Abstract
Cryotherapy is being used increasingly as a minimally invasive treatment option to treat salvage cases of prostate cancer after radiation therapy has failed. The technique of cryotherapy includes freezing the prostate by a number of iceballs created by cryoprobes. The process is monitored by thermosensors and transrectal ultrasound scan. There is a little agreement in the literature on the iceball characteristics; hence, variations of the technique of cryotherapy exist among clinicians particularly as to the positioning of the cryoprobes and thermosensors. The current salvage therapies for prostate cancer have comparable early oncological outcome, and all have some adverse effects. Patients choosing treatment with different modalities tend to experience different morbidities, the significance of which may be subjective to each patient. Hence, the impact on quality of life is an important tool in assessing treatment outcome. In this dissertation, the factors determining the characteristics of the iceballs formed during cryotherapy have been investigated in an in vitro model; aiming to help clinicians to increase the safety and efficacy of the procedure. The impact of cryotherapy on quality of life has also been assessed using several validated instruments. We assessed the correlation between the iceball temperature profile and the impact on quality of life of patients after salvage cryotherapy of the prostate in an aim to reduce the impact of salvage cryotherapy on the quality of life of patients. Material and Methods The thermal properties of three different probes (3. 4mm and 2. 4mm diameter cryoprobes produced by Endocare TM and the 1. 47mm diameter cryoneedles produced by the Seednet TM) were compared in vitro. The temperatures of several points within the iceball created within bovine muscle were measured using thermosensors. The effects of changing the freezing gas flow rate from 100% to 20% on the properties of the resultant iceball were also investigated. The impact of salvage cryotherapy on quality of life was investigated using a prospective study design and a number of validated questionnaires including: EROTC QLQ-C30, EROTC PR-25, IPSS and IIEF. The lowest temperatures at the apex of the prostate, at the external urethral sphincter area and at the Denonvillier's fascia (between prostate and rectum) during salvage cryotherapy were obtained, and correlated to the changes in the global health, urinary problem domains, urinary incontinence question, IPSS and quality of life question of the IPSS at 6 weeks post cryotherapy. 1. There was a significant difference between the thermal properties of the iceballs (p <0. 05). The 2. 4 mm diameter probes produced an iceball with the highest ablative ratio (percentage of lethal iceball/ total iceball volume) and the least non-lethal ice thickness (the outer zone of the iceball where temperature ranges between 0 and 40 C). The 3. 4mm diameter probes produced an iceball, which had larger dimensions than the 2. 4mm probes, but had a statistically significant lower ablative ratio (p<0. 001). The most important feature of the 1. 47mm diameter cryoneedles was that they produced a small iceball with statistically significant short lethal ice (p<0. 001) compared to both Endocare TM cryoprobes, and with smaller ablative ratio (P<0. 001) compared to the 2. 4mm diameter cryoprobes. Reduction of the gas flow rate to 20% resulted in a decrease in the lethal iceball dimensions, cooling rates and the ablative ratios for all the iceballs which was more pronounced when using the 1. 47 cryoneedles. 2. The quality of life study is ongoing and preliminary results are presented. The trend suggested worsening (of "a little" clinical significance) of the global health score temporarily for 3 months after cryotherapy. Urinary problems worsened until 9 months after cryosurgery at which time it became of no clinical significance. There were no clinically significant changes in sexual activity and function after salvage cryosurgery, as the majority (86%) were considered impotent before cryotherapy. 3. The study is ongoing and preliminary results showed no correlation exists between the lowest iceball temperature at the apex of the prostate, the external urethral sphincter or the Denonvillier's fascia and the impact on the quality of life of patients after salvage cryotherapy. Conclusions There are differences between the iceball thermal properties of the different freezing probes, and the 2. 4mm diameter probes appear to be superior to the other probes. (Abstract shortened by ProQuest.).