Applications in Oncology: Tumor-therapy Monitoring

PET is useful in a variety of therapy-monitoring applications, including distinguishing between radiation necrosis and recurrence; determining the resectability of a recurrence; and evaluating response to chemotherapy or radiation therapy.

This is because effective therapy leads to rapid reductions in the glucose uptake levels of tumors. PET tracers can easily reveal this drop in metabolic activity and show - sometimes within minutes or hours - whether a patient is responding positively to a particular course of treatment. With this information, physicians can quickly modify less effective therapy, thereby improving patient outcomes and reducing the cost of ineffective treatment.

Furthermore, PET has demonstrated efficacy for monitoring therapeutic response in a wide range of cancers, including breast, lung, ovarian, head, neck, and thyroid cancers, as well as melanoma and lymphoma.

Clinical Example:

A 61-year-old male presented with a centroblastic high grade non-Hodgkin's lymphoma. Multiple rounds of chemotherapy were administered with intermittent anti-growth factors. PET scans were performed prior to, immediately after, and 6 months following therapy.

Prior to Therapy (left): PET examination indicates platinal, lingual, and pharyngial hypermetabolic lesions with multiple node involvements.

Immediately After Therapy (middle): PET shows no remaining pathologies.

6 Month Follow Up (right): PET shows no evidence of recurrence.

Clinical Example:

12-year-old male. Previous radiation therapy for cerebal tumor 3 months prior to PET scan. Recent MRI demonstrated ring-like region of contrast enhancement.

PET scan performed to discriminate between possible recurrence of the tumor and radiation necrosis. Image shows a hypermetabolic ring surrounding the cortical area of no FDG uptake. This demonstrates a high-grade metabolically active recurrent tumor with a central area of necrosis. Image also shows an area of decreased FDG uptake in left parietal occipital area which is consistent with radiation therapy changes.