Hypofractionation for prostate cancer radiotherapy--what are the issues?

AAPM Task Group Report 267: A joint AAPM GEC-ESTRO report on biophysical models and tools for the planning and evaluation of brachytherapy

Brachytherapy utilizes a multitude of radioactive sources and treatment techniques that often exhibit widely different spatial and temporal dose delivery patterns. Biophysical models, capable of modeling the key interacting effects of dose delivery patterns with the underlying cellular processes of the irradiated tissues, can be a potentially useful tool for elucidating the radiobiological effects of complex brachytherapy dose delivery patterns and for comparing their relative clinical effectiveness. While the biophysical models have been used largely in research settings by experts, it has also been used increasingly by clinical medical physicists over the last two decades. A good understanding of the potentials and limitations of the biophysical models and their intended use is critically important in the widespread use of these models. To facilitate meaningful and consistent use of biophysical models in brachytherapy, Task Group 267 (TG-267) was formed jointly with the American Association of Physics in Medicine (AAPM) and The Groupe Européen de Curiethérapie and the European Society for Radiotherapy & Oncology (GEC-ESTRO) to review the existing biophysical models, model parameters, and their use in selected brachytherapy modalities and to develop practice guidelines for clinical medical physicists regarding the selection, use, and interpretation of biophysical models. The report provides an overview of the clinical background and the rationale for the development of biophysical models in radiation oncology and, particularly, in brachytherapy; a summary of the results of literature review of the existing biophysical models that have been used in brachytherapy; a focused discussion of the applications of relevant biophysical models for five selected brachytherapy modalities; and the task group recommendations on the use, reporting, and implementation of biophysical models for brachytherapy treatment planning and evaluation. The report concludes with discussions on the challenges and opportunities in using biophysical models for brachytherapy and with an outlook for future developments.

Salvage reirradiation for local failure of prostate cancer after curative radiation therapy: Association of rectal toxicity with dose distribution and normal-tissue complication probability models

PURPOSE

This study aimed to assess the impact of radiation dose on rectal toxicity after salvage external beam radiation therapy (EBRT) with or without a brachytherapy boost for exclusive local failures after the primary EBRT for prostate cancer.

METHODS AND MATERIALS

Fourteen patients with no severe residual late toxicity after primary EBRT ± brachytherapy were reirradiated after a median time interval of 6.1 years. The median normalized total dose in 2 Gy fractions (NTD2Gy, α/β ratio = 1.5 Gy for prostate cancer cells) was 74 Gy at primary EBRT and 85.1 Gy at reirradiation. Rectal dose-volume histograms (converted to NTD2Gy_alpha/beta = 3 Gy) and the corresponding normal-tissue complication probability (NTCP) values for gastrointestinal (GI) toxicity were evaluated for 2 groups: High GI toxicity (grade ≥3) and low GI toxicity (grade ≤2).

RESULTS

The 5-year grade ≥3 GI toxicity-free survival rate was 57.1%. The median rectal V70Gy and maximum dose to 1 cm3 (D1ccrect) at primary EBRT were both predictive for grade ≥3 GI toxicity (9% vs 0%; P = .04 and 72.2 Gy vs 66.8 Gy; P < .01, respectively). When adding primary radiation therapy (RT) and reirradiation plans, the median D1ccrect was 139.8 Gy versus 126.7 Gy (P < .01) for high and low GI toxicity groups. NTCP >10% at primary RT was predictive for high GI toxicity at reirradiation (P < .05).

CONCLUSIONS

Even in the absence of residual toxicity after primary RT, rectal doses >70 Gy and NTCP >10% calculated for a first irradiation may be associated with a higher risk of developing high GI toxicity at reirradiation with a possible D1ccrect threshold of 130 Gy.

Acute Toxicity Profiles of Hypofractionated Adjuvant and Salvage Radiation Therapy After Radical Prostatectomy: Results of a Prospective Study

PURPOSE

Hypofractionated radiation therapy (RT) is controversial after radical prostatectomy (RP). In this interim analysis, our prospective observational study assessed acute genitourinary (GU) and gastrointestinal (GI) toxicity after hypofractionated adjuvant and salvage RT, as delivered by helical tomotherapy (HT), in patients with prostate cancer.

METHODS AND MATERIALS

After undergoing RP with or without pelvic lymph node dissection, 112 patients were enrolled. Hypofractionated adjuvant RT (2.25 Gy daily for 29 fractions; total 65.25 Gy) was administered to 40 patients with high-risk features. Hypofractionated salvage RT (2.25 Gy daily for 32 or 33 fractions; total 72-74.25 Gy) was prescribed for 72 patients (24 with biochemical relapse, 48 with local relapse). Toxicity was graded according to the Common Terminology Criteria for Adverse Events version 4.02. The impact of RT on urinary flow was assessed by uroflowmetry.

RESULTS

Acute GU toxicity occurred in 41 of 112 patients (36%) (G1 31, G2 10). Acute GI toxicity was observed in 55 (49%) patients (G1 44, G2 11). Uroflowmetry showed that only salvage RT reduced maximum flow significantly (maximum, 68 vs 50 mL/s; P = .003), perhaps because a higher RT dose had been administered.

CONCLUSIONS

After RP, moderate hypofractionated adjuvant and salvage RT were associated with acceptable incidences of slight-to-moderate acute GU and GI toxicity and had little impact on urinary flow. Prospective trials are warranted with longer follow-up in larger cohorts to confirm these findings.

Moderate hypofractionated radiotherapy after prostatectomy for cancer patients: toxicity and clinical outcome

Background

After radical prostatectomy (RP) radiotherapy (RT) plays a role, both as adjuvant or salvage treatment. If negative features are present such as extracapsular extension, seminal vesicle invasion, lymph invasion, and positive surgical margins, RT after RP reduces the risk of recurrence, although it is associated with an increased risk of acute and late toxicities. An intensified RT delivered in a shortened time could improve clinical outcome and be safely combined with hormonal therapy (HT). The aim of this study was to determine the acute and late toxicities associated with hypofractionated RT and to assess the impact of the addition of HT to RT in high-risk prostate cancer (PC) patients on overall response and toxicity.

Materials and methods

Sixty-four PC patients undergoing RP were included in this retrospective study. All patients were recommended to receive adjuvant or salvage RT. Prescription doses were 62.5 Gy in 25 fractions to prostate bed, 56.25 Gy in 25 fractions to seminal vesicles bed, and 50 Gy in 25 fractions to pelvis if indicated. HT was administered to patients with additional adverse pathologic features including Gleason score >7, prostate-specific antigen >20 ng/mL before surgery, or prostate-specific antigen with rapid doubling time after relapse or nodal involvement. After completion of RT, patients were observed after 4 weeks, and then followed-up every 3–6 months. Acute and late toxicities were assessed using Common Terminology Criteria for Adverse Events v4 and Radiation Therapy Oncology Group scale, respectively.

Results

For acute toxicity, only grade 1 gastrointestinal and genitourinary toxicities were detected in 17% and 11% of patients, respectively. As regards late toxicity, only 5% of the patients developed grade 1 gastrointestinal adverse event; grade 1, grade 2, and grade 3 genitourinary toxicity was recorded in 5%, 3.3%, and 3.3% of patients, respectively. Two and 5 years overall survival were 98% and 96%, respectively. The curves stratified for treatment show a slight difference between patients receiving RT or RT+HT, but the differences did not reach statistical significance (p=0.133).

Conclusion

In patients with PC undergoing RP, hypofractionated RT may contribute to achieve a high overall survival with an acceptable toxicity profile. Combination of RT and HT is also well tolerated and efficacious.

Image-Guided Stereotactic Body Radiation Therapy for Localized Prostate Cancer

Purpose

We report the results of a retrospective study of stereotactic body radiation therapy (SBRT) using CyberKnife for localized prostate cancer. The study focused on the safety and feasibility of this treatment modality.

Materials and methods

Between October 2002 and December 2007, 44 patients suffering from localized adenocarcinoma of the prostate were treated with SBRT using CyberKnife at the Korea Cancer Center Hospital. The patients were divided into 3 groups: a low-risk group (5 patients), an intermediate-risk group (10 patients), and a high-risk group (29 patients). Five patients received 32 Gy in 4 fractions, 28 patients received 34 Gy in 4 fractions, and 11 patients received 36 Gy in 4 fractions.

Results

The median age of the patients was 69 years (range, 53–79 years) and the median duration of follow-up 40 months (range, 12–78 months). There were 6 acute and 3 late grade 2 urinary toxicities, and 4 acute and 5 late grade 2 rectal toxicities, but there were no grade 3 or higher treatment-related toxicities. The 5-year cause-specific survival rate and progression-free survival rate were both 100%. At last follow-up, the biochemical failure-free rate of the low-risk, intermediate-risk and high-risk patients was 100%, 100% and 90.8%, respectively.

Conclusion

SBRT using CyberKnife for localized prostate cancer is safe and well tolerated. We obtained promising results with 34 Gy in a 4-fraction regimen especially for the high-risk patients. Free full text available at www.tumorionline.it

Single Course IMRT Plan to Deliver 45 Gy to Seminal Vesicles and 81 Gy to Prostate in 45 Fractions

We treat prostate and seminal vesicles (SV) to 45 Gy in 25 fractions (course 1) and boost prostate to 81 Gy in 20 more fractions (course 2) with Intensity Modulated Radiation Therapy (IMRT). This two-course IMRT with 45 fractions delivered a non-uniform dose to SV and required two plans and two QA procedures. We used Linear Quadratic (LQ) model to develop a single course IMRT plan to treat SV to a uniform dose, which has the same biological effective dose (BED) as that of 45 Gy in 25 fractions and prostate to 81 Gy, in 45 fractions. Single course IMRT plans were compared with two-course IMRT plans, retrospectively for 14 patients. With two-course IMRT, prescription to prostate and SV was 45 Gy in 25 fractions and to prostate only was 36 Gy in 20 fractions, at 1.8 Gy/fraction. With 45-fraction single course IMRT plan, prescription to prostate was 81 Gy and to SV was 52 or 56 Gy for a α/β of 1 and 3, respectively. 52 Gy delivered in 45 fractions has the same BED of 72 Gy3 as that of delivering 45 Gy in 25 fractions, and is called Matched Effective Dose (MED). LQ model was used to calculate the BED and MED to SV for α/β values of 1–10. Comparison between two-course and single course IMRT plans was in terms of MUs, dose-max, and dose volume constraints (DVC). DVC were: 95% PTV to be covered by at least 95% of prescription dose; and 70, 50, and 30% of bladder and rectum should not receive more than 40, 60, and 70% of 81 Gy. SV Volumes ranged from 2.9–30 cc. With two-course IMRT plans, mean dose to SV was non-uniform and varied between patients by 48% (54 to 80 Gy). With single-course IMRT plan, mean dose to SV was more uniform and varied between patients by only 9.6% (58.2 to 63.8 Gy), to deliver MED of 56 Gy for α/β − 1. Single course IMRT plan MUs were slightly larger than those for two-course IMRT plans, but within the range seen for two-course plans (549–959 MUs, n=51). Dose max for single-course plans were similar to two-course plans. Doses to PTV, rectum and bladder with single course plans were as per DVC and comparable to two-course plans. Single course IMRT plan reduces IMRT planning and QA time to half.

Radiobiological comparison of two radiotherapy treatment techniques for high-risk prostate cancer

BACKGROUND

To make a radiobiological comparison, for high risk prostate cancer (T3a, PSA > 20 ng/ml or Gleason > 7) of two radiotherapy treatment techniques. One technique consists of a treatment in three phases of the pelvic nodes, vesicles and prostate using a conventional fractionation scheme of 2 Gy/fraction (SIMRT). The other technique consists of a treatment in two phases that gives simultaneously different dose levels in each phase, 2 Gy/fraction, 2.25 Gy/fraction and 2.5 Gy/fraction to the pelvic nodes, vesicles and prostate, respectively (SIBIMRT).

MATERIALS AND METHODS

The equivalent dose at fractionation of 2 Gy (EQD2), calculated using the linear quadratic model with α/β prostate = 1.5 Gy, was the same for both treatment strategies. For comparison the parameters employed were D95, mean dose and Tumour Control Probabilities for prostate PTV and D15, D25, D35, D50, mean dose and Normal Tissue Complication Probabilities for the rectum and bladder, with physical doses converted to EQD2. Parameters were obtained for α/β prostate = 1.5, 3 and 10 Gy and for α/β oar = 1, 2, 3, 4, 6 and 8.

RESULTS

For prostate PTV, both treatment strategies are equivalent for α/β prostate = 1.5 Gy but for higher α/β prostate, EQD2 and TCP, decrease for the SIBIMRT technique. For the rectum and bladder when α/β oar ≤ 2 Gy, EQD2 and NTCP are lower for the SIMRT technique or equal in both techniques. For α/β oar ≥ 2-3 Gy, EQD2 and NTCP increase for the SIMRT treatment.

CONCLUSIONS

A comparison between two radiotherapy techniques is presented. The SIBIMRT technique reduces EQD2 and NTCP for α/β oar from 2 to 8 Gy.

Gastrointestinal radiation injury: Symptoms, risk factors and mechanisms

Ionising radiation therapy is a common treatment modality for different types of cancer and its use is expected to increase with advances in screening and early detection of cancer. Radiation injury to the gastrointestinal tract is important factor working against better utility of this important therapeutic modality. Cancer survivors can suffer a wide variety of acute and chronic symptoms following radiotherapy, which significantly reduces their quality of life as well as adding an extra burden to the cost of health care. The accurate diagnosis and treatment of intestinal radiation injury often represents a clinical challenge to practicing physicians in both gastroenterology and oncology. Despite the growing recognition of the problem and some advances in understanding the cellular and molecular mechanisms of radiation injury, relatively little is known about the pathophysiology of gastrointestinal radiation injury or any possible susceptibility factors that could aggravate its severity. The aims of this review are to examine the various clinical manifestations of post-radiation gastrointestinal symptoms, to discuss possible patient and treatment factors implicated in normal gastrointestinal tissue radiosensitivity and to outline different mechanisms of intestinal tissue injury.

Hypofractionated helical tomotherapy using 2.5-2.6 Gy daily fractions for localized prostate cancer

BACKGROUND

The purpose of this study is to evaluate the tolerability of hypofractionated helical tomotherapy (HT) in the treatment of localized prostate cancer.

MATERIALS AND METHODS

We evaluated 48 patients with primary adenocarcinoma of the prostate (cT1-T3N0M0) who were treated with hypofractionated HT from August 2008 through July 2011. Hypofractionated regimens included: 68.04 Gy at 2.52 Gy/fraction, 70 Gy at 2.5 Gy/fraction, and 70.2 Gy at 2.6 Gy/fraction. Genitourinary (GU) and gastrointestinal (GI) toxicity was scored using the Radiation Therapy Oncology Group scoring system.

RESULTS

Thirty-two patients were treated with 68.04 Gy, 5 patients with 70 Gy, and 11 with 70.2 Gy. The median age at diagnosis was 69 years (range 49-87) and the median follow-up 11 months (range 7-40). Grade 2 acute GI toxicity occurred in 9 patients (19 %). No grade 3 or higher acute GI toxicity was observed. Grade 2 and 3 acute GU toxicities occurred in 19 and 6 % of patients, respectively. The incidence of late grade 2 GI and GU toxicity was 4 and 2 %, respectively. No grade 3 or higher late toxicities were observed. Multivariate analysis showed that patients treated at 2.6 Gy/fraction or those who received a total radiation dose ≥70 Gy had higher rates of grade ≥2 acute GU toxicity (P = 0.004 and P = 0.048, respectively).

CONCLUSION

Hypofractionated HT in the treatment of localized prostate cancer is well tolerated with no grade 3 or higher early or late GI and GU toxicities. Further research is needed to assess definitive late toxicity and tumor control.

Dose-escalated simultaneous integrated-boost treatment of prostate cancer patients via helical tomotherapy

PURPOSE

The goal of this work was to assess the feasibility of moderately hypofractionated simultaneous integrated-boost intensity-modulated radiotherapy (SIB-IMRT) with helical tomotherapy in patients with localized prostate cancer regarding acute side effects and dose-volume histogram data (DVH data).

METHODS

Acute side effects and DVH data were evaluated of the first 40 intermediate risk prostate cancer patients treated with a definitive daily image-guided SIB-IMRT protocol via helical tomotherapy in our department. The planning target volume including the prostate and the base of the seminal vesicles with safety margins was treated with 70 Gy in 35 fractions. The boost volume containing the prostate and 3 mm safety margins (5 mm craniocaudal) was treated as SIB to a total dose of 76 Gy (2.17 Gy per fraction). Planning constraints for the anterior rectal wall were set in order not to exceed the dose of 76 Gy prescribed to the boost volume. Acute toxicity was evaluated prospectively using a modified CTCAE (Common Terminology Criteria for Adverse Events) score.

RESULTS

SIB-IMRT allowed good rectal sparing, although the full boost dose was permitted to the anterior rectal wall. Median rectum dose was 38 Gy in all patients and the median volumes receiving at least 65 Gy (V65), 70 Gy (V70), and 75 Gy (V75) were 13.5%, 9%, and 3%, respectively. No grade 4 toxicity was observed. Acute grade 3 toxicity was observed in 20% of patients involving nocturia only. Grade 2 acute intestinal and urological side effects occurred in 25% and 57.5%, respectively. No correlation was found between acute toxicity and the DVH data.

CONCLUSION

This institutional SIB-IMRT protocol using daily image guidance as a precondition for smaller safety margins allows dose escalation to the prostate without increasing acute toxicity.

Evaluation of the effect of prostate volume change on tumor control probability in LDR brachytherapy

Purpose

This study evaluates low dose-rate brachytherapy (LDR) prostate plans to determine the biological effect of dose degradation due to prostate volume changes.

Material and methods

In this study, 39 patients were evaluated. Pre-implant prostate volume was determined using ultrasound. These images were used with the treatment planning system (Nucletron Spot Pro 3.1^®) to create treatment plans using ¹⁰³Pd seeds. Following the implant, patients were imaged using CT for post-implant dosimetry. From the pre and post-implant DVHs, the biologically equivalent dose and the tumor control probability (TCP) were determined using the biologically effective uniform dose. The model used RBE = 1.75 and α/β = 2 Gy.

Results

The prostate volume changed between pre and post implant image sets ranged from –8% to 110%. TCP and the mean dose were reduced up to 21% and 56%, respectively. TCP is observed to decrease as the mean dose decreases to the prostate. The post-implant tumor dose was generally observed to decrease, compared to the planned dose. A critical uniform dose of 130 Gy was established. Below this dose, TCP begins to fall-off. It was also determined that patients with a small prostates were more likely to suffer TCP decrease.

Conclusions

The biological effect of post operative prostate growth due to operative trauma in LDR was evaluated using the concept. The post-implant dose was lower than the planned dose due to an increase of prostate volume post-implant. A critical uniform dose of 130 Gy was determined, below which TCP begun to decline.

The impact of prostate edema on cell survival and tumor control after permanent interstitial brachytherapy for early stage prostate cancers

Previous studies have shown that procedure-induced prostate edema during permanent interstitial brachytherapy (PIB) can cause significant variations in the dose delivered to the prostate gland. Because the clinical impact of edema-induced dose variations strongly depends on the magnitude of the edema, the temporal pattern of its resolution and its interplay with the decay of radioactivity and the underlying biological processes of tumor cells (such as tumor potential doubling time), we investigated the impact of edema-induced dose variations on the tumor cell survival and tumor control probability after PIB with the (131)Cs, (125)I and (103)Pd sources used in current clinical practice. The exponential edema resolution model reported by Waterman et al (1998 Int. J. Radiat. Oncol. Biol. Phys. 41 1069-77) was used to characterize the edema evolutions previously observed during clinical PIB for prostate cancer. The concept of biologically effective dose, taking into account tumor cell proliferation and sublethal damage repair during dose delivery, was used to characterize the effects of prostate edema on cell survival and tumor control probability. Our calculation indicated that prostate edema, if not appropriately taken into account, can increase the cell survival and decrease the probability of local control of PIB. The magnitude of an edema-induced increase in cell survival increased with increasing edema severity, decreasing half-life of radioactive decay and decreasing photon energy emitted by the source. At the doses currently prescribed for PIB and for prostate cancer cells characterized by nominal radiobiology parameters recommended by AAPM TG-137, PIB using (125)I sources was less affected by edema than PIB using (131)Cs or (103)Pd sources due to the long radioactive decay half-life of (125)I. The effect of edema on PIB using (131)Cs or (103)Pd was similar. The effect of edema on (103)Pd PIB was slightly greater, even though the decay half-life of (103)Pd (17 days) is longer than that of (131)Cs (9.7 days), because the advantage of the longer (103)Pd decay half-life was negated by the lower effective energy of the photons it emits (∼21 keV compared to ∼30.4 keV for (131)Cs). In addition, the impact of edema could be reduced or enhanced by differences in the tumor characteristics (e.g. potential tumor doubling time or the α/β ratio), and the effect of these factors varied for the different radioactive sources. There is a clear need to consider the effects of prostate edema during the planning and evaluation of permanent interstitial brachytherapy treatments for prostate cancer.

Internal radiotherapy techniques using radiolanthanide praseodymium-142: a review of production routes, brachytherapy, unsealed source therapy

Radionuclides of rare earth elements are gaining importance as emerging therapeutic agents in nuclear medicine. β(-)-particle emitter 142Pr [T (1/2) = 19.12 h, E(-)β = 2.162 MeV (96.3%), Eγ = 1575 keV (3.7%)] is one of the praseodymium-141 (100% abundant) radioisotopes. Production routes and therapy aspects of 142Pr will be reviewed in this paper. However, 142Pr produces via 141Pr(n, γ) 142Pr reaction by irradiation in a low-fluence reactor; 142Pr cyclotron produced, could be achievable. 142Pr due to its high β(-)-emission and low specific gamma γ-emission could not only be a therapeutic radionuclide, but also a suitable radionuclide in order for biodistribution studies. Internal radiotherapy using 142Pr can be classified into two sub-categories: (1) unsealed source therapy (UST), (2) brachytherapy. UST via 142Pr-HA and 142Pr-DTPA in order for radiosynovectomy have been proposed. In addition, 142Pr Glass seeds and 142Pr microspheres have been utilized for interstitial brachytherapy of prostate cancer and intraarterial brachytherapy of arteriovenous malformation, respectively.

Estimation of α/β for late rectal toxicity based on RTOG 94-06

PURPOSE

To estimate α/β, the parameter ratio from the linear-quadratic (LQ) model, for Grade ≥2 late rectal toxicity among patients treated on Radiation Therapy Oncology Group (RTOG) protocol 94-06; and to determine whether correcting the rectal dose-volume histogram (DVH) for differences in dose per fraction, based on the LQ model, significantly improves the fit to these data of the Lyman-Kutcher-Burman (LKB) normal-tissue complication probability (NTCP) model.

METHODS AND MATERIALS

The generalized LKB model was fitted to the Grade ≥2 late rectal toxicity data in two ways: by using DVHs representing physical dose to rectum, and by using a modified approach in which dose bins in the rectal DVH were corrected for differences in dose per fraction using the LQ model, with α/β estimated as an additional unknown parameter. The analysis included only patients treated with the same treatment plan throughout radiotherapy, so that the dose per fraction to each voxel of rectum could be determined from the DVH. The likelihood ratio test was used to assess whether the fit of the LQ-corrected model was significantly better than the fit of the LKB model based on physical doses to rectum.

RESULTS

The analysis included 509 of the 1,084 patients enrolled on RTOG 94-06. The estimate of α/β from the LQ-corrected LKB model was 4.8 Gy, with 68% confidence interval 0.6 Gy to 46 Gy. The fit was not significantly different from the fit of the LKB model based on physical dose to rectum (p = 0.236).

CONCLUSIONS

The estimated fractionation sensitivity for Grade ≥2 late rectal toxicity is consistent with values of α/β for rectum found previously in human beings and in rodents. However, the confidence interval is large, and there is no evidence that LQ correction of the rectal DVH significantly changes the fit or predictions of the LKB model for this endpoint.

International Conference on Advances in Radiation Oncology (ICARO): outcomes of an IAEA meeting

The IAEA held the International Conference on Advances in Radiation Oncology (ICARO) in Vienna on 27-29 April 2009. The Conference dealt with the issues and requirements posed by the transition from conventional radiotherapy to advanced modern technologies, including staffing, training, treatment planning and delivery, quality assurance (QA) and the optimal use of available resources. The current role of advanced technologies (defined as 3-dimensional and/or image guided treatment with photons or particles) in current clinical practice and future scenarios were discussed.

ICARO was organized by the IAEA at the request of the Member States and co-sponsored and supported by other international organizations to assess advances in technologies in radiation oncology in the face of economic challenges that most countries confront. Participants submitted research contributions, which were reviewed by a scientific committee and presented via 46 lectures and 103 posters. There were 327 participants from 70 Member States as well as participants from industry and government. The ICARO meeting provided an independent forum for the interaction of participants from developed and developing countries on current and developing issues related to radiation oncology.

Dosimetric and physical comparison of IMRT and CyberKnife plans in the treatment of localized prostate cancer

AIM

The aim of our study was the dosimetric and physical evaluation of the CK and IMRT treatment plans for 16 patients with localized prostate cancer.

BACKGROUND

Intensity modulated radiation therapy (IMRT) is one of the recent technical advances in radiotherapy. The prostate is a well suited site to be treated with IMRT. The challenge of accurately delivering the IMRT needs to be supported by new advances such as image-guidance and four-dimensional computed conformal radiation therapy (4DCRT) tomography. CyberKnife (CK) provides real time orthogonal X-ray imaging of the patient during treatment course to follow gold fiducials installed into the prostate and to achieve motion correlation between online acquired X-ray imaging and digital reconstructed radiographs (DRRs) which are obtained from planning computed tomography images by translating and rotating the treatment table in five directions.

METHODS AND MATERIALS

Sixteen IMRT and CK plans were performed to be compared in terms of conformity (CI), heterogeneity indices (HI), percentage doses of 100% (V100), 66% (V66), 50% (V50), 33% (V33) and 10% (V10) volumes of the bladder and rectum. Dose-volume histograms for target and critical organs, (CI) and indices (HI) and isodose lines were analyzed to evaluate the treatment plans.

RESULTS

Statistically significant differences in the percentage rectal doses delivered to V10, V33, and V50 of the rectum were detected in favor of the CK plans (p values; <0.001, <0.001 and 0.019, respectively). The percentage doses for V66 and V100 of the rectum were larger in CK plans (13%, 2% in IMRT and 21%, 3% in CK plans, respectively). Percentage bladder doses for V10 and V33 were significantly lower in CK plans [96% in IMRT vs 48% in CK (p < 0.001) and 34% in IMRT vs 24% in CK (p = 0.047)]. Lower percentage doses were observed for V50, V66 of the bladder for the IMRT. They were 5.4% and 3.45% for IMRT and 13.4% and 8.05% for CK, respectively. Median CI of planning target volume (PTV) for IMRT and CK plans were 0.94 and 1.23, respectively (p < 0.001).

CONCLUSION

Both systems have a very good ability to create highly conformal volumetric dose distributions. Median HI of PTV for IMRT and CK plans were 1.08 and 1.33, respectively (p < 0.001).

Assessment of normal tissue complications following prostate cancer irradiation: comparison of radiation treatment modalities using NTCP models

PURPOSE

Normal tissue complication probability (NTCP) of the rectum, bladder, urethra, and femoral heads following several techniques for radiation treatment of prostate cancer were evaluated applying the relative seriality and Lyman models.

METHODS

Model parameters from literature were used in this evaluation. The treatment techniques included external (standard fractionated, hypofractionated, and dose-escalated) three-dimensional conformal radiotherapy (3D-CRT), low-dose-rate (LDR) brachytherapy (I-125 seeds), and high-dose-rate (HDR) brachytherapy (Ir-192 source). Dose-volume histograms (DVHs) of the rectum, bladder, and urethra retrieved from corresponding treatment planning systems were converted to biological effective dose-based and equivalent dose-based DVHs, respectively, in order to account for differences in radiation treatment modality and fractionation schedule.

RESULTS

Results indicated that with hypofractionated 3D-CRT (20 fractions of 2.75 Gy/fraction delivered five times/week to total dose of 55 Gy), NTCP of the rectum, bladder, and urethra were less than those for standard fractionated 3D-CRT using a four-field technique (32 fractions of 2 Gy/fraction delivered five times/week to total dose of 64 Gy) and dose-escalated 3D-CRT. Rectal and bladder NTCPs (5.2% and 6.6%, respectively) following the dose-escalated four-field 3D-CRT (2 Gy/fraction to total dose of 74 Gy) were the highest among analyzed treatment techniques. The average NTCP for the rectum and urethra were 0.6% and 24.7% for LDR-BT and 0.5% and 11.2% for HDR-BT.

CONCLUSIONS

Although brachytherapy techniques resulted in delivering larger equivalent doses to normal tissues, the corresponding NTCPs were lower than those of external beam techniques other than the urethra because of much smaller volumes irradiated to higher doses. Among analyzed normal tissues, the femoral heads were found to have the lowest probability of complications as most of their volume was irradiated to lower equivalent doses compared to other tissues.

MRS-guided HDR brachytherapy boost to the dominant intraprostatic lesion in high risk localised prostate cancer

Background

It is known that the vast majority of prostate cancers are multifocal. However radical radiotherapy historically treats the whole gland rather than individual cancer foci.

Magnetic resonance spectroscopy (MRS) can be used to non-invasively locate individual cancerous tumours in prostate. Thus an intentionally non-uniform dose distribution treating the dominant intraprostatic lesion to different dose levels than the remaining prostate can be delivered ensuring the maximum achievable tumour control probability.

The aim of this study is to evaluate, using radiobiological means, the feasibility of a MRS-guided high dose rate (HDR) brachytherapy boost to the dominant lesion.

Methods

Computed tomography and MR/MRS were performed for treatment planning of a high risk localised prostate cancer. Both were done without endorectal coil, which distorts shape of prostate during the exams.

Three treatment plans were compared:

- external beam radiation therapy (EBRT) only

- combination of EBRT and HDR brachytherapy

- combination of EBRT and HDR brachytherapy with a synchronous integrated boost to the dominant lesion

The criteria of plan comparison were: the minimum, maximum and average doses to the targets and organs at risk; dose volume histograms; biologically effective doses for organs at risk and tumour control probability for the target volumes consisting of the dominant lesion as detected by MR/MRS and the remaining prostate volume.

Results

Inclusion of MRS information on the location of dominant lesion allows a safe increase of the dose to the dominant lesion while dose to the remaining target can be even substantially decreased keeping the same, high tumour control probability. At the same time an improved urethra sparing was achieved comparing to the treatment plan using a combination of EBRT and uniform HDR brachytherapy.

Conclusions

MRS-guided HDR brachytherapy boost to dominant lesion has the potential to spare the normal tissue, especially urethra, while keeping the tumour control probability high.

A method to separate the rectum from the prostate during proton beam radiotherapy of prostate cancer patients

The use of protons for curative treatment of prostate cancer is increasing, either as a single treatment modality or in combination with conventional radiotherapy. The proximity between prostate (target) and rectum (organ at risk) often leads to a compromise between dose to target and organ at risk.

MATERIAL AND METHODS

The present study describes a method where the distance between prostate and rectum is increased by retraction of the rectum in dorsal direction. Comparative treatment plans with and without retraction of the rectum in the same patients have been studied. Nine patients with biopsy proven, localised adenocarcinoma of the prostate were studied. A cylindrical rod of Perspex was inserted into the rectum. This device allows the rectum to be retracted posteriorly. The patients were given a proton boost of 20 Gy in four fractions of 5 Gy in addition to a conventional photon beam treatment to a dose of 50 Gy in 25 fractions of 2 Gy.

RESULTS

Comparative treatment planning shows that the treatment plan with rectal retraction significantly reduces (p<0.01) the volume of the rectal wall receiving high doses (equal to 70 Gy in 2 Gy fractions) in all patients.

CONCLUSIONS

The proton boost treatment with retraction of rectum during treatment decreases the rectal dose substantially. This is expected to reduce rectal side effects.

Confirmation of a low α/β ratio for prostate cancer treated by external beam radiation therapy alone using a post-treatment repeated-measures model for PSA dynamics

PURPOSE

To estimate the α/β ratio of prostate cancer treated with external beam radiation only by use of a model of long-term prostate-specific antigen (PSA) dynamics.

METHODS AND MATERIALS

Repeated measures of PSA from 5,093 patients from 6 institutions treated for localized prostate cancer by external beam radiation therapy (EBRT) without planned androgen deprivation were analyzed. A biphasic linear mixed model described the post-treatment evolution of PSA, rather than a conventional model of time to biochemical recurrence. The model was adjusted for standard prognostic factors (T stage, initial PSA level, and Gleason score) and cohort-specific effects. The radiation dose fractionation effect was estimated from the long-term rate of rise of PSA level.

RESULTS

Adjusted for other factors, total dose of EBRT and sum of squared doses per fraction were associated with long-term rate of change of PSA level (p = 0.0017 and p = 0.0003, respectively), an increase of each being associated with a lower rate of rise. The α/β ratio was estimated at 1.55 Gy (95% confidence band, 0.46-4.52 Gy). This estimate was robust to adjustment of the linear mixed model.

CONCLUSIONS

By analysis of a large EBRT-only cohort along with a method that uses all the repeated measures of PSA after the end of treatment, a low and precise α/β was estimated. These data support the use of hypofractionation at fractional doses up to 2.8 Gy but cannot presently be assumed to accurately represent higher doses per fraction.

Accelerated hypofractionated radiotherapy as adjuvant regimen after conserving surgery for early breast cancer: interim report of toxicity after a minimum follow up of 3 years

Background

Accelerated hypofractionation is an attractive approach for adjuvant whole breast radiotherapy. In this study we evaluated the adverse effects at least 3 years post an accelerated hypofractionated whole breast radiotherapy schedule.

Methods

From October 2004 to March 2006, 39 consecutive patients aged over 18 years with pTis, pT1-2, pN0-1 breast adenocarcinoma who underwent conservative surgery were treated with an adjuvant accelerated hypofractionated radiotherapy schedule consisting of 34 Gy in 10 daily fractions over 2 weeks to the whole breast, followed after 1 week by an electron boost dose of 8 Gy in a single fraction to the tumour bed. Skin and lung radiation toxicity was evaluated daily during therapy, once a week for one month after radiotherapy completion, every 3 months for the first year and from then on every six months. In particular lung toxicity was investigated in terms of CT density evaluation, pulmonary functional tests, and clinical and radiological scoring. Paired t-test, Chi-square test and non-parametric Wilcoxon test were performed.

Results

After a median follow-up of 43 months (range 36-52 months), all the patients are alive and disease-free. None of the patients showed any clinical signs of lung toxicity, no CT-lung toxicity was denoted by radiologist on CT lung images acquired about 1 year post-radiotherapy, no variation of pulmonary density evaluated in terms of normalised Hounsfield numbers was evident. Barely palpable increased density of the treated breast was noted in 9 out of 39 patients (in 2 patients this toxicity was limited to the boost area) and teleangectasia (<1/cm²) limited to the boost area was evident in 2 out of 39 patients. The compliance with the treatment was excellent (100%).

Conclusion

The radiotherapy schedule investigated in this study (i.e 34 Gy in 3.4 Gy/fr plus boost dose of 8 Gy in single fraction) is a feasible and safe treatment and does not lead to adjunctive acute and late toxicities. A longer follow up is necessary to confirm these favourable results.

Modeling of alpha/beta for late rectal toxicity from a randomized phase II study: conventional versus hypofractionated scheme for localized prostate cancer

BACKGROUND

Recently, the use of hypo-fractionated treatment schemes for the prostate cancer has been encouraged due to the fact that alpha/beta ratio for prostate cancer should be low. However a major concern on the use of hypofractionation is the late rectal toxicity, it is important to be able to predict the risk of toxicity for alternative treatment schemes, with the best accuracy. The main purpose of this study is to evaluate the response of rectum wall to changes in fractionation and to quantify the alpha/beta ratio for late rectal toxicity

METHODS

162 patients with localized prostate cancer, treated with conformal radiotherapy, were enrolled in a phase II randomized trial. The patients were randomly assigned to 80 Gy in 40 fractions over 8 weeks (arm A) or 62 Gy in 20 fractions over 5 weeks (arm B). The median follow-up was 30 months. The late rectal toxicity was evaluated using the Radiation Therapy Oncology Group (RTOG) scale. It was assumed >or= Grade 2 (G2) toxicity incidence as primary end point. Fit of toxicity incidence by the Lyman-Burman-Kutcher (LKB) model was performed.

RESULTS

The crude incidence of late rectal toxicity >or= G2 was 14% and 12% for the standard arm and the hypofractionated arm, respectively. The crude incidence of late rectal toxicity >or= G2 was 14.0% and 12.3% for the arm A and B, respectively. For the arm A, volumes receiving >or= 50 Gy (V50) and 70 Gy (V70) were 38.3 +/- 7.5% and 23.4 +/- 5.5%; for arm B, V38 and V54 were 40.9 +/- 6.8% and 24.5 +/- 4.4%. An alpha/beta ratio for late rectal toxicity very close to 3 Gy was found.

CONCLUSION

The >or= G2 late toxicities in both arms were comparable, indicating the feasibility of hypofractionated regimes in prostate cancer. An alpha/beta ratio for late rectal toxicity very close to 3 Gy was found.

Generation of composite dose and biological effective dose (BED) over multiple treatment modalities and multistage planning using deformable image registration

Currently there are no commercially available tools to generate composite plans across different treatment modalities and/or different planning image sets. Without a composite plan, it may be difficult to perform a meaningful dosimetric evaluation of the overall treatment course. In this paper, we introduce a method to generate composite biological effective dose (BED) plans over multiple radiotherapy treatment modalities and/or multistage plans, using deformable image registration. Two cases were used to demonstrate the method. Case I was prostate cancer treated with intensity-modulated radiation therapy (IMRT) and a permanent seed implant. Case II involved lung cancer treated with two treatment plans generated on two separate computed tomography image sets. Thin-plate spline or optical flow methods were used as appropriate to generate deformation matrices. The deformation matrices were then applied to the dose matrices and the resulting physical doses were converted to BED and added to yield the composite plan. Cell proliferation and sublethal repair were considered in the BED calculations. The difference in BED between normal tissues and tumor volumes was accounted for by using different BED models, alpha/beta values, and cell potential doubling times. The method to generate composite BED plans presented in this paper provides information not available with the traditional simple dose summation or physical dose summation. With the understanding of limitations and uncertainties of the algorithms involved, it may be valuable for the overall treatment plan evaluation.

Some implications of linear-quadratic-linear radiation dose-response with regard to hypofractionation

Recent technological advances enable radiation therapy to be delivered in a highly conformal manner to targets located almost anywhere in the body. This capability has renewed the clinical interest in hypofractionation wherein the tumor is delivered a few fractions of very large dose per fraction. Extrapolating clinical experience from conventional regimens to fractions of high dose is important to designing hypofractionated treatments. The concept of biologically effective dose (BED) based on the linear-quadratic (LQ) formulation e(-(alphaD+betaD2) is a useful tool for intercomparing conventional fractionations but may be hampered if the value of alpha/beta is dose range dependent and/or when extrapolating to fractions of high dose because the LQ curve bends continuously on the log-linear plot. This does not coincide with what is observed experimentally in many clonogenic cell survival studies at high dose wherein radiation dose-response relationships more closely approximate a straight line. Intercomparison of conventional fractionations with hypofractionated regimens may benefit from BED calculations which instead use a dose range independent linear-quadratic-linear (LQ-L) formulation which better fits the experimental data across a wider range of dose. The dosimetric implications of LQ-L are explored using a simple model which requires only the specification of a dose D(T) at which the LQ curve transitions to final linearity and the log(e) cell kill per Gy in the final linear portion of the survival curve at high dose. It is shown that the line tangent to the LQ curve at transition dose D(T) can often be used to approximate the final slope of the dose response curve. When D(T) = 2alpha/ beta Gy, the line tangent to the LQ curve at D(T) intersects the e(-alphaD) and e(-betaD2) curves at dose alpha/ beta Gy and also closely fits the linear response in the high dose region of some classic in vitro cell survival curves for which the value of alpha/beta is low. It is hypothesized that D(T) will increase as the magnitude of alpha/beta increases. Examples are presented illustrating how to recognize LQ-L behavior in multifraction isoeffect studies of late responses such as spinal cord and lung. When planning hypofractionated regimens involving reactions with low alpha/beta, recognizing LQ-L behavior could be important because the dose-response is likely to transition to final linearity within the contemplated range of hypofractional doses.

Clinical experience using hypofractionated radiation schedules in breast cancer

Hypofractionation is attractive for whole- or partial-breast irradiation because it permits treatment to be given with fewer fractions in a shorter period of time and at less cost. A number of cohort studies suggest that hypofractionation may be given to the whole breast safely and with good local control. Recent randomized trials have confirmed that hypofractioned whole-breast irradiation is equivalent to more conventional whole-breast irradiation with respect to local recurrence and cosmetic outcome. Recently, there has been a renewed interest in hypofractionation for the delivery of partial-breast irradiation using a number of techniques including high-dose rate brachytherapy, 3-dimensional conformal radiation using external-beam techniques, and intraoperative therapy. Early cohort studies report good local control and acceptable morbidity. Randomized trials are now underway to compare this approach to conventional whole-breast irradiation.

Association of single nucleotide polymorphisms in SOD2, XRCC1 and XRCC3 with susceptibility for the development of adverse effects resulting from radiotherapy for prostate cancer

The objective of this study was to determine whether an association exists between certain single nucleotide polymorphisms (SNPs), which have previously been linked with adverse normal tissue effects resulting from radiotherapy, and the development of radiation injury resulting from radiotherapy for prostate cancer. A total of 135 consecutive patients with clinically localized prostate cancer and a minimum of 1 year of follow-up who had been treated with radiation therapy, either brachytherapy alone or in combination with external-beam radiotherapy, with or without hormone therapy, were genotyped for SNPs in SOD2, XRCC1 and XRCC3. Three common late tissue toxicities were investigated: late rectal bleeding, urinary morbidity, and erectile dysfunction. Patients with the XRCC1 rs25489 G/A (Arg280His) genotype were more likely to develop erectile dysfunction after irradiation than patients who had the G/G genotype (67% compared to 24%; P=0.048). In addition, patients who had the SOD2 rs4880 T/C (Val16Ala) genotype exhibited a significant increase in grade 2 late rectal bleeding compared to patients who had either the C/C or T/T genotype for this SNP (8% compared to 0%; P=0.02). Finally, patients with the combination of the SOD2 rs4880 C/T genotype and XRCC3 rs861539 T/C (Thr241Met) genotype experienced a significant increase in grade 2 late rectal bleeding compared to patients without this particular genotypic arrangement (14% compared to 1%; P=0.002). These results suggest that SNPs in the SOD2, XRCC1 and XRCC3 genes are associated with the development of late radiation injury in patients treated with radiation therapy for prostate adenocarcinoma.

Comparing two strategies of dynamic intensity modulated radiation therapy (dIMRT) with 3-dimensional conformal radiation therapy (3DCRT) in the hypofractionated treatment of high-risk prostate cancer

Background

To compare two strategies of dynamic intensity modulated radiation therapy (dIMRT) with 3-dimensional conformal radiation therapy (3DCRT) in the setting of hypofractionated high-risk prostate cancer treatment.

Methods

3DCRT and dIMRT/Helical Tomotherapy(HT) planning with 10 CT datasets was undertaken to deliver 68 Gy in 25 fractions (prostate) and simultaneously delivering 45 Gy in 25 fractions (pelvic lymph node targets) in a single phase. The paradigms of pelvic vessel targeting (iliac vessels with margin are used to target pelvic nodes) and conformal normal tissue avoidance (treated soft tissues of the pelvis while limiting dose to identified pelvic critical structures) were assessed compared to 3DCRT controls. Both dIMRT/HT and 3DCRT solutions were compared to each other using repeated measures ANOVA and post-hoc paired t-tests.

Results

When compared to conformal pelvic vessel targeting, conformal normal tissue avoidance delivered more homogenous PTV delivery (2/2 t-test comparisons; p < 0.001), similar nodal coverage (8/8 t-test comparisons; p = ns), higher and more homogenous pelvic tissue dose (6/6 t-test comparisons; p < 0.03), at the cost of slightly higher critical structure dose (D_dose, 1–3 Gy over 5/10 dose points; p < 0.03). The dIMRT/HT approaches were superior to 3DCRT in sparing organs at risk (22/24 t-test comparisons; p < 0.05).

Conclusion

dIMRT/HT nodal and pelvic targeting is superior to 3DCRT in dose delivery and critical structure sparing in the setting of hypofractionation for high-risk prostate cancer. The pelvic targeting paradigm is a potential solution to deliver highly conformal pelvic radiation treatment in the setting of nodal location uncertainty in prostate cancer and other pelvic malignancies.

On the need to compensate for edema-induced dose reductions in preplanned (131)Cs prostate brachytherapy

PURPOSE

Surgical trauma-induced edema and its protracted resolution can lead to significant dose reductions in preplanned (131)Cs prostate brachytherapy. The purpose of this work was to examine whether these dose reductions should be actively compensated for and to estimate the magnitude of the additional irradiation needed for dose compensation.

METHODS AND MATERIALS

The quantitative edema resolution characteristics observed by Waterman et al. were used to examine the physical and radiobiologic effects of prostate edema in preplanned (131)Cs implants. The need for dose compensation was assessed using the dose responses observed in (125)I and (103)Pd prostate implants. The biologically effective dose, calculated with full consideration of edema evolution, was used to estimate the additional irradiation needed for dose compensation.

RESULTS

We found that the edema-induced dose reduction in preplanned (131)Cs implants could easily exceed 10% of the prescription dose for implants with moderate or large edema. These dose reductions could lead to a >10% reduction in the biochemical recurrence-free survival for individual patients if the effect of edema was ignored. For a prescribed dose of 120 Gy, the number of 2-Gy external beam fractions needed to compensate for a 5%, 10%, 15%, 20%, and 25% edema-induced dose reduction would be one, four, six, seven, and nine, respectively, for prostate cancer with a median potential doubling time of 42 days. The required additional irradiation increased for fast-growing tumors and/or those less efficient in sublethal damage repair.

CONCLUSION

Compensation of edema-induced dose reductions in preplanned (131)Cs prostate brachytherapy should be actively considered for those implants with moderate or large edema.

Significant reduction of acute toxicity following pelvic irradiation with Helical Tomotherapy in patients with localized prostate cancer

PURPOSE

To assess and quantify the possible benefit deriving from IMRT with Helical Tomotherapy (HTT) delivery to the pelvic nodal area in patients with prostate cancer in terms of reduction of acute and late toxicities.

METHODS AND MATERIALS

Thirty-five patients candidate to radical or postoperative RT on whole pelvis (WPRT) were treated with HTT, while receiving a concomitant boost to the prostate or the prostatic bed (median 74.2 and 72 Gy, respectively) within a moderately hypofractionated (28-33 fractions; median HTT duration 44 days) regimen. Median and mean doses to whole pelvis were 52 and 54 Gy, respectively. One of the major goals of planning optimisation was to minimize the dose received by the intestinal cavity (IC) outside the nodal PTV.

RESULTS

HTT resulted to be very efficient in sparing the IC even at dose levels below 30-35 Gy and guaranteed a significant sparing of bladder and rectum even at intermediate-low doses (V20-V40). No acute Grade 3 RTOG toxicity was recorded. Eighteen G1 and two G2 GU acute toxicities, 13 G1 upper GI acute toxicities, 8 G1 and 1 G2 acute proctitis were observed; no patient experienced G2 upper GI toxicity. After a median FU of 11.5 months (>10 in 18 patients) one case of late G3 GU toxicity was reported in one post-prostatectomy treated patient; no G2 late rectal bleeding or other GI toxicity was recorded.

CONCLUSIONS

WPRT with HTT resulted in a very low incidence of acute Grade 2 and in the disappearance of acute Grade 3 toxicities.

Is the α/β Value for Prostate Tumours Low Enough to be Safely Used in Clinical Trials?

There has been an intense debate over the past several years on the relevant alpha/beta value that could be used to describe the fractionation response of prostate tumours. Previously it has been assumed that prostate tumours have high alpha/beta values, similar to most other tumours and the early reacting normal tissues. However, the proliferation behaviour of the prostate tumours is more like that of the late reacting tissues, with slow doubling times and low alpha/beta values. The analyses of clinical results carried out in the past few years have indeed suggested that the alpha/beta value that characterises the fractionation response of the prostate is low, possibly even below the 3 Gy commonly assumed for most late complications, and hence that hypofractionation of the radiation treatment might improve the therapeutic ratio (better control at the same or lower complication rate). However, hypofractionation might also increase the complication rates in the surrounding late responding tissues and if their alpha/beta value is not larger that of prostate tumours it could even lead to a decrease in the therapeutic ratio. Therefore, the important question is whether the alpha/beta value for the prostate is lower than the alpha/beta values of the surrounding late responding tissues at risk. This paper reviews the clinical and experimental data regarding the radiobiological differential that might exist between prostate tumours and the late normal tissues around them. Several prospective hypofractionated trials that have been initiated recently in order to determine the alpha/beta value or the range of values that describe the fractionation response of prostate tumours are also reviewed. In spite of several confounding factors that interfere with the derivation of a precise value, it seems that most data support a trend towards lower alpha/beta values for prostate tumours than for rectum or bladder.

Hypofractionated versus conventionally fractionated radiation therapy for prostate carcinoma: Updated results of a phase III randomized trial

PURPOSE

The aim of this study was to compare the toxicity and efficacy of radiation therapy (RT) for localized carcinoma of the prostate, using a hypofractionated (55 Gy/20 fractions/4 weeks) vs. a conventionally fractionated (64 Gy/32 fractions/6.5 weeks) dose schedule.

METHODS AND MATERIALS

A total of 217 patients were randomized to either the hypofractionated (108 patients) or the conventional (109 patients) dose schedule, with planning with two-dimensional (2D) CT scan planning methodology in the majority of cases. All patients were followed for a median of 48 (6-108) months. Gastrointestinal (GI) and genitourinary (GU) toxicity was evaluated before RT and after its completion using modified late effects of normal tissue-subjective, objective, management, analytic (LENT-SOMA) scales and the European Organization for Research and Treatment of Cancer sexual function questionnaire. Efficacy of RT based on clinical, radiologic, and prostate-specific antigen data were also evaluated at baseline and after RT.

RESULTS

Gastrointestinal and GU toxicity persisted 5 years after RT and did not differ between the two dose schedules other than in regard to urgency of defecation. However, 1-month GI toxicity was not only worse in patients with the hypofractionated RT schedule but also adversely affected daily activities. Nadir prostate-specific antigen values occurred at a median of 18.0 (3.0-54.0) months after RT. A total of 76 biochemical relapses, with or without clinical relapses, have occurred since; of these, 37 were in the hypofractionated and 39 in the conventional schedule. The 5-year biochemical +/- clinical relapse-free and overall survival was 55.9% and 85.3% respectively for all patients, and did not differ between the two schedules.

CONCLUSIONS

Radiation therapy for prostate carcinoma causes persistent GI toxicity that is largely independent of the two dose schedules. The hypofractionated schedule is equivalent in efficacy to the conventional schedule.