Detection and chemoradiotherapeutic evaluation of advanced esophageal squamous cell carcinoma using gallium-67 SPET: A preliminary study

About 20 years ago, gallium-67 planar scintigraphy was introduced for the evaluation of advanced esophageal squamous cell carcinoma (AESCC). Although single-photon emission tomography (SPET) is now available in many institutions, there have been no reports regarding the evaluation of AESCC using ⁶⁷Ga SPET. The aims of this preliminary study were to assess the potential of ⁶⁷Ga SPET for the detection of AESCC and to further evaluate whether ⁶⁷Ga SPET can predict the effect of preoperative chemoradiotherapy on AESCC. Thirty-eight patients with histologically proven AESCC (35 men and 3 women, mean age 62±6.9 years) underwent ⁶⁷Ga SPET before and after preoperative chemoradiotherapy. The histological response to the chemoradiotherapy was determined from a surgical specimen of the esophagus: grade 0, 100% viable tumor cells; grade 1a, 99%-67%; grade 1b, 66%-34%; grade 2, 33%-1%; grade 3, no viable cells. Thirty-seven out of 38 AESCCs (97.4%) were detected on pre-chemoradiotherapy SPET. In these 37 cancers, the tumor-to-lung ratio (TLRpre) was 3.5±2 (range 1.5-9.6). Post-chemoradiotherapy SPET exhibited positive results in 22 cancers, with a TLRpost of 1.8±0.4 (range 1.1-2.6). No patient exhibiting a pathologically complete response had a positive post-chemoradiotherapy SPET result, whereas 80% of patients with negative post-chemoradiotherapy SPET (12/15) results had residual tumor. The percent reduction rate was defined as (TLRpre-TLRpost)/TLRpre x100 and did not correlate with histological response grade (P=0.5169 for Kruskal-Wallis test). These results suggest that ⁶⁷Ga SPET is a powerful tool for the detection of AESCC. However, ⁶⁷Ga SPET seems to be of little use in predicting the effects of preoperative chemoradiotherapy on AESCC. Further studies are warranted in order to further clarify the clinical usefulness of ⁶⁷Ga SPET in patients with AESCC.