• immunotherapy
• thyroid
• immune related adverse events

Context and aims: Immune check point inhibitors (ICIs) are a promising novel anti-tumoral treatment for cancer that have been shown to increase the overall survival of patients with different tumors. The hyperactivation of immune system against the cancer induced by ICIs may also favor the onset of inflammatory reaction known as immune related adverse events (irAEs). Endocrinological irAEs are common, especially thyroid dysfunction, involving more than 50% of subjects treated with ICIs. To date, many questions remain unanswered on the incidence, prevalence, and pathogenesis of irAEs as well as the physiologic role of PD-L1 and CTLA-4 (the target of ICIs) in endocrine tissues. Moreover, although most endocrine irAEs are mild and self-limited, some reactions can be severe and potentially life-threatening and evidence on the best management of these conditions is lacking. The main aims of the study were 1) To identify the risk factors associated with the onset of endocrine irAEs; 2) To better characterize thyroid dysfunction induced by ICIs to favor management and treatment; 3) To evaluate the expression of PD-L1 in normal thyroid tissue and in Grave’s disease (GD). Methods: For the first aim, we prospectively followed a cohort of 118 patients before starting immunotherapy and during ICIs treatment. At screening visit and during follow-up we recorded clinical data and performed measurement of thyroid hormone, thyroid antibodies, cortisol, ACTH. Neck ultrasound was performed before starting immunotherapy and one year later. For the second aim, we conducted two different retrospective study. In the first study (part 1), we studied 20 consecutive patients who had normal thyroid function before starting immunotherapy and then experienced thyrotoxicosis upon PD1 or PD-L1 blockade. Clinical assessment was combined with thyroid ultrasound, 99mTechnecium scintiscan and longitudinal thyroid function tests. In the second study (part 2), we compared the course of thyrotoxicosis of 4 patients treated with oral prednisone at the dosage of 25 mg/day (tapered to discontinuation in three weeks) and an enlarged thyroid volume to that of 8 patients with similar thyroid volume who were left untreated. For the third aim, we analyzed the immunohistochemistry (IHC) expression of PD-L1 in 25 normal thyroid tissues and in 25 samples from Graves’ disease (GD) patients. IHC was correlated with clinical and biochemical data at the diagnosis of GD. Results: Prospective study: 87 patients of 118 (73%) experienced at least one endocrine irAEs being thyrotoxicosis the most prevalent. Patients with positive TgAbs and TPOAbs before starting immunotherapy were more prone to develop hypothyroidism during ICIs treatment. Moreover, patients treated with an association therapy (Nivolumab plus Ipilimumab) and patients treated with Avelumab showed a higher rate of endocrine iRAes. Thyroid volume significantly decreased in patients with positive TgAbs and TPOAbs at baseline who experienced hypothyroidism during follow-up. Retrospective study (part 1): Five patients had normal scintigraphic uptake (Sci+), no serum TRAbs and remained hyperthyroid throughout follow-up. The other 15 patients had no scintigraphic uptake (Sci-) and experienced destructive thyrotoxicosis followed by hypothyroidism (N= 9) or euthyroidism (N= 6). Hypothyroidism was more readily seen in those with normal thyroid volume than in those with goiter (P= 0.04). Among Sci- subjects, a larger thyroid volume was associated to a longer time to remission (P<0.05). Methimazole (MMI) was effective only in Sci+ subjects (P<0.05). Retrospective study (part 2): The levels of thyroid hormones were lower in subjects treated with steroids compared to those who were left untreated. The time to remission of thyrotoxicosis was 24 days in patients treated with steroids and 120 days in untreated patients (P<0.001). At 6 months, the rate of hypothyroidism was similar in both groups (4/4 in steroid group vs 7/8 in untreated group, P=0.74) and no difference was found in tumor progression (P=0.89). IHC study: The expression of PD-L1 was higher in samples from GD subjects compared to controls. The expression of PD-L1 was directly correlated to the levels of lymphocytic infiltration in GD. The levels of TgAbs and TPOAbs at diagnosis of GD was correlated with the expression of PD-L1 at univariate analysis but no at multivariate analysis. Conclusions: 1) patients with positive TgAbs and TPOAbs have an increased risk to develop hypothyroidism during ICIs treatment; 2) patients treated with an association therapy (anti-PD1/PD-L1 and anti-CTLA-4) have an increased risk to develop endocrine irAEs; 3) IgG subclasses have a role in the risk of develop endocrine irAEs, especially destructive thyrotoxicosis; 4) patients treated with anti-PD1 or anti-PD-L1 drugs may undergo two types of thyrotoxicosis which do not differ in severity at their onset. Thyroid scintigraphy and ultrasound are useful, low invasive and low cost-benefit tools in the management of thyrotoxicosis induced by PD1 and PD-L1 blockade; 5) in patients with a poor performance status experiencing a severe destructive thyrotoxicosis induced by PD-1 blockade, a short period of administration of oral prednisone is effective in obtaining a quick reduction of the levels of thyroid hormones and related symptoms; 6) the expression of PD-L1 on thyroid cells is higher in subjects with GD compared to healthy controls and is directly corelated to the levels of lymphocytic infiltration.