DOSAGE Study: Upfront Dose-Reduced Chemotherapy in Older Patients with Metastatic Colorectal Cancer

Treating older adults with chemotherapy remains a challenge, as they are strongly underrepresented in clinical trials and no robust guidelines for treating older patients exist. Moreover, older adults are at increased risk of chemotherapy-related toxicity, resulting in decreased quality of life (QoL), increased hospital admissions and high health care costs. Therefore, the aim of the DOSAGE study is to demonstrate that upfront dose-reduced chemotherapy in patients with metastasized colorectal cancer is non-inferior to full-dose treatment with regard to progression-free survival (PFS). Treatment plans (monotherapy or doublet chemotherapy) will be based on expected risk of treatment toxicity for the individual patient (according to the Geriatric 8 (G8) questionnaire). The investigators expect that this treatment strategy will lead to less grade ≥3 toxicity, less early treatment continuation and hospitalizations and a better QoL and physical functioning.

The DOSAGE study is a phase III, open-label, non-inferiority, randomized controlled clinical trial in patients aged ≥70 years with metastasized colorectal cancer eligible for palliative chemotherapy. All participating patients will undergo geriatric screening by the G8 questionnaire and will be classified as "low risk of toxicity" (G8-score of 15 or higher) or "high risk of toxicity" (G8-score of 14 or lower or judged as "high toxicity risk" by their treating oncologist). Patients classified as low risk will be randomized between a fluoropyrimidine and oxaliplatin in either full-dose, or with an upfront dose-reduction of 25%. Patients classified as high risk will be randomized between fluoropyrimidine monotherapy in either full-dose or upfront dose-reduction. Addition of targeted treatment (bevacizumab or epidermal growth factor receptor (EGFR) inhibition) is allowed. Patients with a moderate renal impairment (GFR 30- 50 mL/min) will be treated with 25% reduced starting dose of capecitabine when randomized for full dose treatment and treated with 40% reduced starting dose when randomized for upfront dose reduction.

Primary outcome is PFS. Secondary endpoints include grade ≥3 toxicity, QoL, physical functioning, overall survival, number of treatment cycles, dose reductions, hospital admissions, cumulative received dosage and cost-effectiveness. Given a non-inferiority margin of 8 weeks, 587 patients will be included (293/292 patients per arm).

Inclusion criteria

• Patients aged 70 years or older with colorectal cancer and distant metastases without localized treatment options.
• Patients who are candidates for first-line palliative chemotherapy as judged by their treating oncologist
• Being able to understand the Dutch language
• Adequate bone marrow and organ function: Absolute neutrophil count (ANC) > 1.5 x 10^9 mmol/L, Hemoglobin (Hb) > 6.0 mmol/L, Platelets >100 x 109 / L, Serum bilirubin ≤ 2 x upper limit of normal (ULN), serum transaminases ≤ 3 x ULN without presence of liver metastases or ≤ 5x ULN with presence of liver metastases.

Exclusion criteria

• Patients who received prior palliative chemotherapy
• Patients in whom local treatment of metastases is scheduled (i.e. liver surgery or stereotactic radiotherapy)
• Candidates for triple chemotherapy
• Patients who received prior adjuvant chemotherapy in the one year before inclusion in the study (chemotherapy before that time is allowed)
• Patients with complete or incomplete dihydropyrimidine dehydrogenase (DPD) deficiency
• Patients with Microsatellite instable (MSI)-high colorectal cancer
• Patients with HIV or active hepatitis
• Patients with severe kidney failure (defined as GFR ≤30ml/min)
• Patients with severe cognitive deficits making informed consent not possible