CT assessment of tumour response to treatment: comparison of linear, cross-sectional and volumetric measures of tumour size.

Abstract

Changes in cross-sectional area are currently used to assess tumour response to treatment. The aims of this study were to validate a helical CT technique for volume determination using a series of phantoms and to compare tumour responses indicated by one-, two- and three-dimensional measures of tumour size change in patients treated for germ cell cancer or lymphoma. All studies were performed on an IGE HiSpeed Advantage helical CT scanner with an Advantage Windows workstation. Phantom volumes were calculated using volume reconstruction software and compared with reference volumes determined by water displacement. 20 lymph node masses were studied on serial CT scans in 16 patients treated with chemotherapy for germ cell cancer or lymphoma. For each lesion the maximum diameter, maximum cross-sectional area and volume were determined before and after treatment. Tumour response was assessed using the standard World Health Organisation criteria (i.e. changes in cross-sectional area) and the newly proposed unidimensional response evaluation criteria in solid tumour (RECIST). The CT volume measurement error was 1.0-5.1% for regularly shaped phantoms larger than 35 cm3. In the assessment of treatment response there was 90% agreement between one-dimensional (1D) and two-dimensional (2D) measurements and 100% agreement between 2D and three-dimensional (3D) measurements. CT volume measurements are accurate and reproducible, particularly for larger structures. Assessment of tumour response using 1D, 2D and 3D measures had limited influence on the classification of treatment response. However, the impact of CT assessment of tumour response using 1D, 2D and 3D measurements on clinical decisions and patient outcome remains to be determined.

Recurrent glioblastoma: Volumetric assessment and stratification of patient survival with early posttreatment magnetic resonance imaging in patients treated with bevacizumab

“…Our volumetric approach has the advantage of avoiding areas of necrosis, cysts and surgical cavity, and may potentially estimate tumor size more accurately than linear methods. [15][16][17] With such measurements, volumetric analysis allows for a quantitative method of assessing early tumor change in size that appears to be associated with clinical benefit from bevacizumab treatment. Surprisingly, the same predictive significance of percentage change of enhancing tumor was not observed in a previous study using a volumetric approach.…”

“…Furthermore, recurrent glioblastomas often have imaging components that make traditional measurements challenging including irregular geometry, multifocality, and cystic or necrotic regions. Volumetric methods have the advantage of more reproducibly and precisely measuring the size of tumor, [15][16][17][18] and they are being increasingly used in this setting. For example, volumetric measurement of both the enhancing and nonenhancing tumor have been evaluated as imaging markers for treatment response, 19 PFS, and OS.…”

Radiographic response to neoadjuvant chemotherapy is a predictor of local control and survival in soft tissue sarcomas

“…The craniocaudad, anteroposterior, and transverse dimensions of the tumor were measured and the surrogate tumor volume was calculated as the product of these three values. 4,5 Responses were classified as complete (CR) if there was no residual radiographic evidence of the tumor, partial (PR) if there was a 50% or greater decrease in tumor volume, or minor (MR) if there was a 15-49% decrease in tumor volume. Stable disease (SD) was defined as no significant change (15% increase or decrease) in tumor volume and progressive disease (PD) was defined as a 15% or greater increase in tumor volume.…”

Evaluation of the response to treatment of solid tumours – a consensus statement of the International Cancer Imaging Society

“…Three-dimensional measurement is not addressed within the new criteria but may be important in the future, particularly with the advent of highly sophisticated volumetric scanning techniques (including multichannel CT and volumetric MRI) capable of acquiring isotropic imaging data. The use of 3D volume measurement has already been substantiated in several studies (Eggli et al, 1995;Johnson et al, 1995;Sohaib et al, 2000;Sorenson et al, 2001). * Lymph node involvement by tumour is different from other common soft tissue tumour sites.…”

“…The RECIST criterion of 20% increase in length to indicate progressive disease (PD) does not equate to the 25% increase as judged by the WHO criteria. Indeed a 20% increase in a unidimensional measurement using the RECIST criterion equates to a 44% increase in bidimensional measurement (Sohaib et al, 2000). This discrepancy is partially discussed within the new guidelines, as a concern related to the difficulty of measuring lesions that increase by 12% unidimensionally (mathematically corresponding to the original bidimensional WHO 25%).…”