Clinical Topics & News
Effective Treatment Options for Metastatic Pancreatic Cancer
A discussion on new and emerging treatments for patients with metastatic pancreatic cancer.
The main choice of imaging study for screening suspected bone metastases is usually the bone scan (Figure 3). Plain radiographs are not useful in the early detection of bone metastases, because bone lesions do not show up on plain films until 30% to 50% of the bone mineral is lost.5,9 Although most metastatic bone lesions represent a mixture of osteoblastic and -lytic processes, metastatic lesions of lung cancer and breast cancer are predominantly osteolytic in contrast to mainly osteoblastic lesions of prostate cancer metastases.10
The osteoblastic process of bone metastases is best demonstrated on a bone scan; however, a positive bone scan does not necessarily indicate bone metastases, because it is not highly specific of metastatic disease. Several benign bone lesions (such as osteoarthritis, traumatic injury, and Paget disease) also show positive readings. Magnetic resonance imaging (MRI) is not useful in screening for bone metastases, but it is better in assessing bone metastases compared with a bone scan, because it is more sensitive, especially for spinal lesions. The reported sensitivity of MRI is 91% to 100%, whereas bone scan sensitivity is only 62% to 85%.11,12
Even though the bone scan has been assumed to be the best imaging study for bone metastases, positron emission tomography (PET) scans can be more useful in detecting osteolytic bone metastases, as they can light up areas of increased metabolic activity. Positron emission tomography scans, however, are less sensitive for osteoblastic metastases. An additional advantage of PET scans is that they can be used for whole-body scanning/surveillance to rule out visceral involvement.
Published studies indicate that bone scans better detect sclerotic bone metastases and PET scans are superior in revealing osteolytic metastases.13-15 Furthermore, in contrast to bone scans, PET scans can identify additional lesions in addition to bone lesion. According to recent reports, PET provides higher sensitivity and specificity in demonstrating lytic and sclerotic metastases compared with that of the bone scan.16
Breast Cancer
The role of PET for breast cancer is controversial. A study by Lonneux and colleagues found that PET is highly sensitive in confirming distant metastasis from breast cancer, whereas researchers reported a similar sensitivity but higher specificity.17 Ohta and colleagues reported that PET and bone scan had identical sensitivity (77.7%), but PET was more specific than the bone scan (97.6% vs 80.9%, respectively).14 The study conclusion by Cook and colleagues was that PET is superior to bone scan in the detection of metastatic osteolytic bone lesions from breast cancer, whereas osteoblastic metastatic bone lesions from breast cancer are less likely to be demonstrated on a PET scan.18
Houssami and Costelloe conducted a systematic review of 16 reported studies that comparatively tested the accuracy of imaging modalities for bone metastases in breast cancer.19 Sensitivity was generally similar between PET and bone scans in most studies reviewed. Four studies reported similar sensitivity but higher specificity for PET; the median specificity for PET and bone scan was 92% vs 85.5%, respectively (Figure 4).
Prostate Cancer
Prostate cancer is now established as the “classic” cancer for false-negative results on PET. Positron emission tomography does not perform well in the identification of osteoblastic skeletal metastases from prostate cancer. Yeh and colleagues reported only 18% positivity with PET.20 Interestingly, however, progressive metastatic prostate cancer showed a higher yield of 77% sensitivity with PET, perhaps because active osseous disease can be better picked up by PET scans.21
Related: Prostate Cancer Survivorship Care
Lung Cancer
For non-small cell lung cancer, both bone scan and PET showed a similar sensitivity for bone metastases detection, but the PET scan was more specific than the bone scan. Lung cancer often metastasizes to bone: up to 36% of patients at postmortem study. Lung cancer with bone metastases has a poor prognosis with median survival time typically measured in months. Most patients with bone metastases develop complications, such as severe pain, bone fracture, hypercalcemia, and spinal cord compression. Bone-targeted therapies play a greater role in the management of lung cancer patients, aiming for delaying disease progression and preserving QOL.22,23
Therapeutic Strategy and Management
Major morbidities associated with bone metastases include severe pain, hypercalcemia, bone fractures, spinal compression fractures, and cord or nerve root compression. This section reviews appropriate management techniques reported in the literature, particularly external beam radiation therapy.
Radiation Therapy
Pain is the most serious complication of bone metastases. Radiation therapy has been established as standard therapy and an effective pain palliation modality. Up to 80% of patients achieve partial pain relief, and > 33% of patients experience complete pain relief after radiation (Figure 5).24,25 Although a 3,000 cGy given over a 2-week period has been commonly used, a standard dose-fraction radiation treatment regimen has not been established.
