20 Prostate Cancer

Prostate Cancer

14

THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part II: Clinical Practice Version 1 - 01/12/2014

high risk groups respectively [47]. Differences in described out- comes can be dependent on e.g. patient selection, treatment dif- ferences and follow-up differences. Overall, disease specific sur- vival and overall survival rates are very high in virtually all series. A large systematic analysis of the shows LDR brachytherapy has have a favourable outcome in comparison with prostatectomy or external beam radiotherapy across all risk groups [48] Currently, the Phoenix definition (nadir +2ng/mL) is considered a biochemical recurrence. If nadir +2 occurs the chance of a bounce (no true tumour recurrence) can be considered less than 5%. Two important features of the response after LDR seed brachytherapy are the time taken to reach PSA nadir and the phenomenon of a PSA ‘bounce’. For many patients the PSA nadir is not reached until around three years from implant. In the large US collaborative cohort nadir PSA at three years was a prognostic factor, the 8 year PSA RFS being 88%,69%,57% and 41% after nadir counts of 0-0.49,0.5-0.99,1.0-1.99 and ≥2.0 re- spectively [45]. The PSA bounce is seen in 15-30% of patients when after an ini- tial fall there is a rise in PSA before settling to the nadir [49][50]. This is usually seen between 12 and 24 months after implant with average rises of <2ng/ml being seen during this period in those who demonstrate the bounce. It is important to recognise this phenomenon and continue PSA monitoring rather than pro- ceeding to unnecessary salvage treatment. Most series demonstrate a relationship between implant quali- ty as measured by the D90 and PSA response. In the US series when the D90 for I125 implants was ≥130Gy the PSA RFS was 92% compared to 76% in those patients whose implant had a lower D90 value [51]. Another large series of 1377 patients hav- ing LDR seed brachytherapy reported a 10 year PSA RFS of 87%; when the D90 was <154Gy the 10 year PSA RFS was 69% com- pared to 91% when the D90 was >150Gy [52] Biochemical relapse can precede clinical progression by three to five years. There have been many studies comparing outcome after LDR brachytherapy between younger (aged 60 or 50 years of age and less) and older men, as it was hypothesised younger men might have more aggressive disease and outcome after LDR brachyther- apy might be worse. Up to now all studies showed no difference in outcome between younger and older men [53]. Also obesity has been hypothesised as having more aggressive disease. Again, no differences were shown in several large se- ries comparing outcome between adipose and men with normal weight [54]. LDR boost with external beam radiotherapy LDR seed brachytherapy may be used as a boost with external beam radiotherapy. There are relatively few published results compared to seed monotherapy. As can be seen from the series quoted in table 21.8 the results are favourable and support LDR seed brachytherapy for intermediate and high risk patients with external beam radiotherapy [47,55-57] although there is a less strong radiobiological basis for dose escalation compared to HDR brachytherapy and overall less data for LDR in this setting.

Table 21.6: Reporting recommendations for HDR brachytherapy

advised with annual PSA monitoring indefinitely. Objective follow up should include as a minimum, measurement of the PSA level, urinary function using IPSS or AUA scores and erectile function using IEFS or similar scores. It may take several years for the PSA to gradually achieve its nadir. In cases of persisting PSA rise, Doppler ultrasound or DCE (dy- namic contrast enhanced) MRI can visualise blood perfusion within the prostate and combined with diffusion weighted MR may indicate areas with increased blood flow as a sign of local recurrence. Where urinary symptoms persist urodynamic assessment should be performed by the urologist to monitor the voiding and if nec- essary surgery considered. The probability of biochemical disease free survival is closely re- lated to the prognostic factors. For patients with PSA less than 10, Gleason score less than 7 and stage T2A or less, over 80% are free of biochemical progression at five years. For patients with Gleason score greater than 7 and PSA greater than 20, biochem- ical disease free survival is around 60% or less at five years as shown in table 21.7 [41-46]. LDR seed brachytherapy There is an extensive literature reporting the results of LDR seed brachytherapy with mature results out to 15 years and beyond. A selection of the larger series and with a longer follow up is shown in table 21.7 The largest cohort is that of 2693 patients pooled from 11 US institutes [45] of which 1831 received LDR I125 brachytherapy (median dose 144Gy) and 893 Pd103 implants (median dose 130Gy). The 8 year PSA relapse free survival was 82%, 70% and 48% respectively for low, intermediate and high risk patients using the ASTRO definition of three successive PSA rises and 74%, 61% and 39% respectively using the nadir + 2ng/ ml definition. No significant difference between the two isotopes was found on multivariate analysis. Using the same risk groups the 15 year outcome data from Seattle reports PSA relapse free survivals of 85.8%, 80.3% and 67.8% in low intermediate and 1. External beam dose 2. Implant technique; Number of catheters; 3. Total reference air kerma (TRAK) Total source exposure 4. Pattern of dwell times for each applicator 5. CTV: D90, V100, V150, V200 6. PTV (if defined) : D90, V100, V150, V200 7. Organs at risk: a. Rectum: D2cc, D0.1cc b. Urethra: D0.1cc, D10,D30 Other volumes which may be recorded but are not considered man- datory: GTV, Subvolumes within CTV/PTV and Penile bulb, bladder 12. RESULTS