Low incidence of late recurrence in patients with intermediate-risk prostate cancer treated by intensity-modulated radiation therapy plus short-term androgen deprivation therapy

Impact of prostate position-based image-guidance in intensity-modulated radiation therapy for localized prostate cancer

BACKGROUND/PURPOSE

The long-term clinical impact of prostate position-based image-guided radiotherapy (IGRT) for localized prostate cancer remains unclear.

MATERIALS AND METHODS

We retrospectively compared clinical outcomes following intensity-modulated radiation therapy (IMRT) with cone-beam computed tomography-based prostate position-based IGRT (P-IGRT) or without P-IGRT (non-P-IGRT). From June 2011, we applied P-IGRT in IMRT for intermediate-risk (IR) prostate cancer (PCa) (D'Amico risk classification) (76 Gy in 38 fractions, with smaller margins). Clinical outcomes of patients who received P-IGRT between June 2011 and June 2019 were retrospectively compared with those of patients with IR PCa who received IMRT without P-IGRT between October 2002 and May 2011 in our institution (74 Gy in 37 fractions).

RESULTS

A total of 222 consecutive patients were analyzed: 114 in the P-IGRT cohort and 108 in the non-P-IGRT cohort. The median follow-up period after IMRT was 7.1 years for the P-IGRT cohort and 10.8 years for the non-P-IGRT cohort. The biochemical failure-free rate was significantly better in the P-IGRT cohort (94.9% for the P-IGRT cohort vs 82.7% for the non-P-IGRT cohort at 10 years, p = 0.041). The rate of rectal bleeding which needs intervention including the use of suppositories was significantly lower in the P-IGRT cohort (p < 0.001).

CONCLUSIONS

The use of P-IGRT with higher doses and smaller margins was correlated with significantly better biochemical control, and a lower incidence of rectal bleeding in IMRT for intermediate-risk prostate cancer. The enhanced accuracy using P-IGRT has the potential to independently improve disease control and reduce late rectal bleeding.

Comparison of intensity-modulated radiotherapy with the 5-field technique, helical tomotherapy and volumetric modulated arc therapy for localized prostate cancer

The outcomes of three methods of intensity-modulated radiation therapy (IMRT) for localized prostate cancer were evaluated. Between 2010 and 2018, 308 D'Amico intermediate- or high-risk patients were treated with 2.2 Gy daily fractions to a total dose of 74.8 Gy in combination with hormonal therapy. Overall, 165 patients were treated with 5-field IMRT using a sliding window technique, 66 were then treated with helical tomotherapy and 77 were treated with volumetric modulated arc therapy (VMAT). The median age of patients was 71 years. The median follow-up period was 75 months. Five-year overall survival (OS) and biochemical or clinical failure-free survival (FFS) rates were 95.5 and 91.6% in the 5-field IMRT group, 95.1 and 90.3% in the tomotherapy group and 93.0 and 88.6% in the VMAT group, respectively, with no significant differences among the three groups. The 5-year cumulative incidence of late grade ≥2 genitourinary and gastrointestinal toxicities were 7.3 and 6.2%, respectively, for all patients. Late grade ≥2 gastrointestinal toxicities were less frequent in patients undergoing VMAT (0%) than in patients undergoing 5-field IMRT (7.3%) and those undergoing tomotherapy (11%) (P = 0.025), and this finding appeared to be correlated with the better rectal DVH parameters in patients undergoing VMAT. Other toxicities did not differ significantly among the three groups, although bladder dose-volume parameters were slightly worse in the tomotherapy group than in the other groups. Despite differences in the IMRT delivery methods, X-ray energies and daily registration methods, all modalities may be used as IMRT for localized prostate cancer.

Evaluation of internal margins for prostate for step and shoot intensity-modulated radiation therapy and volumetric modulated arc therapy using different margin formulas

PURPOSE

This feasibility study evaluated the intra-fractional prostate motion using an ultrasound image-guided system during step and shoot intensity-modulated radiation therapy (SS-IMRT) and volumetric modulated arc therapy (VMAT). Moreover, the internal margins (IMs) using different margin formulas were calculated.

METHODS

Fourteen consecutive patients with prostate cancer who underwent SS-IMRT (n = 5) or VMAT (n = 9) between March 2019 and April 2020 were considered. The intra-fractional prostate motion was observed in the superior-inferior (SI), anterior-posterior (AP), and left-right (LR) directions. The displacement of the prostate was defined as the displacement from the initial position at the scanning start time, which was evaluated using the mean ± standard deviation (SD). IMs were calculated using the van Herk and restricted maximum likelihood (REML) formulas for SS-IMRT and VMAT.

RESULTS

For SS-IMRT, the maximum displacements of the prostate motion were 0.17 ± 0.18, 0.56 ± 0.86, and 0.18 ± 0.59 mm in the SI, AP, and LR directions, respectively. For VMAT, the maximum displacements of the prostate motion were 0.19 ± 0.64, 0.22 ± 0.35, and 0.14 ± 0.37 mm in the SI, AP, and LR directions, respectively. The IMs obtained for SS-IMRT and VMAT were within 2.3 mm and 1.2 mm using the van Herk formula and within 1.2 mm and 0.8 mm using the REML formula.

CONCLUSIONS

This feasibility study confirmed that intra-fractional prostate motion was observed with SS-IMRT and VMAT using different margin formulas. The IMs should be determined according to each irradiation technique using the REML margin.

Outcomes of intensity-modulated radiation therapy for intermediate- or high-risk prostate cancer: a single-institutional study

BACKGROUND

There are few reports from Japan about the outcomes of intensity-modulated radiation therapy for localized prostate cancer. This study was aimed at assessing the efficacy and toxicity of intensity-modulated radiation therapy in patients with intermediate- or high-risk prostate cancer.

METHODS

We conducted a review of the data, retrieved from our institutional database, of patients who had received intensity-modulated radiation therapy for localized prostate cancer at a radiation dose of 78 Gy in 39 fractions. Data of 201 patients with intermediate-risk prostate cancer and 311 patients with high-risk prostate cancer were analyzed.

RESULTS

The median follow-up period after the completion of intensity-modulated radiation therapy was 100 months (range, 24-154). The rates of cause-specific survival, overall survival, metastasis-free survival and biochemical recurrence-free survival in the intermediate-risk patients were 99, 95, 95 and 94% at 5 years and 99, 91, 90 and 86% at 8 years, respectively; the corresponding rates in the high-risk patients were 100, 97, 91 and 84% at 5 years and 96, 92, 84 and 76% at 8 years, respectively. The crude incidence of late grade 2-3 genitourinary toxicity was 28.1%, and that of late grade 3 genitourinary toxicity was 2.0%. The crude incidence of late grade 2 gastrointestinal toxicity was 5.1%, and there were no cases of late grade 3 gastrointestinal toxicity.

CONCLUSIONS

Our data demonstrated that intensity-modulated radiation therapy is effective for patients with localized intermediate-risk or high-risk prostate cancer while having minimal toxicity.

Image quality evaluation of intra-irradiation cone-beam computed tomography acquired during one- and two-arc prostate volumetric-modulated arc therapy delivery: A phantom study

Purpose

To evaluate (a) the effects of megavoltage (MV)‐scatter on concurrent kilovoltage (kV) projections (P_MVkV) acquired during rotational delivery, and (b) the image quality of intra‐irradiation cone‐beam computed tomography (ii‐CBCT) images acquired during prostate volumetric‐modulated arc therapy (VMAT) delivery.

Methods

Experiment (1): P_MVkVs were acquired with various MV beam parameters using a cylindrical phantom: field size (FS), MV energy (6 or 15 MV), dose rate (DR), and gantry speed. The average pixel values were calculated in a region on each P_MVkV which were extracted at eight equally spaced gantry angles. Experiment (2): 11 one‐arc and seven two‐arc 15 MV prostate VMAT plans were used along with a pelvis phantom. One plan was selected from each of arc plans and its MV energy was changed to 6 MV. After P_MVkVs were acquired, projections consisting of MV‐scatter only (P_MVS) were acquired with closing kV blades and subtracted from P_MVkV (P_MVScorr). Projections by kV beams only were acquired (P_kV). The corresponding CBCT images were reconstructed (CBCT_MVkV, CBCT_MVScorr, and CBCT_kV). The root‐mean‐square errors (RMSEs) were calculated in prostate region and 3D gamma analysis was conducted, in which the CBCT‐number was used instead of doses between ii‐CBCT images and CBCT_kV (30 HU/1 mm).

Results

Experiment (1): The MV‐scatters were dependent on the FSs, MV energies, and DRs. Experiment (2): The median RMSEs for CBCT_MVScorr were decreased by 107.5 HU (1‐arc) and 42.9 HU (2‐arc) compared to those for CBCT_MVkV. The median GPRs for CBCT_MVScorr were 94.7% (1‐arc) and 93.4% (2‐arc), while those for CBCT_MVkV were 61.1% and 79.9%, respectively. GPRs for 6 MV plans were smaller than those for 15 MV plans.

Conclusions

The number of MV‐scatters increased with larger FSs and DRs, and smaller MV energy. The MV‐scatters were corrected on the CBCT_MVScorr regardless of the number of arcs.

Increased risk of disease progression in younger men: Analysis of factors predicting biochemical failure and castration-resistant prostate cancer after high-dose intensity-modulated radiation therapy for nonmetastatic prostate cancer

BACKGROUND

The aim of this study was to investigate the clinical significance of the effect of age on disease control in men who received high-dose intensity-modulated radiation therapy (IMRT) for nonmetastatic prostate cancer (NMPCa).

METHODS

NMPCa patients with favorable intermediate to very high-risk features (National Comprehensive Cancer Network risk classification) treated with IMRT at our institution between September 2000 and May 2011 were analyzed retrospectively. Treatment consisted of high-dose IMRT (74-78 Gy/37-39 fractions) combined with 6 months of neoadjuvant hormonal therapy. Multivariable analysis using Fine and Gray's regression model was performed to evaluate whether age at initiation of IMRT was associated with biochemical failure (BF) and castration-resistant prostate cancer (CRPC) progression.

RESULTS

A total of 367 patients were analyzed. The median follow-up period was 8.8 years after IMRT. The 5- and 10-year BF rates were 22.1 and 31.7%, and those of CRPC rates were 4.5 and 12.6%, respectively. Multivariable analysis revealed that a younger age (cut-off: 70 years old) at the initiation of IMRT was significantly correlated with both a higher BF rate (hazard ratio: 1.691, P= 0.0064) and higher CRPC rate (hazard ratio: 2.579, P = 0.0079).

CONCLUSIONS

Younger men with NMPCa had increased risks of BF and CRPC after high-dose IMRT, and may benefit from more intensive treatments. Our findings should be further tested in prospective studies.

Long-term clinical outcomes of salvage pelvic radiation therapy for oligo-recurrent pelvic lymph nodes after definitive external-beam radiation therapy for non-metastatic prostate cancer

Although salvage external-beam radiation therapy (EBRT) is an attractive treatment option for pelvic lymph nodal recurrence (PeNR) in patients with prostate cancer (PCa), limited data are available regarding its long-term efficacy. This study examined the long-term clinical outcomes of patients who underwent salvage pelvic radiation therapy (sPRT) for oligo-recurrent pelvic lymph nodes after definitive EBRT for non-metastatic PCa. Patients who developed PeNR after definitive EBRT and were subsequently treated with sPRT at our institution between November 2007 and December 2015 were retrospectively analyzed. The prescribed dose was 45-50.4 Gy (1.8-2 Gy per fraction) to the upper pelvis, with up to 54-66 Gy (1.8-2 Gy per fraction) for recurrent nodes. Long-term hormonal therapy was used as neoadjuvant and/or adjuvant therapy. The study population consisted of 12 consecutive patients with PeNR after definitive EBRT (median age: 73 years). The median follow-up period was 58.9 months. The 5-year overall survival, PCa-specific survival, biochemical failure-free, clinical failure-free, and castration-resistant PCa-free rates were 82.5, 100.0, 62.3, 81.8, and 81.8%, respectively. No grade 2 or higher sPRT-related late toxicities occurred. In conclusion, more than half of the study patients treated with sPRT had a long-term disease-free status with acceptable morbidities. Moreover, most of the patients maintained hormonal sensitivity. Therefore, this approach may be a promising treatment method for oligo-recurrent pelvic lymph nodes.