Evaluation of Atypical Low Energy Fractures in Patients Affected by Multiple Myeloma Treated with Bispohosphonates

Bisphosphonates (BP) are standard supportive care in patients affected by symptomatic multiple myeloma (MM) with skeletal lesions. Despite the long term use of BP in the clinic, many of the effects of this category of drugs and their optimal schedule of administration are still matter of debate. In the recent past the identification of osteonecrosis of the jaw induced clinicians and researchers to reevaluate the schedule of administration of BP in myeloma, questioning about their effects on other cells than osteoclasts. Therefore a better definition of risks and benefits of anti-catabolic agents may help addressing future studies in this field. Recently a growing number of publications alerted orthopedics and endocrinologists about a rare but serious event called “atypical low energy fractures” (LEF) in patients affected by osteoporosis treated with long term BP (1–3). LEF refer to stress fractures, mainly localized in the subtrochanteric region, spontaneous or secondary to minor trauma, often preceded by local pain, with specific radiologic patterns and sometimes delayed healing. Localizations in bones different than femur have been reported. Still debated is the association with BP and the pathophysiology of this condition. So far three cases of fractures with the characteristics of LEF have been described in MM patients.

in order to evaluate the possible existence of other cases of LEF in patients with MM we started a retrospective survey in hematological centers, collecting the cases of MM followed by each center between January 2005 and December 2010, and any case of atypical fracture not related to MM or major trauma. Inclusion criteria for LEF were so defined: diagnosis of MM; treatment with BP; fractures induced by minor trauma or spontaneous, not associated with MM localization; radiological aspect of stress fracture; +/− prodromic pain. Central revision of patients history and radiology will be conducted with the support of an orthopedic in the patients with atypical fractures, followed by bone histomorphometry on bone marrow biopsy.

The study is ongoing. At present seven centers reported a total of 1065 patients affected by MM followed between 2005 and 2010 and five cases of suspect LEF. The first patient is a woman diagnosed with anaplastic myeloma in 2002, apparently in complete remission after 4 lines of treatment. In June 2008 the patient was diagnosed with an atraumatic left fracture of the fifth metatarsal bone, followed by a right metatarsal fracture one month later and second right metatarsal stress fracture in 2011. The fractures were not related to myeloma localization. Other four cases of fractures are under investigation in other two center.

MM patients are exposed to high rate of bone fractures related to the hematological disease and at the best of our knowledge the frequency of stress fractures in this population is unknown. With the present study, over a population of more than one thousand patients, we observed five cases of possible LEF that will undergo detailed analysis through central revision of patients history, radiology and bone histomorphometry with the aim to identify individual risk factors. Despite LEF is a rare and still controversial condition, the identification of individual risks to develop fractures not secondary to MM, may help clinicians tailoring the treatment for bone disease, much needed in an era of new drug discoveries for bone treatment.

Palumbo:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria; Amgen: Honoraria.