Lead-time bias in studies of cinacalcet prescriptions

Recommendations for cancer screening would be different if we measured endpoints that are valid, reliable, specific, and important to patients

BACKGROUND

Despite enthusiasm for cancer screening, systematic reviews consistently fail to show that screening reduces all-cause mortality. This narrative review explores conceptual issues, and inconsistencies between evidence and opinion about screening.

REVIEW

We examined the interpretation of screening studies in relation to three intellectual traditions: (1) The relationship between prevention and cure; (2) Confirmation bias and the challenge of incorporating new data: less care may produce better outcomes than more care; (3) The answers to three structured questions about efficacy, effectiveness, and value of treatments proposed by Sir Archie Cochrane and Sir Austin Bradford Hill.

SYNTHESIS

When considering extensions of life expectancy or all-cause mortality, systematic reviews typically show cancer screening to have only small effects and often non-significant effects on all-cause mortality. Early diagnosis does not assure application of an intervention that alters the pathway toward demise. The interpretation of screening results is also affected by several known biases. Investigators and advocates are encumbered by an over focus on studies designed to determine if a treatment can work under ideal circumstances. To advance the field, we need a greater emphasis on evaluations that ask 'Does the treatment work under real-world conditions?', and 'Is the treatment worth it?' in terms of outcomes that are meaningful to patients.

Calcimimetic and calcilytic drugs for treating bone and mineral-related disorders

The calcium-sensing receptor (CaSR) plays a pivotal role in regulating systemic Ca(2+) homeostasis and is a target for drugs designed to treat certain disorders of bone and mineral metabolism. Calcimimetics are agonists or positive allosteric modulators of the CaSR; they inhibit parathyroid hormone (PTH) secretion and stimulate renal Ca(2+) excretion. The first calcimimetic drug is cinacalcet, a positive allosteric modulator of the CaSR that is approved for treating secondary hyperparathyroidism (HPT) in patients on renal replacement therapy and for some forms of primary HPT characterized by clinically significant hypercalcemia. Cinacalcet is also being investigated as a therapy for other hypercalcemic conditions and certain hypophosphatemic disorders. Calcilytics are CaSR inhibitors that stimulate the secretion of PTH and decrease renal excretion of Ca(2+). Although calcilytics have failed thus far as anabolic therapies for osteoporosis, they are currently being evaluated as novel therapies for new indications involving hypocalcemia and/or hypercalciuria.