Multiple myeloma of an extremity: must the entire bone be treated?

Radiation of the entire shaft of a long bone affected by multiple myeloma (MM) is often advocated to prevent recurrent disease in the bone remote from the symptomatic site. Our standard of care has been to irradiate only the symptomatic area. We investigated the pattern of recurrence in patients treated in this manner.

163 patient with MM were treated between 1971 and 1994. Twenty-seven patients received treatment to a long bone with 41 sites irradiated (17 humeri, 22 femurs, 1 radius, 1 ulna). The most common long bone treated was the femur. All patients were treated with megavoltage therapy. The symptomatic lesion, plus a margin of 1-2 cm was treated with no attempt to treat the entire shaft. Mean radiation dose was 27.82 Gy (range 6.00-44.80 Gy). The length of the field was measured in centimeters and expressed as both an absolute (AL) and relative (RL) length (i.e., percentage of total length of bone).

The mean total AL and RL for femur fields was 18 cm and 42%, respectively. For the humerus, the AL and RL were 20 cm and 68%, respectively. Only four patients developed progressive disease in the same bone but outside the previously irradiated field. In three of the four patients the RL was between 20 and 30%. The dose of radiation given to these patients was 12.50, 21.00, 30.00, and 35.00 Gy. In all of these four cases, treatment of progressive disease in adjacent sites provided effective palliation of symptoms.

Radiation therapy to the symptomatic portion of a long bone affected by MM is effective for palliation. Symptomatic recurrence out of the irradiated field is uncommon and can be effectively treated. Potential benefits of this approach include irradiation of less normal marrow and elimination of use of pairs of fields or extended distance treatment to cover the entire femur.