Adjuvant androgen deprivation impacts late rectal toxicity after conformal radiotherapy of prostate carcinoma

Fitting late rectal bleeding data using different NTCP models: results from an Italian multi-centric study (AIROPROS0101)

BACKGROUND AND PURPOSE

Recent investigations demonstrated a significant correlation between rectal dose-volume patterns and late rectal toxicity. The reduction of the DVH to a value expressing the probability of complication would be suitable. To fit different normal tissue complication probability (NTCP) models to clinical outcome on late rectal bleeding after external beam radiotherapy (RT) for prostate cancer.

PATIENTS AND METHODS

Rectal dose-volume histograms of the rectum (DVH) and clinical records of 547 prostate cancer patients (pts) pooled from five institutions previously collected and analyzed were considered. All patients were treated in supine position with 3 or 4-field techniques: 123 patients received an ICRU dose between 64 and 70 Gy, 255 patients between 70 and 74 Gy and 169 patients between 74 and 79.2 Gy; 457/547 patients were treated with conformal RT and 203/547 underwent radical prostatectomy before RT. Minimum follow-up was 18 months. Patients were considered as bleeders if showing grade 2/3 late bleeding (slightly modified RTOG/EORTC scoring system) within 18 months after the end of RT. Four NTCP models were considered: (a) the Lyman model with DVH reduced to the equivalent uniform dose (LEUD, coincident with the classical Lyman-Kutcher-Burman, LKB, model), (b) logistic with DVH reduced to EUD (LOGEUD), (c) Poisson coupled to EUD reduction scheme and (d) relative seriality (RS). The parameters for the different models were fit to the patient data using a maximum likelihood analysis. The 68% confidence intervals (CI) of each parameter were also derived.

RESULTS

Forty six out of five hundred and forty seven patients experienced grade 2/3 late bleeding: 38/46 developed rectal bleeding within 18 months and were then considered as bleeders The risk of rectal bleeding can be well calculated with a 'smooth' function of EUD (with a seriality parameter n equal to 0.23 (CI 0.05), best fit result). Using LEUD the relationship between EUD and NTCP can be described with a TD50 of 81.9 Gy (CI 1.8 Gy) and a steepness parameter m of 0.19 (CI 0.01); when using LOGEUD, TD50 is 82.2 Gy and k is 7.85. Best fit parameters for RS are s=0.49, gamma=1.69, TD50=83.1 Gy. Qualitative as well as quantitative comparisons (chi-squared statistics, P=0.005) show that the models fit the observed complication rates very well. The results found in the overall population were substantially confirmed in the subgroup of radically treated patients (LEUD: n=0.24 m=0.14 TD50=75.8 Gy). If considering just the grade 3 bleeders (n=9) the best fit is found in correspondence of a n-value around 0.06, suggesting that for severe bleeding the rectum is more serial.

CONCLUSIONS

Different NTCP models fit quite accurately the considered clinical data. The results are consistent with a rectum 'less serial' than previously reported investigations when considering grade 2 bleeding while a more serial behaviour was found for severe bleeding. EUD may be considered as a robust and simple parameter correlated with the risk of late rectal bleeding.

Gastro-intestinal and genito-urinary morbidity after 3D conformal radiotherapy of prostate cancer: observations of a randomized trial

BACKGROUND AND PURPOSE

The late morbidity of a randomized study was analyzed after a follow up of 2 years. The difference in intestinal morbidity was analyzed as a function of the treatment arm and dose volume parameters. The correlation with acute toxicity and (pre-existing) bowel complaints was investigated.

PATIENTS AND METHODS

266 T1-4N0M0 prostate cancer patients were randomized for conventional (open fields) and 3D conformal radiotherapy using beams eye view blocked fields with the same dose (66 Gy) and gross target volume-planning target volume margin (15 mm). Apart from the RTOG toxicity scoring system a patient self-assessment questionnaire was used to obtain detailed information on morbidity.

RESULTS

At 2 years there is only a trend for less rectal toxicity (grade >/=1) in favor of the conformal radiotherapy (grade 1, 47 versus 40% and grade 2, 10 versus 7% for conventional and conformal radiotherapy, respectively (P=0.1). A significant relation was found between late rectal toxicity (grade >/=1) and the volume of the anus and rectum exposed to >/=90% tumor dose (TD). A highly significant relationship is observed between acute rectum and anal toxicity and late rectal toxicity. The patient self-assessment questionnaire analysis revealed that patients are most bothered by compliance related symptoms like urgency, soiling and fecal loss. In a multivariate analysis, all other variables loose significance, when anal volume exposed to >/=90% TD and pre-treatment defaecation frequency are accounted for. Late anal toxicity is low and related only to acute anal toxicity. Late bladder toxicity is related solely to pre-treatment frequency and overall urological symptoms. The incidence of grade 2 toxicity increases with a factor 2.5-4 when (stool or urine) frequency is unfavorable at the start of treatment.

CONCLUSIONS

Conformal radiotherapy at the dose level of 66 Gy does not significantly decrease the incidence of rectal, anal and bladder toxicity compared to conventional radiotherapy. There is a significant relationship between acute and late toxicity and the anal volume exposed to 90% TD. Intestinal (and urological) symptoms at start have a major impact on late toxicity.

Impact of mean rectal dose on late rectal bleeding after conformal radiotherapy for prostate cancer: Dose–volume effect

PURPOSE

To identify the clinical and dosimetric factors predictive of a greater risk of Grade 2 or worse late rectal bleeding in patients with localized prostate cancer treated with three-dimensional conformal radiotherapy in a prospective dose-escalation study.

METHODS AND MATERIALS

We performed a retrospective analysis of the clinical records and dose-volume histograms of 107 patients with Stage T1c-T3 prostate cancer treated at our institution with three-dimensional conformal radiotherapy who had a minimal follow-up of 1 year. Of the 107 patients, 21 were treated at dose level 1 (70.0 Gy), 57 at dose level 2 (72.0 Gy), and 29 at dose level 3 (75.6 Gy). The mean International Commission on Radiation Units and Measurements reference dose was 76.5 Gy (range, 69.8-82.6 Gy).

RESULTS

The 4-year actuarial incidence of Grade 2 or worse late rectal bleeding was 7.7% +/- 2.5%. The results of the multivariate analysis indicated that the mean rectal dose (rectal D(mean); p = 0.003) and the percentage of rectum receiving >60 Gy (Vr(60); p = 0.002) correlated with Grade 2 or worse rectal bleeding. The receiver operating characteristic curve analysis showed that this logistic regression model using both Vr(60) and rectal D(mean) had good reliability to predict the risk of late rectal bleeding. The area under the curve for Vr(60) and rectal D(mean) was 0.889 and 0.892, respectively.

CONCLUSION

The results of the present study provide clear evidence of a dose-volume effect and the importance of intermediate doses (60.0 Gy) on the risk of rectal bleeding at this prescription dose level. On the basis of these results, new constraints have been implemented in our institution to keep the risk of developing Grade 2 rectal bleeding reasonably low (rectal D(mean) 50.0 Gy and Vr(60) 42%).

Ki-67 staining is a strong predictor of distant metastasis and mortality for men with prostate cancer treated with radiotherapy plus androgen deprivation: Radiation Therapy Oncology Group Trial 92-02

PURPOSE

The Ki-67 staining index (Ki67-SI) has been associated with prostate cancer patient outcome; however, few studies have involved radiotherapy (RT) -treated patients. The association of Ki67-SI to local failure (LF), biochemical failure (BF), distant metastasis (DM), cause-specific death (CSD) and overall death (OD) was determined in men randomly assigned to short term androgen deprivation (STAD) + RT or long-term androgen deprivation (LTAD) + RT.

PATIENTS AND METHODS

There were 537 patients (35.5%) on Radiation Therapy Oncology Group (RTOG) 92-02 who had sufficient tissue for Ki67-SI analysis. Median follow-up was 96.3 months. Ki67-SI cut points of 3.5% and 7.1% were previously found to be related to patient outcome and were examined here in a Cox proportional hazards multivariate analysis (MVA). Ki67-SI was also tested as a continuous variable. Covariates were dichotomized in accordance with stratification and randomization criteria.

RESULTS

Median Ki67-SI was 6.5% (range, 0% to 58.2%). There was no difference in the distribution of patients in the Ki-67 analysis cohort (n = 537) and the other patients in RTOG 92-02 (n = 977) by any of the covariates or end points tested. In MVAs, Ki67-SI (continuous) was associated with LF (P =.08), BF (P =.0445), DM (P <.0001), CSD (P <.0001), and OD (P =.0094). When categoric variables were used in MVAs, the 3.5% Ki67-SI cut point was not significant. The 7.1% cut point was related to BF (P =.09), DM (P =.0008), and CSD (P =.017). Ki67-SI was the most significant correlate of DM and CSD. A detailed analysis of the hazard rates for DM in all possible covariate combinations revealed subgroups of patients treated with STAD + RT that did not require LTAD.

CONCLUSION

Ki67-SI was the most significant determinant of DM and CSD and was also associated with OD. The Ki67-SI should be considered for the stratification of patients in future trials.

Is There a “Curative” Role of Radiotherapy for Clinically Localized Hormone Refractory Prostate Cancer?

Whether definitive radiotherapy (RT) is still an option for patients with clinically prostate-confined prostate cancer treated with androgen deprivation (AD) alone who develop a rising prostate-specific antigen (PSA) is not clear. In this retrospective series, we report the outcome of 29 such patients treated with "curative" radiotherapy at our institution between 1991 and 2000. At initial diagnosis, all patients had evidence of prostate-confined disease and for several reasons underwent AD alone. Afterward all patients developed rising PSA, but again, without clinical evidence of distant/pelvic node disease. All underwent RT with curative intent up to 70 Gy (66 to 76 Gy). Median follow-up after radiotherapy is 33.1 month (range: 7-134.2 months). For living patients, minimum and median follow-ups are 30.4 and 55.4 months, respectively. Twenty-three patients (79%) developed overt clinical disease, most of which (19/23, 83%) involved distant sites, whereas isolated locoregional failure was observed in only 4 patients (4/23, 17%). The estimates of locoregional control rate (LRC), actuarial incidence of distant metastases, and overall survival at 5 years are 89 +/- 7%, 68 +/- 9%, and 28 +/- 9%, respectively. Although we were unable to find any predictor of LRC at univariate analysis, patients with low Gleason score at diagnosis, lower PSA at RT, lower risk category and advanced age were less likely to develop distant disease. RT has a palliative role, because most patients with still presumed localized hormone refractory prostate cancer will develop distant metastases. A subset of patients, those with more differentiated tumor at diagnosis and with pre-RT PSA less than 20 ng/mL, might be considered for a more aggressive locoregional approach.

Reducing the toxicity associated with the use of radiotherapy in men with localized prostate cancer

The risk for serious complications associated with modern radiotherapy is relatively low. Compared with conventional radiotherapy, 3DCRT and IMRT allow higher doses to be given more safely. The use of IMRT increases the time and effort required by physicians and physicists. Although there is a clear move toward IMRT, 3DCRT is considered standard. The quality assurance procedures for and fundamental questions regarding IMRT are evolving, including the radiobiologic consequences of altered time-dose fractionation and the greater dose heterogeneity in the target. Defining an accurate target volume and routinely correcting for set-up error and organ movement before each treatment promise to reduce the complications associated with EBRT in the next 5 years. Complications following prostate brachytherapy are better understood now than 10 years ago. Dosimetric or patient selection factors that correlate with a higher risk for complications, such as acute retention, strictures, severe prolonged urinary symptoms, fistulas, proctitis, and impotence, often can be accounted for or avoided. Finally, the role of radiation protectors is beginning to be addressed. It is hoped that these advances will eliminate toxicity associated with radiotherapy and increase cure rates.

Impact of neoadjuvant androgen ablation and other factors on late toxicity after external beam prostate radiotherapy

PURPOSE

To evaluate the late toxicity profile of prostate cancer patients treated with external beam radiotherapy, to investigate the possible risk factors for late toxicity, and to determine whether neoadjuvant androgen ablation (NAA) is a factor.

METHODS AND MATERIALS

The study population consisted of 1192 patients with > or =24 months' follow-up. Late GI and GU toxicities were scored with a modified Radiation Therapy Oncology Group/Subjective, Objective, Management, and Analytic scale. All patients were treated with external beam radiotherapy (52.5 Gy in 20 fractions to 72 Gy in 36 fractions), using either conventional or three-dimensional conformal techniques. Of the 1192 patients, 40% received NAA (median 5 months). Risk factors investigated on multivariate analysis were age, past medical history, use of pelvic fields, dose, fractionation, use and duration of neo- and adjuvant androgen ablation, and acute toxicity (Grade 2 or greater).

RESULTS

The median follow-up for the group was 49 months (range 24-105). The incidence of late Grade 2-3 GI or GU toxicity was 30% at 5 years (GI 12% and GU 20%). The incidence of late Grade 3 GI or GU toxicity was 8% at 5 years (GI 2.7% and GU 5.5%). No Grade 4 toxicity occurred. The risk factors of significance in relation to the development of late Grade 3 GU toxicity were coexisting GU disease (p = 0.02), prior transurethral resection of the prostate or transurethral resection of bladder tumor (p <0.0001), and presence of acute GU toxicity (p = 0.012). For late Grade 3 GI toxicity, short-term (< or =2 months) NAA (p = 0.0002) and coexisting GI disease (p = 0.017) were risk factors.

CONCLUSION

Short-term (< or =2 months) NAA, but not longer durations of NAA, increases the risk of developing Grade 3 GI late toxicity. The possible mechanism of this phenomenon is unclear.

Influence of hormonal therapy on late rectal function after permanent prostate brachytherapy with or without supplemental external beam radiotherapy

PURPOSE

Recent clinical studies have reported a relationship between the use of hormonal therapy and degradation in rectal function after external beam radiotherapy. Using a patient-administered quality-of-life instrument, we evaluated the effect of hormonal therapy on late rectal function after permanent prostate brachytherapy with or without supplemental external beam radiotherapy.

METHODS AND MATERIALS

A total of 189 patients were mailed the Rectal Function Assessment Score (R-FAS), which consists of nine questions (score range 0-27, with higher scores indicative of poorer bowel function). Of the 189 surveys sent out, 187 (98.4%) were returned. Of the 187 patients, 149 (79.7%) were hormone naive, and 38 (20.3%) had received hormonal manipulation (median duration 4 months, range 3-36). The median follow-up for the entire group was 66.3 months. The effect of hormonal therapy on bowel function was evaluated by comparing the R-FAS scores across time, by each of the individual nine questions, and by means of a summary question evaluating the patient's perception of overall bowel function. The two groups were also evaluated in terms of clinical, treatment, and dosimetric parameters, including follow-up, age, Gleason score, clinical stage, pretreatment prostate-specific antigen level, number of pretreatment bowel movements/d, prostate volume, and rectal dosimetry.

RESULTS

The two groups were well matched in all clinical, treatment, and dosimetric parameters, except the patients receiving hormonal therapy had a statistically shorter follow-up (63.9 vs. 69.4 months, p <0.001) and higher pretreatment prostate-specific antigen level (12.0 vs. 9.8 ng/mL, p = 0.024). The R-FAS scores for the hormone-naive and hormonally manipulated patients were comparable (3.76 vs. 4.55, p = 0.083). In terms of the nine individual R-FAS questions, no statistically significant difference was reported for any question when stratified by hormonal status, including rectal bleeding (p = 0.735). Only 12% and 13% of hormone-naive and hormonally manipulated patients, respectively, reported bowel function to be worse after implantation. With time, a trend for improvement in the R-FAS was noted in both cohorts.

CONCLUSION

After permanent prostate brachytherapy, no statistically significant difference in bowel habits was discerned when stratified by hormonal status. In addition, only 12% of brachytherapy patients reported deterioration in bowel function after implantation.

RTOG 94-06: Is the addition of neoadjuvant hormonal therapy to dose-escalated 3D conformal radiation therapy for prostate cancer associated with treatment toxicity?

PURPOSE

This study determines the effect on toxicity of adding neoadjuvant hormonal therapy (NHT) to three-dimensional conformal radiation therapy (3D-CRT) in RTOG 94-06.

METHODS AND MATERIALS

Between August 1994 and February 2000, 583 eligible prostate cancer patients enrolled on the first 3 dose levels of RTOG 94-06, a Phase I/II dose escalation 3D-CRT trial. Two hundred and seven men initiated hormonal therapy (HT) between 2 to 3 months before 3D-CRT, and completed all HT no longer than 3 months after radiotherapy. Thirty-three patients receiving longer-duration HT were excluded. The 547 patients were treated at dose level I (68.4 Gy), level II (73.8 Gy), or level III (79.2 Gy). All dose prescriptions were to the minimum isodose surface encompassing the planning target volume (dose levels I and II) or the clinical target volume (dose level III). Men were stratified into three risk groups according to their relative risk of seminal vesicle invasion: <15% (Group 1) vs. >15% (Group 2), or to T stage (T1, 2 vs. T3 tumors [Group 3]). In Group 2 patients, there was a clinical target volume reduction to treat only the prostate after delivery of 55.8 Gy to a planning target volume including the seminal vesicles. All HT consisted of a luteinizing hormone-releasing hormone agonist with or without a nonsteroidal anti-androgen.

RESULTS

On univariate analysis, NHT significantly increased the likelihood of Grade 2 acute genitourinary (GU) complications (22% to 32%, p = 0.009). Hormonal therapy did not have a significant univariate effect on any other acute or late toxicity. On multivariate analysis, the percent of the bladder (< or =30% vs. >30%) receiving > or = the reference dose (68.4 Gy, 73.8 Gy, or 79.2 Gy) (p = 0.0009, relative risk = 2.07, confidence interval: 1.88-2.28) was a significant predictor of acute GU effects. Although NHT was not significant in itself, in the multivariate analysis its interaction with baseline urinary status was an important factor (p = 0.011, relative risk = 4.31, confidence interval: 1.68-5.29).

CONCLUSION

Neoadjuvant HT did not show an independent effect on the risk of side effects after 3D-CRT in patients treated on RTOG 94-06. However, this combined modality therapy significantly increased the risk of acute GU effects compared to 3D-CRT alone in men with poor baseline urinary function.

Finding dose–volume constraints to reduce late rectal toxicity following 3D-conformal radiotherapy (3D-CRT) of prostate cancer

BACKGROUND AND PURPOSE

The rectum is known to display a dose-volume effect following high-dose 3D-conformal radiotherapy (3D-CRT). The aim of the study is to search for significant dose-volume combinations with the specific treatment technique and patient set-up currently used in our institution.

PATIENTS AND METHODS

We retrospectively analyzed the dose-volume histograms (DVH) of 135 patients with stage T1b-T3b prostate cancer treated consecutively with 3D-CRT between 1996 and 2000 to a total dose of 76 Gy. The median follow-up was 28 months (range 12-62). All late rectal complications were scored using RTOG criteria. Time to late toxicity was assessed using the Kaplan-Meyer method. The association between variables at baseline and > or=2 rectal toxicity was tested using chi(2) test or Fisher's exact test. A multivariate analysis using logistic regression was performed.

RESULTS

Late rectal toxicity grade > or=2 was observed in 24 of the 135 patients (17.8%). A 'grey area' of increased risk has been identified. Average DVHs of the bleeding and non-bleeding patients were generated. The area under the percent volume DVH for the rectum of the bleeding patients was significantly higher than that of patients without late rectal toxicity. On multivariate analysis the correlation between the high risk DVHs and late rectal bleeding was confirmed.

CONCLUSIONS

The present analysis confirms the role of the rectal DVH as a tool to discriminate patients undergoing high-dose 3D-CRT into a low and a high risk of developing late rectal bleeding. Based on our own results and taking into account the data published in the literature, we have been able to establish new dose-volume constraints for treatment planning: if possible, the percentage of rectal volume exposed to 40, 50, 60, 72 and 76 Gy should be limited to 60, 50, 25, 15 and 5%, respectively.