Abstract 58: Subcutaneous tumor volume measurements: The method matters

Abstract In preclinical studies, tumor volumes are important indicators of cancer progression and the response to therapy with selected drug candidates. The most common method of tumor volume assessment, due to its simplicity and cost-effectiveness, is measuring length, width, and height with a caliper, and calculating the volume using the ellipsoid formula. However, many tumors, even if inoculated by an experienced operator, show irregular shapes that deviate from the idealized ellipsoid volume which may lead to over- or underestimation of the actual tumor volume. In such cases, more specialized techniques like TumorImager® using structured light or ultrasound imaging can potentially be a better solution. The purpose of this study was to compare three different methods of tumor measurements: the caliper, the TumorImager®, and ultrasound imaging, and observe any correlation between the volumes obtained by each technique. CT26 and B16F10 cancer cells were inoculated subcutaneously on the flank of 6-week-old male mice (Balb/c and C57Bl6/J, respectively). Tumors were measured on days 8, 15 and 22 after cancer cell inoculation. Ultrasound, caliper and TumorImager® measurements were always performed by the same person to maintain replicability. The last measurements were performed on the day mouse sacrificed, and data collected was compared with the dissected tumor volume. Obtained tumor volumes were analyzed to compare the differences between the techniques used and determine the level of correlation between them. Our results showed that the measurements obtained with a caliper were similar to those based on an ultrasound 3D model. In this case, the biggest differences observed were of tumors significantly deviating from the ellipsoid shape. Measurements acquired with the TumorImager® differed significantly from those taken with calipers and ultrasound imaging. This study emphasizes the importance of choosing the right method of tumor measurement and understanding the differences between them. With an experienced operator, choosing either the caliper or ultrasound imaging is the right choice; the decision should be made based on information that needs to be obtained. Ultrasound imaging is the most informative method since it can be used, for example, to visualize the vascularity of the tumor. However, it has the greatest impact on animal welfare because the animals need to be anesthetized for the procedure. Moreover, it is important to acknowledge that the formula chosen for the study considers the tumor height, which is crucial in the case of tumors growing deeply into the animal’s body. The TumorImager® does not record this height dimension and therefore the highest deviations in relation to ultrasound were observed. However, based on a correlation between the techniques deployed. we were able to find constant coefficients enabling the scaling of TumorImager® volumes to the true volume of a tumor. Citation Format: Katarzyna Urbańska, Irmina Przydatek, Agnieszka Drzał, Karina Adamowicz, Fabio dell'Aquila, Magdalena Chwalisz, Miłosz Gawenda, Martyna Sniegocka. Subcutaneous tumor volume measurements: The method matters [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 58.