Reduced survival rates in colorectal cancer patients with obesity potentially connected to administration of lower chemotherapy doses

In a groundbreaking study, researchers led by Corinna Slawinski have found that the cumulative relative dose of adjuvant chemotherapy is a significant factor in the survival of patients with colorectal cancer. The study, titled "Average cumulative relative dose of adjuvant chemotherapy is more important than average relative dose intensity for colorectal cancer survival, with implications for treating obese patients: the OCTOPUS consortium," was presented at the European Society for Medical Oncology (ESMO) Virtual Congress 2021.

The study analysed data for 7269 patients who received adjuvant chemotherapy after curative surgery for colon and/or rectal cancer. The researchers found that doses for obese patients were often lower than for non-obese patients, relative to their body surface area. This was due to concerns about increased side-effects and doses being capped or based on an idealized weight.

The study demonstrated an association between increasing body mass index (BMI) and modest reductions in the cumulative relative dose of adjuvant chemotherapy. Each BMI increase of 5kg/m2 was associated with a 2% reduction in the relative dose of chemotherapy in the first cycle and 1% reductions in both ACRD and ARDI.

Interestingly, the study found that ACRD 5% increments were associated with significant improvements in disease-free survival, overall survival, and cancer-specific survival. Conversely, no significant relationship was demonstrated for ARDI in relation to survival.

Within-study effect modification was demonstrated for ARDI in female patients compared to males. No significant sex-interactions were found for both ACRD and ARDI.

Elizabeth Smyth, a member of the ESMO Faculty for Gastrointestinal tumours, commented that dose reductions for high BMI may be associated with lower cure rates in resected colon cancer treated with adjuvant chemotherapy. The study supports the recently published ASCO guidance that full, weight-based chemotherapy doses should be used to treat obese adult patients.

The OCTOPUS study included individual participant-level data from MOSAIC, SCOT, PROCTORSCRIPT, and CHRONICLE (CRC-ACT) randomized-trials. The study was funded by the OCTOPUS consortium and was supported by Cancer Research UK via the funding to Cancer Research UK Manchester Centre. All authors have declared no conflicts of interest.

The abstract O-4 titled 'Average cumulative relative dose (ACRD) of adjuvant chemotherapy is more important than average relative dose intensity (ARDI) for colorectal cancer survival' will be presented by Corinna Slawinski during Session VII on July 2, 2021. The findings of this study could have significant implications for the treatment of colorectal cancer, particularly in relation to dosing for obese patients.

Reduced survival rates in colorectal cancer patients with obesity potentially connected to administration of lower chemotherapy doses