PCNSL outcomes diverge between a majority of patients who achieve long term remission and a minority who have an aggressive disease course and die in the first year. Sarcopenia, loss of muscle mass and function over time, has been recognized as a powerful predictor of mortality in brain and systemic cancers. TMT is a validated radiographic measure of sarcopenia. We hypothesized that patients with TMT less than one standard deviation below the mean (“very thin TMT”) have a higher chance of relapse and early mortality.

Utilize temporalis muscle thickness (TMT) as a measure of sarcopenia on pretreatment MRI to predict survival and risk of relapse in patients with primary CNS lymphoma (PCNSL).

On univariate analysis, TMT predicted early progression (HR 4.25, 95% CI 1.95 – 9.29, p<0.001) and early mortality (HR 4.38, 95% CI 2.25 – 8.53, p<0.001). These effects were maintained in subgroups of patients both <65 and ≥ 65 years of age. Very thin TMT predicted mortality more robustly than IELSG or MSKCC scores. Patients with very thin TMT received fewer cycles of high-dose methotrexate (HD-MTX) and were less likely to receive consolidation. On multivariate analysis which included age, sex, TMT, ECOG, BMI, lifetime doses of HD-MTX, and consolidation, very thin TMT was independently associated with both early progression (HR = 7.87, 95% CI = 3.55 – 17.45, p<0.001) and short survival (HR 4.49, 95% CI = 1.94 – 10.40, p<0.001).

We conclude that PCNSL patients with very thin TMT are at high risk for relapse and short survival. Further, TMT provides additional data in stratifying patients at the time of diagnosis for individualized treatment regimens.