubicin (PLD) treatment is unknown. Computerized pharmacy records were searched at a large, multi-center healthcare system for patients who received PLD. Electronic medical records were searched to identify the patient's age at treatment initiation of PLD, diagnosis for which they were treated with PLD, number of courses and total cumulative dose of PLD (TCDPLD) and secondary malignancies. Published PLD associated HNC was utilized to determine the lowest and median TCDPLD doses associated with HNC. One thousand two hundred ninety eligible patients who had been treated with PLD were identified. The lowest TCDPLD associated HNC in the literature is 405 mg/m2. In our healthcare system, 275 patients received more than 400 mg/m2 yielding a risk of 0.004%. One hundred fifty-one patients received the lowest TCDPLD associated with HNC cancer in our series which was 640 mg/m2 yielding a risk of 0.007%. Four of 30 patients (13.3%) developed HNC who received the median TCDPLD associated with HNC in the literature of 1440 mg/m2. Five of 20 patients (25%) receiving 1650 mg/m2 developed HNC in our healthcare system. Prolonged therapy with PLD is associated with an increased risk of HNC. This risk appears to be related to the cumulative dose varying from 0.004 to 13.3% at the lowest and median TCDPLD of reported cases in the literature, respectively. Oncologists need to be aware of this risk and to screen patients appropriately.

Requisite Role of Kv1.5 Channels in Coronary Metabolic Dilation.

RATIONALE: In the working heart, coronary blood flow is linked to the production of metabolites, which modulate tone of smooth muscle in a redox-dependent manner. Voltage-gated potassium channels (Kv), which play a role in controlling membrane potential in vascular smooth muscle, have certain members that are redox-sensitive. OBJECTIVE: To determine the role of redox-sensitive Kv1.5 channels in coronary metabolic flow regulation. METHODS AND RESULTS: In mice (wild-type [WT], Kv1.5 null [Kv1.5(-/-)], and Kv1.5(-/-) and WT with inducible, smooth muscle-specific expression of Kv1.5 channels), we measured mean arterial pressure, myocardial blood flow, myocardial tissue oxygen tension, and ejection fraction before and after inducing cardiac stress with norepinephrine. Cardiac work was estimated as the product of mean arterial pressure and heart rate. Isolated arteries were studied to establish whether genetic alterations modified vascular reactivity. Despite higher levels of cardiac work in the Kv1.5(-/-) mice (versus WT mice at baseline and all doses of norepinephrine), myocardial blood flow was lower in Kv1.5(-/-) mice than in WT mice. At high levels of cardiac work, tissue oxygen tension dropped significantly along with ejection fraction. Expression of Kv1.5 channels in smooth muscle in the null background rescued this phenotype of impaired metabolic dilation. In isolated vessels from Kv1.5(-/-) mice, relaxation to H2O2 was impaired, but responses to adenosine and acetylcholine were normal compared with those from WT mice. CONCLUSIONS: Kv1.5 channels in vascular smooth muscle play a critical role in coupling myocardial blood flow to cardiac metabolism. Absence of these channels disassociates metabolism from flow, resulting in cardiac pump dysfunction and tissue hypoxia.