Tumor size, that is.
Doctors monitor tumor size throughout cancer treatment to determine whether or not the selected therapies are working. If, despite treatment, the tumors continue to grow, doctors know that their approach is not improving the patient’s prognosis. At that point, they may need to turn to a different treatment plan.
Sometimes, though, measuring the tumors is easier said than done.
There are so many factors that contribute to tumor measurement — including thickness and overall volume — that it’s not always easy for researchers to measure its actual size.
New findings from the University of Chicago, though, suggest a more efficient way to indirectly measure the size and growth of pleural mesothelioma tumors: measure the lung volume instead.
“We were happy to find a high correlation between increasing disease volume and decreasing lung volume,” said project researchers Zachariah Labby and Samuel Armato III. “Since lung volumes are substantially easier to measure with software than disease volumes, this may lead to quicker and easier assessment of tumor response.”
The research team explains it like this:
Your body has a certain amount of space in the pleural cavity, which contains the lungs and other vital organs. The ribs, the heart and other surrounding organs form a boundary, and the lung — with or without mesothelioma tumors — must fit inside that cavity.
“If the disease is growing, the amount of space for the lung decreases,” Labby and Armato explain. “And as the tumor increases in size, it tends to squeeze the lung.”
Conversely, if the tumor shrinks, the lung is allowed to take up more space in the pleural cavity.
As one measurement changes, the other typically changes at a comparable rate. In the University of Chicago study, lung volume increased by an average of 8 percent as tumor volume decreased by an average of 11 percent.
“We believe that this correlation may allow researchers to use lung volumes to assess tumor response, instead of direct measurements of tumor volume,” Labby and Armato projected.
Most patients — including those enrolled in clinical trials — already receive regular CT scans as part of their medical care. In the University of Chicago study, 61 patients received a total of 216 CT scans as they received chemotherapy, without the researchers adding any additional scans to their standard schedule.
Since the patients are getting those scans anyways, it may be beneficial for doctors to extract prognostic data from those images, the team theorizes.
It’s easier for computerized programs to measure lung volume than tumor volume, according to the team. But all three major measurements — tumor thickness, total disease volume and overall lung volume — “individually demonstrated significant association with patient survival.”
Increasing tumor thickness, increasing total disease volume, and decreasing lung volume are all associated with poorer prognoses.
No single measurement was more accurate than another at predicting survival. And the measurement data still produced accurate prognoses when the researchers included additional proven prognostic factors, such as cell type and performance status.