Thursday, 19 October 2017

PSA (prostate specific antigen) density

PSA density (ng/mLor ng/mL/cc) is calculated preoperatively during the biopsy procedure by using transrectal ultrasound by dividing the maximum preoperative PSA value and prostate volume [1]. The latter is calculated based on the ellipse dimension theory formula [2] (D1 × D2 × D3 × pi/6), where D1 is the maximum transverse diameter, D2 is the maximum anteroposterior diameter, D3 is the maximum longitudinal diameter, and pi is a mathematical constant approximately equal to 3.14.
A study of a large cohort of patients (1662 patients) found a significant trend of worsening pathological features as PSA density increases [3]. Other studies [4,5] found that PSA density (using a pathological weight of the surgical specimen) was a better predictor of extracapsular disease, positive surgical margins, seminal vesicle invasion, lymph node invasion and biochemical recurrence than PSA.
«It is used because an elevated PSA might not arouse suspicion in a man with a very enlarged prostate. The use of PSA density to interpret PSA results is controversial because prostate cancer might be overlooked in a man with an enlarged prostate» [6].
Bibliographic references:
[1] Sfoungaristos S, Perimenis P. Evaluating PSA Density as a Predictor of Biochemical Failure after Radical Prostatectomy: Results of a Prospective Study after a Median Follow-Up of 36 Months. ISRN Urol. 2013 May 16;2013:984951. Available at: https://doi.org/10.1155/2013/984951.
[2] Wolff JM, Boeckmann W, Mattelaer P, et al. Determination of prostate gland volume by transrectal ultrasound: correlation with radical prostatectomy specimens. Eur Urol. 1995;28(1):10-2. Available at: https://doi.org/10.1159/000475012.
[3] Kundu SD, Roehl KA, Yu X, et al. Prostate specific antigen density correlates with features of prostate cancer aggressiveness. J Urol. 2007 Feb;177(2):505-9. Available at: https://doi.org/10.1016/j.juro.2006.09.039.
[4] Freedland SJ, Wieder JA, Jack GS, et al. Improved risk stratification for biochemical recurrence after radical prostatectomy using a novel risk group system based on prostate specific antigen density and biopsy Gleason score. J Urol. 2002 Jul;168(1):110-5. Available at: http://dx.doi.org/10.1016/S0022-5347(05)64841-0.
[5] Sfoungaristos S, Perimenis P. PSA density is superior than PSA and Gleason score for adverse pathologic features prediction in patients with clinically localized prostate cancer. Can Urol Assoc J. 2012 Feb;6(1):46-50. Available at: https://doi.org/10.5489/cuaj.11079.
[6] Definition of PSA density. Phoenix5org. 2002. Available at: http://www.phoenix5.org/glossary/PSA_density.html. Accessed October 19, 2017.

Biochemical failure in prostate cancer

«The definition of biochemical recurrence following radiation therapy is complicated by the incomplete ablation of all functioning prostatic epithelium, which creates difficulty in establishing a meaningful absolute nadir and the phenomenon of “PSA bounce”» [4]. Biochemical failure after external beam radiotherapy with or without hormonal therapy in men with clinically localized prostate cancer by 2005 RTOG-ASTRO Phoenix Consensus Conference is: 1) prostate-specific antigen (PSA) rise by 2 ng/mL or more above the nadir PSA; and 2) a recurrence evaluation should be considered when PSA has been confirmed to be increasing after radiation even if the rise above nadir is not yet 2 ng/mL, especially in candidates for salvage local therapy who are young and healthy [1]. «This definition accepts some limitation on sensitivity in the interest of increased specificity for detecting failures associated with clinical outcomes other than cure» [4].
Following radical prostatectomy, a cutoff of 0.2 ng/mL has been associated with a high likelihood of subsequent PSA progression [2]. More recently, 0.4 ng/mL and rising has been proposed as a definition associated more closely with the development of distant metastases [3].
Bibliographic references:
[1] Roach M 3rd, Hanks G, Thames H Jr, et al. Defining biochemical failure following radiotherapy with or without hormonal therapy in men with clinically localized prostate cancer: recommendations of the RTOG-ASTRO Phoenix Consensus Conference. Int J Radiat Oncol Biol Phys. 2006 Jul 15;65(4):965-74. Available at: https://doi.org/10.1016/j.ijrobp.2006.04.029.
[2] Freedland SJ, Sutter ME, Dorey F, Aronson WJ. Defining the ideal cutpoint for determining PSA recurrence after radical prostatectomy. Prostate-specific antigen. Urology. 2003 Feb;61(2):365-9. Available at: http://dx.doi.org/10.1016/S0090-4295(02)02268-9.
[3] Amling CL, Bergstralh EJ, Blute ML, et al. Defining prostate specific antigen progression after radical prostatectomy: what is the most appropriate cut point? J Urol. 2001 Apr;165(4):1146-51. Available at: http://dx.doi.org/10.1016/S0022-5347(05)66452-X.
[4] Nielsen ME, Partin AW. The Impact of Definitions of Failure on the Interpretation of Biochemical Recurrence Following Treatment of Clinically Localized Prostate Cancer. Rev Urol. 2007 Spring;9(2):57-62.

Sunday, 15 October 2017

AFU

Association Française d’Urologie, the French Association of Urology.

GETUG

Groupe d'Études des Tumeurs Uro-Génitales, the French Genitourinary Study Group.

Electromagnetic tracking system (EMTS)

Image-guided therapy relies on the localization of the equipment with respect to the patient. This localization in three-dimensional space is referred to as tracking and is a key enabling technology for computer-assisted interventions. Electromagnetic (EM) tracking has emerged as the method of choice that enables localization of small EM sensors in a given EM field without the requirement for line-of-sight [3]. The introduction of continuous EM tracking has allowed the intrafraction motion to be measured and corrected in real-time during treatment [2]. When a receiving sensor moving in space, an EMTS can accurately calculate its position and orientation, it can provide dynamic, real-time measuring position and orientation angle [1].
«The term “electromagnetic” to describe the tracking phenomenon arises from the fact that electromagnets are responsible for producing changing or quasi-static magnetic fields, which induce currents in solenoids or fluxgate sensors embedded in the detectors. The phenomenon responsible for the operation of these tracking systems relies solely on magnetic induction rather than any strict electromagnetic effect. Nevertheless, while this technology is referred to by both the terms “magnetic tracking” (MT) and “electromagnetic tracking” (EMT), the latter has become the more common, having been adopted by the manufacturers of these devices, (...) [3].»
Bibliographic references:
[1] Zhang Z, Liu G. The Design and Analysis of Electromagnetic Tracking System. Journal of Electromagnetic Analysis and Applications. 2013;5:85-9. Available at: http://dx.doi.org/10.4236/jemaa.2013.52014.
[2] Litzenberg DW, Gallagher I, Masi KJ, et al. A measurement technique to determine the calibration accuracy of an electromagnetic tracking system to radiation isocenter. Med Phys. 2013 Aug;40(8):081711. Available at: https://doi.org/10.1118/1.4813910.
[3] Franz AM, Haidegger T, Birkfellner W, et al. Electromagnetic tracking in medicine - a review of technology, validation, and applications. IEEE Trans Med Imaging. 2014 Aug;33(8):1702-25. Available at: https://doi.org/10.1109/TMI.2014.2321777.

SPECT (single photon emission computed tomography)

SPECT, or less commonly, SPET [3], is a medical imaging technique that is based on conventional nuclear medicine imaging, using gamma rays, and tomographic reconstruction methods. It is «performed by using a gamma camera to acquire multiple two-dimensional (2D) images from multiple angles» [4]. «The images reflect functional information about patients similar to that obtained with positron emission tomography (PET). Both SPECT and PET (...) give information based on the spatial concentration of injected radiopharmaceuticals» [1]. It «is a type of nuclear imaging test that shows how blood flows to tissues and organs» [2]. It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, scintigraphy), but, it is able to provide true three-dimensional (3D) information [3]. A computer is used to apply a tomographic reconstruction algorithm to the multiple 2D projections, yielding a 3D dataset. «This dataset may then be manipulated to show thin slices along any chosen axis of the body» [4]. SPECT can be used to complement any gamma imaging study, where a true 3D representation can be helpful, (e.g., tumor imaging, infection (leukocyte) imaging, thyroid imaging or bone scintigraphy). Because SPECT permits accurate localization in 3D space, it can be used to provide information about the localized function in internal organs, such as functional cardiac or brain imaging [3].
Bibliographic references:
[1] National Research Council (US) and Institute of Medicine (US) Committee on the Mathematics and Physics of Emerging Dynamic Biomedical Imaging. Mathematics and Physics of Emerging Biomedical Imaging. Washington (DC): National Academies Press (US); 1996. Chapter 5, Single Photon Emission Computed Tomography. Available at: https://www.ncbi.nlm.nih.gov/books/NBK232492/. Accessed October 15, 2017.
[2] SPECT (single photon emission computed tomography) scan. Mayfield Brain & Spine. 2016. Available at: https://www.mayfieldclinic.com/PE-SPECT.htm. Accessed October 15, 2017.
[3] Single-photon emission computed tomography. Enwikipediaorg. 2017. Available at: https://en.wikipedia.org/wiki/Single-photon_emission_computed_tomography. Accessed October 15, 2017.
[4] Hricak H, Akin O, Vargas HA. (2013). C. In: L. Brady and T. Yaeger, ed., Encyclopedia of Radiation Oncology, 1st ed. Springer-Verlag Berlin Heidelberg, pp.790.

Monday, 25 September 2017

Dia do Interno Radioncologia (Portuguese) (Radiation Oncology Resident's Day)




  • Venue: October 20, 2017 - Hospital de Santa Maria, Centro Hospitalar Lisboa Norte, EPE, Lisbon, Portugal:

Monday, 11 September 2017

ITV (internal target volume)

It consists of an internal margin added to the CTV to compensate for internal physiologic movement and variations in size, shape, and position of the CTV [1]. It's an expansion of CTV for internal (e.g. breathing) movement [2].
Bibliographic references:
[1] Reiff J. E. (2013). C. In: L. Brady and T. Yaeger, ed., Encyclopedia of Radiation Oncology, 1st ed. Springer-Verlag Berlin Heidelberg, pp.343-399.
[2] Balter J. Target definition (margin selection) for radiotherapy (IMRT). aapmorg. 2017. Available at: https://www.aapm.org/meetings/03SS/Presentations/Balter.pdf. Accessed September 11, 2017.

Tuesday, 25 July 2017

Conformity index (CI)

It is defined as the ratio of the treated volume to the PTV (planning target volume) [1]. It is a tool for treatment plan analysis in conformal radiotherapy [2].
Bibliographic references:
[1] International Commission on Radiation Units and Measurements. ICRU Report 62. Prescribing, Recording and Reporting Photon Beam Therapy. Supplement to ICRU Report 50. Bethesda, MD: ICRU; 1999.
[2] Kataria T, Sharma K, Subramani V, et al. Homogeneity Index: An objective tool for assessment of conformal radiation treatments. J Med Phys. 2012 Oct;37(4):207-13. Available at https://doi.org/10.4103/0971-6203.103606.

Sunday, 18 June 2017

PARP (poly-[adenosine diphosphate-ribose] polymerase)

Poly-(ADP)-ribose polymerase is «a family of proteins involved in a number of cellular processes involving mainly DNA [deoxyribonucleic acid] repair and programmed cell death. The PARP family comprises 17 members (10 putative). They have all very different structures and functions in the cell. One important function of PARP is assisting in the repair of single-strand DNA breaks [1]». It is «a SSB [single-strand break] detector protein» [2].
«Drugs which inhibit (...) PARP (...) are particularly effective in tumors with HR [homologous recombination] deficiencies, such as breast tumors with BCRA1 or BCRA2 [breast cancer 1 or 2] deficiencies. (...) probably (...) PARP inhibitors suppress SSB repair, resulting in greater numbers of unrepaired SSBs, which therefore have a greater chance of hitting a replication fork. Under normal circumstances, the resulting DSB [double-strand break] would be repaired by HR, so the absence or reduction of this backup pathway leads to a substantial increase in DSBs and thus cellular lethality [2].»
Bibliographic references:
[1] Tortora, G., Bergmann, L., Lindh, M., Cervantes-Ruiperez, A., Dziadziuszko, R., Eckhardt, S., Lenz, H., Normanno, N., Perez, D., Scarpa, A., Syrigos, K., Tabernero, J. and Troiani, T. (2014). ESMO glossary in molecular biology of cancer. Viganello-Lugano, Switzerland: European Society for Medical Oncology, p.127.
[2] Joiner, M. and Kogel, A. (2009). Basic clinical radiobiology. 1st ed. Boca Raton, Florida: CRC Press, p.24.

Monday, 15 May 2017

Cytoreduction

It is the debulking, or reduction «(...) of the size of, a cancerous tumor. Surgery and radiation therapy are two common cytoreductive treatments used to debulk tumors. Debulking means to remove as much of the cancer as possible [1].» «(...) "cytoreduction" refers to reducing the number of tumor cells [2].» «Tumor debulking may increase the chance that chemotherapy or radiation therapy will kill all the tumor cells. It may also be done to relieve symptoms or help the patient live longer [3].» 
Bibliographic references:
[1] CancerCenter.com. (2017). Cytoreductive Therapy : Cancer Glossary | CTCA. [online] Available at: http://www.cancercenter.com/terms/cytoreductive-therapy/ [Accessed 15 May 2017].
[2] En.wikipedia.org. (2017). Debulking. [online] Available at: https://en.wikipedia.org/wiki/Debulking [Accessed 15 May 2017].
[3] National Cancer Institute. (n.d.). NCI Dictionary of Cancer Terms. [online] Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms?cdrid=46635 [Accessed 15 May 2017].

Wednesday, 10 May 2017

Adjuvant therapy

It is an «additional cancer treatment given after the primary treatment to lower the risk that (...) cancer will come back. Adjuvant therapy may include chemotherapy, radiation therapy, hormone therapy, targeted therapy, or biological therapy.»
Bibliographic reference: National Cancer Institute. (n.d.). NCI Dictionary of Cancer Terms. [online] Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms?CdrID=45587 [Accessed 10 May 2017].

Monday, 8 May 2017

p53

It «(...) is one of the most commonly mutated tumor suppressors whose function is to regulate genes that control both cell cycle checkpoints and (...) apoptosis. Consequently, activation of p53 after irradiation can lead either to a block in proliferation or directly to cell death. (...) in unstressed normal cells, p53 is made continuously but is degraded and thus non-functional. Following DNA [deoxyribonucleic acid] damage, ATM [ataxia telangiectasia mutated] phosphorylates both p53 and MDM2 [murine double minute 2]. These events destabilize the p53-MDM2 interaction, and (...) p53 protein is no longer degraded. In addition to this stabilization, direct phosphorylation of p53 by ATM leads to its activation as a transcription factor and thus the upregulation of its many target genes [1].»
«Cells irradiated in the G1 phase are influenced by the action of p53. ATM protein is activated by double-strand DNA breaks and phosphorylates both MDM2 and p53. This leads to stabilization and activation of p53, which induces genes that can promote apoptosis (Bax [Bcl-2-associated X], Puma [p53 upregulated modulator of apoptosis]) and induces checkpoints. (...) cells are blocked at the G1/S border [1].»
Is has «(...) a mass of 53 kDa (hence its name); p53 protein is normally induced in cells having undergone DNA damage, (...); its principal effects are to stop the cell cycle and prevent the cell from undergoing mitosis; thus, DNA mutations/damage can either be repaired or a damaged cell can be eliminated from the organism, for example via apoptosis. p53 is also known as the guardian of the genome [2].»
Bibliographic references:
[1] Joiner, M. and Kogel, A. (2009). Basic clinical radiobiology. 1st ed. Boca Raton, Florida: CRC Press, p.17.
[2] Tortora, G., Bergmann, L., Lindh, M., Cervantes-Ruiperez, A., Dziadziuszko, R., Eckhardt, S., Lenz, H., Normanno, N., Perez, D., Scarpa, A., Syrigos, K., Tabernero, J. and Troiani, T. (2014). ESMO glossary in molecular biology of cancer. Viganello-Lugano, Switzerland: European Society for Medical Oncology, p.117.

Saturday, 18 March 2017

Ratio

It's the relationship between two sets with different characteristics. The numerator is not included in the denominator. It is different from proportion.