Radiation therapy alone can lead to long-term remission in patients with limited-stage follicular lymphoma, according to a Canadian study.

The study, which was published in Blood, reported outcomes from a cohort of 237 patients treated with curative-intent radiation therapy and followed for a median of 16 years.

Early patients in the cohort were treated with involved regional radiotherapy (IRRT) while later enrolments received involved site radiotherapy (ISRT) which covered only the involved nodes.

The study found freedom from progression (FFP) of 66±3% at five years, 49±3% at 10 years and 43±4% at 15 years.

“Corresponding estimates for PFS were 61±3%, 40± 3%, 28±3%, respectively,” the study said.

Long-term disease-specific survival (DSS) was 83±3% at 10 years and 78±3% at 15 years.

The cumulative incidence of transformation to aggressive lymphoma was 9±2% at 5 years, 17±3% at 10 years and 20±3% at 15 years.

Authors of the study said their findings confirm the long-term efficacy of reducing fields from IRRT to ISRT.

Radiotherapy field size was not significantly associated with FFP, PFS, DSS or OS.

Instead, other factors including male gender (HR 1.48), older age (1.39), stage II (HR 1.51), larger mass size (HR 4.01) and elevated LDH (HR 1.99) were associated with inferior FFP, and other outcomes.

“Given the excellent outcomes in this population-based analysis, and the known low risk of serious RT-induced toxicity, ISRT-alone remains a proven, effective and safe treatment for limited-stage FL,” they concluded.

Commenting on the study, Professor Chan Cheah from Blood Cancer Research WA, told the limbic that involved field radiation therapy (IFRT) was widely used and a reasonable standard of care for limited stage follicular lymphoma in Australia.

“However, in the Trans-Tasman Oncology Group 99.03 trial, MacManus et al showed a PFS advantage for combined modality therapy (6 cycles of R-CVP following IFRT) over IFRT alone, with estimated 10-year PFS in the IFRT + R-CVP cohort around 80%. This trial has influenced many Australian clinicians to adopt this approach.”

“The area is controversial but the data favour prolongation of PFS when R-chemo is added to IFRT. Particularly for younger patients I think that this benefit is meaningful and I recommend R-CVP after IFRT for patients with stage I/II follicular lymphoma who are <60 years of age in particular.”