Changes in the level of circulating Tregs in the peripheral blood
might also be very important for patient prognosis and predicting
therapy response. Formerly, Wolf et al. showed increased levels of
circulating Tregs in the blood of patients with different malignancies
but did not correlate Treg numbers to either prognosis or therapy
response [51]. Increased blood Treg levels in glioblastoma
patients were reported after concomitant temozolomide and radiotherapy,
which might impact the outcome of immunotherapy
combined with RCT [104]. Lissoni et al. found that blood Treg
numbers in cervix and rectal cancer patients treated by pelvic irradiation
were not influenced by radiotherapy, while the number
of other lymphocytes decreased [142]. Circulating Treg levels were
measured by Schmidt et al. in breast and colorectal cancer patients
before and 1 week after RCT. They found that colorectal cancer
patients had higher levels of pre-treatment Tregs. In addition, patients
with favorable tumor stage had higher levels of Tregs after
5 days of RCT. The authors concluded that circulating Treg levels
in colorectal cancer patients receiving RCT might be useful for treatment
individualization and that a dramatic decrease of Treg after
in vivo irradiation might be an indicator for necessary dose adjustments
in the radiation therapy of these patients