I have a 66y/o Female with Metastatic Recurrent ER 50%, PR 25% Ki-67 40%, Her 2 neg (2+/FISH neg) patient with Brachial plexus involvement resulting in Loss of function of Right arm and significant bone metastasis. She has been started on letrozole, and is starting XRT with radiation oncology. The XRT is planned for next 6 weeks. Biopsy of distant metastasis to confirm receptors is pending. My question is - Is it safe to start Ribociclib while patient is on XRT or should we wait for XRT to complete and then start CDK 4/6 - And is there anything else you recommend in this case. She is not in visceral crisis, but the local right chest wall causing significant involvement of brachial plexus and almost complete loss of function in Right upper arm needs chemotherapy to control disease. - will be starting Bisphosphonates as well.
I totally agree with you in her case. I would have her continue letrozole for now and start ribociclib after XRT is over. There is a concern that concurrent CDK4/6i can increase radiation-inducted toxicities, so I will often wait to initiate until XRT is over (can be started immediately after). There are some active trials right now to assess this further, but right now I will still wait for XRT to complete.Agree with CDK4/6i-based therapy, rather than chemotherapy, as survival appears better, even for those patients with significant disease burden (Right Choice trial). Also agree with bisphosphonates, definitely.
