@angelicbreeze: Thank you for coming to Mayo Clinic Connect, an online support forum for patients, family and caregivers where we as mentors and other contributors, such as yourself, can exchange experiences, emotional support and general tips.

I'm sorry to hear about your husband's fairly recent diagnosis of stage 4 metastatic melanoma although it appears as if he was able to get started on immunotherapy rather quickly after the initial findings. I was also diagnosed with stage 4 MM and started on Keytruda (monotherapy) a month later, in November of 2025, that has been effective to date. These new treatments have been remarkably effective in treating even advanced and complex presentations, such as your husband's, and one reason a PET scan is performed to evaluate the effectiveness. Sometimes an initial PET scan can show growth even though the immunotherapy is working, an effect known as "pseudoprogression" - essentially, the tumor has become swollen in response, much as say a joint may swell after injury. Radiologists must review the imaging to determine this.

I'm not sure what you mean by "and the dr on this site either information" but Mayo Clinic Connect is a peer support network; we do not have medical professionals on staff to provide medical advice, recommendations or review records. Those findings would need to be discussed with the professional(s) overseeing care to your husband. Hopefully, this backgound information has provided some backgroud and guidance. This is an overall guideline for people dealing with this condition that I found helpful: https://www.mayoclinic.org/diseases-conditions/melanoma/diagnosis-treatment/drc-20374888

Has this helped to answer some of your concerns?