Response to Treatment:
The objective of this study was to determine how accurately changes in tumor volume and stiffness could be measured in support of the longer term goal of using such changes to predict patient response to treatment. In a preliminary study we monitored nine patients undergoing neoadjuvant chemotherapy. Since the SoftVue scans are fast and safe, it was possible to monitor the patients continuously during their treatment regimen and track the properties of tumors in response to chemotherapy. Such monitoring with MRI or PET is not economically feasible since the imaging costs would be greater than the cost of the treatment.
Changes in tumor volume and mean sound speed were successfully tracked for each patient. It was found that values of both parameters declined for all patients, though the rate of decline was variable. Illustrations of changing tumor size and sound speed are shown below.
(Left) Thresholded UST sound speed images superposed on UST reflection images taken at two-week intervals, show strong response. Both tumor size and its average sound speed are rapidly declining and this patient achieved complete response. (Right). Thresholded UST sound speed images superposed on UST reflection images taken at two-week intervals show partial clinical response as indicated by the relatively slow decline of the tumor size and its average sound speed. This patient did not achieve complete response.
The next figure shows quantitative tumor sound speed changes in response to chemotherapy for all nine patients. As can be seen, these parameters decline markedly during treatment. More than just tumor size alone, these results imply that we are measuring the softening of tissue as it responds to the therapy. The rate of change of this "softening" already seems to predict complete from partial pathologic response. If validated in larger studies, this would be a breakthrough method of quantifying tumor response by a non-ionizing, low-cost imaging technique.
Tumor sound speeds plotted as a function of time. The partial responders show a slower decline compared to the average suggesting that response could be predicted.
These results also indicate that strong, measurable changes in the acoustic properties of the tumor occur during neoadjuvant chemotherapy. The study concludes that such changes can potentially predict the patient’s degree of response and may improve clinical decision-making for oncologists.
The above results also indicate that tumor volume can be accurately measured over a range of tumor sizes from 5 mm to 6 cm. . Furthermore, sound speed changes as small as 0.002 km/s can also be measured. The combined ability to measure tumor size and stiffness (via the sound speed measurement) suggest that SoftVue may be an ideal system not only for monitoring tumor response to treatment but also for monitoring growth of tumors. In light of the American Cancer Society (ACR)’s recent announcement that screening uncovers too many tumors that do not evolve into lethal cancer, SoftVue may play an important role in future “watchful waiting” scenarios, particularly for elderly patients.
"SoftVue is currently under development and has not received clearance from the FDA at this time"