Scintigraphic prediction of response to chemotherapy in patients with breast cancer: Technetium 99m-tetrofosmin and thallium-201 dual single photon emission computed tomography.

We have investigated the usefulness of dual-isotope single photon emission computed tomography (SPECT) for predicting the response to chemotherapy in patients with breast cancer. Twenty-five patients with breast cancer were analyzed by SPECT using both 99m-technetium-tetrofosmin ( 99m Tc-TF) and 201-thallium-chloride ( 201 Tl). The relationship between response to chemotherapy and retention of each tracer was analyzed. 99m Tc-TF retention was significantly higher in responders (42.0±37.9) than in non-responders (-11.3±34.6) (p=0.003). Ten of 13 patients (76.9%) with high 99m Tc-TF retention (>15%) showed good response to chemotherapy, whereas 11 of 12 patients (91.7%) with low 99m Tc-TF retention (<15%) did not respond to the therapy. The overall predictability to the response to chemotherapy was 84.0%. 201 Tl retention (responders, 47.5±60.2% vs. non-responders, 55.8±45.0%; p=0.443) was not useful in therapeutic prediction, but was required to identify the lesion on the SPECT image. This is the first report to find that dual-isotope SPECT using 99m Tc-TF and 201 Tl is useful in predicting the response to chemotherapy in patients with breast cancer. Low 99m Tc-TF retention is a strong predictor of therapeutic resistance, and high 99m Tc-TF retention suggests a favorable response to chemotherapy.