title: The role of PET/CT in decreasing inter-observer variability in treatment planning and evaluation of response for cervical cancer.
abstract: We have previously introduced anatomic biologic contouring (ABC) with PET/CT, using a distinct "halo" to unify contouring methods in treatment planning for lung and head and neck cancers. The objective of this study is to assess the utility of PET/CT in planning and treatment response for cervical cancer. Forty-two patients with stages II-IIIB cervix cancer were planned for irradiation using PET/CT. A CT-based Gross Tumor Volume (GTV-CT) was delineated by two independent observers while the PET remained obscured. The Planning Target Volume (PTV) was obtained by adding a 1.5 cm margin around the GTV. The same volumes were recontoured using PET/CT data and termed GTV-ABC and PTV-ABC, respectively. The values of GTV-CT and GTV-ABC and the absolute differences between the two observers were analyzed. Additionally, 23 of these patients had PET/CT performed 3 months after treatment. The anatomic biologic value (ABV) was calculated using the product of maximum diameter and mean SUV of the cervical tumor. The pre- and post-treatment ABVs were compared. A "halo" was observed around areas of maximal SUV uptake. The mean halo SUV was 1.91 ± 0.56 (SD). The mean halo thickness was 2.12 ± 0.5 (SD) mm. Inter-observer GTV variability decreased from a mean volume difference of 55.36 cm(3) in CT-based planning to 12.29 cm(3) in PET/CT-based planning with a respective decrease in standard deviation (SD) from 55.78 to 10.24 (p <0.001). Comparison of mean pre-treatment and post-treatment ABV's revealed a decrease of ABV from 48.2 to 7.8 (p<0.001). PET/CT is a valuable tool in radiation therapy planning and evaluation of treatment response for cervical cancer. A clearly visualized "halo" was successfully implemented in GTV contouring in cervical cancer, resulting in decreased inter-observer variability in planning. PET/CT has the ability to quantify treatment response using anatomic biologic value.
authors.affiliation: Department of Radiation Oncology, New York Methodist Hospital Brooklyn, New York, USA.
authors.forename: Ajay
authors.initials: A
authors.lastname: Tejwani
authors.forename: Amir
authors.initials: A
authors.lastname: Lavaf
authors.forename: Kapila
authors.initials: K
authors.lastname: Parikh
authors.forename: Bahaa
authors.initials: B
authors.lastname: Mokhtar
authors.forename: Uma
authors.initials: U
authors.lastname: Swamy
authors.forename: Joana
authors.initials: J
authors.lastname: Emmolo
authors.forename: Adel
authors.initials: A
authors.lastname: Guirguis
authors.forename: Hani
authors.initials: H
authors.lastname: Ashamalla
keywords: Cervical cancer; PET/CT; inter-observer variability; positron emission tomography; treatment planning