The prognosis post relapse following primary radiotherapy was found to be excellent for patients with localized follicular lymphoma (FL), according to a retrospective analysis.
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But patients who experienced early relapse – at 1 year or less after diagnosis – had significantly worse survival.
While primary radiotherapy may be curative for localized FL, about 30%-50% of patients will relapse and optimal salvage therapy is not well defined, Michael S. Binkley, MD, of Stanford (Calif.) University, and his colleagues wrote in the International Journal of Radiation Oncology, Biology, Physics.
The researchers retrospectively studied 512 patients with localized FL using data from multiple centers under the direction of the International Lymphoma Radiation Oncology Group (ILROG). Clinical information was collected, including method of detection, age at relapse, location of recurrence, and response to salvage therapy.
The team defined disease recurrence as lymphoma nonresponsive to primary radiotherapy inside of the prescribed dose volume, which included having no radiographic or clinical response within 6 months of initial radiotherapy treatment.
With a median follow-up of 52 months, Dr. Binkley and his colleagues found that 29.1% of patients developed relapsed lymphoma at a median 23 months (range, 1-143 months) following primary radiotherapy.
The team reported that the 3-year overall survival rate was 91.4% for patients with lymphoma recurrence after primary radiotherapy. In total, 16 deaths occurred during follow-up: eight were lymphoma specific deaths, three were from other causes, and in five patients the cause was unknown.
Of the 149 cases of relapsed lymphoma, 93 were indolent. There were also three cases of FL grade 3B/not otherwise specified and 18 cases of diffuse large B-cell lymphoma. In 35 patients who relapsed, biopsies were not performed.
“The excellent prognosis observed for this relapse cohort emphasizes that primary radiation for localized follicular lymphoma is an excellent treatment option,” the researchers wrote.
When the researchers examined survival based on the time of relapse, they found that overall survival was “significantly worse” for patients who had relapsed 12 months or less after the date of diagnosis, at 88.7%, compared with all others at 95.8% (P = .01).
They found no difference in overall survival between patients who received immediate salvage treatment, compared with observation after relapse (P = .28). There was also no significant difference in survival between patients who relapsed in 1 year or less but underwent immediate treatment, compared to early relapsed patients who were observed (log-rank P = .34).
“[A]ny decision to offer treatment at time of relapse must be weighed with the risk of acute and late adverse effects. Greater than 60% of patients in our cohort with indolent recurrence who underwent salvage treatment received rituximab, likely contributing to the excellent outcomes,” the researchers wrote. “However, nearly 60% of patients with indolent recurrence who were observed did not have disease progression nor [did they] receive treatment within 3 years.”
The researchers reported having no conflicts of interest.
SOURCE: Binkley MS et al. Int J Radiat Oncol Biol Phys. 2019 Mar 8. doi: 10.1016/j.ijrobp.2019.03.004.