We read the recently published editorial entitled “‘The same old story’: thoughts on
authorised doses of anticancer drugs” in this journal with great interest.[1] In particular, we were interested in its observations regarding the use of a flat dose
for nivolumab and pembrolizumab. Significant concerns have been raised regarding the cost
effectiveness of flat dosing of these agents.[1] Multiple analyses have demonstrated the use of a flat dose rather than a weight-based
dose for these agents leads to higher doses administered to patients, which in turn leads to
higher costs.[2-5] It is with this background that we present the results of an investigation
of the cost effectiveness of flat-dosing in nivolumab and pembrolizumab at a large Irish
oncology centre: Cork University Hospital.We used pharmacy records to identify all patients who had received flat-dosed pembrolizumab
and nivolumab at Cork University Hospital in the period starting 1 January 2018 and ending 20
November 2019. Pharmacy records and online patient records were used to retrieve weights for
all patients. We used retrieved weights to calculate a hypothetical weight-based dose for each
patient by using 2mg/kg dose for pembrolizumab and 3 mg/kg dose for nivolumab. We also used
cost per vial of each agent in 2018 and 2019 to extrapolate a hypothetical cost for each dose
of the agents for patients. The cost per vial of agent was obtained from the local hospital
pharmacy.A total of 28 patients were found to have undergone flat dosed pembrolizumab in 2018 and
2019. The mean and median weights for our cohort were 72.3 kg and 71.2 kg, respectively. While
the flat dose of pembrolizumab was 200 mg every 3 weeks, the calculated median weight-based
dose was 142.5 mg. Only two patients had a dose higher than the 200 mg flat dose. While the
cost per flat dose of pembrolizumab was Euro (€) 8086, the median hypothetical weight-based
cost per dose was € 5758.5. We calculated that if weight-based dosing were used, it would
translate into a total cost saving of € 635,417.5 for the entire cohort receiving
pembrolizumab during the period.Similarly for nivolumab, we found a total of 26 patients who had received nivolumab during
the period at our centre. The mean and median weights for our cohort were 70.7 kg and 69.4 kg,
respectively. While the flat dose of nivolumab was 240mg every 2 weeks, our median
weight-based dose of nivolumab was 208 mg. There were seven patients with weight-based doses
higher than the flat dose of 240 mg. We also calculated that while the cost per flat dose was
€ 3872, the median hypothetical weight-based cost per dose was € 3355. The total potential
cost saving for the entire cohort receiving nivolumab from the use of weight-based dosing
during the period was calculated as € 104,461.These results support the observations by Meriggi and Zaniboni regarding the use of flat
doses in the case of nivolumab and pembrolizumab. We have shown that the concerns raised
elsewhere regarding the use of flat dosing of agents, and the potential for increased doses
and costs, are equally valid with regard to oncology services in Ireland. Potentially shifting
to a weight-based dosing policy for targeted agents, could thus represent significant cost
savings.