Intensity-modulated and 3D-conformal radiotherapy for whole-ventricular irradiation as compared with conventional whole-brain irradiation in the management of localized central nervous system germ cell tumors

Primary suprasellar germinoma: A series of 15 cases

Primary suprasellar germinoma (PSG) is a rare malignant tumor of the central nervous system. This study aimed to explore the clinical characteristics, treatment protocol, and prognosis of patients with PSG. This case series retrospectively analyzed the clinical data of patients with PSG in Tianjin Huanhu Hospital diagnosed between January 2016 and December 2021. Fifteen patients with an average age of 19.6 years were included, in which nine of them were males. The mean duration between initial symptoms and admission was 17.0 months. The mean follow-up was 40.8 months. Ten patients had polydipsia and polyuria, visual impairments were observed in 8 patients, and 2 cases (13.3%) had symptoms both from suprasellar and pineal regions. All 15 cases were histopathologically confirmed as germinoma through craniotomy or biopsy. Most patients (80%) underwent radiotherapy combined with chemotherapy. During follow-up, all the patients showed a reduction in tumor size, especially in the bifocal cases. Symptoms of polydipsia, polyuria, and visual impairment were markedly relieved to different degrees. All patients had recovered well at discharge. Patients with polydipsia and polyuria took desmopressin daily. A histological confirmation by open biopsy through craniotomy or endoscopic biopsy might be recommended for PSG to start the appropriate treatments. Patients with PSG will usually have a good prognosis, but attention should be paid to the treatment of endocrine deficiencies.

A simple analytical model for a fast 3D assessment of peripheral photon dose during coplanar isocentric photon radiotherapy

Considering that cancer survival rates have been growing and that nearly two-thirds of those survivors were exposed to clinical radiation during its treatment, the study of long-term radiation effects, especially secondary cancer induction, has become increasingly important. To correctly assess this risk, knowing the dose to out-of-field organs is essential. As it has been reported, commercial treatment planning systems do not accurately calculate the dose far away from the border of the field; analytical dose estimation models may help this purpose. In this work, the development and validation of a new three-dimensional (3D) analytical model to assess the photon peripheral dose during radiotherapy is presented. It needs only two treatment-specific input parameter values, plus information about the linac-specific leakage, when available. It is easy to use and generates 3D whole-body dose distributions and, particularly, the dose to out-of-field organs (as dose–volume histograms) outside the 5% isodose for any isocentric treatment using coplanar beams [including intensity modulated radiotherapy and volumetric modulated arc therapy (VMAT)]. The model was configured with the corresponding Monte Carlo simulation of the peripheral absorbed dose for a 6 MV abdomen treatment on the International Comission on Radiological Protection (ICRP) 110 computational phantom. It was then validated with experimental measurements using thermoluminescent dosimeters in the male ATOM anthropomorphic phantom irradiated with a VMAT treatment for prostate cancer. Additionally, its performance was challenged by applying it to a lung radiotherapy treatment very different from the one used for training. The model agreed well with measurements and simulated dose values. A graphical user interface was developed as a first step to making this work more approachable to a daily clinical application.

Pineal germinoma in a young adult: A case report

BACKGROUND

Intracranial germinomas (GN) are rare cancers that primarily affect children, making them rarer still in adults. Standard treatment for this neoplasm includes neoadjuvant chemotherapy (NC) followed by radiotherapy (RT) or RT at a higher dose and larger field. These recommendations are based on studies focused mostly on children; it is currently unclear whether this treatment is applicable to adults.

CASE

We present a case of a 23-year-old adult male with no underlying pathologies, drug allergies, or family history of cancer, who presented for medical evaluation with blurred vision, diplopia, forgetfulness, and weight loss starting 3-4 months before the evaluation. Clinical examination indicated Parinaud's Syndrome. Magnetic resonance imaging (MRI) and computed tomography (CT) revealed a pineal tumor with ependymal dissemination in both lateral ventricles, which was causing obstructive hydrocephalus. The patient had surgery consisting of ventriculostomy, Holter shunt insertion, cisternal ventricular intubation, and cisterna magna anastomosis to improve ventricular drainage. Pathology confirmed pineal germinoma. Cerebrospinal fluid cytology and MRI of the axis were negative. Four cycles of NC were given to the patient (carboplatin, etoposide, and ifosfamide), with reduced dosage. Once a partial volumetric response was confirmed, whole-ventricular radiotherapy (WVR) was initiated with a total tumor bed dose of 45 Gy over 25 sessions in 5 weeks. Optimum clinical results were observed, and no short-term (<90 day) radiation toxicity was observed. The patient was able to resume his normal activities soon after treatment. Follow-ups over 2 years post-surgery indicated continued control of the lesion and absence of symptoms except for mild diplopia.

CONCLUSION

Although this is a case report, these data suggest that a reduced NC course and WVR may effectively treat adult GN. This protocol likely decreases the risk of undesirable NC and RT secondary effects, while providing excellent local control; however, using a narrower RT field is not recommended.

Comparison on epidemiology, tumor location, histology, and prognosis of intracranial germ cell tumors between Mayo Clinic and Japanese consortium cohorts

OBJECTIVE

Central nervous system (CNS) germ cell tumors (GCTs) are rare malignant neoplasms that arise predominantly in adolescents and young adults. CNS GCTs demonstrate characteristic trends in national associations, with implications for both tumor incidence and genetics. Although the incidence of CNS GCTs is markedly higher in East Asia than Western countries, direct comparative analyses between these CNS GCT populations are limited.

METHODS

In Japan, to facilitate the genomic analyses of CNS GCTs, the Intracranial Germ Cell Tumor Genome Analysis Consortium was established in 2011, and more than 200 cases of GCTs are available for both tumor tissue and clinical data, which is organized by the National Cancer Center (NCC) Japan. At the Mayo Clinic, there have been 98 cases of intracranial GCTs treated by the Department of Neurologic Surgery since 1988. In this paper, the authors compared the epidemiology, clinical presentation including location and histology, and prognosis between cases treated in the US and Japan.

RESULTS

There was no significant difference in age and sex distributions between the databases. However, there was a significant difference in the tumor locations; specifically, the frequency of basal ganglia was higher in the NCC database compared with the Mayo Clinic (8.4% vs 0%, p = 0.008), and bifocal location (neurohypophysis and pineal gland) was higher at the Mayo Clinic than at the NCC (18.8% vs 5.8%, p = 0.002). There was no difference in histological subdivisions between the databases. There was no difference in progression-free survival (PFS) and overall survival (OS) of germinoma cases and OS of nongerminomatous GCT (NGGCT) cases treated with chemotherapy and radiation therapy covering whole ventricles. However, PFS of NGGCTs differed significantly, and was better in the NCC cohorts (p = 0.04).

CONCLUSIONS

There appears to be a differential distribution of GCTs by neuroanatomical location between major geographic and national groups. Further study is warranted to better characterize any underlying genomic, epigenetic, or environmental factors that may be driving the phenotypic differences.

Kidney-sparing whole abdominal irradiation in Wilms tumor: Potential advantages of VMAT technique

PURPOSE

To present a preliminary clinical experience and a dosimetric comparison of kidney-sparing volumetric modulated arc therapy (VMAT) with three-dimensional conformal radiotherapy (3D-CRT) for whole abdominal irradiation (WAI), in the setting of Wilms tumor (WT) treatment.

MATERIALS AND METHODS

From a total of 20 consecutive WT cases treated with adjuvant irradiation, seven were submitted to WAI with VMAT. Renal function and survival rates were evaluated, and, for comparison purposes, similar VMAT and 3D-CRT treatment plans were performed for WAI patients, and differences were dosimetrically evaluated regarding doses to the remaining kidney and other organs at risk and the planning target volume (PTV).

RESULTS

After a median follow-up time of 40.8 months (35.3-52.2), no acute significant intestinal toxicity was observed, and median creatinine clearance was 110.1 and 103.3 mL/min/1.73 m², respectively, before treatment and at last follow-up for WAI patients (P = 0.128). For comparative plans, maximum and median doses were lower for the remaining kidney with VMAT than with 3D-CRT. VMAT was associated with better PTV coverage as compared with 3D-CRT, with superior results for all the evaluated parameters (D95, D2, V100%, V98%, V95%; P = 0.018).

CONCLUSION

The use of VMAT technique is associated with lower radiation doses to the remaining kidney and better coverage to the PTV than 3D-CRT technique for WAI, with preliminary clinical experience showing a favorable toxicity profile. Long-term results from prospective studies might prove the ability of VMAT to spare renal function in the setting of WT treatment.

Intensity-modulated ventricular irradiation for intracranial germ-cell tumors: Survival analysis and impact of salvage re-irradiation

Background and purpose

The roles of surgery, chemotherapy, and parameters of radiation therapy for treating very rare central nervous system germ cell tumors (CNS-GCT) are still under discussion. We aimed to evaluate the survival and recurrence patterns of patients with CNS-GCT treated with chemotherapy followed by whole ventricle irradiation with intensity-modulated radiation therapy.

Materials and methods

We reviewed the clinical outcomes of 20 consecutive patients with CNS-GCT treated with chemotherapy and intensity-modulated radiation therapy from 2004 to 2014 in two partner institutions.

Results

Twenty children with a median age of 12 years were included (16 males). Sixteen tumors were pure germinomas, and 4 were non-germinomatous germ cell tumors (NGGCT). All patients were treated with intensity-modulated radiation therapy guided by daily images, and 70% with volumetric intensity-modulated arc radiotherapy additionally. The median dose for the whole-ventricle was 25.2 Gy (range: 18–30.6 Gy) and 36 Gy (range: 30–54 Gy) for the tumor bed boost. The median post-radiation therapy follow-up was 57.5 months. There were 3 recurrences (2 NGGCT and 1 germinoma that recurred as a NGGCT), with 1 death from the disease and the other 2 cases each successfully rescued with chemotherapy and craniospinal irradiation. The overall survival at 5 years was 95% and disease-free survival was 85%.

Conclusions

The results of this study suggest that the combined use of chemotherapy followed by whole ventricle irradiation with intensity-modulated radiation therapy is effective for CNS-GCTs, especially pure germinomas. Even being rescued with craniospinal irradiation, the NGGCT cases have markedly worse prognoses and should be more rigorously selected for localized treatment.

Reduced-volume radiotherapy for patients with localized intracranial nongerminoma germ cell tumors

Craniospinal irradiation is standard radiotherapy (RT) for localized intracranial nongerminoma germ cell tumors (NGGCT). Given its toxicity, there is interest in using smaller fields. We examined outcomes of NGGCT patients receiving reduced-volume RT at a single institution. Records of 16 patients who received reduced-volume RT as part of definitive treatment between 1996 and 2016 were reviewed. Median age at presentation was 10.8 years (range 4.6-41.0 years). Ten patients had pineal tumors and 6 had suprasellar tumors. All received chemotherapy and 9 patients received second-look surgery thereafter. RT volume was tumor-only to a median of 54 Gy (range 50.4-54 Gy) in 3 patients and whole-ventricle irradiation to a median of 30.6 Gy (range 30.6-36 Gy) with a boost to 54 Gy in 13 patients. Median follow-up was 4.1 years (range 1.9-19.3 years). Three patients recurred locally at a median 9.9 months (range 9.6-10.6 months) after diagnosis, and one of these developed leptomeningeal relapse after 30 months. One patient expired from disease 2.6 years post-diagnosis and another due to stroke 19.3 years post-diagnosis. Fourteen patients are alive with no evidence of disease. Kaplan-Meier estimates of the 4-year overall survival and failure-free survival are 92% (95% confidence interval [CI], 57-99%) and 81% (95% CI 53-94%), respectively. Excellent disease control was observed in these patients with no initial relapses outside of these RT fields. The results of ACNS1123 may better delineate patterns of failure and identify subgroups likely to benefit from this approach.

Intensity-Modulated Radiation Therapy With Dose Painting: A Brain-Sparing Technique for Intracranial Germ Cell Tumors

BACKGROUND

We sought to assess patterns of failure in pediatric patients with intracranial germ cell tumors (GCT) treated with intensity-modulated radiation therapy with dose painting (DP-IMRT).

PROCEDURE

Between July 2007 and October 2013, 11 patients with localized GCT-five germinomas and six nongerminoma GCT (NGGCT)-received definitive treatment with DP-IMRT. Three representative patients were selected for replanning with (i) whole ventricular irradiation (WVI) with opposed lateral beams plus IMRT to the primary tumor and (ii) sequential IMRT. These plans were compared to the patients' original DP-IMRT plans for dosimetric analyses.

RESULTS

Four patients with germinoma received radiation therapy alone: 45 Gy in 1.8 Gy fractions to the primary tumor and 25 Gy in 1.0 Gy fractions to whole ventricles using a dose-painting plan. One patient with germinoma received a reduced dose of 30.6 Gy to the primary tumor after neoadjuvant chemotherapy. Patients with NGGCT (n = 6) underwent multimodality treatment including chemotherapy (n = 6) and surgery (n = 3). These patients received 54 Gy to the primary tumor and 32.4-36 Gy to the whole ventricles. Dosimetric analyses showed DP-IMRT delivered decreased mean dose to whole brain, temporal lobes, hippocampi, cochleae, and optic nerves. With median follow-up of 4 years, 3-year failure-free survival was 100% for patients with germinoma and 67% for patients with NGGCT. One patient with a pineal NGGCT experienced a local recurrence within the high dose-volume while another experienced an isolated biochemical failure.

CONCLUSIONS

DP-IMRT is dosimetrically superior to standard IMRT techniques for sparing of normal tissues. Disease control in this small series appears at least comparable to published results.

Differential dosimetric benefit of proton beam therapy over intensity modulated radiotherapy for a variety of targets in patients with intracranial germ cell tumors

Background

We performed dosimetric comparisons between proton beam therapy and intensity modulated radiotherapy (IMRT) of intracranial germ cell tumors (ICGCTs) arising in various locations of the brain.

Materials

IMRT, passively scattered proton therapy (PSPT), and spot scanning proton therapy (SSPT) plans were performed for four different target volumes: the whole ventricle (WV), pineal gland (PG), suprasellar (SS), and basal ganglia (BG). Five consecutive clinical cases were selected from the patients treated between 2011 and 2014 for each target volume. Total 20 cases from the 17 patients were included in the analyses with three overlap cases which were used in plan comparison both for the whole ventricle and boost targets. The conformity index, homogeneity index, gradient index, plan quality index (PQI), and doses applied to the normal substructures of the brain were calculated for each treatment plan.

Results

The PQI was significantly superior for PSPT and SSPT than IMRT for ICGCTs in all locations (median; WV: 2.89 and 2.37 vs 4.06, PG: 3.38 and 2.70 vs 4.39, SS: 3.92 and 2.49 vs 4.46, BG: 3.01 and 2.49 vs 4.45). PSPT and SSPT significantly reduced the mean dose, and the 10 and 15 Gy dose volumes applied to the normal brain compared with IMRT (p ≤ 0.05). PSPT and SSPT saved significantly greater volumes of the temporal lobes and hippocampi (p < 0.05) in the SS and PG targets than IMRT. For tumors arising in the BG, PSPT and SSPT also saved greater volumes of the contralateral temporal lobes.

Conclusions

PSPT and SSPT provide superior target volume coverage and saved more normal tissue compared with IMRT for ICGCTs in various locations. Future studies should assess whether the extent of normal tissue saved has clinical benefits in children with ICGCTs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-015-0441-5) contains supplementary material, which is available to authorized users.

Understanding the Treatment Strategies of Intracranial Germ Cell Tumors: Focusing on Radiotherapy

Intracranial germ cell tumors (ICGCT) occur in 2-11% of children with brain tumors between 0-19 years of age. For treatment of germinoma, relatively low radiation doses with or without chemotherapy show excellent 10 year survival rate of 80-100%. Past studies showed that neoadjuvant chemotherapy combined with focal radiotherapy resulted in unacceptably high rates of periventricular tumor recurrence. The use of generous radiation volume which covers the whole ventricular space with later boost treatment to primary site is considered as standard treatment of intracranial germinomas. For non-germinomatous germ cell tumors (NGGCT), 10-year overall survival rate is still much inferior than that of intracranial germinoma despite intensive chemotherapy and high-dose radiotherapy. Craniospinal radiotherapy combined with cisplatin-based chemotherapy provides the best treatment outcome for NGGCT; 60-70% of overall survival rate. There is a debate on the surgical role whether surgery can contribute to improved treatment outcome of NGGCT when added to combined chemoradiotherapy. Because higher dose of radiotherapy is required for treatment of NGGCT than for germinoma, it is tested whether whole ventricular irradiation can replace craniospinal irradiation in intermediate risk group of NGGCT to minimize radiation-related late toxicity in the recent studies. To minimize the treatment-related neural deficit and late sequelae while maintaining long-term survival rate of ICGCT patients, optimized administration of chemotherapy and radiotherapy should be selected. Use of technically upgraded radiotherapy modalities such as intensity-modulated radiotherapy or proton beam therapy is expected to bring an improved neurocognitive outcome with longitudinal assessment of the patients.

Predictors of long-term survival following postoperative radiochemotherapy for pathologically confirmed suprasellar germ cell tumors

The aim of this study was to evaluate the predictors of long-term survival following postoperative therapy for suprasellar germ cell tumors (GCTs). A total of 23 patients with pathologically confirmed suprasellar GCTs were reviewed between April, 1987 and October, 2008. The predictors were identified with a univariate Cox proportional hazards model and the results were used to group patients according to outcome. The overall survival (OS) and progression-free survival (PFS) rates for the good- and poor-prognosis two groups were estimated with Kaplan-Meier analysis, with log-rank tests used to assess differences between the groups. The OS rate for all patients was 82.6% at 5 and 72.9% at 10 years. Lesion size (2-4 vs. >4 cm) and pathological type (pure germinoma vs. mixed GCT) were the only significant predictors of OS (P<0.05). The OS rate for the good-prognosis group was 92.9% at both 5 and 10 years, whereas the corresponding rates for the poor-prognosis group were 66.7 and 40.0%, respectively (P=0.020). The PFS rate for the good-prognosis group was 92.9% at 5 and 85.7% at 10 years, whereas the corresponding PFS rates for the poor-prognosis group were 44.4 and 33.3%, respectively (P=0.007). Lesion size and histology predicted outcome following postoperative therapy for suprasellar GCT. Therefore, pathological diagnosis is recommended whenever possible, as histology may dictate the choice of treatment.

Current concepts and future strategies in the management of intracranial germinoma

Radiation therapy is the backbone in the management of intracranial germinoma. In localized disease chemotherapy followed by whole brain irradiation is the present standard providing cure rates in excess of 90%. Craniospinal irradiation alone in metastatic disease provides equally excellent outcome. Chemotherapy is able to convert macroscopic to microscopic disease permitting a dose reduction to the tumor site and possibly the ventricular system and is investigated in prospective trials. Chemotherapy alone cannot replace radiotherapy as sole treatment. Whole-ventricular radiotherapy followed by a boost to tumor site without chemotherapy might be feasible. New treatment technologies such as intensity-modulated radiotherapy or proton therapy permit a dose reduction to non-target brain. Data on functional outcome are conflicting and based on small heterogeneous series only mandating prospective investigations.

Volumetric-modulated arc therapy vs conventional fixed-field intensity-modulated radiotherapy in a whole-ventricular irradiation: a planning comparison study

This study evaluated the dosimetric difference between volumetric-modulated arc therapy (VMAT) and conventional fixed-field intensity-modulated radiotherapy (cIMRT) in whole-ventricular irradiation. Computed tomography simulation data for 13 patients were acquired to create plans for VMAT and cIMRT. In both plans, the same median dose (100% = 24 Gy) was prescribed to the planning target volume (PTV), which comprised a tumor bed and whole ventricles. During optimization, doses to the normal brain and body were reduced, provided that the dose constraints of the target coverage were satisfied. The dose-volume indices of the PTV, normal brain, and body as well as monitor units were compared between the 2 techniques by using paired t-tests. The results showed no significant difference in the homogeneity index (0.064 vs 0.065; p = 0.824) of the PTV and conformation number (0.78 vs 0.77; p = 0.065) between the 2 techniques. In the normal brain and body, the dose-volume indices showed no significant difference between the 2 techniques, except for an increase in the volume receiving a low dose in VMAT; the absolute volume of the normal brain and body receiving 1 Gy of radiation significantly increased in VMAT by 1.6% and 8.3%, respectively, compared with that in cIMRT (1044 vs 1028 mL for the normal brain and 3079.2 vs 2823.3 mL for the body; p<0.001). The number of monitor units to deliver a 2.0-Gy fraction was significantly reduced in VMAT compared with that in cIMRT (354 vs 873, respectively; p<0.001). In conclusion, VMAT delivers IMRT to complex target volumes such as whole ventricles with fewer monitor units, while maintaining target coverage and conformal isodose distribution comparable to cIMRT; however, in addition to those characteristics, the fact that the volume of the normal brain and body receiving a low dose would increase in VMAT should be considered.

Potential for improved intelligence quotient using volumetric modulated arc therapy compared with conventional 3-dimensional conformal radiation for whole-ventricular radiation in children

PURPOSE

To compare volumetric modulated arc therapy (VMAT) with 3-dimensional conformal radiation therapy (3D-CRT) in the treatment of localized intracranial germinoma. We modeled the effect of the dosimetric differences on intelligence quotient (IQ).

METHOD AND MATERIALS

Ten children with intracranial germinomas were used for planning. The prescription doses were 23.4 Gy to the ventricles followed by 21.6 Gy to the tumor located in the pineal region. For each child, a 3D-CRT and full arc VMAT was generated. Coverage of the target was assessed by computing a conformity index and heterogeneity index. We also generated VMAT plans with explicit temporal lobe sparing and with smaller ventricular margin expansions. Mean dose to the temporal lobe was used to estimate IQ 5 years after completion of radiation, using a patient age of 10 years.

RESULTS

Compared with the 3D-CRT plan, VMAT improved conformality (conformity index 1.10 vs 1.85), with slightly higher heterogeneity (heterogeneity index 1.09 vs 1.06). The averaged mean doses for left and right temporal lobes were 31.3 and 31.7 Gy, respectively, for VMAT plans and 37.7 and 37.6 Gy for 3D-CRT plans. This difference in mean temporal lobe dose resulted in an estimated IQ difference of 3.1 points at 5 years after radiation therapy. When the temporal lobes were explicitly included in the VMAT optimization, the mean temporal lobe dose was reduced 5.6-5.7 Gy, resulting in an estimated IQ difference of an additional 3 points. Reducing the ventricular margin from 1.5 cm to 0.5 cm decreased mean temporal lobe dose 11.4-13.1 Gy, corresponding to an estimated increase in IQ of 7 points.

CONCLUSION

For treatment of children with intracranial pure germinomas, VMAT compared with 3D-CRT provides increased conformality and reduces doses to normal tissue. This may result in improvements in IQ in these children.

Helical tomotherapy in the treatment of pediatric malignancies: a preliminary report of feasibility and acute toxicity

Background

Radiation therapy plays a central role in the management of many childhood malignancies and Helical Tomotherapy (HT) provides potential to decrease toxicity by limiting the radiation dose to normal structures. The aim of this article was to report preliminary results of our clinical experience with HT in pediatric malignancies.

Methods

In this study 66 consecutive patients younger than 14 years old, treated with HT at our center between January 2006 and April 2010, have been included. We performed statistical analyses to assess the relationship between acute toxicity, graded according to the RTOG criteria, and several clinical and treatment characteristics such as a dose and irradiation volume.

Results

The median age of patients was 5 years. The most common tumor sites were: central nervous system (57%), abdomen (17%) and thorax (6%). The most prevalent histological types were: medulloblastoma (16 patients), neuroblastoma (9 patients) and rhabdomyosarcoma (7 patients). A total of 52 patients were treated for primary disease and 14 patients were treated for recurrent tumors. The majority of the patients (72%) were previously treated with chemotherapy. The median prescribed dose was 51 Gy (range 10-70 Gy). In 81% of cases grade 1 or 2 acute toxicity was observed. There were 11 cases (16,6%) of grade 3 hematological toxicity, two cases of grade 3 skin toxicity and one case of grade 3 emesis. Nine patients (13,6%) had grade 4 hematological toxicity. There were no cases of grade 4 non-hematological toxicities. On the univariate analysis, total dose and craniospinal irradiation (24 cases) were significantly associated with severe toxicity (grade 3 or more), whereas age and chemotherapy were not. On the multivariate analysis, craniospinal irradiation was the only significant independent risk factor for grade 3-4 toxicity.

Conclusion

HT in pediatric population is feasible and safe treatment modality. It is characterized by an acceptable level of acute toxicity that we have seen in this highly selected pediatric patient cohort with clinical features of poor prognosis and/or aggressive therapy needed. Despite of a dosimetrical advantage of HT technique, an exhaustive analysis of long-term follow-up data is needed to assess late toxicity, especially in this potentially sensitive to radiation population.