PET Scan More Accurate Predictor of Treatment Response for Soft Tissue Sarcomas

Posted on March 8th, 2009 by

PET Scan More Accurate Predictor of Treatment Response for Soft Tissue Sarcomas

Positron emission tomography (PET) scans were found to be significantly more accurate than standard methods in judging response to first-line treatment for high-grade soft tissue sarcomas. These results were reported in Clinical Cancer Research.

Soft tissues connect or support surrounding structures and organs of the body. Sarcomas are cancers that affect these connective and supportive tissues, which include bones, muscles, tendons, ligaments, fat, blood vessels, and fibrous tissues. Although there is no known cause for sarcomas, it is thought that exposure to certain chemicals or radiation and certain genetic diseases may increase risk. Fortunately, sarcomas are relatively uncommon. Current treatments for soft tissue sarcomas may include a combination of surgery, radiation, and chemotherapy.

A recent study evaluated the best technique to accurately determine a patient’s response to first-line therapy for soft tissue sarcomas. First-line (neoadjuvant) therapy is given in preparation for subsequent treatments; for example, chemotherapy given prior to surgery. Neoadjuvant therapy is often delivered to shrink the size of the cancer to allow for optimal surgical removal or to delay systemic (full-body) therapy.

To evaluate anticancer responses to therapy, researchers used a PET scan, a powerful imaging technique that provides information regarding cellular function of the body or tumor. During a PET scan, a sugar-based infusion is given to the patient. This substance can be seen on the scan as it enters healthy and cancerous cells. Cells that replicate quickly, such as cancer cells, absorb greater amounts of the sugary substance than ordinary healthy cells. As the cancer grows, cellular activity (as viewed on the PET scan) will increase, and if the cancer dies, activity will decrease.

In cancer patients PET scans may be able to detect cellular changes before they can otherwise be measured. Physicians can thus more accurately determine the extent of spread and locations of the cancer, as well as monitor response to treatment.

The study, conducted between 2005 and 2007, included 42 patients with surgically operable, high-grade (aggressive) sarcomas. Each patient underwent a PET scan before and after neoadjuvant treatment to evaluate cellular function of the cancer.

  • Results of the study found that among the patients who had a response to treatment (19%), PET scan showed a significant reduction in uptake of the sugary substance, indicating a reduction in cellular activity.
  • Unfortunately this benefit was only seen among the patients who had responded to preliminary treatment.
  • Further analysis revealed that when PET scan results were compared with standard methods for measuring a tumor’s response to treatment, PET scans were more accurate for detecting a response to treatment.

Researchers were encouraged to find that PET scans are significantly more accurate than standard evaluation techniques in detecting cellular response to therapy for high-grade sarcomas.

Patients are encouraged to discuss the use of PET scans with their physician.

Reference: Evilevitch, V., Weber, W., Tap, W., et al. Reduction of glucose metabolic activity is more accurate than change in size at predicting histopathologic response to neoadjuvant therapy in high-grade soft-tissue sarcomas. Clinical Cancer Research. 2008. 14: 715-720.

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