SAN DIEGO - PET/CT is a soup to nuts modality in oncology, offering useful clinical information before, during, and after treatment, according to a presentation Saturday at the Society of Nuclear Medicine (SNM) meeting.
Dr. Lale Kostakoglu of New York-Presbyterian Hospital in New York City reviewed some general scenarios for when PET/CT can be deployed in three types of cancer: head and neck (including thyroid), non-small cell lung cancer (NSCLC), and breast cancer.
Kostakoglu, who also serves with the SNM's PET Center of Excellence, outlined the pros and cons of oncologic PET/CT.
Head and neck
FDG-PET in this cancer subtype offers several advantages over anatomic imaging, including detecting unknown primaries as well as post-therapeutic residual disease, Kostakoglu said. The modality's sensitivity and specificity are on par with MRI and CT.
But PET/CT can go one better than contrast-enhanced CT or MRI, supplanting those modalities, she said. Contrast-enhanced PET/CT can spot locally advanced disease and confirm distant metastases.
For cancer recurrence, PET/CT is the superior imaging choice, although Kostakoglu did suggest performing a whole-body scan to increase sensitivity.
However, PET/CT may not be the right modality for the job in some circumstances, she explained. In node-negative disease, for example, PET/CT has not proved superior and cannot be used as a basis for surgical management, most likely elective neck dissection, she said.
In addition, cost is a sticking point with PET/CT in cancer response. At this juncture, the exam is not fully reimbursed, although it has shown a 95% negative predictive value, Kostakoglu said. In locally advanced disease, its utility as a monitoring technique remains unclear and may simply not be cost-effective, she added.
In thyroid cancer, iodine-131 whole-body imaging remains the scan of choice, Kostakoglu said, although PET/CT may have a role in defining papillary, follicular, and medullary disease. However, she pointed out that PET and CT image fusion is better than side-by-side PET and CT interpretation.
NSCLC
For non-small cell lung cancer, pulmonary nodules remain a challenge, Kostakoglu said. PET/CT combined with diagnostic chest CT has shown a sensitivity of 97% and a specificity of 78%. But she warned that this is not an easy exam as it may require full inhalation on CT.
For preoperative lung cancer staging, PET has shown 15% to 30% higher sensitivity than CT alone, especially for evaluating the extent of lymph node involvement. But a CT scan will still be necessary for anatomic markers, she said.
In distant metastases, contrast-enhanced PET/CT has the potential to increase the accuracy of staging and pinpoint distant metastases. The presence or absence of the latter is important for deciding if a patient must undergo invasive mediastinoscopy or can be treated with neoadjuvant therapy, Kostakoglu explained.
For NSCLC recurrence, FDG-PET has been valuable in selecting patients who would benefit from repeat surgery. Again, PET/CT with diagnostic chest CT can offer useful information about disease recurrence, but cannot take the place of histologic diagnosis, she emphasized.
Breast cancer
In this setting, PET/CT is adept at finding small-volume axillary metastases. However, sentinel lymph node biopsy is still superior to PET/CT and most likely more cost-effective, Kostakoglu said.
For locally advanced breast cancer, PET/CT can reveal unsuspected distant metastases, especially bone metastases. In recurrence, PET/CT has turned in 93% sensitivity and can alter clinical management, she explained. The modality has shown the ability to separate treatment responders from nonresponders, which can result in a change in therapeutic regimen.
Kostakoglu pointed out that as PET/CT continues to gain ground in oncology imaging, the following issues will need to considered:
- Risk to patient from exposure to imaging test
- Validity of test based on disease prevalence
- Cost-effectiveness
- Reproducibility of test results
- Access to equipment
- Effect of test on survival and cure rates
Finally, she posed the question of whether PET/CT results will change patient management and, if so, does an effective intervention method exist to justify the imaging exam.
By Shalmali Pal
AuntMinnie.com staff writer
June 4, 2006
Related Reading
PET/CT shows strength for staging cervical cancer, May 31, 2006
PET, PET/CT help determine RFA outcomes in lung cancer treatment, May 12, 2006
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