Tumor volume doubling time of pulmonary metastases predicts overall survival and can guide the initiation of multikinase inhibitor therapy in patients with metastatic, follicular cell-derived thyroid carcinoma.

BACKGROUND

The current study was conducted to better characterize the association between overall survival (OS) from metastatic thyroid cancer and the rate of structural disease progression.

METHODS

In this retrospective study, the average tumor volume doubling time (midDT) of 2 dominant lung metastases was used to group patients into 6 clinically relevant cohorts. OS was calculated from the time of metastasis diagnosis and from the time the pulmonary lesions crossed over the 1-cm diameter threshold.

RESULTS

The tumor growth rate was remarkably constant in lung metastases from thyroid cancer over a median follow-up of 8.5 years (median correlation coefficient, 0.92; coefficient of determination, 0.85). Patients with a midDT ≤1 year were found to have worse OS compared with those with a higher midDT (log-rank P = .01). The 5-year OS rate from the 1-cm diameter time point was 20% for patients with a midDT ≤1 year (15 patients), 50% for patients with a midDT of 1 to 2 years (19 patients), 53% for patients with a midDT of 2 to 3 years (9 patients), 80% for patients with a midDT of 3 to 4 years (6 patients), and 80% for patients with a midDT of ≥4 years or who were negative (12 patients). Within the group of patients with a midDT ≤1 year, the 2-year OS rate from the 1-cm diameter point was 88% in the patients treated with multikinase inhibitors (8 patients) versus 43% in the nontreated group (7 patients) (P = .13).

CONCLUSIONS

The midDT of lung metastases appears to be a good prognostic indicator of OS in patients with metastatic thyroid cancer. Unlike the thyroglobulin DT, the midDT alone can be used to predict eligibility for multikinase inhibitor therapy. Cancer 2017;123:2955-64. © 2017 American Cancer Society.