A whole new class of drugs for cancer treatment has been developed in the last ten years. They are called immune checkpoint inhibitors, a confusing term at best. They act by binding to receptors on lymphocytes, the white blood cells whose functions include surveillance for cancer and killing cancer cells, which they recognize as foreign. There are proteins on tumor cells that inactivate the killer lymphocyte. This new class of drugs prevents the cancer-related proteins from paralyzing the killer lymphocytes, and allow those cells to do their job — killing cancer. They work through a variety of mechanisns within the description above. There are six drugs currently FDA approved to treat a variety of human cancers, from genitourinary cancer, through lung cancer to advanced malignant melanoma, where some of the greatest advances have been made against a disease that was previously quickly and monotonously fatal. As with many things in medicine there is no free lunch.
Described in a recent issue of JAMA Oncology is a study by a group of investigators from several Harvard teaching hospitals. Click here for the abstract; Dr. Stark can provide the entire article ir you request it by filling out the form to the right of this page. The authors reviewed the incidence of serious auto-immune reactions to checkpoint inhibitors in the endocrine system — that is, the thyroid, adrenals, pancreas, etc. They focused mostly on the thyroid gland. Here is what they found: both underactive and overactive thyroid conditions were found (hypothyroidism and hyperthyroidism). The incidence depended on which drug was used. In those cases in which a combination of checkpoint inhibitors was used the incidence was about 10%. These changes tend to be permanent even if the drug is stopped.
Dr. Stark weighs in: My endocrinology friends say the oncologic community has created a whole new disease with which they have had to become familiar. Ironically since these drugs can produce very long remissions the endocrine dysfunctio could last for years. It is up to the oncologist to look for subtle signes of endocrine dysfunction and have a plan of how to deal with it.