Tumor Surveillance

Although the use of positron emission tomography (PET) to assess rapidity of response to therapy appears to have prognostic value in Hodgkin lymphoma and some types of NHL observed in adult patients, it remains under investigation in pediatric NHL. To date, there are insufficient data for pediatric NHL to support a finding that early response to therapy assessed by PET has prognostic value.

Diagnosing relapsed disease solely based on imaging requires caution because false-positive results are common.[25-28] Data also demonstrate that PET scanning can produce false-negative results.[29] A study of young adults with primary mediastinal B-cell lymphoma demonstrated that 9 of 12 patients who had residual mediastinal masses at the end of therapy had positive PET scans. Seven of these nine patients had the masses resected, but no viable tumor was found.[30] Before changes in therapy are undertaken based on residual masses noted by imaging, even if the PET scan is positive, a biopsy to prove residual disease is warranted.[28]