Wednesday, 10 August 2016

Tpot (potential doubling time without cell loss)

It describes the proliferation rate of the tissues, which can be measured from biopsies by flow cytometry after administration in situ to the patient of a deoxyribonucleic acid thymidine tracer [2]. "This is difficult to determine in vivo." It is "the time which the cell population of tumor doubles if there is no cell loss" [3]. Tp (potential doubling time or cell doubling time after cell loss) is a little shorter than Tpot (measured before the tumour has received any cytotoxic treatment) [1].

Pretreatment Tpot measured in human tumor biopsies [2].
Tumor
Median (days)
Range (days)
Larynx
4
2-19
Tongue
4-6
2-16
Mouth, cheek
3.4
2-15
Esophagus
5
2.5-20
Cervix
5
3-20
Rectum
5
3-18
Prostate
42
15-70
Breast
14
3-70


Bibliographic references:
[1] Fowler, JF. 21 years of Biologically Effective Dose. Br J Radiol. 2010 Jul; 83(991): 554–568. Available at: http://dx.doi.org/10.1259%2Fbjr%2F31372149.
[2] Fowler JF. The radiobiology of prostate cancer including new aspects of fractionated radiotherapy. Acta Oncol. 2005;44(3):265-76. Available at: http://dx.doi.org/10.1080/02841860410002824.
[3] The timely delivery of radical radiotherapy: standards and guidelines for the management of unscheduled treatment interruptions. (2008). 3rd ed. London, United Kingdom: Board of Faculty of Clinical Oncology, The Royal College of Radiologists. Available at: https://www.rcr.ac.uk/sites/default/files/publication/BFCO(08)6_Interruptions.pdf [Accessed 17 Jul. 2016].