Careful measurement of tumors on digital scan.

Precision Matters: How Accurate Tumor Measurement Impacts Cancer Treatment

Lena Kashyap in Health & Wellness December 2025 • 5 min read.

"A new study reveals the challenges in manually measuring tumors and how it can affect treatment decisions, especially for liver metastases."

In the fight against cancer, accurately gauging how tumors respond to treatment is critical. For years, doctors have relied on systems like RECIST (Response Evaluation Criteria in Solid Tumors) to measure tumors on medical images and determine if a treatment is working. However, RECIST isn't perfect. One major challenge lies in the variability and potential inaccuracies that can occur when tumors are manually measured on scans.

A recent study published in European Radiology Experimental dives deep into this issue, focusing specifically on the precision of manual two-dimensional (2D) segmentations – essentially, tracing the outline of tumors on CT scans – for lung and liver metastases. Metastases are cancer cells that have spread from the primary tumor to other parts of the body. The goal was to understand how precise these manual measurements truly are and what impact any uncertainty might have on assessing a patient's response to treatment.

The study aimed to evaluate the precision of manual segmentation of lung and liver metastases and to quantify the uncertainty in tumor response assessment. This has significant implications for how we interpret imaging results and make treatment decisions.

The Challenge of Manual Tumor Measurement

Careful measurement of tumors on digital scan.

The researchers had a group of physicians and scientists manually outline a large number of tumors (520 segmentations) from CT images of both livers and lungs. This was done to mimic the variability you'd see in a real-world clinical setting. The people outlining the tumors didn't consult with each other, each contouring the tumors independently. They followed RECIST guidelines, and then on a preselected slice.

After the segmentations were complete, the researchers extracted key measurements like diameters and areas of the tumors. Using these measurements, they calculated standard deviations and confidence intervals to understand the range of potential error in the manual segmentations. This allowed them to build regression models and determine confidence intervals (95% CI) for tumor size and thresholds for progressive disease (PD) and partial response (PR) according to RECIST 1.1.

In lung, uncertainty decreased as the diameter of the segmented tumor increased.
In liver, uncertainty increased as the diameter of segmented tumor increased.
The accuracy of manual segmentation is not by the experience of the operator

The study revealed that while inter-observer agreement was generally excellent (meaning the different observers tended to produce similar measurements), there were still notable uncertainties, especially in the liver. In the lungs, the precision of measurements tended to improve as the size of the tumor increased. But in the liver, the opposite was true: larger tumors had greater measurement variability. These findings suggest that experience doesn't affect segmentation, however, manual segmentation remains uncertain for large liver metastases.

What This Means for Cancer Patients and the Future of Tumor Measurement

This study highlights some important limitations of manual tumor measurement, especially when it comes to liver metastases. While RECIST remains a valuable tool, it's essential to recognize that there's inherent uncertainty in the process, and this uncertainty can influence treatment decisions.

So, what's the solution? The researchers suggest that these findings justify the continued development and integration of alternative, more quantitative methods for assessing tumor response. This could include things like volumetric assessment (measuring the entire 3D volume of the tumor) or the use of functional imaging techniques, which look at the biological activity of the tumor rather than just its size. Also, computer-aided detection software for tumor response assessment is helpful.

Ultimately, the goal is to move towards more precise and reliable ways to track how tumors are responding to treatment, ensuring that patients receive the most effective and appropriate care possible. These findings underscore the need for further research and development in the field of cancer imaging and response assessment. As technology advances, we can hopefully move towards more objective and accurate methods for measuring tumors and guiding treatment decisions.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1186/s41747-017-0015-4, Alternate LINK

Title: Precision Of Manual Two-Dimensional Segmentations Of Lung And Liver Metastases And Its Impact On Tumour Response Assessment Using Recist 1.1

Subject: Radiology, Nuclear Medicine and imaging

Journal: European Radiology Experimental

Publisher: Springer Science and Business Media LLC

Authors: F. H. Cornelis, M. Martin, O. Saut, X. Buy, M. Kind, J. Palussiere, T. Colin

Published: 2017-10-30

Everything You Need To Know

What is the main focus of the study regarding tumor measurement?

The study focuses on the accuracy of manual two-dimensional (2D) segmentations of tumors, specifically in the context of liver and lung metastases. It investigates the precision of measuring tumors on CT scans, highlighting the variability and potential inaccuracies in this process. The goal is to quantify how much uncertainty exists when assessing a patient's response to treatment based on these manual measurements, particularly using RECIST guidelines. This is crucial because precise tumor measurement directly influences treatment decisions.

What is RECIST, and why is it important in this context?

RECIST (Response Evaluation Criteria in Solid Tumors) is a system used by doctors to evaluate how tumors respond to cancer treatments. It involves measuring tumors on medical images, like CT scans, to determine if a treatment is effective. Although valuable, RECIST relies on manual measurements of tumors, which this study points out can have variability and inaccuracies. Recognizing these limitations is important because treatment decisions are often based on RECIST assessments. The study's focus on RECIST helps understand how measurement errors can affect the evaluation of treatment effectiveness, especially for liver and lung metastases.

What did the study reveal about the precision of manual tumor measurements?

The study found that manual segmentation, the process of physicians and scientists manually outlining tumors on CT scans, has inherent uncertainties. While there was good agreement among observers, the precision varied. In the lungs, larger tumors showed more precise measurements. However, in the liver, larger tumors had greater measurement variability, highlighting a significant challenge. The study suggests that even though there can be high levels of agreement, manual segmentation introduces uncertainty that can affect the assessment of treatment response. This variability can influence the interpretation of imaging results and treatment decisions.

Did the experience of the operator affect the accuracy of manual tumor measurements?

The study's findings suggest that the accuracy of manual segmentation is not affected by the experience of the operator. The study showed that the level of experience did not correlate with improved precision in the measurements, which indicates that even experienced professionals face challenges. This insight is important because it emphasizes the limitations of relying solely on manual measurements for assessing treatment response. The study's results suggest that despite the observer's experience, manual segmentation remains uncertain for large liver metastases.

Why are the study's findings important for cancer patients?

This study's findings on manual tumor measurement have implications for cancer patients because the accuracy of tumor measurements directly affects treatment decisions. The study emphasizes the need to recognize the limitations of current methods, especially for liver metastases. While RECIST is used to evaluate treatment effectiveness, the uncertainties identified in manual segmentation can lead to potential misinterpretations of imaging results. This may influence whether a patient is considered to have a partial response or progressive disease, highlighting the importance of improving measurement precision and potentially integrating more automated, precise techniques in the future.