Baseline tumor size and OS in melanoma patients treated with Keytruda

Not exactly news here, as we have long known that immunotherapy tends to be most effective in those with lower tumor burden...but still...

Baseline Tumor Size Is an Independent Prognostic Factor for Overall Survival in Patients With Melanoma Treated With Pembrolizumab. Joseph, Elassaiss-Schaap, Kefford, et al.  Clin Cancer Res. 2018 Apr 23.

To assess the association of baseline tumor size (BTS) with other baseline clinical factors and outcomes in pembrolizumab-treated patients with advanced melanoma in KEYNOTE-001 (NCT01295827).

BTS was quantified by adding the sum of the longest dimensions of all measurable baseline target lesions. BTS as a dichotomous and continuous variable was evaluated with other baseline factors using logistic regression for objective response rate (ORR) and Cox regression for overall survival (OS). Nominal P values with no multiplicity adjustment describe the strength of observed associations.

Per central review by RECIST v1.1, 583 of 655 patients had baseline measurable disease and were included in this post hoc analysis. Median BTS was 10.2 cm (range, 1-89.5). Larger median BTS was associated with Eastern Cooperative Oncology Group performance status 1, elevated lactate dehydrogenase (LDH), stage M1c disease, and liver metastases (with or without any other sites). In univariate analyses, BTS below the median was associated with higher ORR (44% vs 23%) and improved OS. In multivariate analyses, BTS below the median remained an independent prognostic marker of OS but not ORR. In 459 patients with available tumor programmed death ligand 1 (PD-L1) expression, BTS below the median and PD-L1-positive tumors were independently associated with higher ORR and longer OS.

BTS is associated with many other baseline clinical factors but is also independently prognostic of survival in pembrolizumab-treated patients with advanced melanoma.

Out of 655 patients these peeps treated with pembrolizumab (Keytruda), 583 of them had baseline measurable disease for which the BTS [baseline tumor size] was determined, a figure the researchers quantified by "adding the sum of the longest dimensions of all measurable baseline target lesions".  In those patients, when they looked at lower than average BTS alone, it was associated with higher overall response rates (44% vs 23%) and improved overall survival.  However, when other factor were included in the analysis, smaller BTS was still associated with improved overall survival, but not with overall response rate.

What tangled webs melanoma weaves.  Keep looking, researchers ~ keep looking.  We need to learn ALL the factors that facilitate a response...AND...how to attain an effective response for the melanoma peeps who don't happen to have them!!! - c