Image guided intensity modulated hypofractionated radiotherapy in high-risk prostate cancer patients treated four or five times per week: analysis of toxicity and preliminary results

Acute and late toxicity patterns of moderate hypo-fractionated radiotherapy for prostate cancer: a systematic review and meta-analysis

Introduction

Moderate hypofractionated (HF) radiotherapy is becoming the new standard in radiotherapy for prostate cancer patients. It is established as safe, but it might be associated with increased acute toxicity levels. We conducted a systematic review on moderate HF to establish acute toxicity levels and their required clinical management; late toxicity was reported as a secondary outcome.

Material and methods

Using PRISMA guidelines, we conducted a systematic review for studies published until June 2022. We identified 17 prospective studies, with 7796 localised prostate cancer patients, reporting acute toxicity of moderate hypofractionation (2.5-3.4 Gy/fraction). A meta-analysis was done for 10/17 studies with a control arm (standard fractionation (SF)), including evaluation of late toxicity rates. We used Cochrane bias assessment and Newcastle-Ottawa bias assessment tools for randomized controlled trials (RCTs) RCT and non-RCTs, respectively.

Results

Pooled results showed that acute grade ≥ 2 gastro-intestinal (GI) toxicity was increased by 6.3 % (95 % CI for risk difference = 2.0 %-10.6 %) for HF vs SF. Acute grade ≥ 2 Genito-urinary (GU) and late toxicity were not significantly increased. The overall risk of bias assessment revealed a low risk in the meta-analysis of included studies. Data on management of toxicity (medication, interventions) was only reported in 2/17 studies.

Conclusion

HF is associated with increased acute GI symptoms, needing adequate monitoring and management. Reports on toxicity management were very limited. Pooled late GI and GU toxicity showed similar levels for SF and HF.

"Meta-analysis of elective pelvic nodal irradiation using moderate hypofractionation for high-risk prostate cancer" (MENHYP-ENI)

OBJECTIVES

Despite several advances in planning and delivery of radiotherapy (RT) for prostate cancer, the role of elective pelvic nodal irradiation (EPNI) remains controversial for high-risk disease. We performed a meta-analysis to evaluate the outcomes of patients treated with moderate hypofractionated RT (MHF-RT) with EPNI using modern radiotherapy techniques.

METHODS

Eligible studies were identified on Medline, Embase, the Cochrane Library, and proceedings of annual meetings through October 2021. We followed the PRISMA and MOOSE guidelines. A meta-regression analysis was performed to assess a possible correlation between selected variables and outcomes. A p-value <0.05 was considered significant.

RESULTS

Eighteen studies with a total of 1745 patients, median follow-up 61 months, treated with EPNI employing MHF-RT were included. The biochemical relapse-free survival (bRFS) at 5-, 7- and 10-year was 90% (95% CI 88-94%), 83% (95%CI 78-91%) and 78% (95%CI 68-88%). The 5-year prostate cancer-specific survival, disease-free survival, distant metastases-free survival and overall survival were 98% (95%CI 97-99%), 88.7% (95%CI 85-93%), 91.2% (95%CI 88-92%), and 93% (95%CI 90-96%), respectively. The rates of local, pelvic, and distant recurrence were 0.38% (95%CI 0-2%), 0.13% (95%CI 0-1.5%), and 7.35% (95%CI 2-12%), respectively. The rate of late GI and GU toxicity grade ≥ 2 were 6.7% (95%CI 4-9%), and 11.3% (95%CI 7.6-15%), with heterogeneity, but with rare cases of toxicity grade 3-5.

CONCLUSION

EPNI with concomitant MHF-RT provides satisfactory bRFS in the long-term follow-up, with low rates of GU and GI severe toxicities and minimal pelvic and local failure.

Technical Note: Three-dimensional QA of simultaneous integrated boost radiotherapy treatments by a dose-volume histogram methodology and its comparison with 3D gamma results

PURPOSE

Intensity-modulated radiotherapy with simultaneous integrated boost (SIB) presents several attractive advantages to be employed in clinical practice. Its secure application demands a rigorous quality assurance (QA) procedure, ideal for three-dimensional (3D) dose distribution measurements. Thus, a gel dosimetry methodology to evaluate the dose delivery of SIB treatments is presented and compared to conventional gamma evaluation.

METHODS

MAGIC-f gel dosimeter with magnetic resonance images for dose reading were used following its standard procedures. Four SIB QA plans created in gel dosimeter phantoms were used. The gel measured and treatment planning system (TPS) calculated doses were compared using 3D gamma analyses (3%/3mm/15% threshold). Two structures were artificially on the TPS dose distribution expected on the phantom by converting the 1.7 and 2.0 Gy isodose levels into structures to represent the treatment. The gel and TPS dose-volume histogram (DVH) were compared based on five dose points: D95%, D90%, D50%, D10%, and D5%.

RESULTS

Approvals of 93%, 96%, 98%, and 92% were achieved in the 3D gamma analyses for the plans QA 1, 2, 3, and 4. In the DVH analyses, QA plan 1 measured and expected curves showed a good agreement. QA plan 2 showed deviations in the highest doses for both structures with a maximum deviation (Δ_máx ) of 8.0%. QA plans 3 and 4 showed the highest dose variation between the gel and TPS in the smaller doses of the DVH (Δ_máx of 7.2% and -8.9%, respectively). For QA plan 4, the curves of the 1.7 Gy structure presented a good agreement, but deviations in the smaller dose region of the DVH occurred for the 2 Gy structure (Δ_máx of 7.7%).

CONCLUSIONS

A methodology for 3D dose evaluation of complex SIB treatments was proposed. It provided an important overview of the dose distributions. Their results significantly complemented the usual gamma analysis results.

Elective Pelvic Nodal Irradiation With a Simultaneous Hypofractionated Integrated Prostate Boost for Localised Prostate Cancer: Ready for Prime Time?

External beam radiotherapy is a standard treatment option for localised prostate cancer and hypofractionation has become an alternative to conventionally fractionated radiotherapy. In patients who receive external beam radiotherapy, elective pelvic nodal irradiation is sometimes delivered, especially in patients with unfavourable disease who are at risk of micrometastatic spread of cancer into the regional nodes. One elegant approach to combine prostate hypofractionation with elective pelvic nodal irradiation is with a simultaneous integrated boost technique, where a radical hypofractionated dose is delivered to the prostate while the regional pelvic nodes receive a lower microscopic dose simultaneously in a single radiotherapy plan over the same number of treatment fractions. This article reviews the existing published literature evaluating such an approach.

Variations in dosimetric distribution and plan complexity with collimator angles in hypofractionated volumetric arc radiotherapy for treating prostate cancer

Purpose

Hypofractionated radiotherapy can reduce treatment durations and produce effects identical to those of conventionally fractionated radiotherapy for treating prostate cancer. Volumetric arc radiotherapy (VMAT) can decrease the treatment machine monitor units (MUs). Previous studies have shown that VMAT with multileaf collimator (MLC) rotation exhibits better target dose distribution. Thus, VMAT with MLC rotation warrants further investigation.

Methods and materials

Ten patients with prostate cancer were included in this study. The prostate gland and seminal vesicle received 68.75 and 55 Gy, respectively, in 25 fractions. A dual‐arc VMAT plan with a collimator angle of 0° was generated and the same constraints were used to reoptimize VMAT plans with different collimator angles. The conformity index (CI), homogeneity index (HI), gradient index (GI), normalized dose contrast (NDC), MU, and modulation complexity score (MCS_V) of the target were analyzed. The dose–volume histogram of the adjacent organs was analyzed. A Wilcoxon signed‐rank test was used to compare different collimator angles.

Results

Optimum values of CI, HI, and MCS_V were obtained with a collimator angle of 45°. The optimum values of GI, and NDC were observed with a collimator angle of 0°. In the rectum, the highest values of maximum dose and volume receiving 60 Gy (V_60 Gy) were obtained with a collimator angle of 0°, and the lowest value of mean dose (D_mean) was obtained with a collimator angle of 45°. In the bladder, high values of D_mean were obtained with collimator angles of 75° and 90°. In the rectum and bladder, the values of V_60 Gy obtained with the other tested angles were not significantly higher than those obtained with an angle of 0°.

Conclusion

This study found that MLC rotation affects VMAT plan complexity and dosimetric distribution. A collimator angle of 45° exhibited the optimal values of CI, HI, and MCSv among all the tested collimator angles. Late side effects of the rectum and bladder are associated with high‐dose volumes by previous studies. MLC rotation did not have statistically significantly higher values of V_60 Gy in the rectum and bladder than did the 0° angle. We thought a collimator angle of 45° was an optimal angle for the prostate VMAT treatment plan. The findings can serve as a guide for collimator angle selection in prostate hypofractionated VMAT planning.

Predicting toxicity in radiotherapy for prostate cancer

This comprehensive review addresses most organs at risk involved in planning optimization for prostate cancer. It can be considered an update of a previous educational review that was published in 2009 (Fiorino et al., 2009). The literature was reviewed based on PubMed and MEDLINE database searches (from January 2009 up to September 2015), including papers in press; for each section/subsection, key title words were used and possibly combined with other more general key-words (such as radiotherapy, dose-volume effects, NTCP, DVH, and predictive model). Publications generally dealing with toxicity without any association with dose-volume effects or correlations with clinical risk factors were disregarded, being outside the aim of the review. A focus was on external beam radiotherapy, including post-prostatectomy, with conventional fractionation or moderate hypofractionation (<4Gy/fraction); extreme hypofractionation is the topic of another paper in this special issue. Gastrointestinal and urinary toxicity are the most investigated endpoints, with quantitative data published in the last 5years suggesting both a dose-response relationship and the existence of a number of clinical/patient related risk factors acting as dose-response modifiers. Some results on erectile dysfunction, bowel toxicity and hematological toxicity are also presented.

Intra-fraction motion of the prostate is not increased by patient couch shifts

BACKGROUND

During a fraction of external beam radiotherapy for prostate cancer, a mismatch between target volume and dose coverage may accumulate over time due to intra-fraction motion. One way to remove the residual error is to perform a couch shift in opposite direction. In principle, such couch shifts could cause secondary displacements of the patient and prostate. Hence it is interesting to investigate if couch shifts might amplify intra-fraction motion.

FINDINGS

Intra-fraction motion of the prostate and patient couch position were simultaneously recorded during 359 fractions in 15 patients. During this time, a total of 22 couch shifts of up to 31.5 mm along different axes were recorded. Prostate position and couch position were plotted before, during and after each couch shift. There was no visible impact of couch shifts on prostate motion. The standard deviation of prostate position was calculated before, during and after each couch shift. The standard deviation did not significantly increase during couch shifts (by 3 % on average, p = 0.88) and even slightly decreased after a couch shift (by 37 % on average; p = 0.02).

CONCLUSIONS

Shifts of the patient couch did not adversely affect the motion of the prostate relative to the patient couch. Hence, shifts of the patient couch may be a viable way to correct the position of the prostate relative to the dose distribution.