Outcome of patients with localized prostate cancer treated by radiotherapy after confirming the absence of lymph node invasion

The Impact of Placement Errors on the Tumor Coverage in MRI-Guided Focal Cryoablation of Prostate Cancer

RATIONALE AND OBJECTIVES

There have been multiple investigations defining and reporting the effectiveness of focal cryoablation as a treatment option for organ-confined prostate cancer. However, the impact of cryo-needle/probe placement accuracy within the tumor and gland has not been extensively studied. We analyzed how variations in the placement of the cryo-needles, specifically errors leading to incomplete ablation, may affect prostate cancer's resulting cryoablation.

MATERIALS AND METHODS

We performed a study based on isothermal models using Monte Carlo simulations to analyze the impact of needle placement errors on tumor coverage and the probability of positive ablation margin. We modeled the placement error as a Gaussian noise on the cryo-needle position. The analysis used retrospective MRI data of 15 patients with biopsy-proven, unifocal, and MRI visible prostate cancer to calculate the impact of placement error on the volume of the tumor encompassed by the -40°C and -20°C isotherms using one to four cryo-needles.

RESULTS

When the standard deviation of the placement error reached 3 mm, the tumor coverage was still above 97% with the -20°C isotherm, and above 81% with the -40°C isotherm using two cryo-needles or more. The probability of positive margin was significantly lower considering the -20°C isotherm (0.04 for three needles) than using the -40°C isotherm (0.66 for three needles).

CONCLUSION

The results indicated that accurate cryo-needle placement is essential for the success of focal cryoablation of prostate cancer. The analysis shows that an admissible targeting error depends on the lethal temperature considered and the number of cryo-needles used.

Treatment of locally advanced prostate cancer (Stage T3)

Objective

Formerly, locally advanced prostate cancer exhibited poorly prognosis. In the late 1990s, new surgical and radiation technologies were introduced in combination with androgen deprivation. To evaluate respective strategies, outcomes were examined.

Patients and methods

Between 2001 and 2010, 224 patients with T3N0M0 (10.9% of all prostate cancer cases) were treated with prostatectomy, external beam radiation therapy with/without androgen deprivation or hormone alone. Complete records were obtained by the end of 2015.

Results

Operation group first started without adjuvant treatment and prostate-specific antigen (PSA) relapse occurred in 39% of cases. Radiation therapy group was alternatively divided into two subgroups, that received either monotherapy or combination with androgen deprivation, and PSA relapse rates were 65 and 16%, respectively. High rates of PSA relapse in both the operation and radiation therapy groups were observed in patients without adjuvant therapy, but after relapse androgen deprivation proceeded favorable outcomes. In the radiation subgroups, PSA relapse rates were different, but both subsequent survival rates were the same. This may be due to the effect of androgen deprivation after relapse, indicating effect of delayed therapy. PSA relapse rate in the hormone therapy group was 25% and after relapse, patients applied to treatment with other hormonal and anticancer drugs. Overall survival rates were 91, 88 and 67% in the operation, radiation therapy and hormone therapy groups, respectively.

Conclusion

Aggressive treatment with short-term androgen deprivation for locally advanced prostate cancer could be beneficial and not harmful when suitable candidates are selected. Delayed androgen deprivation was effective for no adjuvant patients after PSA relapse.

Percutaneous MR-guided focal cryoablation for recurrent prostate cancer following radiation therapy: retrospective analysis of iceball margins and outcomes

OBJECTIVES

To evaluate iceball margins after magnetic resonance (MR)-guided focal salvage prostate cryoablation and determine the correlation with local outcome.

METHODS

A retrospective review was performed on 47 patients that underwent percutaneous MR-guided focal cryoablation for biopsy-proven locally recurrent prostate cancer after primary radiotherapy. Preprocedural diagnostic and intraprocedural MR images were analysed to derive three-directional iceball margins. Local tumour progression after cryoablation was defined as evident tumour recurrence on follow-up MRI, positive MR-guided biopsy or biochemical failure without radiological evidence of metastatic disease.

RESULTS

Mean iceball margins were 8.9 mm (range -7.1 to 16.2), 10.1 mm (range 1.1-20.3) and 12.5 mm (range -1.5 to 22.2) in anteroposterior, left-right and craniocaudal direction respectively. Iceball margins were significantly smaller for tumours that were larger (P = .008) or located in the posterior gland (P = .047). Significantly improved local progression-free survival at 1 year post focal cryoablation was seen between patients with iceball margin >10 mm (100%), 5-10 mm (84%) and <5 mm (15%) (P < .001).

CONCLUSIONS

Iceball margins appear to correlate with local outcome following MR-guided focal salvage prostate cryoablation. Our initial data suggest that freezing should be applied at minimum 5 mm beyond the border of an MR-visible recurrent prostate tumour for successful ablation, with a wider margin appearing desirable.

KEY POINTS

• Shortest iceball margin most often occurred in anteroposterior direction • Margins were smaller in tumours that were larger or posteriorly located • Minimum iceball margin was a predictor of early local tumour progression • A minimum 5-mm margin seems required for effective cryoablation of recurrent PCa.

MR imaging-guided focal cryoablation in patients with recurrent prostate cancer

PURPOSE

To assess the feasibility of magnetic resonance (MR) imaging-guided focal cryoablation in patients with locally recurrent prostate cancer after radiation therapy.

MATERIALS AND METHODS

This was a prospective study, and informed consent was obtained from all patients. Ten consecutive patients with histopathologically proved recurrent prostate cancer after radiation therapy, without evidence of distant metastases, were treated while under general anesthesia in a 1.5-T MR unit. A urethral warmer was inserted. Cryoneedles were transperineally inserted under real-time MR imaging. Then, a rectal warmer was inserted. Ice ball growth was continuously monitored under MR imaging guidance. Two freeze-thaw cycles were performed. Follow-up consisted of a visit to the urologist, measurement of prostate-specific antigen level, and multiparametric MR imaging at 3, 6, and 12 months. Potential complications were recorded.

RESULTS

All patients were successfully treated. In one patient, the urethral warmer could not be inserted and the procedure was cancelled. Two months later, the procedure was successfully repeated. Another patient had urinary retention. Follow-up data were available for all patients. A local recurrence or remnant tumor was found in two patients after 6 months and in another patient after 12 months. These three patients underwent successful retreatment with MR imaging-guided focal cryoablation.

CONCLUSION

MR imaging-guided focal cryoablation of recurrent prostate cancer after radiation therapy is feasible and safe. Initial results are promising; however, longer follow-up is needed and more patients must be studied.

Salvage cryotherapy for radiation-recurrent prostate cancer: outcomes and complications

Potentially curative salvage options for radio-recurrent prostate cancer include prostatectomy, brachytherapy, high-intensity focused ultrasound, and cryotherapy. Salvage cryoablation technology, surgical technique, oncologic outcomes, and complication rates have improved dramatically over the past few decades, shifting this treatment modality from investigational status to an established therapeutic option. In this review, we focus on the most up-to-date oncologic and functional outcomes, as well as complications of salvage cryotherapy for radiation-recurrent prostate cancer.