Osteonecrosis of the Jaw in Multiple Myeloma Patients. Experience of Two Hospitals.

Introduction of bisphsophonates (BPs) treatment has changed the history of bone symptoms in multiple myeloma (MM) patients, as well as in metastasic cancers (MC). However, osteonecrosis of the jaw (ONJ) has been recently described in these patients. No clear mechanism is known, although length of BPs treatment, as well as dental procedures, have been argued as possible causes. We reviewed MM patients treated with BPs from two hospitals, in the last 7 years, with the aim of studying the incidence on ONJ and their correlation with: kind of BPs administered, time of treatment and dental procedures. MC patients treated with BPs were also reviewed in order to establish the influence of the disease in ONJ development. Non-parametric Mann-Whitney U-test was used in statistical analysis. From January 1999 to June 2006 a total of 225 MM patients were diagnosed in our two hospitals, 143 of them received BPs: 49 pamidronate (P) only, 64 zoledronic acid (Z) only, and 30 received P and Z (PZ) sequentially. P was administered at a doses of 90 mg every 4 weeks, and Z at a doses of 4 mgr every 4 weeks. 14 MM patients treated with BPs suffered ONJ: one patient (2%) treated with P, six (9,3%) with Z, and seven (23.3%) in the group receiving PZ. In the same period of time 353 MC patients were treated with BPs, two of them (0.6%) developed ONJ. Length of treatment, expressed in months, is shown in the table (in MC patients, only Z group was analyzed).

The longest administration of treatment was in PZ patients compared with P and Z(p<0.02), followed by P group that was longer than Z group (p<0.01). No difference was found between MC and MM groups in Z treatment length, neither between patients with and without ONJ inside each Z and ZP groups. Five ONJ patients suffered from dental procedures along BPs administration. In our series the incidence of ONJ is higher than that described in literature (4–10%), and it is very surprising the elevated incidence reached in patients treated with both BPs (23%). In our opinion, coincidental with other authors, the lasting of treatment might be one, but not the only, important factor, because in patients receiving P treatment duration was longer than Z but, ONJ incidence was lesser. For this reason we think that more potent BPs might have a role in ONJ development. Since MC patients receiving the same schedule of treatment with Z than MM do not develop ONJ so frequently, so it seems that the disease itself might play a role in ONJ incidence.