Comparison of FDG-PET/CT and CT for Delineation of Lumpectomy Cavity for Partial Breast Irradiation

Journal Article · Sun Jun 01 04:00:00 EDT 2008 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2008.02.004· OSTI ID:21124294

Lavely, William C ^[1]; Frassica, Deborah A; Myers, Lee T; Asrari, Fariba ^[2]; Wahl, Richard L ^[1]; Zellars, Richard C ^[2]

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1. Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, MD (United States)
2. Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University, Baltimore, MD (United States)

Purpose: The success of partial breast irradiation critically depends on proper target localization. We examined the use of fluorodeoxyglucose-positron emission tomography (FDG-PET)/computed tomography (CT) for improved lumpectomy cavity (LC) delineation and treatment planning. Methods and Materials: Twelve breast cancer patients underwent FDG-PET/CT on a GE Discovery scanner with a median time from surgery to PET/CT of 49 days. The LC was contoured on the CT scan by a radiation oncologist and, together with a nuclear medicine physician, on the PET/CT scan. The volumes were calculated and compared in each patient. Treatment planning target volumes (PTVs) were calculated by expanding the margin 2 cm beyond the LC, maintaining a 5-mm margin from the skin and chest wall, and the treatment plans were evaluated. In addition, a study with a patient-like phantom was conducted to evaluate the effect that the window/level settings might have on contouring. Results: The margin of the LC was well visualized on all FDG-PET images. The phantom results indicated that the difference between the known volume and the FDG-PET-delineated volume was <10%, regardless of the window/level settings. The PET/CT volumes were larger than the CT volumes in all cases (median volume ratio, 1.68; range, 1.24-2.45; p = 0.004). The PET/CT-based PTVs were also larger than the CT-based PTV (median volume ratio, 1.16; range, 1.08-1.64; p = 0.006). In 9 of 12 patients, a CT-based treatment plan did not provide adequate coverage of the PET/CT-based PTV (99% of the PTV received <95% of the prescribed dose), resulting in substantial cold spots in some plans. In these cases, treatment plans were generated which were specifically designed to cover the larger PET/CT-based PTV. Although these plans showed an increased dose to the normal tissues, the increases were modest: the non-target breast volume receiving {>=}50 Gy, lung volume receiving {>=}30 Gy, and heart volume receiving {>=}5 Gy increased by 5.7%, 0.8%, and 0.2%, respectively. The normal tissue dose-volume objectives were still met with these plans. Conclusion: The results of our study have shown that FDG-PET/CT can be used to define the LC volume. The increased FDG uptake was likely a result of postoperative inflammation in the LC. The targets defined using PET/CT were significantly larger than those defined with CT alone. Our results have shown that treatment plans can be generated to cover these larger PET/CT target volumes with only a modest increase in irradiated tissue volume compared with CT-determined PTVs.

• OSTI ID: 21124294
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 2 Vol. 71; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
CHEST
COMPUTERIZED TOMOGRAPHY
FLUORODEOXYGLUCOSE
IMAGES
INFLAMMATION
IRRADIATION
LUNGS
MAMMARY GLANDS
MEDICAL PERSONNEL
NEOPLASMS
NUCLEAR MEDICINE
PATIENTS
PHANTOMS
POSITRON COMPUTED TOMOGRAPHY
SKIN
SURGERY