Startling data from an international multi-center trial provide growing evidence that sentinel node imaging is more effectively accomplished with hybrid functional imaging with single photon emission computed tomography (SPECT) and computed tomography (CT) than with another molecular imaging technique called lymphoscintigraphy.

This conclusion held after imaging a range of cancers displaying a variety of lymphatic drainage types associated with melanoma, an aggressive skin cancer; breast carcinoma; and malignancies of the pelvis, such as prostate and cervical cancer. The research was presented at the 2014 Society of Nuclear Medicine and Molecular Imaging Annual Meeting in St Louis, Missouri.

Lymph node imaging is an essential tool in the context of surgical resection, because cancer spreads first to the lymph nodes—specifically the sentinel lymph nodes—before navigating the bloodstream and developing new malignancies elsewhere in the body. Molecular imaging of these sentinel nodes provides a surgical map that can improve a patient’s chances of becoming cancer free.

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“We found significantly more sentinel lymph node involvement with SPECT/CT, which altered surgical planning for many of our patients—a finding that was repeated across all malignancies and clinical institutions,” said Thomas N.B. Pascual, MD, co-author of the study and a research scientist from the section of nuclear medicine and diagnostic imaging and division of human health of the International Atomic Energy Agency in Vienna, Austria. “These results could potentially inform new clinical practice and shape appropriate use of SPECT/CT imaging for patients selected for surgery.”

Study findings showed that SPECT/CT breast imaging caught 13% more cancerous sentinel nodes—2,165 nodes versus 1,892 using planar lymphoscintigraphy. The hybrid SPECT system also caught 11.5% more sentinel nodes when imaging for melanoma, with 602 versus 532 nodes detected. In addition, 29.2% more nodes were imaged using SPECT/CT to detect pelvic cancer—195 nodes found versus 138 with planar imaging.

Changes in surgical planning as dictated by SPECT/CT were substantial—16.9% of breast cancer surgeries underwent a change in management, 37% of surgeries for melanoma changed, and 64.1% of surgical plans for pelvic cancer were changed due to detection of additional sentinel nodes. 

Calculated mismatch between sentinel nodes and lymphatic territories using the two imaging systems was gauged at 17% for breast carcinoma, 11.2% for melanoma, and 50% for pelvic imaging. The significantly higher mismatch in pelvic tumors was thought to be a result of relatively deeper lymphatic drainage and location of pelvic sentinel nodes.