The impact of androgen deprivation therapy on setup errors during external beam radiation therapy for prostate cancer

The effect of dose-escalation radiotherapy with simultaneous-integrated-boost on the use of short-term androgen deprivation therapy in patients with intermediate risk prostate cancer

PURPOSE

To compare the biochemical failure (FFBF) and prostate cancer specific survival (PCSS) rates of patients with intermediate-risk prostate cancer (IR-PC) who were treated with 6 months of androgen deprivation therapy (ADT) with 78 Gy to the prostate, those treated with ADT and focal boost (FB) of 86 Gy to intraprostatic lesion (IPL) using the simultaneous-integrated boost (SIB) technique, and those treated with SIB alone.

MATERIALS AND METHODS

A retrospective analysis of 320 IR-PC patients treated between January 2012 and April 2021 was performed. Patients were divided into three groups based on their treatment arm: 78 + ADT (109 patients, 34.1%), 78/86 (102 patients, 31.8%), and 78/86 + ADT. Univariable and multivariable analyses were used to determine prognostic factors for FFBF and PCSS.

RESULTS

Median follow-up was 8.8 years. The 8-year FFBF and PCSS rates were 88.6% and 99.0%. Patients who received ADT had significantly higher pretreatment PSA levels and clinical tumor stage. Disease progression occurred in 45 patients (7.3%) at a median of 41.9 months after definitive radiotherapy (RT). Younger age, positive core biopsy (PCB) ≥ 50%, and the absence of ADT were all independent predictors of poor FFBF in multivariate analysis, whereas patients with PCB < 50% who were also given ADT had better PCSS. Patients treated with 78/86 Gy alone had worse FFBF than those treated with 78 Gy and ADT (Hazard ratio [HR] = 3.39 [95% CI = 1.46-7.88]; p = 0.005), as well as than those treated with 78/86 Gy and ADT (HR = 3.21 [95% CI = 1.23-6.46]; p = 0.009). However, FB to IPL has no effect on PCSS in multivariable analysis. There was no significant difference between treatment groups in terms of acute and late Grade ≥2 genitourinary or gastrointestinal toxicity.

CONCLUSIONS

Our findings demonstrated that patients who received 78/86 alone did worse than patients who received ADT with either 78 or 78/86 Gy. However, because IR-PC patients are so diverse, additional prospective trials are needed to validate our findings.

The impact of margin reduction on radiation dose distribution of ultra-hypofractionated prostate radiotherapy utilizing a 1.5-T MR-Linac

BACKGROUND

We examined the effects of reducing the planning target volume (PTV) margin in MR-guided radiotherapy (MRgRT) on the distribution of radiation dose to target volumes and organs-at-risk (OARs). Thus, we compared MR-Linac (MRL) plans with and without reduced margin and intensity-modulated radiotherapy (IMRT) plan with conventional linac for low-risk prostate cancer patients receiving 36.25 Gy in five fractions of ultra-hypofractionated radiation therapy.

MATERIALS AND METHODS

Twenty low-risk prostate cancer patients treated with 1.5 T MR-Linac were evaluated. The same planning CT images were used for four plans: the MRL-R plan with reduced margin planning target volume (PTV-R) and the MRL-N plan with normal margin PTV (PTV-N), which is also used for IMRT plan. In four plans, PTV doses, organs-at-risk (OARs) doses, the homogeneity index (HI), and monitor units were compared.

RESULTS

All plans met the criteria for PTV coverage and OARs dose constraints. The maximum and mean PTV doses were significantly higher in the MRL-R and MRL-N plans compared to the IMRT plan. The HI was lowest in the IMRT plan (0.040 ± 0.013) and highest in the MRL-N plan (0.055 ± 0.012; p < 0.001). There was no significant difference in the PTV dosimetric parameters between the MRL-R and the MRL-N plans. The high doses in the rectum was significantly lower in the MRL-R compared to other plans. The bladder V36.25 Gy was significantly lower in the MRL-R plan (2.43 ± 1.87 Gy) compared to MRL-N (4.50 ± 2.42 Gy; p < 0.001), and IMRT plans (4.76 ± 2.77 Gy; p < 0.001). There was no significant difference in the low-dose volumes of the body, maximum femur doses, or monitor units across each plan.

CONCLUSIONS

Ultra-hypofractionated MR-guided RT with 1.5 T MRL is dosimetrically feasible for patients with prostate cancer. The improved soft tissue contrast and the online adaptive plan for 1.5 T MR-Linac allows for PTV margin reduction resulted in a significant dose reduction in OARs.

Treatment outcomes of simultaneous integrated boost to intraprostatic lesions with external beam radiotherapy in localized prostate cancer patients

BACKGROUND

To evaluate the treatment outcomes and toxicity of definitive radiotherapy (RT) for prostate cancer (PC) patients using the simultaneous integrated boost (SIB) technique, which delivered 78 Gy to the entire prostate and 86 Gy to the intraprostatic lesion (IPL) in 39 fractions.

MATERIALS AND METHODS

Univariable and multivariable analyses were conducted of the prognostic factors for freedom from biochemical failure (FFBF), progression-free survival (PFS), and PC-specific survival (PCSS) of 619 PC patients who received definitive RT between September 2012 and August 2021. Predictors of late Grade ≥2 genitourinary (GU) and gastrointestinal (GI) toxicities were also identified using logistic regression.

RESULTS

The median follow-up for entire cohort was 68.5 months. The 5-year FFBF, PFS, and PCSS rates were 93.2%, 83.2%, and 98.6%, respectively. They were predicted by the serum prostate-specific antigen, Gleason score (GS), clinical nodal stage, and D'Amico risk group. Only 45 patients (7.3%) developed disease recurrence 41.9 months after RT. The 5-year FFBF rates for low-, intermediate-, and high-risk disease were 98.0%, 93.1%, and 88.5%, respectively (p < 0.001). The 5-year PFS and PCSS rates according to risk groups were 91.0%, 82.1%, and 77.4% (p < 0.001), and 99.2%, 96.4%, and 95.9% (p = 0.03), and, respectively. GS > 7 and lymph node metastasis negatively predicted FFBF and PCSS in multivariable analysis. Ninety (14.6%) and 44 (7.1%) patients had acute Grade ≥2 GU and GI toxicities, respectively, and 42 (6.8%) and 27 (4.4%) patients had late Grade ≥2 GU and GI toxicities, respectively. Diabetes and transurethral resection independently predicted late Grade 2 GU toxicity, but no significant predictor of late Grade ≥2 GI toxicity was found.

CONCLUSIONS

Localized PC was effectively and safely treated with definitive RT using the SIB technique to deliver 86 Gy to the IPL in 39 fractions without severe late toxicity. This finding must be validated with long-term results.

The impact of the apparent diffusion coefficient for the early prediction of the treatment response after definitive radiotherapy in prostate cancer patients

PURPOSE

We assessed early changes in apparent diffusion coefficient (ADC) and serum prostate specific antigen (PSA) values after definitive radiotherapy (RT) without androgen deprivation treatment in low- and intermediate-risk prostate cancer (PC) patients.

MATERIALS AND METHODS

The clinical data and ADC parameters of 229 PC patients were retrospectively evaluated. Pre-treatment and post-treatment serum PSA and primary tumor ADC values were calculated. Post-treatment DW-MRI was performed median 4.1 months after completion of definitive RT. The prognostic factors predicting freedom from biochemical failure (FFBF) and progression-free survival (PFS) were analyzed using univariable and multivariable analyses.

RESULTS

With a median follow-up time of 80.8 months, the 5-year FFBF and PFS rates were 95.9% and 89.3%, respectively. Eleven patients (4.8%) had PSA relapse, with a median of 34.4 months after the completion of RT. A statistically significant difference in post-treatment ADC values was noted between patients with and without recurrence (0.94 ± 0.07 vs. 1.10 ± 0.20 × 10^-3 mm²/sec; p < 0.001). Patients with a Gleason score (GS) of 6 and low-risk disease had significantly higher post-treatment tumor ADC and PSA levels than patients with a GS of 7 and intermediate-risk disease. The 5-year FFBF rate in patients with tumor ADC ≤ 0.96 × 10^-3 mm²/sec was significantly lower than patients with tumor ADC > 0.96 × 10^-3 mm²/sec (85.5% vs. 100; p < 0.001). In the multivariable analysis, a lower ADC value, GS 4 + 3 and intermediate-risk disease were independent predictors of worse FFBF. In the multivariate analysis, a lower post-treatment ADC value and a GS of 4+3 were significant prognostic factors for a lower PFS.

CONCLUSION

These findings suggest that the post-treatment tumor ADC value could be used for early treatment response evaluation after definitive RT in PC patients.

The prognostic value of mean apparent diffusion coefficient measured with diffusion-weighted magnetic resonance image in patients with prostate cancer treated with definitive radiotherapy

PURPOSE

To assess the correlation between initial tumor apparent diffusion coefficient (ADC) values and clinicopathological parameters in prostate cancer (PCa) patients treated with definitive radiotherapy (RT). Additionally, the prognostic factors for freedom from biochemical failure (FFBF) and progression-free survival (PFS) in this patient cohort were analyzed.

MATERIALS AND METHODS

The clinical data of 503 patients with biopsy-confirmed PCa were evaluated retrospectively. All patients had clearly evident tumors on diffusion-weighted magnetic resonance imaging (DW-MRI) for ADC values. Univariable and multivariable analyses were used to determine prognostic factors for FFBF and PFS.

RESULTS

The median follow-up was 72.9 months. The 5-year FFBF and PFS rates were 93.2% and 86.2%, respectively. Significantly lower ADC values were found in patients with a high PSA level; advanced clinical stage; higher ISUP score, and higher risk group than their counterparts. Receiver operating characteristic (ROC) curve analysis revealed an ADC cut-off value of 0.737 × 10^-3 mm²/sec for tumor recurrence. Patients who progressed had a lower mean ADC value than those who did not (0.712±0.158 vs. 1.365±0.227 × 10^-3 mm²/sec; p<0.001). There was a significant difference in 5-year FFBF (96.3% vs. 90%; p<0.001) and PFSrates (83.8% vs. 73.5%; p=0.002) between patients with higher and lower mean ADC values. The FFBF and PFS were found to be correlated with tumor ADC value and ISUP grades in multivariable analysis. Additionally, older age was found to be a significant predictor of worse PFS.

CONCLUSIONS

Lower ADC values were found in patients with high-risk characteristics such as a high serum PSA level, stage or grade of tumor, or high-risk disease, implying that ADC values could be used to predict prognosis. Lower ADC values and higher ISUP grades were associated with an increased risk of BF and progression, implying that treatment intensification may be required in these patients.