Detection of sentinel lymph nodes by SPECT/CT and planar scintigraphy: The influence of age, gender and BMI

Background : The most important prognostic factor in melanomas, breast cancers and gynecologic tumors is the state of the lymph nodes (LNs). There is not suitable pre-surgery examination procedure of detection of impacted LNs. The use of lymphatic mapping of sentinel lymph node (SLN) helps reduce the morbidity of surgery. Accurate visualization of the SLN is required for the best results. The aim is to assess the role of planar lymphoscintigraphy and fusion imaging of SPECT/CT in SLN detection in patients with various types of tumors and estimation of some factors influencing detection success – age, gender and body mass index (BMI). Methods : Planar scintigraphy and hybrid modality SPECT/CT were performed in 550 patients (pts) (mean age 58.1 ± 13.1 years): 69 pts with gynecological tumors (37 with cervical cancer, 25 pts with endometrial cancer, 7 pts with vulvar carcinoma); in 161 pts with melanomas; and in 318 women and 2 men with breast cancer. The radiopharmaceutical was injected around the tumor, subareolar or around the scar. Planar and SPECT/CT images were interpreted separately by two nuclear medicine physicians. Efficacy of these two techniques to image SLN were compared. We have estimated the influence of the age, gender and BMI on the succes rate of SLN detection. Student's paired t -test was used for comparing numbers of found SLN by both techniques; F-test, Student's t -test, and Fisher's exact test were utilized for age, gender and BMI characteristics comparisons. Values were considered significant when P <0.05. Results : Planar scintigraphy did not image SLN in 77 pts in total (14.0 %); in 8 pts with gynecologic tumors, in 23 pts with melanomas and in 46 pts with breast cancer. SPECT/CT was negative in 49 pts (8.9 %) in total; in 4 pts with gynecologic tumors, in 12 pts with melanomas and in 33 pts with breast cancer. In 199 (36.2 %) pts the number of SLNs captured on SPECT/CT was higher than on planar imaging. 35 foci of uptake (3.1 % from totally visible 1134 foci on planar images) interpreted on planar images as hot LNs were found to be false positive non-nodal sites of uptake when further assessed on SPECT/CT. Influence of the age, gender and BMI: The group of patients with higher number of detected SLN on SPECT/CT than on planar scintigraphy had lower average age than the group of patients with the same number of detected SLN on SPECT/CT and on planar scintigraphy, the difference was statistically significant ( P =0.008). BMI did not differ in these two groups. There has been proportionally higher number of men than women who have had higher detected SLNs on SPECT/CT than on planar scintigrams (difference statistically significant P =0.04). It follows that gender influences the difference of detected SLNs on SPECT/CT and planar scintigraphy in favor of male gender. Conclusion: In some patients with gynecologic, including breast cancers and melanomas SPECT/CT improves detection of SLNs as compared to planar scintigraphy. It can image nodes not visible on planar scintigrams, excludes false positive uptake and it improves anatomical localization of SLNs. We have found the influence of the age and gender on the difference of detected numbers of SLNs by the fusion of SPECT/CT and planar lymphoscintigraphy. This difference was not influenced by BMI.