Trial Information

Improving Pelvic Cancer Patient Chemoradiotherapy Outcomes With FLT PET Imaging

Overall survival of pelvic cancer patients depends on control of systemic disease. If local
radiation therapy depletes bone marrow function to such an extent that systemic therapies
must be withheld, chances of metastatic failure increase significantly. This may be more
significant for this group of patients because approximately one third of adult bone marrow
is located in the pelvic region. Strategies to minimize toxicities would benefit a range of
pelvic cancer patients including gynecologic, anal, rectal, and prostate. New chemoradiation
combinations improve outcomes for these disease sites, but come at the cost of higher levels
of toxicity. As many as 40% of cervical cancer patients miss at least one chemotherapy cycle
due to hematologic toxicity and 36% of anal cancer patients experience grade 3 or 4
hematologic toxicity when undergoing chemoradiation therapy. A clinical trial of concurrent
chemoradiation therapy for rectal cancer was terminated due to toxicity, including
hematologic toxicities. Concurrent chemoradiation therapy shows promise for advanced stage
prostate cancers, but it also increases grade 3 and 4 toxicities. To successfully limit
hematologic toxicities for pelvic cancers, it is extremely advantageous to avoid irradiating
the highly proliferative compartments of the pelvic bone marrow. However, the complex
structure of the pelvis makes it difficult to assess the efficacy of radiation therapy (RT)
planning strategies to avoid areas critical to hematopoiesis. Uptake of [18F]fluorothymidine
imaged with positron emission tomography (FLT PET/CT) can be an accurate and sensitive tool
for identifying and monitoring the effects of chemoradiation on proliferative pelvic bone
marrow. Clinically validating the utility of FLT PET/CT imaging for identifying active bone
marrow in the design of bone marrow sparing RT-plans and the important bone marrow
assessment time points would provide a method to reduce acute and chronic hematologic
toxicities for pelvic cancer patients.