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What are the treatment goals in Pagets Disease of Bone?
Response to therapy is typically assessed with bone turnover markers. The preferred marker, ALP, normally decreases 1 to 2 weeks after zoledronate, reaching a nadir by 3 to 6 months. Bone resorption markers (e.g., serum collagen type 1 cross-linked C-telopeptide, urinary collagen type 1 cross-linked N-telopeptide) fall more rapidly after treatment but are more expensive and cumbersome to obtain due to diurnal variation (e.g., must be drawn on fasting morning serum or second void morning urine, respectively). Other bone formation markers (e.g., P1NP, BSAP) may be trended if ALP cannot be used (e.g. liver disease). Sustained remission may be indicated by bone turnover markers in the lower half of the reference range, and retreatment may be considered if pagetic symptoms recur or bone turnover markers become elevated. There are no data to support that ALP normalization decreases risk of long-term complications; however, trials have been limited in size and duration.
What are the side effects of pharmacological therapy?
Bisphosphonates have been associated with a small increased risk of osteonecrosis of the jaw (particularly with invasive dental procedures and in cancer patients) and atypical (subtrochanteric) femoral fractures. Bisphosphonates can be nephrotoxic and are contraindicated in patients with impaired renal function (creatinine clearance < 35 mL/minute/). Hypocalcemia can occur with bisphosphonate treatment, especially in those patients with vitamin D deficiency. Different formulations have specific side effects that should be considered. Oral formulations can cause esophagitis/dyspepsia. IV bisphosphonates (e.g., zoledronate) can cause a significant acute-phase response (fever, myalgias, arthralgia) lasting for 2 to 3 days after the infusion. Patients should be premedicated with acetaminophen before the infusion. Calcium and vitamin D should be supplemented daily to prevent secondary hyperparathyroidism and/or hypocalcemia.
