*3.3. Survival Analysis*

The Kaplan–Meier plots showed that there was no significant difference between patients with SUVmax ≤ median (6.62) compared to those with SUVmax > median (6.62), *p*-value = 0.0905 (Figure 1).

The bivariate log-rank test showed significant difference in predicting survival using the log-rank test: MTV ≤ median (8.06 cm3) vs. MTV > median (8.06 cm3) (*p*-value = 0.0506); TLG ≤ median (19.49) vs. TLG > median (19.49) (*p*-value < 0.0291); whole-body MTV ≤ median (33.36 cm3) vs. whole-body MTV > median (33.36 cm3) (*p*-value = 0.0001) and whole-body TLG ≤ median (462.89) vs. whole-body TLG > median (462.89) (*p*-value < 0.001). Higher MTV, TLG, whole-body MTV and whole-body TLG were associated with lower survival (see Figures 2–4).

**Figure 2.** Kaplan–Meier curves for overall survival in restaging melanoma with respect to metabolic tumor volume (MTV) (**A**), whole-body MTV (**B**), total lesion glycolysis (TLG) (**C**), and whole-body TLG (**D**).

**Figure 3.** A 50-year-old male, diagnosed with malignant melanoma of the right groin with inguinal lymph node metastases, excision and resection of metastatic inguinal nodes, presented with right groin recurrence. Maximal intensity projection image (**A**), coronal 18F-FDG- PET (**B**), fused (**C**) and CT (**D**) images demonstrating right inguinal recurrence (arrow). He also had abdominal and retroperitoneal lesions. MTV 174.59 cm3, TLG 1611.46, SUVmax 22.12, whole-body MTV 780.55 cm<sup>3</sup> and whole-body TLG 28,279.33. Overall survival was 5 months.

**Figure 4.** A 32-year-old female, acral lentiginous melanoma resected from the left foot, presented with a recurrence and nodal metastases. Maximal intensity projection image (**A**), coronal 18F-FDG PET (**B**), fused (**C**) and CT (**D**) images demonstrating large inguinal node metastases. Maximal intensity projection image (**E**), Coronal 18F-FDG PET of lower limbs (**F**), fused (**G**) and CT (**H**) images demonstrating left foot primary with subcutaneous and nodal metastases in the left leg. MTV 126.73 cm3, TLG 567.75, SUVmax 10.78, whole-body MTV 635.48 cm<sup>3</sup> and whole-body TLG 9964.33. Overall survival was 8 months.

#### *3.4. Univariate Analysis of Demographic and Clinicopathology in Relation to Overall Survival*

In relation to overall survival, patients aged >65 years had a 1.88-fold statistically significant increased risk of death compared to those who were aged <65 years (*p*-value = 0.08). Male patients had a 2.26-fold increased risk of death compared to females (*p*-value = 0.027). Patients with MTV > 12.39 cm<sup>3</sup> were 2.53 times more likely to die compared to those with MTV ≤ 12.39 cm<sup>3</sup> (*p*-value = 0.01), while patients with TLG > 36.84 had an increased risk factor of 2.43 compared to TLG ≤ 36.84 (*p*-value < 0.014). The risk of mortality was 4.09 times higher amongs<sup>t</sup> patients with a whole-body MTV > 51.15 cm<sup>3</sup> compared to those with a wholebody MTV ≤ 51.15 cm<sup>3</sup> (*p*-value < 0.001), while patients with a whole-body TLG > 564.47 were 4.33 times more likely to die compared to those with a whole-body TLG ≤ 564.47 (*p*-value < 0.001). This is shown in Table 3.


**Table 3.** Univariate analysis of demographic and clinicopathology in relation to overall survival.

HR: Hazards ratio; CI: Confidence interval.
