Difference in rectal dosimetry between pre-plan and post-implant analysis in transperineal interstitial brachytherapy for prostate cancer

A cold spot compensation technique using a combination of trans-rectal ultrasonography and intraoperative computed tomography for interstitial permanent prostate brachytherapy: a single-arm prospective trial

Purpose

To evaluate the efficacy of a cold spot compensation technique using a combination of trans-rectal ultrasonography (TRUS) and computed tomography (CT) for permanent interstitial prostate brachytherapy.

Material and methods

Sixty-five patients were treated with the cold spot compensation technique using TRUS-CT fusion. The prescribed dose was set at 145 Gy. The dose to 90% of prostate volume (D₉₀) was planned to be within 195 Gy (134%) and 205 Gy (141%). After implantation using the conventional technique, additional seeds were implanted if cold spots were detected on TRUS-CT fusion images.

Results

Cold spots were detected in 32 of 65 patients (49%) and were compensated by additional seeds. Median number of additional seeds was 3 (range, 1-5). A CT scan 1 month later revealed that the percentage of patients receiving an undesirably low D₉₀ (160-180 Gy) was significantly reduced in the examination arm compared to historical controls. However, mean operation time was significantly longer in the examination arm (64 min) than in historical controls (49 min, p < 0.001). With median follow-up of 18 months (range, 9-24 months), no grade 3 or worse toxicity was encountered.

Conclusion

The cold spot compensation technique using TRUS-CT fusion appears effective for patients receiving permanent interstitial prostate brachytherapy.

Variability of treatment planning of seed implantation: A Japanese multicenter simulation study

PURPOSE

This multicenter study was conducted to evaluate the current variability of treatment planning of seed implantation in Japanese centers and the feasibility of two virtual trials.

METHODS AND MATERIALS

Two types of contour data were sent to 12 radiation oncologists with a request letter that asked them to make treatment plans on the data in the same manner as in their own practice. Five of the 12 radiation oncologists were asked to participate in the two virtual trials in which the D90 (dose to the hottest 90% of prostate volume) was 1) required to be set at just 180 Gy and 2) increased as much as possible without violating other limitations.

RESULTS

A relatively high dose with a small deviation was irradiated to the prostate in Japanese centers (mean D90 = 188 Gy; SD = 10 Gy). In the virtual trials, all five physicians could achieve 180 Gy for the D90 with a very small deviation, although the urethral dose showed relatively large deviations. Dose escalation without increase of urethral dose or V150 was difficult, although the rectum could be spared by most of the physicians.

CONCLUSION

Our study showed a relatively high dose with a small deviation was prescribed to the prostate in Japanese centers. Consolidated protocols such as D90 = 180 Gy could be available for future trials. Meanwhile, our study suggested that some cautions might be needed for urethral dose and the V150, even when a relatively low D90 was requested.

Multi-institutional retrospective analysis of learning curves on dosimetry and operation time before and after introduction of intraoperatively built custom-linked seeds in prostate brachytherapy

This multi-institutional retrospective analysis examined learning curves for dosimetric parameters and operation time after introduction of intraoperatively built custom-linked (IBCL) seeds. Data from consecutive patients treated with seed implantation before and after introduction of IBCL seeds (loose seed, n = 428; IBCL seed, n = 426) were collected from 13 centers. Dose-volume histogram parameters, operation times, and seed migration rates were compared before and after introduction of IBCL seeds. At the 1-month CT analysis, no significant differences were seen in dose to 90% of prostate volume between before and after IBCL seed introduction. No learning curve for dosimetry was seen. Prostate and rectal volume receiving at least 150% of prescription dose (V150 and RV150) were higher in the loose-seed group than in the IBCL-seed group. Operation time was extended by up to 10 min when IBCL seeds were used, although there was a short learning curve of about five patients. The percentage of patients with seed migration in the IBCL-seed group was one-tenth that in the loose-seed group. Our study revealed no dosimetric demerits, no learning curve for dosimetry, and a slightly extended operation time for IBCL seeds. A significant reduction in the rate of seed migration was identified in the IBCL-seed group.

Recovery of serum testosterone following neoadjuvant and adjuvant androgen deprivation therapy in men treated with prostate brachytherapy

AIM: To investigate the time course of testosterone (T) recovery after cessation of androgen deprivation therapy (ADT) in patients treated with brachytherapy.

METHODS: One-hundred and seventy-four patients treated between June 1999 and February 2009 were studied. Patients were divided into a short-term usage group (≤ 12 mo, n = 91) and a long-term usage group (≥ 36 mo, n = 83) according to the duration of gonadotropin-releasing hormone agonist therapy. Median follow-up was 29 mo in the short-term group and was 60 mo in the long-term group.

RESULTS: Cumulative incidence rates of T recovery to normal and supracastrate levels at 24 mo after cessation were 28.8% and 74.6%, respectively, in the long-term usage group, whereas these values were 96.4% and 98.8% in the short-term usage group. T recovery to normal and supracastrate levels occurred significantly more rapidly in the short-term than in the long-term usage group (P < 0.001 and P < 0.001, respectively). Five years after cessation, 22.6% of patients maintained a castrate T level in the long-term usage group. On multivariate analysis, lower T levels (< 10 ng/dL) at cessation of ADT was significantly associated with prolonged T recovery to supracastrate levels in the long-term usage group (P = 0.002).

CONCLUSION: Lower T levels at cessation of ADT were associated with prolonged T recovery in the long-term usage group. Five years after cessation of long-term ADT, approximately one-fifth of patients still had castrate T levels. When determining the therapeutic effect, especially biochemical control, we should consider this delay in T recovery.

Comparison of prostate volume, shape, and contouring variability determined from preimplant magnetic resonance and transrectal ultrasound images

PURPOSE

To compare preimplant prostate contours and contouring variability between magnetic resonance (MR) and transrectal ultrasound images.

METHODS AND MATERIALS

Twenty-three patients were imaged using ultrasound (US) and MR before permanent brachytherapy treatment. Images were anonymized, randomized, and duplicated, and the prostate was independently delineated by five radiation oncologists. Contours were compared in terms of volume, dimensions, posterior rectal indentation, and observer variability. The Jaccard index quantified spatial overlap between contours from duplicated images.

RESULTS

The mean US/MR volume ratio was 0.99±0.08 (p=0.5). The width, height, and length ratios for the prostate were 0.98±0.06 (p=0.09), 0.99±0.08 (p=0.4), and 1.05±0.14 (p=0.1). Rectal indentation was larger on US by 0.18mL (p=0.01) and correlated with prostate volume (p<0.01). MR and US interobserver variability in volume were similar at 3.5±1.7 and 3.3±1.9mL (p=0.6). Intraobserver variability was smaller on US at 1.4±1.1mL compared with MR at 2.4±2.2mL (p=0.01). Local intraobserver variability was lower on US at the midgland slice (p<0.01) but lower on MR at the base (p<0.01) and apex (p<0.01) slices.

CONCLUSIONS

US is comparable to MR for preimplant prostate delineation, with no significant difference in volume and dimensions. Rectal indentation because of the transrectal ultrasound probe was measurable, although the effects were small. Intraobserver variability was lower on US for the prostate volume but was lower on MR locally at the base and apex. However, the difference was not observed for the interobserver variability, which was similar between MR and US.

Image guided, adaptive, accelerated, high dose brachytherapy as model for advanced small volume radiotherapy

Brachytherapy has consistently provided a very conformal radiation therapy modality. Over the last two decades this has been associated with significant improvements in imaging for brachytherapy applications (prostate, gynecology), resulting in many positive advances in treatment planning, application techniques and clinical outcome. This is emphasized by the increased use of brachytherapy in Europe with gynecology as continuous basis and prostate and breast as more recently growing fields. Image guidance enables exact knowledge of the applicator together with improved visualization of tumor and target volumes as well as of organs at risk providing the basis for very individualized 3D and 4D treatment planning. In this commentary the most important recent developments in prostate, gynecological and breast brachytherapy are reviewed, with a focus on European recent and current research aiming at the definition of areas for important future research. Moreover the positive impact of GEC-ESTRO recommendations and the highlights of brachytherapy physics are discussed what altogether presents a full overview of modern image guided brachytherapy. An overview is finally provided on past and current international brachytherapy publications focusing on "Radiotherapy and Oncology". These data show tremendous increase in almost all research areas over the last three decades strongly influenced recently by translational research in regard to imaging and technology. In order to provide high level clinical evidence for future brachytherapy practice the strong need for comprehensive prospective clinical research addressing brachytherapy issues is high-lighted.

Differences between intraoperative ultrasound-based dosimetry and postoperative computed tomography-based dosimetry for permanent interstitial prostate brachytherapy

PURPOSE

To compare the results of intraoperative ultrasound (US)-based dosimetry with those of postimplant computed tomography (CT)-based dosimetry after (125)I prostate brachytherapy.

METHODS AND MATERIALS

Subjects comprised 160 patients who underwent prostate brachytherapy using (125)I seed implants. Prescribed dose was set as 145 Gy to the periphery of the prostate. Implantation was performed using an intraoperative interactive technique. Postimplant dosimetry was performed on Days 1 and 30 after implantation using CT. Dosimetric results for the prostate, urethra, and rectum were compared among intraoperative US and CT on Day 1 (CT(1)) and Day 30 (CT(30)).

RESULTS

Mean minimal dose received by 90% of prostate volume was 133.7%, 115.6%, and 125.8% of the prescribed dose on US, CT(1), and CT(30), respectively: This value temporarily decreased on Day 1 and increased on Day 30. Other parameters for the prostate and urethra showed similar trends. Conversely, mean rectal volume receiving 100% of the prescribed dose was 0.69, 0.46, and 1.02 mL on US, CT(1), and CT(30), respectively. Rectal parameters tended to be underestimated on US relative to CT(30)-based dosimetry. A positive linear relationship was identified between US and CT observations for every prostate parameter and the dose covering 30% of the urethra.

CONCLUSIONS

Our results demonstrate significant differences between dosimetric parameters obtained by US, CT(1), and CT(30). However, significant correlations also exist between US and CT, at least in prostate and urethral parameters. Clarification of the degrees of difference might make US planning more feasible.

Prostate-specific antigen 'bounce' after permanent 125I-implant brachytherapy in Japanese men: a multi-institutional pooled analysis

OBJECTIVE

To examine the incidence, timing, and magnitude of the prostate-specific antigen (PSA) level 'bounce' after permanent prostate brachytherapy (BT) and correlate the PSA bounce with clinical and dosimetric factors in Japanese patients with prostate cancer.

PATIENTS AND METHODS

A multi-institutional pooled analysis was carried out in 388 consecutive patients with T1-T2N0M0 prostate cancer treated with (125)I-seed implant BT with no hormonal therapy or external beam radiotherapy. All patients had >or=1 year of follow-up and at least three follow-up PSA level measurements. Three definitions of PSA bounce were used: definition A, a PSA level rise of 0.1 ng/mL; definition B, a PSA level rise of 0.4 ng/mL; and definition C, a PSA level rise of 35% over the previous value, followed by a subsequent fall.

RESULTS

The actuarial likelihood of having PSA bounce at 24 months was 50.8% for definition A, 23.5% for definition B, and 19.4% for definition C. The median time to develop PSA bounce was 12 months for definition A, 18 months for definition B, and 18 months for definition C. There was a PSA bounce magnitude of 2 ng/mL in 5.3% of patients, and 95.3% of PSA bounce occurred within 24 months after (125)I-BT. Among the before and after (125)I-BT factors, clinical stage, initial PSA level, and Gleason score did not predict for PSA bounce using any definition; only being younger predicted for PSA bounce on multivariate analysis (P < 0.001).

CONCLUSIONS

PSA bounce is a common phenomenon after (125)I-BT and occurred at a rate of 19-51% in the Japanese men who underwent (125)I-BT, depending on the definition used. It is more common in younger patients, and early PSA bounce should be considered when assessing a patient with a rising PSA level after (125)I-BT, before implementing salvage interventions. Furthermore, PSA bounce magnitude might be lower in Japanese than in Caucasian patients.

Four-year experience of interstitial permanent brachytherapy for Japanese men with localized prostate cancer

OBJECTIVE

To report 4 year results obtained with our initial 100 patients with localized prostate cancer treated by interstitial permanent brachytherapy.

METHODS

One-hundred Japanese men with clinically localized prostate cancer underwent interstitial permanent prostate brachytherapy using (125)I seeds. Median follow-up was 36 months (range, 30-42 months). Median initial prostate-specific antigen (PSA) level was 6.7 ng/ml (range, 1.5-25.2 ng/ml). Of these 100 patients, 31 received neoadjuvant hormone therapy for several months. Treatment morbidities were assessed using Radiation Therapy Oncology Group (RTOG) scale and National Cancer Institute Common Toxicity Criteria.

RESULTS

A mean of 95 seeds (range, 48-123 seeds) were successfully implanted in patients with prostate cancer. Mean prostate volume receiving at least 100% dose (V100) and dose to 90% of prostate volume (D90) for the 100 patients were 96.6% and 166.1 Gy, respectively. Urinary morbidity was common, but was usually not severe. Only four patients needed catheterization for urinary retention (Grade 3) during follow-up. Most patients displayed no rectal morbidity after implantation, with only 3% of patients showing RTOG Grade 2 rectal morbidity and no patients showing morbidity of Grade 3 or more. Three patients experienced biochemical failure according to Phoenix consensus definition during follow-up. One patient displayed clinical failure with lymph node recurrence.

CONCLUSIONS

These results indicate that interstitial permanent brachytherapy is safe and effective for Japanese patients with localized prostate cancer. The import of matured techniques developed in Western countries might allow bypass of the trial-and-error process in Japanese institutions.