David S. Siegel, MD, PhD
With approximately 80% to 90% of multiple myeloma patients developing osteolytic bone lesions at some point during the course of their disease, it is important for oncologists to monitor these patients, and to design and administer appropriate bone health treatments at the earliest stages, in an effort to prevent or minimize the effects of skeletal-related events (SREs).
For many years, the standard method of assessing the extent of bone disease in multiple myeloma patients has been a skeletal survey, which consists of a series of x-rays across the whole skeletal system that can detect “punched out” lesions caused by multiple myeloma. This method detects approximately 80% of cases of myeloma that have metastasized to the bone.
However, not only does this method not catch every case of bone disease, it only detects them if lytic bone disease has caused at least 30% of the trabecular bone to be lost. Likewise, it is not sensitive enough to assess how patients respond to therapies designed to prevent SREs or maintain bone mass.
The use of combination PET-CT scans is one method of following a patient after he or she has been prescribed a medication used to mitigate bone disease.
“A PET-CT can give you a real-time image of whether the disease is progressing,” said David S. Siegel, MD, PhD, Chief of the Division of Multiple Myeloma at John Theurer Cancer Center in Hackensack, New Jersey.
CT scans utilize a higher level of radiation, so they are not typically used for screening. However, in combination, PET-CT scans are able to detect small lesions that could not have been detected through whole-body x-rays. Because the lesions detected through PET-CT scans are small, there is a higher probability of obtaining false-positive results.
MRI allows for the assessment of myeloma involvement in bone marrow. It has been shown to have greater sensitivity than radiographs when used to detect asymptomatic bone disease.
“An MRI is a great way of looking at whether the myeloma is diffuse and has presented itself in other parts of the bone structure,” Siegel said.
Siegel noted that one method being investigated is the use of PET and MRI scans together. Additionally, PET scans have become much more sensitive as different isotopes, such as (18)F-fluoride, have been utilized, making multiple myeloma lesions easier to identify.
A study published in the European Journal of Radiology in August compared the accuracy of (18) F-fluorodeoxyglucose (FDG) PET-CT scans with contrast- enhanced MRI for multiple myeloma. These are the two most sensitive imaging techniques currently available for patients with multiple myeloma. The study was a retrospective analysis of 210 PET-CT and 210 MRI studies of multiple myeloma patients.
PET-CT scans had a greater impact on downstaging: 11 of 62 patients who received PET-CT scans (17.7%) had their disease down-staged compared with only 1 patient who had an MRI (1.6%). Additionally, in 27 of 40 patients (67.5%) who achieved good or complete clinical response to therapies, the normalization of findings was faster for PET-CT scans than for MRI (P < .001).
In 90 patients who received the scans for followup, however, MRI was better at detecting disease recurrence. Of those 90 patients, 10 of the patients presented with clinical recurrence. MRI was able to detect active lesions in 8 of the 10 patients (80.0%) compared with 5 patients by PET-CT scans (50.0%).
“The skeletal survey is still the standard,” Siegel said. “However, PET and MRI scans are extremely useful and have improved tremendously over time and are a necessary part of following up with these patients.”
MSN, BSN, APN-C
Bone disease is so prevalent in multiple myeloma patients that the time to begin examining a myeloma patient’s bones is right at baseline, according to Elizabeth Bilotti, MSN, BSN, APN-C, who works in the myeloma division at John Theurer Cancer Center in Hackensack, New Jersey. She said that it is important to interview the patient at baseline to see if he or she reports being symptomatic, complains of bone pain, or exhibits any other signs that might indicate bone disease, in addition to a skeletal survey. “All of that needs to be part of the work-up when trying to provide a diagnosis.”
While early diagnostic tests are important, Bilotti said that follow-up tests utilizing PET-CT scans or MRI scans are crucial when it comes to following the course of disease.
“A PET-CT can be a great way of determining whether a patient is developing plasmacytoma,” Bilotti said, indicating that plasmacytoma denotes a lesion that appears to be an isolated form of myeloma, and therefore has not yet spread throughout the bone.
Bilotti cautioned that a combination PET-CT scan is not perfect. Even when a head-to-toe PET scan is performed, there is a high probability of obtaining a false-positive.
This is why Bilotti recommends employing multiple imaging methods in every patient when available. In Bilotti’s experience, a MRI scan is not as good a method for looking at the bone, but it’s a better method of looking at the marrow and soft tissue in general. For example, a MRI scan is better for looking at the spinal cord and determining whether the disease has caused any cord compression.
“If a patient is experiencing cord compression fractures, MRIs are a good way of identifying and following those fractures,” Bilotti said.
Drugs like zoledronic acid are recommended by several treatment guidelines as a method of addressing these bone issues, but Bilotti said that nothing on the market as of yet reverses the bone damage caused by multiple myeloma.
“When looking at these images, we’re not expecting to see a reversal of the lesions or the fractures,” Bilotti said. “We’re looking to compare these lesions to baseline and make sure that their progression is being kept to a minimum.”