Characterization of on-target adverse events caused by TRK inhibitor therapy

BACKGROUND

The tropomyosin receptor kinase (TRK) pathway controls appetite, balance, and pain sensitivity. While these functions are reflected in the on-target adverse events (AEs) observed with TRK inhibition, these AEs remain under-recognized, and pain upon drug withdrawal has not previously been reported. As TRK inhibitors are approved by multiple regulatory agencies for TRK or ROS1 fusion-positive cancers, characterizing these AEs and corresponding management strategies is crucial.

PATIENTS AND METHODS

Patients with advanced or unresectable solid tumors treated with a TRK inhibitor were retrospectively identified in a search of clinical databases. Among these patients, the frequency, severity, duration, and management outcomes of AEs including weight gain, dizziness or ataxia, and withdrawal pain were characterized.

RESULTS

Ninety-six patients with 15 unique cancer histologies treated with a TRK inhibitor were identified. Weight gain was observed in 53% [95% confidence interval (CI), 43%-62%] of patients and increased with time on TRK inhibition. Pharmacologic intervention, most commonly with glucagon-like peptide 1 analogs or metformin, appeared to result in stabilization or loss of weight. Dizziness, with or without ataxia, was observed in 41% (95% CI, 31%-51%) of patients with a median time to onset of 2 weeks (range, 3 days to 16 months). TRK inhibitor dose reduction was the most effective intervention for dizziness. Pain upon temporary or permanent TRK inhibitor discontinuation was observed in 35% (95% CI, 24%-46%) of patients; this was more common with longer TRK inhibitor use. TRK inhibitor reinitiation was the most effective intervention for withdrawal pain.

CONCLUSIONS

TRK inhibition-related AEs including weight gain, dizziness, and withdrawal pain occur in a substantial proportion of patients receiving TRK inhibitors. This safety profile is unique relative to other anticancer therapies and warrants careful monitoring. These on-target toxicities are manageable with pharmacologic intervention and dose modification.

Flu vaccination rate of patients with severe immune-related adverse events

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Background: Infection with influenza in adults with cancer carries an increased risk of morbidity and mortality. Vaccination against seasonal influenza (Flu-V) can decrease the incidence of influenza, shorten its course, and reduce influenza-associated morbidity. Recent data has suggested that the administration of the Flu-V to patients on an ICI leads to an exaggerated inflammatory response and an increased risk of irAE. However, this trend was demonstrated in a small cohort of patients with lung cancer. Current recommendation for annual Flu-V in patients treated with ICI is unclear and literature about safety is limited. We compared rates of Flu-V for patients on ICI admitted with severe toxicity vs those patients on ICI who were admitted for reasons other than toxicity. We also evaluated rate of Flu-V among oncology patients who had received non-immunotherapy modalities. Methods: We retrospectively evaluated patients treated with ICI who were admitted to Massachusetts General Hospital from February 5, 2011- June 12, 2017. Patients received ipilimumab, pembrolizumab, nivolumab, atezolizumab, durvalumab, avelumab, or a combination in treatment of an advanced solid tumor malignancies including melanoma, NSCLC, SCCHN. Admissions due to irAE were confirmed by review of clinical, radiologic, and pathologic features. Flu-V status was determined by rigorous chart review. Nearest neighbor matching was used to create a control group of cancer patients treated with non-ICI modalities. Descriptive statistics compared rates and timing of Flu-V relative to admission. Statistical significance was determined using Fischer’s Exact Test, p < 0.05. Results: Of 540 patients on ICI, 28% were admitted for irAE, 72% had a non-irAE reason for admission. The rate of Flu-V in the flu season prior to admission for irAE group was lower than for non-irAE (18.5% vs 29.6%; p value = 0.01). There were no differences in vaccination rates within ≤30 days (2.7% vs 3.6%, p = 0.80), ≤90 days (4.0% vs 9.3%, p = 0.05), or ≤180 days of admission (11.9% vs 18.5%, p = 0.07). Flu-V rate overall in patients on ICI was 26.5%. In comparison, Flu-V rate in the nearest neighbor non-immunotherapy oncology patients was 67% (n = 101). Conclusions: Flu-V rates were much lower in patients treated with ICI compared to patients treated with non-ICI modalities. We did not see a higher rate of Flu-V in patients admitted with irAE compared to non-irAE which suggests that Flu-V and severe irAE may not be linked in clinical practice. Additional studies are needed, but Flu-V in patients on ICI holds potential to improve care.