Effectiveness of adjuvant imatinib in patients with gastrointestinal stromal tumor: results of a population-based, matched-cohort study

Impact of pharmacy channel on adherence to oral oncolytics

BACKGROUND

Oral chemotherapy is increasingly prescribed to treat cancer. Despite its benefits, concerns have been raised regarding adherence to therapy. The study objective was to compare and measure adherence, persistence, and abandonment in patients filling prescriptions in traditional retail (TR) versus specialty pharmacy (SP) channels.

METHODS

Using a retrospective cohort design, we selected newly treated patients aged ≥18 years with a prescription for erlotinib, capecitabine, or imatinib during 2007-2011 from a Medco population of both United States commercial and Medicare health plans. Patients were classified according to pharmacy channel providing the medication. Abandonment was defined as a reversal following initial approval of the index prescription claim with no additional paid claims for agent within 90 days of reversal. Patients were considered adherent if the proportion of days covered between the date of the first and last oral prescription was ≥80%.

RESULTS

In our retrospective cohort, 11,972 filled their prescriptions within the SP channel, and 30,394 filled their prescriptions within the TR channels, respectively. The SP channel had the highest proportion of adherent patients compared with TR (71.6% vs. 56.4%, P < .001). Abandonment of the initial prescription was low with overall rates of only 1.7%. In multivariate models controlling for demographic characteristics, index oncolytic, days of supply, and copay, SP channel (relative to TR) was significantly associated with lower rates of abandonment and increased adherence.

CONCLUSIONS

Pharmacy channel may be influential on abandonment and adherence. Lower rates of abandonment and higher rates of adherence were observed among SP patients versus TR.

The economic burden of gastrointestinal stromal tumor (GIST) recurrence in patients who have received adjuvant imatinib therapy

OBJECTIVE

To estimate the economic burden of gastrointestinal stromal tumor (GIST) recurrence in patients who received imatinib adjuvant therapy.

METHODS

Data from the MarketScan and PharmMetrics databases between January 2000 and March 2013 were extracted. Patients who had received at least one diagnosis of GIST, had undergone a primary surgery for GIST, and had received at least one prescription for imatinib were included in the analysis. An algorithm was applied to identify those who had a subsequent GIST recurrence. Patients who experienced a recurrence and those who did not have a recurrence were compared for differences in healthcare utilization measures and healthcare costs within 6 months after the recurrence, while adjusting for potential confounding factors.

RESULTS

A total of 540 patients with primary resectable GIST who received imatinib adjuvant therapy were identified, including 444 (82.2%) patients who did not experience GIST recurrence and 96 (17.8%) patients who did experience recurrence. Patients who experienced GIST recurrence utilized significantly more healthcare resources in all categories than patients who did not have a recurrence, including the number of hospitalizations, days of hospitalization, emergency room visits, outpatient visits, and other medical services (all p-values <0.01). The total healthcare cost was significantly higher for patients with GIST recurrence, with a difference of $4464 per patient per month (p < 0.01). Both the medical and pharmacy costs were significantly higher with adjusted differences of $3488 and $1423 per patient per month, respectively (both p-values <0.01).

CONCLUSIONS

Patients who had GIST recurrence after surgical resection incurred significantly more healthcare resource utilization and greater healthcare costs within 6 months after the recurrence than patients who did not have recurrence. These findings suggest that GIST recurrence is associated with a substantial economic burden.