Primary treatment modification strategies among older adults with advanced cancer.

1512 Background: Primary treatment modification (PTM; any change in dose or agents of the planned chemotherapy regimen from the standard guidelines) is a common therapeutic approach among older adults with advanced cancer due to their geriatric vulnerabilities. However, strategies to employ these modifications are understudied. This study compares a PTM strategy based on Geriatric Assessment (PTM-GA) intervention vs. usual care strategy based on oncologist’s impression (PTM-UC) on treatment tolerability in older adults with advanced cancer starting new chemotherapy regimens. Methods: In this subgroup analysis of the GAP 70+ study (NCT02054741; PI: Mohile), we included patients aged ≥ 70 with incurable solid tumors who initiated a chemotherapy course with PTM (n=298). For the first (PTM-GA) group, PTM was guided by GA results and recommendations while for the second (PTM-UC) group, PTM was guided by the treating oncologist's estimate only. Tolerability outcomes were assessed within 3 months of treatment and included: 1) any grade 3-5 clinician-rated toxicity according to National Cancer Institute Common Toxicity Criteria; 2) subsequent dose reduction; 3) Activity of Daily Living (ADL) decline; 4) unplanned hospitalization. We used multivariable, cluster-weighted generalized estimating equations models to examine the association of PTM-GA vs. PTM-UC and outcomes adjusting for confounders. Results: Mean age was 77 years. The most common cancer types were gastrointestinal (37%) followed by lung cancer (26%). PTM-GA versus PTM-UC was associated with reduced risk of grade 3-5 toxicity (relative risk (RR)= 0.77, 95% CI, 0.61- 0.90) and subsequent dose reduction (RR, 0.46; 95% CI, 0.29-0.73). Point estimates suggest that patients with PTM-GA may have a lower risk of unplanned hospitalization but results did not reach statistical significance (RR, 0.69; 95% CI, 0.46–1.02). PTM-GA vs. PTM-UC was not associated with ADL decline (RR, 1.05; 95% CI, 0.74–1.49). Conclusions: Older patients with advanced cancer who had PTM guided by GA recommendations had improved treatment tolerability compared to those who PTM based on oncologist’s estimate only. Integrating GA into treatment dosing decisions may lead to improved outcomes in this vulnerable population.