Cardiac 18F‑FDG uptake and new‑onset rectal cancer

The present study aimed to investigate the factors affecting the cardiac uptake of 18F-fluorodeoxyglucose (18F-FDG) during 18F-FDG positron emission tomography (PET) for new-onset rectal cancer and new-onset colon cancer (ascending, transverse, descending, sigmoid colon cancer) and to examine the association between the cardiac uptake of 18F-FDG and prognosis. The participants were diagnosed with new-onset rectal cancer and new-onset colon cancer (ascending, transverse, descending, sigmoid cancer) at the Iga City General Hospital (Iga, Japan) between January 1, 2013, and March 31, 2018, and underwent an 18F-FDG PET scan for pretreatment staging. The relationship between cardiac maximum standard uptake value (SUVmax), the presence/absence of distant metastasis and prognosis was examined. A total of 26 patients (14 men and 12 women) aged 72.0±10 years with new-onset rectal cancer were selected for the study. No patients had multiple simultaneous cancers. The median cardiac SUVmax was 3.8 and 2.5 in patients with no distant metastasis and distant metastasis, respectively, revealing a statistically significant difference (P<0.01). The median tumor volume on PET-computed tomography (CT) images was 7,815 cm² and was 66,248 cm² in patients with no distant metastasis and distant metastasis, respectively, revealing a statistically significant difference (P<0.01). Echocardiography findings revealed no significant difference between patients with and without distant metastasis. The correlation coefficient between cardiac SUVmax and total tumor volume on PET/CT images (primary + lymph + distant metastases) was statistically significant (r=-0.42, P=0.03). Analysis of the association between the occurrence of distance metastasis and cardiac SUVmax as a continuous variable gave a statistically significant result [hazard ratio (HR): 0.30, 95% confidence interval (CI): 0.09-0.98, P=0.045]. Receiver operating characteristic analysis showed a cardiac SUVmax of 2.6 with an area under the curve of 0.86 for determining the presence of distant metastasis (95% CI: 0.70-1.00). The median observation time was 56 months, and nine patients died during observation. Analysis of the association between the overall survival and cardiac SUVmax (cutoff: 2.6) showed 95% CI: 0.01-0.45 and HR: 0.06 (P<0.01); that between the overall survival and total tumor volume on PET images showed 95% CI: 1.00-1.00 and HR: 1.00 (P<0.01); and that between the overall survival and presence of distant metastasis showed 95% CI: 1.72-116.4 and HR: 14.1 (P<0.01). Furthermore, 25 patients (16 men and nine women) aged 71.4±14.2 years with new-onset colon cancer were selected for the study. Analysis of new-onset colon cancer revealed no statistically significance between the cardiac SUVmax and distant metastasis.