KEY POINTS
- This retrospective single-institution study evaluated pretreatment biopsies from 110 patients with non-metastatic prostate adenocarcinoma treated with radical accelerated hypofractionated radiotherapy. Biochemical relapse occurred in 33 patients.
- Radiotherapy was delivered in 14 consecutive fractions over 18 days, using 3.8 Gy per fraction to the prostate, 3.5 Gy to the seminal vesicles, and 2.75 Gy to pelvic lymph nodes when indicated. Sixty-six patients also received pelvic irradiation and 18 months of androgen deprivation therapy.
- High lactate dehydrogenase-5 expression was present in 56 of 110 tumors (51%) and was associated with advanced tumor stage, higher Gleason score, and lower tumor-infiltrating lymphocyte density.
- Low maximum tumor-infiltrating lymphocyte density was independently associated with poorer biochemical relapse-free survival when analyzed as a dichotomous variable: hazard ratio 2.60 (95% confidence interval 1.30–5.17; P = .006).
- The combined high lactate dehydrogenase-5 and low lymphocyte phenotype independently identified higher relapse risk: hazard ratio 2.83 using mean lymphocyte density and 2.66 using maximum density. The association was not consistently retained when lymphocyte density was modeled continuously.
CLINICAL TAKEAWAY
Combined assessment of tumor glycolytic activity and lymphocytic infiltration may identify a subgroup of patients at increased risk of biochemical relapse after prostate radiotherapy. However, the small retrospective cohort, tissue-selection bias, cutoff-dependent results, and absence of external validation mean this biomarker should not yet guide treatment intensification.