[Results of a randomized prospective trial comparing postoperative abdominopelvic radiotherapy with postoperative chemotherapy in early ovarian cancer]

[Radiotherapy for ovarian carcinoma management: Literature review]

Ovarian cancer is the fifth most common cancer in women in France with 4714 new cases in 2017. More than 70% of patients whose disease is initially locally advanced will present locoregional or distant recurrence. Therapeutic options in this situation are not consensual. They are based on chemotherapy possibly associated with an iterative cytoreductive surgery when it is bearable by the patient. The place of radiotherapy in the management of the disease is hidden in the vast majority of national or international standards. We conducted a general review of the literature to clarify the role of irradiation in the global management of ovarian cancers, particularly in recurrence.

Radiation Treatment in Women with Ovarian Cancer: Past, Present, and Future

Ovarian cancer is the most lethal of the gynecologic cancers, with 5-year survival rates less than 50%. Most women present with advanced stage disease as the pattern of spread is typically with dissemination of malignancy throughout the peritoneal cavity prior to development of any symptoms. Prior to the advent of platinum-based chemotherapy, radiotherapy was used as adjuvant therapy to sterilize micrometastatic disease. The evolution of radiotherapy is detailed in this review, which establishes radiotherapy as an effective therapy for women with micrometastatic disease in the peritoneal cavity after surgery, ovarian clear cell carcinoma, focal metastatic disease, and for palliation of advanced disease. However, with older techniques, the toxicity of whole abdominal radiotherapy and the advancement of systemic therapies have limited the use of radiotherapy in this disease. With newer radiotherapy techniques, including intensity-modulated radiotherapy (IMRT), stereotactic body radiotherapy (SBRT), and low-dose hyperfractionation in combination with targeted agents, radiotherapy could be reconsidered as part of the standard management for this deadly disease.

Adjuvant (post-surgery) chemotherapy for early stage epithelial ovarian cancer

BACKGROUND

This is the second update of the review first published in the Cochrane Database of Systematic Reviews in 2009, Issue 1. Epithelial ovarian cancer is diagnosed in over 200,000 women worldwide each year. Ten to 20% of women are diagnosed early, when there is still a good possibility of cure. The treatment of early-stage (stage I and IIa) disease involves surgery to remove the disease, often followed by chemotherapy (adjuvant chemotherapy). The largest clinical trials of adjuvant chemotherapy show an overall survival (OS) advantage with platinum-based chemotherapy; however the precise role and type of this treatment in subgroups of women with differing prognoses needs to be defined.

OBJECTIVES

To undertake a systematic review of the evidence for adjuvant chemotherapy in early-stage epithelial ovarian cancer to determine whether chemotherapy following surgery offers a survival advantage over the policy of observation following surgery (with chemotherapy reserved for treatment of disease recurrence); and to determine if clinical subgroups of women with differing prognoses, based on histological subtype or completeness of surgical staging, have more or less to gain from adjuvant chemotherapy.

SEARCH METHODS

We performed an electronic search using the Cochrane Gynaecological Cancer Specialized Register, Cochrane Central Register of Controlled Trials (CENTRAL 2015, Issue 3), MEDLINE (1948 to March week 5, 2015), and EMBASE (1980 to week 14, 2015). We developed the search strategy using free-text and medical subject headings (MeSH). We also searched registers of clinical trials and citation lists of included studies for potentially relevant studies.

SELECTION CRITERIA

We included randomised clinical trials (RCTs) of women with early stage (I/IIa) epithelial ovarian cancer staged at laparotomy.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed study quality of included RCTs. We resolved any disagreements by discussion with a third review author. We used random-effects methods for all meta-analyses, including subgroup analyses.

MAIN RESULTS

The original version of this Cochrane review included five RCTs involving 1277 women. In this 2015 update, no new studies met the inclusion criteria but we included an additional paper with mature data (10-year follow-up) relating to a previously included study (ICON1).We included four studies in the meta-analyses and considered them to be at a low risk of bias. Most study participants (> 95%) had stage I ovarian cancer. Meta-analysis of five-year data from three studies indicated that women who received adjuvant platinum-based chemotherapy had better overall survival (OS) than those who did not (Hazard ratio (HR) 0.71, 95% confidence interval (CI) 0.53 to 0.93; 1008 women; 3 studies; I² statistic = 0%; high quality evidence). Likewise, meta-analysis of five-year data from four studies indicated that women who received adjuvant chemotherapy had better progression-free survival (PFS) than those who did not (HR 0.67, 95% CI 0.53 to 0.84; 1170 women, 4 studies; I² statistic = 0%; high quality evidence). These findings were robust over time, with 10-year HR estimates of 0.72 (95% CI 0.57 to 0.92; 925 women, 2 studies) and 0.67 (95% CI 0.53 to 0.83; 925 women, 2 studies) for OS and PFS, respectively (high quality evidence). The risk of death at 10 years follow-up favoured the adjuvant chemotherapy arm (0.76, 95% CI 0.62 to 0.94; 923 women, 2 studies; I² statistic = 0%), as did the findings for risk of progression at 10 years (RR 0.72, 95% CI 0.60 to 0.87; 925 women, 2 studies; I² statistic = 0%). Low quality evidence suggested that women with high-risk disease may have the most to gain from adjuvant chemotherapy. However, subgroup analyses could neither confirm nor exclude survival benefits in lower risk disease or in optimally staged disease. We found insufficient data to compare adverse events and long term risks between chemotherapy and observation groups.

AUTHORS' CONCLUSIONS

High-quality evidence indicates that adjuvant platinum-based chemotherapy is effective in prolonging survival in women with early stage (FIGO stage I/IIa) epithelial ovarian cancer. It remains uncertain whether women with low- and intermediate-risk early stage disease will benefit as much from adjuvant chemotherapy as women with high-risk disease. Decisions to use adjuvant chemotherapy (AC) in these women should be mindful of this uncertainty, and the uncertainty regarding adverse events. Treatment of women with lower risk disease should be individualised to take into account individual factors.

Radiotherapy for ovarian cancers - redefining the role

Radiation therapy in ovarian cancers has been considered an outdated concept for many years, mainly due to toxicity and failure to show benefit in terms of survival. Chemotherapy has been extensively used after surgery for these cancers and it has almost replaced radiation therapy as an adjuvant treatment. Nevertheless, failures in ovarian cancers continue to occur even with the use of newer and effective chemotherapy regimens. About 70% patients demonstrate recurrence in the abdomen or pelvis after first line chemotherapy in ovarian cancers. With advances in technology and sophistication of radiation techniques, along with the molecular and biological knowledge of distinct histological subtypes, there is a need to redefine the role of radiation therapy. This review article focuses on the literature on use of radiation in ovarian cancers and its rationale and indications in the present day. For this, a literature pub med/medline search was performed from January 1975 to March 2014 to redefine the role of radiotherapy in ovarian cancers.

Adjuvant (post-surgery) chemotherapy for early stage epithelial ovarian cancer

BACKGROUND

Epithelial ovarian cancer is diagnosed in 4500 women in the UK each year of whom 1700 will ultimately die of their disease.Of all cases 10% to 15% are diagnosed early when there is still a good possibility of cure. The treatment of early stage disease involves surgery to remove disease often followed by chemotherapy. The largest clinical trials of this adjuvant therapy show an overall survival (OS) advantage with adjuvant platinum-based chemotherapy but the precise role of this treatment in subgroups of women with differing prognoses needs to be defined.

OBJECTIVES

To systematically review the evidence for adjuvant chemotherapy in early stage epithelial ovarian cancer to determine firstly whether there is a survival advantage of this treatment over the policy of observation following surgery with chemotherapy reserved for treatment of disease recurrence, and secondly to determine if clinical subgroups of differing prognosis based on histological sub-type, or completeness of surgical staging, have more or less to gain from chemotherapy following initial surgery.

SEARCH METHODS

We performed an electronic search using the Cochrane Gynaecological Cancer Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL 2011, Issue 3), MEDLINE (1948 to Aug week 5, 2011) and EMBASE (1980 to week 36, 2011). We developed the search strategy using free-text and medical subject headings (MESH).

SELECTION CRITERIA

We selected randomised clinical trials that met the inclusion criteria set out based on the populations, interventions, comparisons and outcome measures.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality. Disagreements were resolved by discussion with a third review author. We performed random-effects meta-analyses and subgroup analyses.

MAIN RESULTS

Five randomised controlled trials (RCTs), enrolling 1277 women, with a median follow-up of 46 to 121 months, met the inclusion criteria. Four trials were included in the meta-analyses and we considered them to be at a low risk of bias. Meta-analysis of five-year data from three trials indicated that women who received adjuvant platinum-based chemotherapy had better overall survival (OS) than those who did not (1008 women; hazard ratio (HR) 0.71; 95% confidence interval (CI) 0.53 to 0.93). Likewise, meta-analysis of five-year data from four trials indicated that women who received adjuvant chemotherapy had better progression-free survival (PFS) than those who did not (1170 women; HR 0.67; 95% CI 0.53 to 0.84). The trials included in these meta-analyses gave consistent estimates of the effects of chemotherapy. In addition, these findings were robust over time (10-year PFS: two trials, 925 women; HR 0.67; 95% CI 0.54 to 0.84).Subgroup analysis suggested that women who had optimal surgical staging of their disease were unlikely to benefit from adjuvant chemotherapy (HR for OS 1.22; 95% CI 0.63 to 2.37; two trials, 234 women) whereas those who had sub-optimal staging did (HR for OS 0.63; 95% CI 0.46 to 0.85; two trials, 772 women). One trial showed a benefit from adjuvant chemotherapy among women at high risk (HR for OS 0.48; 95% CI 0.32 to 0.72) but not among those at low/medium risk (HR for OS 0.95; 95% CI 0.54 to 1.66). However, these subgroup findings could be due to chance and should be interpreted with caution.

AUTHORS' CONCLUSIONS

Adjuvant platinum-based chemotherapy is effective in prolonging the survival of the majority of patients who are assessed as having early (FIGO stage I/IIa) epithelial ovarian cancer. However, it may be withheld from women in whom there is well-differentiated encapsulated unilateral disease (stage 1a grade 1) or those with comprehensively staged Ib, well or moderately differentiated (grade 1/2) disease. Others with unstaged early disease or those with poorly differentiated tumours should be offered chemotherapy. A pragmatic approach may be necessary in clinical settings where optimal staging is not normally performed/achieved. In such settings, adjuvant chemotherapy may be withheld from those with encapsulated stage Ia grade 1 serous and endometrioid carcinoma and offered to all others with early stage disease.

Adjuvant (post-surgery) chemotherapy for early stage epithelial ovarian cancer

BACKGROUND

Epithelial ovarian cancer is diagnosed in 4500 women in the UK each year of whom 1700 will ultimately die of their disease. Ten to fifteen percent of all cases are diagnosed early when there is still a good possibility for cure. The treatment of early stage disease involves surgery to remove disease often followed by chemotherapy. The largest clinical trials of this adjuvant therapy show an overall survival (OS) advantage with adjuvant platinum based chemotherapy but the precise role of this treatment in sub-groups of patients with differing prognoses needs to be defined.

OBJECTIVES

To systematically review the evidence for adjuvant chemotherapy in early stage epithelial ovarian cancer to determine; firstly whether there is a survival advantage of this treatment over the policy of observation following surgery with chemotherapy reserved for treatment of disease recurrence, and secondly; to determine if clinical sub-groups of differing prognosis based on histological sub-type or completeness of surgical staging, have more or less to gain from chemotherapy following initial surgery.

SEARCH STRATEGY

An electronic search was performed using the Cochrane Gynaecological Cancer Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL, Issue 2, 2008), MEDLINE (1966 to 2008), EMBASE (1980 to 2008) and CancerLit. The search strategy was developed using free text and medical subject headings (MESH).

SELECTION CRITERIA

The review authors selected those clinical trials that met the inclusion criteria set out based on the populations, interventions, comparisons and outcome measures.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality. Disagreements were resolved by discussion with a third review author. Random effects meta-analyses and sub-group analyses were conducted.

MAIN RESULTS

Five randomised controlled trials (RCTs), enrolling 1277 women, with 46 to 110 months follow-up, met the inclusion criteria. These trials had low risk of bias. Meta-analysis of three trials with adequate data, assessing 1008 women, indicated that women who received adjuvant platinum-based chemotherapy had better overall survival (OS) than those who did not (hazard ratio (HR) 0.71; 95% CI 0.53 to 0.93). Likewise, meta-analysis of four trials with adequate data, assessing 1170 women, indicated that women who received adjuvant chemotherapy had better progression-free survival (PFS) than those who did not (HR 0.67; 95% CI 0.53 to 0.84). The trials included in these meta-analyses gave consistent estimates of the effects of chemotherapy.Sub-group analysis suggested that women who had optimal surgical staging of their disease were unlikely to benefit from adjuvant chemotherapy (HR for OS 1.22; 95% CI 0.63 to 2.37) whereas those who had sub-optimal staging did (HR for OS 0.63; 95% CI 0.46 to 0.85). One trial showed a benefit from adjuvant chemotherapy among women at high risk (HR for OS 0.48; 95% CI 0.32 to 0.72) but not among those at low risk (HR for OS 0.95; 95% CI 0.54 to 1.66). However, these sub-group findings could be due to chance.

AUTHORS' CONCLUSIONS

Adjuvant platinum based chemotherapy is effective in prolonging the survival of the majority of patients who are assessed as having early stage epithelial ovarian cancer. However, even given the limits of sub-group analyses, there is strong evidence that optimal surgical staging identifies patients who have either little or nothing to gain from adjuvant chemotherapy. Taken together with the lack of a survival advantage seen in patients with "low-risk" cancers in the ICON1 trial, it appears safe to withhold adjuvant chemotherapy from optimally staged patients with well differentiated tumours.

Adjuvant (post-surgery) chemotherapy for early stage epithelial ovarian cancer

BACKGROUND

Epithelial ovarian cancer kills about 1700 in the UK each year. Ten to fifteen percent of all cases are diagnosed early when there is still a good chance of cure. The treatment of early stage disease involves surgery to remove disease often followed by chemotherapy. The largest clinical trials of this adjuvant therapy show an overall survival (OS) advantage with adjuvant platinum based chemotherapy but the precise role of this treatment in sub-groups of patients with differing prognoses needs to be defined.

OBJECTIVES

To systematically review the evidence for adjuvant chemotherapy in early stage epithelial ovarian cancer to determine; firstly whether there is a survival advantage of this treatment over the policy of observation following surgery with chemotherapy reserved for treatment of disease recurrence, and secondly; to determine if clinical sub-groups of differing prognosis based on histological sub-type or completeness of surgical staging, have more or less to gain from chemotherapy following initial surgery.

SEARCH STRATEGY

An electronic search was performed using the Cochrane Gynaecological Cancer Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL, Issue 2 2008), MEDLINE (1966 to 2008), EMBASE (1980 to 2008) and CancerLit. The search strategy was developed using free text and medical subject headings (MESH). This yielded a large number of article titles which were sifted down by two review authors to a limited number of articles, the full text versions of which were independently reviewed to select out clinical trials of direct and specific relevance to the review question. Hand searches of the clinical literature were conducted where appropriate to identify additional full-text papers or abstracts of other directly relevant clinical trials.

SELECTION CRITERIA

The review authors selected those clinical trials that met the inclusion criteria set out based on the populations, interventions , comparisons and outcome measures as detailed in the full text review.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality. Disagreements were resolved by discussion or a third reviewer. Random effects meta-analyses and sub-group analyses were conducted.

MAIN RESULTS

Five randomised controlled trials (RCTs), enrolling 1277 women, with 46 to 110 months follow-up, met our inclusion criteria. These trials had low risk of bias. Meta-analysis of three trials with adequate data, assessing 1008 women, indicated that women who received adjuvant platinum-based chemotherapy had better overall survival (OS) than those who did not (hazard ratio (HR) 0.71; 95% CI 0.53 to 0.93). Likewise, meta-analysis of four trials with adequate data, assessing 1170 women, indicated that women who received adjuvant chemotherapy had better progression-free survival (PFS) than those who did not (HR 0.67; 95% CI 0.53 to 0.84). The trials included in these meta-analyses gave consistent estimates of the effects of chemotherapy.Sub-group analysis suggested that women who had optimal surgical staging of their disease were unlikely to benefit from adjuvant chemotherapy (HR for OS 1.22; 95% CI 0.63 to 2.37) whereas those who had sub-optimal staging did (HR for OS 0.63; 95% CI 0.46 to 0.85). One trial showed a benefit from adjuvant chemotherapy among women at high risk (HR for OS 0.48; 95% CI 0.32 to 0.72) but not among those at low risk (HR for OS 0.95; 95% CI 0.54 to 1.66). However, these sub-group findings could be due to chance.

AUTHORS' CONCLUSIONS

Adjuvant platinum based chemotherapy is effective in prolonging the survival of the majority of patients who are assessed as having early stage epithelial ovarian cancer. However, even given the limits of sub-group analyses, there is strong evidence that optimal surgical staging identifies patients who have either little or nothing to gain from adjuvant chemotherapy. Taken together with the lack of a survival advantage seen in patients with "low-risk" cancers in the ICON1 trial, it appears safe to withhold adjuvant chemotherapy from optimally staged patients with well differentiated tumours.

Adjuvant chemotherapy for early-stage ovarian cancer: review of the literature

PURPOSE

This overview summarizes studies with acceptable quality and validity and presents a synthesis of the effectiveness on adjuvant therapy after surgery for early ovarian cancer (EOC) patients.

METHODS

The literature published between 1970 and 2006 was identified systematically by computer-based searches in MEDLINE and Cochrane library.

RESULTS

Twenty-two prospective randomized studies were analyzed, which included 4,626 patients. No difference between adjuvant chemotherapy (AC) and radiotherapy was found. There is agreement on that patients with stage IA, grade 1 tumors have excellent survival and do not need postsurgical therapy. The International Collaborative Ovarian Neoplasm 1/Adjuvant Chemotherapy in Ovarian Neoplasm trials were the first to show an effect on survival of AC, but in patients with adequate surgical staging, there was no additional effect of AC. For patients who are staged incompletely at the time of initial surgery, completion of the staging procedure with either laparoscopy or laparotomy is a reasonable approach before a final decision is made regarding the need for AC. If full staging cannot be performed due to medical contraindication or patient refusal, consideration of AC is reasonable in selected patients. Using prognostic variables such as grade, International Federation of Gynecology and Obstetrics substage, pretreatment of CA-125 < or = 30 U/mL, and DNA ploidy, it is possible to divide patients into risk groups to avoid overtreatment. Gynecologic Oncology Group study 157 suggests that it may be possible to minimize chemotherapy-induced toxicity by using three instead of six cycles of AC, although it is not known fully whether this will compromise effectiveness.

CONCLUSION

Future randomized studies in EOC will include the investigation of new targeted therapies and new prognostic factors in adequately staged patients.

Chemotherapy for early ovarian cancer

PURPOSE OF REVIEW

The treatment of early ovarian cancer has long been based on non-randomized studies and on a small number of randomized studies without sufficient power. Adjuvant chemotherapy is often given to high-risk patients, but the benefit of such an approach has never been proven and the definition of high-risk early ovarian cancer differs widely. Recently, the results of the two largest randomized clinical trials on early ovarian cancer became available. Both trials are discussed, and their results are related to the other relevant literature of the last three years.

RECENT FINDINGS

A meta-analysis of over 1500 patients from the year 2001 confirmed tumor grade as a strong prognostic factor but it also demonstrated the adverse effect of capsule rupture before and during surgery. The Adjuvant Chemotherapy in Ovarian Neoplasm trial (European Organization for Research and Treatment of Cancer) randomized 448 patients to either adjuvant chemotherapy following surgery or observation. Adjuvant chemotherapy improved overall survival and disease-free survival in non-optimally staged patients but showed no benefit in optimally staged patients. The Medical Research Council International Collaborative Ovarian Neoplasm 1 trial randomized 477 patients in a similar way. Overall survival and disease-free survival were improved by adjuvant chemotherapy. It was argued that the study population of the International Collaborative Ovarian Neoplasm 1 trial probably represents non-optimally staged patients, and this hypothesis explains why the results of this trial were in accord with those of the Adjuvant Chemotherapy in Ovarian Neoplasm trial.

SUMMARY

The implications of these data are that a complete surgical staging is of utmost importance and should be pursued. In cases of non-optimal staging and contraindications for restaging, adjuvant chemotherapy is indicated to deal with unnoticed residual tumor deposits that exist in approximately 25% of cases.

Systematic review of adjuvant therapy for early stage (epithelial) ovarian cancer

A systematic review and meta analysis has been undertaken in order to evaluate the effectiveness of adjuvant therapy following surgery for early ovarian cancer. Trials reported since 1990 have been of a higher quality enabling a meta analysis of adjuvant chemotherapy vs adjuvant radiotherapy and a meta analysis of adjuvant chemotherapy vs observation. There was no significant difference between radiotherapy and chemotherapy, though these comprised studies which demonstrated considerable heterogeneity. Chemotherapy did confer significant benefit over observation in terms of both overall and disease free survival. Except for women in whom adequate surgical staging has revealed well differentiated disease confined to one or both ovaries with intact capsule, platinum chemotherapy should be offered to reduce risk of recurrence.

IMRT of large fields: whole-abdomen irradiation

PURPOSE

To assess the feasibility of inverse planning for whole-abdomen intensity-modulated radiation therapy (IMRT) with bone marrow and kidney sparing and to develop approaches to circumventing field size restrictions in the application of whole-abdomen IMRT using dynamic multileaf collimators (DMLC).

METHODS AND MATERIALS

The entire peritoneal cavity as derived from serial computerized tomography scans was defined as the gross target volume, whereas the planning target volume (PTV) was defined as the gross target volume plus a 5-mm margin extending 1 cm superiorly and inferiorly. In 10 randomly selected patients, the PTV ranged from 5629 to 12578 cc (median 7935 cc), and the superior-inferior, lateral, and anterior-posterior dimensions of the PTV ranged from 37 to 46 cm (median 42.5 cm), 27 to 33 cm (median 29 cm), and 18 to 23 cm (median 20 cm), respectively. A single isocenter was defined for patients with field length <40 cm. For patients with fields >40 cm, two isocenters were defined: one in the abdominal region, and the other in the pelvis. For IMRT planning, five 15-MV intensity-modulated beams at gantry angles of 180 degrees, 105 degrees, 35 degrees, 325 degrees, and 255 degrees were used. Optimization was designed to spare kidneys and bones. To fully account for the significant scattered dose contributions, an iterative process for dose calculations was implemented in the optimization. To overcome the 15-cm field width limit of our DMLC delivery system, fields with a width >15 cm were split into two or more subfields. To minimize field match errors, adjacent subfields overlapped by at least 2 cm, with intensity "feathering" in the overlap region. For patients with two isocenters, fields were overlapped and feathered in the cephalad-caudad direction by at least 3 cm. For comparison, conventional anterior-posterior/posterior-anterior 6-MV photon beams with posterior kidney blocks at extended distance were also generated for each patient.

RESULTS

Treatment plan optimization calculations required 20-80 min on a 500-MHz DEC alpha workstation. Including beam splitting, an average of 16 DMLC beams was used per patient. Delivery of 150 cGy required, on average, 1442 monitor units. For the same dose constraints on the kidneys, whole-abdomen IMRT resulted in significant dose reduction to the bones and improved PTV coverage as compared to conventional treatment. For a prescription dose of 30 Gy, the volume of the pelvic bones receiving more than 21 Gy was reduced on average by almost 60% with IMRT, and the mean dose to all bones was reduced from 24.0 +/- 1.5 Gy to 18.5 +/- 1.0 Gy (p = 0.002). PTV coverage, as measured by V95 (the volume receiving 95% of the prescription dose), improved from 71.7 +/- 4.8% with conventional treatment to 83.5 +/- 3.9% with IMRT (p = 0.002), although small regions of underdose in areas near the kidneys could not be avoided completely. The high-dose regions within the PTV, as measured by D05 (the dose covering 5% of PTV volume), increased slightly from 31.2 +/- 0.6 Gy with conventional treatment to 32.8 +/- 0.2 Gy with IMRT.

CONCLUSION

We have developed a process to plan and deliver whole-abdomen IMRT using standard linear accelerators and DMLC. IMRT can achieve better PTV coverage with the same level of kidney sparing and improved sparing of the bone marrow. These methods may be applicable also to other sites requiring large-field irradiation.