Six Questions to Ask Before We Shorten Radiation Treatments for Intact Prostate Cancer

Long-Term Analysis of NRG Oncology RTOG 0415: A Randomized Phase III Noninferiority Study Comparing Two Fractionation Schedules in Patients With Low-Risk Prostate Cancer

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.NRG Oncology RTOG 0415 is a randomized phase III noninferiority (NI) clinical trial comparing conventional fractionation (73.8 Gy in 41 fractions) radiotherapy (C-RT) with hypofractionation (H-RT; 70 Gy in 28) in patients with low-risk prostate cancer. The study included 1,092 protocol-eligible patients initially reported in 2016 with a median follow-up of 5.8 years. Updated results with median follow-up of 12.8 years are now presented. The estimated 12-year disease-free survival (DFS) is 56.1% (95% CI, 51.5 to 60.5) for C-RT and 61.8% (95% CI, 57.2 to 66.0) for H-RT. The DFS hazard ratio (H-RT/C-RT) is 0.85 (95% CI, 0.71 to 1.03), confirming NI (P < .001). Twelve-year cumulative incidence of biochemical failure (BF) was 17.0% (95% CI, 13.8 to 20.5) for C-RT and 9.9% (95% CI, 7.5 to 12.6) for H-RT. The HR (H-RT/C-RT) comparing biochemical recurrence between the two arms was 0.55 (95% CI, 0.39 to 0.78). Late grade ≥3 GI adverse event (AE) incidence is 3.2% (C-RT) versus 4.4% (H-RT), with relative risk (RR) for H-RT versus C-RT 1.39 (95% CI, 0.75 to 2.55). Late grade ≥3 genitourinary (GU) AE incidence is 3.4% (C-RT) versus 4.2% (H-RT), RR 1.26 (95% CI, 0.69 to 2.30). Long-term DFS is noninferior with H-RT compared with C-RT. BF is less with H-RT. No significant differences in late grade ≥3 GI/GU AEs were observed between assignments (ClinicalTrials.gov identifier: NCT00331773).

Hypofractionated, Dose Escalation Radiation Therapy for High-Risk Prostate Cancer: The Safety Analysis of the Prostate Cancer Study-5, a Groupe de Radio-Oncologie Génito-Urinaire de Quebec Led Phase 3 Trial

PURPOSE

The low α\β ratio of 1.2 to 2 for prostate cancer (PCa) suggests high radiation-fraction sensitivity and predicts a therapeutic advantage of hypofractionated (HF) radiation therapy (RT). To date, no phase 3 randomized clinical trial has compared moderately HF RT with standard fractionation (SF) exclusively in high-risk PCa patients. We are reporting the safety of moderate HF RT in high-risk PCa in an initially noninferiority-designed phase 3 clinical trial.

METHODS AND MATERIALS

From February 2012 to March 2015, 329 high-risk PCa patients were randomized to receive either SF or HF RT. All patients received neoadjuvant, concurrent, and long-term adjuvant androgen deprivation therapy. Standard fractionation RT consisted of 76 Gy in 2 Gy per fraction to the prostate, where 46 Gy was delivered to the pelvic lymph nodes. Hypofractionated RT included concomitant dose escalation of 68 Gy in 2.72 Gy per fraction to the prostate and 45 Gy in 1.8 Gy per fraction to the pelvic lymph nodes. The coprimary endpoints were acute and delayed toxicity at 6 and 24 months, respectively. The trial was originally designed as a noninferiority with a 5% absolute margin. Given the lower-than-expected toxicities in both arms, the noninferiority analysis was completely dropped.

RESULTS

Of the 329 patients, 164 were randomized to the HF and 165 to the SF arms. In total, there were more grade 1 or worse acute gastrointestinal (GI) events in the HF arm, 102 versus 83 events in the HF and SF arm, respectively (P = .016). This did not remain significant at 8 weeks of follow-up. There were no differences in grade 1 or worse acute GU events in the 2 arms, 105 versus 99 events in the HF and SF arm, respectively (P = .3). At 24 months, 12 patients in the SF arm and 15 patients in the HF arm had grade 2 or worse delayed GI-related adverse events (hazard ratio, 1.32; 95% CI, 0.62-2.83; P = .482). There were 11 patients in the SF arm and 3 patients in the HF arm with grade 2 or higher delayed genitourinary (GU) toxicities (hazard ratio, 0.26; 95% CI, 0.07-0.94; P = .037). There were 3 grade 3 GI and one grade 3 GU delayed toxicities in the HF arm and 3 grade 3 GU and no grade 3 GI toxicities in the SF arm. No grade 4-toxicities were reported.

CONCLUSIONS

This is the first study of moderate HF dose-escalated RT in exclusively high-risk patients with prostate cancer treated with long-term androgen deprivation therapy and pelvic RT. Although our data were not analyzed as a noninferiority, our results demonstrate that moderately HF RT is well-tolerated, similar to SF RT at 2 years, and could be considered an alternative to SF RT.

Consensus Quality Measures and Dose Constraints for Prostate Cancer From the Veterans Affairs Radiation Oncology Quality Surveillance Program and American Society for Radiation Oncology Expert Panel

PURPOSE

There are no agreed upon measures to comprehensively determine the quality of radiation oncology (RO) care delivered for prostate cancer. Consequently, it is difficult to assess the implementation of scientific advances and adherence to best practices in routine clinical practice. To address this need, the US Department of Veterans Affairs (VA) National Radiation Oncology Program established the VA Radiation Oncology Quality Surveillance (VA ROQS) Program to develop clinical quality measures to assess the quality of RO care delivered to Veterans with cancer. This article reports the prostate cancer consensus measures.

METHODS AND MATERIALS

The VA ROQS Program contracted with the American Society for Radiation Oncology to commission a Blue Ribbon Panel of prostate cancer experts to develop a set of evidence-based measures and performance expectations. From February to June 2021, the panel developed quality, aspirational, and surveillance measures for (1) initial consultation and workup, (2) simulation, treatment planning, and delivery, and (3) follow-up. Dose-volume histogram (DVH) constraints to be used as quality measures for definitive and post-prostatectomy radiation therapy were selected. The panel also identified the optimal Common Terminology Criteria for Adverse Events, version 5.0 (CTCAE V5.0), toxicity terms to assess in follow-up.

RESULTS

Eighteen prostate-specific measures were developed (13 quality, 2 aspirational, and 3 surveillance). DVH metrics tailored to conventional, moderately hypofractionated, and ultrahypofractionated regimens were identified. Decision trees to determine performance for each measure were developed. Eighteen CTCAE V5.0 terms were selected in the sexual, urinary, and gastrointestinal domains as highest priority for assessment during follow-up.

CONCLUSIONS

This set of measures and DVH constraints serves as a tool for assessing the comprehensive quality of RO care for prostate cancer. These measures will be used for ongoing quality surveillance and improvement among veterans receiving care across VA and community sites. These measures can also be applied to clinical settings outside of those serving veterans.

Driving quality improvement through better data: The story of New Zealand's radiation oncology collection

Aotearoa/New Zealand is one of the first nations in the world to develop a comprehensive, high-quality collection of radiation therapy data (the Radiation Oncology Collection, ROC) that is able to report on treatment delivery by health region, patient demographics and service provider. This has been guided by radiation therapy leaders, who have been instrumental in overseeing the establishment of clear and robust data definitions, a centralised database and outputs delivered via an online tool. In this paper, we detail the development of the ROC, provide examples of variation in practice identified from the ROC and how these changed over time, then consider the ramifications of the ROC in the wider context of cancer care quality improvement. In addition to a review of relevant literature, primary data were sourced from the ROC on radiation therapy provided nationally in New Zealand between 2017 and 2020. The total intervention rate, number of fractions and doses are reported for select cancers by way of examples of national variation in practice. Results from the ROC have highlighted areas of treatment variation and have prompted increased uptake of hypofractionation for curative prostate and breast cancer treatment and for palliation of bone metastases. Future development of the ROC will increase its use for quality improvement and ultimately link to a real time cancer services database.

Impact of superparamagnetic iron oxide nanoparticles on in vitro and in vivo radiosensitisation of cancer cells

PURPOSE

The recent implementation of MR-Linacs has highlighted theranostic opportunities of contrast agents in both imaging and radiotherapy. There is a lack of data exploring the potential of superparamagnetic iron oxide nanoparticles (SPIONs) as radiosensitisers. Through preclinical 225 kVp exposures, this study aimed to characterise the uptake and radiobiological effects of SPIONs in tumour cell models in vitro and to provide proof-of-principle application in a xenograft tumour model.

METHODS

SPIONs were also characterised to determine their hydrodynamic radius using dynamic light scattering and uptake was measured using ICP-MS in 6 cancer cell lines; H460, MiaPaCa2, DU145, MCF7, U87 and HEPG2. The impact of SPIONs on radiobiological response was determined by measuring DNA damage using 53BP1 immunofluorescence and cell survival. Sensitisation Enhancement Ratios (SERs) were compared with the predicted Dose Enhancement Ratios (DEFs) based on physical absorption estimations. In vivo efficacy was demonstrated using a subcutaneous H460 xenograft tumour model in SCID mice by following intra-tumoural injection of SPIONs.

RESULTS

The hydrodynamic radius was found to be between 110 and 130 nm, with evidence of being monodisperse in nature. SPIONs significantly increased DNA damage in all cell lines with the exception of U87 cells at a dose of 1 Gy, 1 h post-irradiation. Levels of DNA damage correlated with the cell survival, in which all cell lines except U87 cells showed an increased sensitivity (P < 0.05) in the linear quadratic curve fit for 1 h exposure to 23.5 μg/ml SPIONs. There was also a 30.1% increase in the number of DNA damage foci found for HEPG2 cells at 2 Gy. No strong correlation was found between SPION uptake and DNA damage at any dose, yet the biological consequences of SPIONs on radiosensitisation were found to be much greater, with SERs up to 1.28 ± 0.03, compared with predicted physical dose enhancement levels of 1.0001. In vivo, intra-tumoural injection of SPIONs combined with radiation showed significant tumour growth delay compared to animals treated with radiation or SPIONs alone (P < 0.05).

CONCLUSIONS

SPIONs showed radiosensitising effects in 5 out of 6 cancer cell lines. No correlation was found between the cell-specific uptake of SPIONs into the cells and DNA damage levels. The in vivo study found a significant decrease in the tumour growth rate.

Laparoscopic closure of the pouch of Douglas by a peritoneal running suture. A minimally invasive and prosthetic-free technique to prevent excessive dose delivery to the small bowel during pelvic irradiation for prostate cancer

BACKGROUND AND PURPOSE

Prostate radiotherapy relies on the delivery of high doses that can be obstructed when a small bowel loop descends in the pelvis. We present a laparoscopic minimally invasive prosthetic-free technique closing the Douglas' pouch with a peritoneal running suture to cordon off the bowel from the pelvis and hence allow optimal irradiation.

MATERIALS AND METHODS

Prostate cancer patients referred for radiotherapy and whose planning-CT revealed a bowel loop trapped in the pelvis were proposed the procedure, followed by a new planning-CT. This proof-of-concept study reports postoperative follow-up and dosimetric benefits.

RESULTS

The procedure was performed in ten patients (2016-2020) as a same-day surgery for nine. Median operative time was 34 min (range 22-50) and no relevant intraoperative complication occurred. The third patient of the series presented a small bowel hernia through the peritoneal suture at the 15th postoperative day requiring a laparotomic desincarceration without major consequences. Regarding the small bowel, median D1cc (dose to 1 cc) was 65.5 Gy and 55.5 Gy (p = 0.005) before and after procedure. Median V60 (volume receiving ≥60 Gy) was 10.2 cc and 0.0 cc (p = 0.005). In the immediate vicinity of the small bowel (5 mm), median D1cc was 68.3 Gy and 57.7 Gy (p = 0.005). Radiotherapy was safely delivered to all patients.

CONCLUSION

Laparoscopic closure of the Douglas' pouch by a peritoneal suture is an efficient technique to cordon off inconvenient ectopic small bowel loops. It prevents excessive bowel irradiation and hence facilitates curative prostate radiotherapy. The technique could be applied to other pelvic malignancies.

Imputing radiobiological parameters of the linear-quadratic dose-response model from a radiotherapy fractionation plan

The objective in cancer radiotherapy is to maximize tumor-kill while limiting toxic effects of radiation dose on nearby organs-at-risk (OAR). Given a fixed number of treatment sessions, planners thus face the problem of finding a dosing sequence that achieves this goal. This is called the fractionation problem, and has received steady attention over a long history in the clinical literature. Mathematical formulations of the resulting optimization problem utilize the linear-quadratic (LQ) framework to characterize radiation dose-response of tumors and OAR. This yields a nonconvex quadratically constrained quadratic program. The optimal dosing plan in this forward problem crucially depends on the parameters of the LQ model. Unfortunately, these parameters are difficult to estimate via in vitro or in vivo studies, and as such, their values are unknown to treatment planners. The clinical literature is thus replete with debates about what parameter values will make specific dosing plans effective. This paper formulates this as an inverse optimization problem. The LQ dose-response parameters appear in the objective function, the left hand side, and the right hand side of the forward problem, and none of the existing generic methods can provide an exact solution of the inverse problem. This paper exploits the structure of the problem and identifies all possible parameter values that render the given dosing plan optimal, in closed-form. This closed-form formula is applied to dosing-plans from three clinical studies published within the last two years.

Quality of Life in Patients With Low-Risk Prostate Cancer Treated With Hypofractionated vs Conventional Radiotherapy: A Phase 3 Randomized Clinical Trial

IMPORTANCE

Hypofractionated radiotherapy (HRT) would be more convenient for men with low-risk prostate cancer and cost less than conventional radiotherapy (CRT) as long as HRT is noninferior to CRT in terms of survival and quality of life (QOL) is not found to be worse.

OBJECTIVE

To assess differences in QOL between men with low-risk prostate cancer who are treated with HRT vs CRT.

DESIGN, SETTING, AND PARTICIPANTS

In this phase 3 randomized clinical trial, men with low-risk prostate cancer were enrolled from sites within the National Cancer Institute's National Clinical Trials Network in the United States, Canada, and Switzerland.

INTERVENTIONS

Random assignment to CRT (73.8 Gy in 41 fractions over 8.2 weeks) or to HRT (70 Gy in 28 fractions over 5.6 weeks).

MAIN OUTCOMES AND MEASURES

Quality of life was assessed using the Expanded Prostate Index Composite questionnaire measuring bowel, urinary, sexual, and hormonal domains; the 25-item Hopkins Symptom Checklist measuring anxiety and depression; and the EuroQol-5 Dimension questionnaire measuring global QOL. All data were collected at baseline and 6, 12, 24, and 60 months. Change scores were compared between treatment arms using the Wilcoxon signed rank test. A significance level of .0125 to adjust for multiple comparisons was used for an overall 2-sided type 1 error of .05. Clinical significance was determined for the Expanded Prostate Index Composite change scores by an effect size of 0.5.

RESULTS

Of 1092 patients analyzable for the primary end point, 962 (mean [SD] age, 66.6 [7.4] years) consented to the QOL component. No statistically significant differences with regard to baseline characteristics nor any of the QOL baseline domains were measured between arms. There were no differences in change score between arms with respect to any of the Expanded Prostate Index Composite questionnaire domain scores except at 12 months when the HRT arm had a larger decline than the CRT arm in the bowel domain (mean score, -7.5 vs -3.7, respectively; P<.001), but it did not reach clinical significance (effect size = 0.29). There were no differences between arms at any time point for the Hopkins Symptom Checklist nor EuroQol-5 Dimension questionnaire.

CONCLUSIONS AND RELEVANCE

Treatment with HRT is noninferior to CRT in men with low-risk prostate cancer in terms of disease-free survival and, as shown in the present study, in prostate cancer-specific (eg, bowel, bladder, sexual) and general QOL, as well as in anxiety and depression. This study provides evidence to affirm that HRT is a practice standard for men with low-risk prostate cancer.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00331773.

Moderate hypofractionation for prostate cancer: A user's guide

Three large randomised controlled trials have been published in the last year demonstrating the non-inferiority of moderate hypofractionation compared to conventional fractionation for localised prostate cancer with respect to both disease control and late toxicity at 5 years. Furthermore, no clinically significant differences in patient-reported outcomes have emerged. More mature follow-up data are now also available from phase 2 studies confirming that moderate hypofractionation is associated with low rates of significant toxicity at 10 years. Moving forward it is likely that appropriate patient selection, integration of androgen deprivation and attention to optimising technique will play a more important role than modest differences in dose-fractionation schedules. Here we briefly review the evidence, discuss issues of patient selection and provide an approach to implementing moderately hypofractionated radiation therapy for prostate cancer in clinical practice.

Conventional Versus Hypofractionated Radiation Therapy for Localized Prostate Cancer: A Meta-analysis of Randomized Noninferiority Trials

CONTEXT

Whether hypofractionated radiation therapy (RT) compared with conventionally fractionated RT provides comparable or possibly improved cancer control without increased toxicity in localized prostate cancer (PC) remains unknown.

OBJECTIVE

Realizing from the CHHiP trial that outcomes are highly sensitive to the dose fractionation schedule and number of treatments, we conducted a systematic review and meta-analysis selecting only the randomized noninferiority trials, because the randomized arms closely approximated one another in terms of the dose fractionation schedule, and compared cancer control and toxicity of hypofractionated RT with conventionally fractionated RT for localized PC.

EVIDENCE ACQUISITION

Randomized noninferiority trials evaluating hypofractionated (2.4-4Gy daily fractions for 15-30 treatments) versus conventionally fractionated RT (1.8-2Gy daily fractions for 40-45 treatments) in men with localized PC were selected. Studies that were not noninferiority trials, used extreme hypofractionation, or treated metastatic disease were excluded. Three studies were retained for analysis. Data were pooled using a random-effects model to determine hazard ratio (HR) and risk ratio (RR). Heterogeneity was assessed via chi-square test, I² statistics, and metaregression. The primary outcome was disease-free survival (DFS), defined as death from any cause or biochemical, local, regional, or distant progression.

EVIDENCE SYNTHESIS

Of the 5484 men, 3553 (64.8%) had intermediate-risk PC. Hypofractionated RT as compared with conventionally fractionated RT was associated with significantly improved DFS (HR 0.869; 95% confidence interval [CI], 0.757, 0.998; p=0.047), whereas overall survival was not (HR 0.84; 95% CI, 0.66, 1.07; p=0.16). Acute grade 2 or higher gastrointestinal toxicity was significantly increased with hypofractionation (RR 1.42; 95% CI 1.15, 1.77; p=0.002); however, this did not translate into late grade 2 or higher gastrointestinal toxicity. An increase in late grade 2 or higher genitourinary complications was observed (RR 1.18; 95% CI 0.98, 1.43; p=0.08).

CONCLUSIONS

Hypofractionated RT as compared with conventionally fractionated RT could improve DFS in men with intermediate-risk PC and, therefore, would be reasonable to consider in men who do not have risk factors for late genitourinary complications.

PATIENT SUMMARY

Treatment with a shorter course of radiation, using higher doses per treatment over fewer days, may be the preferred approach in appropriately selected patients with localized prostate cancer.

Conventional Versus Hypofractionated Radiation Therapy for Localized or Locally Advanced Prostate Cancer: A Systematic Review and Meta-analysis along with Therapeutic Implications

PURPOSE

A systematic review and meta-analysis were conducted to evaluate the therapeutic outcomes of conventional radiation therapy (CRT) and hypofractionated radiation therapy (HRT) for localized or locally advanced prostate cancer (LLPCa).

METHODS AND MATERIALS

A total of 599 abstracts were extracted from 5 databases and screened in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Only phase III trials randomized between CRT and HRT in LLPCa with a minimum of 5 years of follow-up data were considered. The evaluated endpoints were biochemical failure, biochemical and/or clinical failure, overall mortality, prostate cancer-specific mortality, and both acute and late gastrointestinal (GI) and genitourinary (GU) (grade ≥2) toxicity.

RESULTS

Ten trials from 9 studies, with a total of 8146 patients (CRT, 3520; HRT, 4626; 1 study compared 2 HRT schedules with a common CRT regimen), were included in the evaluation. No significant differences were found in the patient characteristics between the 2 arms. However, the RT parameters differed significantly between CRT and HRT (P<.001 for all). The use of androgen deprivation therapy varied from 0% to 100% in both groups (mean ± standard deviation 43.3% ± 43.6% for CRT vs HRT; P=NS). The odds ratio, risk ratio, and risk difference (RD) between CRT and HRT for biochemical failure, biochemical and/or clinical failure, overall mortality, prostate cancer-specific mortality, acute GU toxicity, and late GU and GI toxicities were all nonsignificant. Nevertheless, the incidence of acute GI toxicity was 9.1% less with CRT (RD 0.091; odds ratio 1.687; risk ratio 1.470; P<.001 for all). On subgroup analysis, the patient groups with ≤66.8% versus >66.8% androgen deprivation therapy (RD 0.052 vs 0.136; P=.008) and <76% versus ≥76% full seminal vesicles in the clinical target volume (RD 0.034 vs 0.108; P<.001) were found to significantly influence the incidence of acute GI toxicity with HRT.

CONCLUSIONS

HRT provides similar therapeutic outcomes to CRT in LLPCa, except for a significantly greater risk of acute GI toxicity. HRT enables a reduction in the overall treatment time and offers patient convenience. However, the variables contributing to an increased risk of acute GI toxicity require careful consideration.

Extreme hypofractionation for high-risk prostate cancer: Dosimetric correlations with rectal bleeding

PURPOSE

We explored the association of dosimetric parameters with late rectal bleeding among high-risk prostate cancer patients treated with hypofractionated simultaneous in-field boost (H-SIB) to prostate with nodal treatment.

METHODS AND MATERIALS

Rectal toxicity results and dose-volume histogram (DVH) information from patients treated on FASTR and SATURN were combined. Patients in both trials received long-term androgen deprivation and H-SIB with prescription dose 40 Gy to the prostate and proximal seminal vesicles and 25 Gy to the lymph nodes delivered over 5 weekly fractions using image guidance with cone beam computed tomography. Mean rectal DVH values at 5-Gy intervals and mean DVH curves were compared between patients with rectal bleeding (B) versus no bleeding (NB).

RESULTS

There were 12 B and 33 NB patients in the pooled group. Rectal bleeding was more frequent and of higher grade among FASTR patients (8/15, 5 grade 2 or higher) than among SATURN patients (4/30, all grade 1). For any bleeding (grade ≥1), individual dose-volume points in the 20 to 40 Gy range were significantly different (2-sided P < .05) between the B and NB groups, with the 40 Gy point being the most significant (B: V40 = 1.53%, standard deviation (SD), 1.32; NB: V40 = 0.69%, SD, 1.46; P = .006). For grade ≥2 bleeding, the V20 Gy was most significant (B: 68.4%, SD, 4.76; NB: 40.45%, SD, 13.9; P < .001).

CONCLUSIONS

The higher relative dose volumes to the rectum (V20-V40) were most strongly associated with clinically significant bleeding in this analysis and are consistent with findings of series that used H-SIB to treat prostate only. Differences in the prostate target volumes and planning margins likely account for the differences in the rates and grades of rectal bleeding observed between trials.