Cryoablation as a Primary Treatment for Localized Prostate Cancer

Prostate cancer presents a spectrum of disease ranging from relatively nonaggressive, low-risk disease to very aggressive, high-risk disease. Therefore, assessment of treatment outcome is best done by stratifying patients into those with low-, intermediate-, and high-risk disease, as done by d'Amico et al. [13]. Low risk is defined as T1-2a, Gleason score of 6 or less, and PSA less than 10ng/ml. Intermediate risk is defined as one of the following: stage higher than T2a, Gleason score greater than 6, or PSA greater than 10ng/ml. High risk is defined as two or more of the following: stage higher than T2a, Gleason score greater than 6, and PSA greater than 10ng/ml. Figure 3 (reprinted with permission from Katz and Rewcastle [44]) shows a range of outcomes for the three risk groups from published papers with a minimum 5-year follow-up. These results show excellent outcomes, particularly for patients with higher-risk disease, which is notoriously difficult to treat successfully. Figures 4 and 5, also from Katz and Rewcastle [44], show cryosurgical outcomes compared with those of radical prostatectomy, brachytherapy, and external-beam radiation. Of particular interest are the results of cryoablation in intermediate- and high-risk patients. Although the number of publications on cryoablation with 5-year follow-up is limited, and the patient numbers are low in comparison to those undergoing surgery and external-beam radiation, the published results are at least equivalent, if not superior, to those for all forms of radiotherapy and surgery in moderate- and high-risk patients.

Posttreatment biopsies have been performed by many authors reporting the results of cryoablation as primary treatment for localized prostate cancer (Table 1). Bahn et al. [14] report an overall positive biopsy rate of 13% in patients, with a mean follow-up of 5.72 years. Our own series shows that 72 of 73 patients exhibited negative biopsies. This negative biopsy rate was achieved, in part, as the result of repeat cryoablation in 11 patients. The ability to retreat the patient is one of the advantages of cryoablation. In our own pilot series of 76 patients,

Fig. 3. Comparison of biochemical disease-free rates as reported in the literature since 1992 for low-risk disease
Fig. 4. Comparison of biochemical disease-free rates as reported in the literature since 1992 for moderate-risk disease

follow-up biopsy was initially positive in 11 cases. Four of these 11 were from the first 10 patients we ever treated, and these 10 patients had a single freeze cycle.The remaining 7 positive biopsies were found in the subsequent 66 patients. Patients with positive biopsies were retreated, and eventually 72 of the 73 patients from this series who underwent biopsy were biopsy negative. Reported biopsy outcomes for brachytherapy, conformal-beam radiotherapy, and external-

Table 1. Positive biopsy results observed following radiation therapy and cryoablation

Study

Therapy

N

Pretreatment

Gleason score

Clinical

Median

% positrv

PSA (ng/ml)

T stage

follow-up

biopsy

Stock et al. 1996 [17]

Brachytherapy

97

75% <20

82% <

7

T1-T2

18mo

26%

Ragde et al. 1997 [15]

Brachytherapy

126

78.7% < 10; median 5.0

2-6

T1-T2

7yr

5%a

Ragde et al. 1998 [16]

Brachytherapy

152

Median 11.0

91% <

8

98% < T3

lOyr

15%

Zelefsky et al. 1998 [51]

3D-CRT

743

Median 15

81<

8

T1-T3

>30 mo

48%

Dinges et al. 1998 [19]

XRT

82

Median 14.0

T2-T3

24 mo

27%

Crook et al. 1998 [18]

XRT

102

T1-T3

40 mo

20%"

Babaian et al. 1995 [24]

XRT

31

70% > 10

T1-T3

51mo

71%

Laverdiere et al. 1997 [22]

XRT

120

Median 11.2

24.3% >

6

T1-T3

24 mo

62%

Ljung et al. 1995 [23]

XRT

55

35% >

6

T1-T3

6.8yr

67%

Bahn et al. 2002 [14]

Cryoablation

590

24.5% > 10

58.4% >

6

T1-T4

5.72 yr

13%

Donnelly et al. 2002 [24]

Cryoablation

76

38% > 10

56% >

6

T1-T3

5.1yr

15%

PSA, prostate-specific antigen; 3D-CRT, three-dimensional conformai radiation therapy ; TCAP, targeted cryoablation of the prostate; XRT, external-beam radiation therapy ° 13% indeterminate b 15% indeterminate

Fig. 5. Comparison of biochemical disease-free rates as reported in the literature since 1992 for high-risk disease

beam radiotherapy yield significantly lower results. The rate of positive biopsies following brachytherapy [15-17] ranges from 5% to 26%, with follow-up periods ranging from 18 months to 10 years. The series reporting the 5% positive biopsy rate was composed solely of patients in the low-risk category [15]. Crook and Bunting [18] reported a 48% positive biopsy rate in their series of conformal-beam radiotherapy in patients with more than 30 months of follow-up, and other series report rates of positive biopsy between 20% and 71%, with follow-up periods ranging from 2 to 6.8 years [19-23].

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