Standard DNA-based Next-Generation Sequencing (NGS) can miss critical gene fusions, like ROS1. RNA sequencing is much more effective at identifying these specific alterations, so clinicians should ensure their chosen assay includes RNA analysis to avoid missing opportunities for targeted therapy.
Despite immunotherapy's success in other lung cancers, it is completely ineffective for patients with ROS1 fusions. A large global data series showed a 0% response rate. These genetically-driven cancers are "cold tumors," making upfront genomic testing critical to avoid futile and toxic treatment with checkpoint inhibitors.
While newer ROS1 inhibitors have overlapping efficacy, their side effect profiles differ. Repotrectinib is more associated with neurological issues, while taletrectinib can cause more gastrointestinal distress. This allows clinicians to sequentially switch patients between these agents to find a tolerable long-term option.
Newer ROS1 inhibitors can cause hyperphagia (extreme hunger) and substantial weight gain. This is a "bystander effect" from unintended inhibition of the TRK protein, which helps regulate appetite centers in the brain. This can be a distressing and hard-to-manage side effect for patients on long-term therapy.
While newer targeted therapies often improve both efficacy and safety, this isn't universal. The third-generation ALK inhibitor lorlatinib offers exceptional disease control but introduces unique, significant neurotoxicities like mood and personality changes, which were not prominent with earlier, less effective agents.
Cancers evolve under therapeutic pressure, often developing new resistance mutations. Re-testing the tumor via tissue or liquid biopsy upon progression is essential, as it can identify acquired mutations that make the cancer susceptible to a different, next-generation targeted therapy, extending patient survival.
Next-gen ROS1 inhibitors like repotrectinib also inhibit the TRK protein, leading to a highly unusual side effect: severe, full-body withdrawal pain if the drug is held for surgery or radiation. The pain, which resolves within hours of restarting the pill, highlights a unique withdrawal phenomenon clinicians must anticipate.
Patients on targeted therapy often become anxious about dose reductions, fearing the treatment will lose its effectiveness. Clinicians should explain that these drugs are developed with a therapeutic buffer, ensuring that even at a reduced dose, the drug is still effectively hitting its target while improving tolerability.