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Metabolic tumour volume refined treatment selection in early NK/T-cell lymphom

An MTV threshold of 50 mL identified patients with poorer survival who appeared to benefit from combined-modality treatment.

RadOncToday · ·1 min read

KEY POINTS

  • The retrospective study included 122 previously untreated patients with stage I–II extranodal nasal-type NK/T-cell lymphoma and baseline FDG PET/CT. All received involved-site IMRT; 77 received combined-modality therapy and 45 radiotherapy alone.
  • Median follow-up was 66 months. Five-year overall and progression-free survival for the complete cohort were 79.4% and 68.8%, respectively.
  • Receiver-operating-characteristic analysis identified cutoffs of 50 mL for metabolic tumour volume and 8.3 for SUVmax. MTV provided stronger discrimination for mortality, with an area under the curve of 0.735 versus 0.580 for SUVmax.
  • MTV of at least 50 mL was the only independent predictor of overall survival, with a 3.79-fold higher mortality risk than lower MTV (95% CI 1.17–12.31; p = 0.027). SUVmax was not independently prognostic.
  • Five-year distant metastasis incidence was 35.1% with MTV ≥50 mL versus 7.7% below 50 mL (p < 0.001). Mediation analysis estimated that distant metastasis statistically accounted for 98.2% of the relationship between MTV and overall survival.
  • Among intermediate- and high-risk patients, five-year overall survival was 91.0% with MTV <50 mL versus 65.6% with MTV ≥50 mL; corresponding progression-free survival was 80.0% versus 60.4%, with both comparisons p = 0.002. Patients with lower MTV performed similarly to the conventionally defined low-risk group.
  • After entropy balancing, radiotherapy alone and combined treatment produced comparable outcomes for MTV below 50 mL. For MTV of at least 50 mL, outcomes significantly favored combined-modality therapy, with reported hazard ratios of 4.12 for progression and 6.30 for death, both p < 0.001.
  • Transcriptomic analysis of 16 tumours linked higher MTV with hypoxia-, angiogenesis-, and VEGF-related pathways, with correlations of approximately 0.54–0.56. This exploratory result provides a possible biological explanation for the elevated distant-failure risk.

CLINICAL TAKEAWAY

Baseline metabolic tumour volume may distinguish clinically high-risk patients who remain suitable for radiotherapy alone from those who need effective systemic therapy. However, the 50 mL threshold was derived and tested in the same single-centre dataset, treatment was not randomized, and the findings should not yet be used to omit chemotherapy.

SOURCE

International Journal of Radiation Oncology, Biology, Physics