Comparison of 1- and 2-dimensional measurements with volumetric measurements for evaluation of change in tumor size

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Background: Change in tumor size is commonly used as a surrogate endpoint for clinical outcome. Measurement of tumor volume, the gold standard for determining tumor size, is not clinically practical. The 2 most commonly used measurements of tumor size ie, longest diameter in axial plane (LD, used in RECIST) and cross product (CP) of LD and the longest perpendicular dimension in axial plane (used in WHO), are surrogates for tumor volume and assume simple tumor geometry. Since most tumors grow and regress irregularly, we determined which of these measurements most accurately reflects change in tumor volume by comparing change in tumor volume calculated using LD or CP with change in measured tumor volume. Methods: Computed tomography (CT) scans of the chest, abdomen, and pelvis were acquired at baseline and 8-week intervals during treatment in 22 patients (pts) enrolled in 2 first-in-human (FIH) clinical trials. CT scans were analyzed by a central reader to obtain LD, CP, and tumor volume. LD (assuming spherical tumor geometry) or CP (assuming spherical or elliptical tumor geometry) was used to calculate volume. The mean bias (μ: mean difference between measured and calculated percent change in tumor volume from baseline [%ΔVol]) and limits of agreement (μ ± 2s [s = standard deviation of difference]) from Bland-Altman analyses (used for assessing agreement between 2 measurement methods) were used for comparisons between measured and calculated %ΔVol. A nested effects model (tumor lesions considered as nested within pts) was used to test significance of differences between measured and calculated %ΔVol. Results: Bland-Altman analyses showed that μ ± 2s was -5% ± 70% for LD, 5% ± 38% for CP (spherical), and 7% ± 33% for CP (elliptical). Nested analyses indicated consistent results with an observed significant difference (p-value = 0.02) between measured and calculated %ΔVol using LD and non-significant differences (p-values = 0.28 and 0.05) using CP (assuming elliptical and spherical geometry respectively). Conclusions: In this diverse FIH population, 2-dimensional tumor measurements (using CP) are better than 1-dimensional tumor measurements (using LD) in representing changes in tumor volume and should decrease noise in the measurement of treatment response.

No significant financial relationships to disclose.

Applications of magnetic resonance in model systems: tumor biology and physiology

A solid tumor presents a unique challenge as a system in which the dynamics of the relationship between vascularization, the physiological environment and metabolism are continually changing with growth and following treatment. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) studies have demonstrated quantifiable linkages between the physiological environment, angiogenesis, vascularization and metabolism of tumors. The dynamics between these parameters continually change with tumor aggressiveness, tumor growth and during therapy and each of these can be monitored longitudinally, quantitatively and non-invasively with MRI and MRS. An important aspect of MRI and MRS studies is that techniques and findings are easily translated between systems. Hence, pre-clinical studies using cultured cells or experimental animals have a high connectivity to potential clinical utility. In the following review, leaders in the field of MR studies of basic tumor physiology using pre-clinical models have contributed individual sections according to their expertise and outlook. The following review is a cogent and timely overview of the current capabilities and state-of-the-art of MRI and MRS as applied to experimental cancers. A companion review deals with the application of MR methods to anticancer therapy.

Interaction between flavone acetic acid (LM-975, NSC 349512) and radiation in Glasgow's osteogenic sarcoma in vivo

Flavone acetic acid (FAA) is a new anticancer agent in Phase II trials in Europe. In preclinical testing FAA showed broad activity against murine solid tumors and minimal activity against murine leukemias. Our interest in studying the combination of FAA and radiation was based on two of its biological effects which might modify radiation damage. First, FAA depletes ATP and inhibits macromolecular synthesis which are needed to repair radiation-induced DNA strand breaks; and second, inhibition of tumor blood flow by FAA could lead to radiobiological hypoxia. Various schedules of FAA (170 mg/kg I.V.) (n = 9, SF = 0.44) and radiation (10 Gy) (n = 9, SF = 0.37) were investigated against s.c. implanted Glasgow osteogenic sarcoma. In the same model we studied both the kinetics of ATP depletion by 31P-Nuclear Magnetic Resonance Spectroscopy and the repair of radiation induced single and double strand breaks by alkaline elution. The combined response was not significantly different from log-additive when radiation was given 24, 5 or 1 hr before FAA. When FAA was given immediately before radiation an increase in tumor response, significantly different from log-additive (p = 0.03) was observed. This enhancement disappeared when radiation was delayed for between 1 and 48 hr after FAA. While decreased ATP levels and increased response to radiation occurred within minutes after FAA administration, no effect of FAA at either 180 or 200 mg/kg was observed on the repair of radiation induced single or double strand breaks (10 and 50 Gy, respectively; 5 hr after FAA) in spite of significant ATP depletion in the tumors.