Table 1 summarizes the results of our comparison of the demographic and clinicopathological features of the patients with sporadic and hereditary MTC. The median age at surgery of the patients with hereditary MTC was significantly lower than the ages of the patients with sporadic MTC (p < 0.001). There was no significant difference in sex, max. tumor size, extrathyroid extension, Ki67 labeling index, pN, or TNM stage between the sporadic MTC patients and the hereditary MTC patients, both groups having biochemically persistent disease postoperatively.
The Ct-DRs (/year) after surgery in the 46 patients ranged from − 1.25 to 5.70 with a median of 0.17. The hTV-DR values (/year) before surgery ranged from 0.26 to 3.65 with a median of 0.60. The hTV-DR values were significantly higher than the Ct-DR values (p < 0.001), suggesting that the tumor growth in these patients was more rapid before surgery (Table 1, Fig. 1).
We divided the patients' Ct-DR values into four categories: rather rapid growth, slow growth, stable, and decrease, using cutoffs at 0.5, 0.1, and − 0.1 per year. In the 46 patients, the Ct-DR (/year) was > 0.5, 0.1–0.5, − 0.1–0.1, and ≤ 0.1 for 9, 21, 12, and 4 patients, respectively (Table 2). The patients with sporadic MTC and those with hereditary MTC showed similar distributions of Ct-DR values (p = 0.923). Although these 46 patients had biochemically persistent disease, 26% of them showed stable disease and 9% of them showed a decrease in serum Ct values that may indicate shrinkage of their tumors. By definition, the hTV-DR should be larger than 0. The hTV-DR (/year) values were > 1, 0.5–0.1, 0.1–0.5, and < 0.1 in 11, 21, 14, and 0 patients, respectively (Table 3). The 18 patients with hereditary MTC had significantly higher hTV-DR values compared to the 28 patients with sporadic MTC (p < 0.001).
Table 2
Calcitonin doubling rates in 28 patient with sporadic MTC and 18 patients with hereditary MTC
| n | > 0.5 | 0.1–0.5 | −0.1 to 0.1 | ≤ 0.1 |
| | Rather rapid growth | Slow growth | Stable | Decrease |
Sporadic MTC | 28 | 5 (18%) | 13 (46%) | 8 (29%) | 2 (7%) |
Hereditary MTC | 18 | 4 (22%) | 8 (44%) | 4 (22%) | 2 (11%) |
All patients | 46 | 9 (20%) | 21 (46%) | 12 (26%) | 4 (9%) |
*p = 0.923. MTC; medullary thyroid carcinoma. |
Table 3
Hypothetical tumor-volume doubling rates in 28 patient with sporadic MTC and 18 patients with hereditary MTC
| n | > 1 | 0.5–1.0 | 0.1–0.5 | < 0.1 |
| | Rapid growth | Rather rapid growth | Slow growth | Very slow |
Sporadic MTC | 28 | 1 (4%) | 13 (46%) | 14 (50%) | 0 (0%) |
Hereditary MTC | 18 | 10 (56%) | 8 (44%) | 0 (0%) | 0 (0%) |
All patients | 46 | 11 (24%) | 21 (46%) | 14 (30%) | 0 (0%) |
In the 28 patients with sporadic MTC, their Ct-DR values (/year) (median 0.17, range − 0.42–5.70) were significantly lower than their hTV-DR values (/year) (median 0.50, range 0.26–1.10) (p = 0.009) (Fig. 2). However, the Ct-DR values of four patients were higher than their hTV-DR values, suggesting that the preoperative tumor growth was slower than the postoperative growth, or the tumor arose much later than at birth in these patients. On the other hand, in all 18 of the patients with hereditary MTC, the Ct-DR values (/year) (median 0.21, range − 1.25–1.90) were significantly lower than the hTV-DR values (/year) (median 1.21, range 0.50–3.65) (p = 0.001), suggesting there was a more rapid tumor growth phase before surgery in all of these patients (Fig. 3).