Ngcezu, Sonwarile Arthur. Student no 0200932R. MSc Thesis. Physics. Faculty of Science. 2006. Supervisor: Prof D van der Merwe. / Purpose: A retrospective study was conducted to calculate biological objective functions [Tumor control probability (TCP) for the prostate and normal tissue complication probability (NTCP), in particular for the rectum] for patients treated at Johannesburg hospital during the years 2002 – 2003 for prostate cancer and to correlate these values with observed clinical outcome. Ultimately these results were used to evaluate the effects of dose escalation on tumor control and rectal complications following radiotherapy using conformal external beam radiotherapy.
Methods and materials: To calculate the TCP and the NTCP use was made of BIOPLAN, a PC-based software. This software allows the user to evaluate a treatment plan from the point of view of the biological response of the irradiated tissue, providing at the same time flexibility in the use of models (Poisson Statistics for TCP and Lyman-Kutcher-Burman for NTCP) and parameters. The clinical analysis was based on reports from on treatment review and follow-up visits made by the patients periodically after the treatment. PSA was used as a measure of biochemical failure and correlated with calculated TCP. Also, reported complications were compared to NTCP values calculated by BIOPLAN. The follow-up data were about 2 months to 2.5 years old.
Results: Complications reported after therapy were all less than grade 3 (RTOG) for the patients, which means only mild complications were reported. No patient reported having necrosis, perforation or a fistula for all the prognostic groups. The calculated average NTCP (mild complications) was 36.3 ± 33.3 % and it was 3.9 ± 3.6 % for severe complications. The calculated TCP had an average of 84.3 ± 7.4 % and no biochemical failure was detected on the follow-ups. As the total dose was elevated through 70-Gy, 72-Gy, 76-Gy, and 86-Gy (2 Gy equivalent), the average TCP increased through 76.2 ± 3.8 %, 77.7 ± 2.6 %, 81.5 ± 4 % and 92.5 ± 2.5 %, respectively. The TCP therefore increased about 22 % by increasing prescribed doses from 70 Gy to 86 Gy. The relation between rectal overlap volume and the NTCP was not obvious (scattered).
Conclusions The model predictions gave a reasonable reflection of the reported clinical outcome. A more comprehensive study requires derivation and use of accurate model parameters, and more mature follow-up data.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/2272 |
| Date | 15 March 2007 |
| Creators | Ngcezu, Sonwabile Arthur |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 651762 bytes, application/pdf, application/pdf |
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