When I was going through my early stage cancer stuff, I did join a group. It monitored by the local hospital social worker. The group was located at the cancer center at the hospital. Very helpful group therapy sessions. We were all type of breast cancer survivors. Some had mastectomies, some had reconstructive surgery, some chose to be flat, and some like myself had lumpectomies and going through, or waiting to go through treatment. It helped me go through my early fears. During the pandemic, the meetings went to Zoom and I lost interest.
IF the conversation turned to someone selling/discussing MLM schemes or products, they would be told not to discuss and perhaps suggested nicely to leave. We agreed to confidentiality before joining. We were NOT a special interest group.