Active Surveillance of Papillary Thyroid Cancer-A Feasibility Experience from a Tertiary Care Centre

Abstract

The 2015 American Thyroid Association (ATA) guidelines recommend active surveillance (AS) as an alternative for very low-risk papillary thyroid cancer (PTC) based on evidence from observational and cohort studies in Japan and Korea that demonstrated low rates of disease progression. Adopting AS presents unique challenges in India given the need for proper understanding, adequate sonographic expertise, meticulous follow-up and acceptance of the patients and clinicians for active surveillance of diagnosed PTC. We present our data on the feasibility of AS at our centre in the last 7 years. We started adopting AS for patients with PTC or suspected PTC under AS in July 2017. Most of the patients had FNAC category Bethesda V or VI and/or USG category ACR-TIRADS TR4 or TR5 nodules. In all patients, the PTC was discovered incidentally. A baseline CT scan of the neck and chest was performed if indicated and in select patients, serial serum thyroglobulin (Tg) and anti-thyroglobulin (anti-Tg) were done. Patients were followed up semi-annually with neck ultrasound performed by a single operator. We have been following 17 patients with PTC under the AS clinic. The mean (SD) age of the cohort was 45.17 (14.7) years with 13 females and a median follow-up of 40 months (IQR 40-46; range 13-86), and none have undergone thyroid surgery. The PTC was discovered incidentally in 12 patients during a neck sonogram for evaluation of painful swallowing or salivary gland-related symptoms and evaluation of primary hyperparathyroidism; 2 patients on CT chest for pulmonary symptoms and 3 were "PETomas" during evaluation of their primary cancer (colon cancer, breast cancer and multiple myeloma). Out of the 3 patients who underwent FDG-PET scan, the SUV max of the PTC was 4, 4.8 and 14.6. All except one were uni-focal PTC with size (largest dimension on USG) ranging from 4.8 to 21 mm and median volume 0.21 mL (IQR 0.21-0.37 mL). The baseline median Tg levels were 12.95 ng/mL (range is 0.07 to 51 ng/mL), and anti-Tg was elevated in 4 patients (132 IU/mL, 156 IU/mL, 696 IU/mL, 4000 IU/mL). Serial Tg and anti Tg levels were measured over time in 4 patients. The patient with the largest PTC (21 mm) who is currently under AS had Eisenmenger syndrome. The longest duration of follow-up in the AS cohort is 86 months. One patient conceived and had a healthy baby during active surveillance with no significant increase in the size of the tumour. On follow-up, the volume change in the nodules ranged from - 44 to 335% with 35% (6/17) showing decrement and 65% (11/17) showing increment. The change in the largest dimension ranged from - 28 to 154% with a decrement of 41% (7/17) and increment of 59% (10/17). However, a significant increase in the volume (> 50%) was noted only in 2 patients, and a significant increase in tumour dimension (> 3 mm) was documented in only 2 patients on follow-up. None of the patients has developed regional or distant metastasis, and none has undergone surgery. Our study provides insights into the clinical characteristics and outcomes of patients with incidentally diagnosed PTC undergoing active surveillance. Our findings support the feasibility and safety of this approach in select individuals, with emphasis on meticulous periodic neck sonography by a single operator, and a like-minded supportive thyroid cancer team.

Keywords: Active surveillance; Neck ultrasound; Papillary thyroid cancer.