San Francisco, CA—For the second- line treatment of patients with metastatic colorectal cancer (CRC), the total costs were 14% lower with bevacizumab (Avastin) than with cetuximab (Erbitux), according to an analysis presented at the 2013 Gastrointestinal Cancers Symposium.
The study was presented by Elaine Yu, PharmD, of Genentech. The analysis was conducted using the UnitedHealthcare claims database and Medicare Advantage plan of patients who had 2 claims for CRC at least 30 days apart between 2007 and 2011, and evidence of 2 lines of therapy.
“This analysis gives a more accurate picture to the payers of what bevacizumab and cetuximab really cost in the real world,” Dr Yu said. She maintained that there is a frequent misperception that a course of bevacizumab costs $100,000, “and this is not so,” she said.
Administrative claims databases are useful for examining healthcare costs but are limited by algorithms that are used to identify lines of therapy. Corroboration of algorithms with medical evidence can improve the accuracy of claims analyses, Dr Yu pointed out.
“We wanted to see how well the algorithm was performing, so we did a smaller chart review to determine if patients judged to have treatment in the second line were truly second-line patients. The first time around, the match rate was not very high,” she noted. “The algorithm, therefore, was not picking up patients accurately. We found that there was room for improvement.”
After refining the algorithm, the match rate increased. The initial positive predictive value of the algorithm for second-line therapy was 68.5%, which increased to 85.3% with refinement. “Corroboration with medical chart data led to algorithm refinements that improved the predictive performance of the claims-based algorithm in identifying metastatic colorectal cancer patients with 2 lines of therapy and targeted agents in the second-line setting,” Dr Yu explained.
The final algorithm identified 2 mutually exclusive second-line cohorts receiving either bevacizumab (N = 450) or cetuximab (N = 119). The baseline characteristics were similar between the groups.
The investigators found that patients using bevacizumab in the second-line setting often had received this drug in the first-line setting. (Bevacizumab recently became approved by the US Food and Drug Administration for both indications.) In the second-line setting, bevacizumab was more often used with oxaliplatin (Eloxatin), whereas cetuximab was used with irinotecan (Camptosar), which is indicated for this use, Dr Yu said.
The adjusted total costs for treatment were significantly lower among the bevacizumab cohort (Table). The per-patient cost difference (adjusted, in the multivariate analysis) was $12,318 for the duration of second-line therapy and $2728 for a month of treatment compared with cetuximab, Dr Yu reported.
For the duration of second-line chemotherapy, the total costs per patient were $70,867 for cetuximab and $61,360 for bevacizumab. The costs for a month of treatment were $19,630 and $17,578, respectively. Medical costs were $69,480 and $58,313, respectively, for the duration of treatment and $19,167 and $16,791, respectively, for a month, Dr Yu reported.
The total medical cost for treatment was the sum of all health plan- and patient-paid amounts for all medical expenses (ie, inpatient, outpatient, office, and emergency department visits, and other services) and pharmacy claims.
“Cetuximab is a more expensive drug, and the associated medical costs are also higher,” she said. “The cost differences may be even higher for patients treated with bevacizumab in combination with oxaliplatin since the 2012 (poststudy) availability of generic oxaliplatin.”
The cost of the targeted agent for the course of treatment was $43,459 for cetuximab and $30,639 for bevacizumab, and the costs monthly were $12,012 and $8833, respectively.
The backbone chemotherapy, however, was more expensive for the patients receiving bevacizumab: $15,371 versus $9080 for cetuximab, which was an adjusted difference of $7738.
Although the adjusted targeted therapy cost was lower with bevacizumab, there was no difference in the cost of the regimen because of significantly higher adjusted chemotherapy agent costs with bevacizumab versus cetuximab, Dr Yu noted.
Dr Yu acknowledged that although costs were adjusted to account for potential demographic and clinical differences between cohorts, there may have been other unobserved differences (eg, patient performance status, disease severity, and other factors unavailable in claims data) between the cohorts.
