Clinical use of a wing field with transmission block for the treatment of the pelvis including the inguinal node

Technical aspects of radiation therapy for anal cancer

Historically treated with surgery, current practice recommends anal carcinoma to be treated with a combination of chemotherapy and radiation. This review will examine the anatomy, modes of disease spread and recurrence, and evaluate the existing evidence for treatment options for these tumors. An in-depth examination of specific radiation therapy (RT) techniques-such as conventional 3D-conformal RT and intensity-modulated RT-will be discussed along with modern dose constraints. RT field arrangement, patient setup, and recommended gross and clinical target volume (CTV) contours will be considered. Areas in need of further investigation, such as the role in treatment for positron emission tomography (PET) will be explored.

Organ sparing by conformal avoidance intensity-modulated radiation therapy for anal cancer: dosimetric evaluation of coverage of pelvis and inguinal/femoral nodes

PURPOSE

To describe a novel and straightforward conformal avoidance intensity-modulated radiation therapy (IMRT) technique for coverage of pelvis and inguinal/femoral nodes and to compare the dosimetry of the new method with that of other traditional methods of radiation treatment.

METHODS AND MATERIALS

Data of 2 patients with anal cancer were used as example cases to illustrate details and advantages of conformal avoidance IMRT technique. Conventional photons with enface electrons design was created first, thereby providing "outermost boundaries" defined as planning target volume (PTV) for subsequent conformal avoidance IMRT design. Organs at risk (OARs), including femoral head and neck and external genitalia, were contoured as conformal avoidance structures. A step-and-shoot inverse IMRT planning was subsequently generated. For dosimetric comparison, a recently published technique by modified segmental boost was also generated. These treatment techniques were evaluated by dose-volume histogram (DVH) of PTV and OARs. Dose profiles at four different depths from each treatment planning were generated for comparison.

RESULTS

The DVH of PTV showed that coverage of the PTV was comparable among three treatment techniques. Percent volume of PTV receiving more than 90% prescription dose was in the range 94-98% for the three treatment techniques, and all had only 0-2% of PTV receiving more than 110% of prescription dose. The DVH of OARs confirmed that both femoral head and neck and external genitalia could be spared well by conformal avoidance IMRT as compared with the other two techniques. Although greater inhomogeneity of dose distribution within the PTV was noted by conformal avoidance IMRT technique, as shown by dose profiles at four different depths, the maximum doses at different depths were less than 115%, which was comparable to those planned by modified segmental boost technique. Planning by photons and enface electrons technique, however, showed a greater dose variation up to 134% of the prescription dose at 1.5 cm depth along photon-electron match-line.

CONCLUSIONS

To cover pelvis and inguinal/femoral nodes, conformal avoidance IMRT is technically simple to simulate, plan, and execute. Dosimetric study has demonstrated that it achieves comparable PTV coverage compared with other approaches while at the same time significantly sparing the surrounding OARs.

Radiochemotherapy in the conservative treatment of anal canal carcinoma: retrospective analysis of results and radiation dose effectiveness

PURPOSE

This retrospective analysis reports the results on patients with anal canal carcinoma treated by combined radiotherapy and chemotherapy.

METHODS AND MATERIALS

Between March 1993 and December 2001, 43 patients with anal canal carcinoma were treated with radiochemotherapy at the Hospital do Cancer A.C. Camargo. Stage distribution was as follows: I, 3 (7%); II, 23 (53.5%); IIIA, 8 (18.6%); and IIIB, 9 (21%). The median age was 56 years (range, 36-77 years) with most patients being women (4:1). External radiotherapy (RT) was delivered at the whole pelvis followed by a boost at the primary tumor. The median dose of RT at the whole pelvis and at the primary tumor was 45 Gy and 55 Gy, respectively. Chemotherapy was carried out during the first and last 4 days of RT with continuous infusion of 5-fluorouracil (1000 mg/m(2)) and bolus mitomycin C (10 mg/m(2)). Median overall treatment time was 51 days (range, 30-129 days). Thirty-four patients (79%) did not receive elective RT at the inguinal region. Patient's age, tumor stage, overall treatment time, and RT dose at primary tumor were variables analyzed for survival and local control.

RESULTS

Median follow-up time was 42 months (range, 4-116 months). Overall survival and colostomy-free survival at 5 years was 68% and 52%, respectively. Overall survival according to clinical stage was as follows: I, 100%; II, 82%; IIIA, 73%; and IIIB, 18% (p = 0.0049). Complete response was observed in 40 patients (93%). Local recurrence occurred in 9 (21%) patients, and of these, 6 were rescued by surgery. Local control with a preserved sphincter was observed in 34 patients (79%). According to the RT dose, local control was higher among patients who received more than 50 Gy at primary tumor (86.5% vs. 34%, p = 0.012). Inguinal failure was observed in 5 patients (15%) who did not receive inguinal elective RT. Distant metastasis was observed in 11 patients (25.6%). Temporary interruption of the treatment as a result of acute toxicity was necessary in 12 patients (28%). Four patients developed mild chronic complications.

CONCLUSIONS

This analysis suggests that the treatment scheme employed was effective for anal sphincter preservation and local control; however, the incidence of distant metastases was relatively high. The clinical stage was the main prognostic factor for overall survival. Local control was higher in patients treated with doses of more than 50 Gy at primary tumor. The high incidence of inguinal failure implies the need for elective RT in this region.

Tratamento conservador do carcinoma do canal anal

OBJETIVO: Relatar os resultados do tratamento conservador do carcinoma de canal anal com radioterapia e quimioterapia do Centro de Tratamento e Pesquisa Hospital do Câncer A.C. Camargo. MÉTODO: De março de 1993 a dezembro de 2001, 47 pacientes com diagnóstico histológico de carcinoma do canal anal foram tratados de forma conservadora. A dose mediana de radioterapia na pelve e no tumor primário foi respectivamente de 45 e 55 Gy. A quimioterapia foi realizada com 5- Fluorouracil e Mitomicina-C, com doses medianas de 1000 mg/m² por quatro dias e 10 mg/m² por ciclo, respectivamente. Trinta e oito (80,8%) pacientes não receberam radioterapia em região inguinal. O tempo de seguimento mediano foi de 40 meses (oito dias a 116 meses). RESULTADOS: A resposta completa foi alcançada em 40 pacientes (85,1%). O controle local foi obtido em 31 (66%), e a função esfincteriana foi preservada em 38 (80,9%) casos. Metástases à distância foram detectadas em sete (14,9%) pacientes. A sobrevida global e sobrevida livre de doença em cinco anos foram de 61,5% e 50,1%, respectivamente. A sobrevida global e a sobrevida livre de doença em cinco anos para os pacientes que tiveram controle local foram 77,8% (p < 0,001) e 74,4% (p < 0,001). A sobrevida global e livre de doença em cinco anos para os pacientes com linfonodo inguinal clinicamente tumoral foi de 70,7% e 56,7%, respectivamente (p = 0,0085 e p = 0,0207). Doze (25,5%) pacientes necessitaram de interrupção temporária do tratamento. Cinco pacientes tiveram complicações crônicas leves. CONCLUSÃO: O tratamento realizado foi efetivo tanto para preservação do esfíncter anal quanto para controle local de doença. A presença de linfonodo inguinal clinicamente tumoral e a ausência de recidiva foram os principais fatores prognósticos para sobrevida global e sobrevida livre de doença. A taxa relativamente alta de recidiva em região inguinal sugere a necessidade de radioterapia eletiva nessa região.

Irradiating the groin nodes without breaking a leg: A comparison of techniques for groin node irradiation

The purpose of this study was to determine the optimal technique for delivering postoperative radiotherapy for vulvar cancer and other tumors requiring treatment of the inguinal nodes. This project compared tumor coverage and normal tissue sparing for the 5 main radiotherapy techniques that are used to treat vulvar cancer. The intensity-modulated radiation therapy (IMRT) plan was undesirable because it resulted in an excessive dose to portions of the central pelvic structures. The photon thunderbird with skin match was unacceptable because it underdosed a portion of the groin region. The electron thunderbird was ideal for thin patients but was not applicable for most patients because of excessive dose to the skin and subcutaneous tissues. The photon through-and-through and the photon thunderbird with deep match were acceptable in most situations. In thin patients, where the depth of the inguinal vessels is less than 3 cm, the electron thunderbird is the technique of choice. In the average-sized patient, both the photon through-and-through and the photon thunderbird with deep match are reasonable options. The available literature suggests that the risk of femoral neck fracture or necrosis of the femoral head is approximately 11% at 5 years using the photon through-and-through technique. In our opinion, this is an acceptable price to pay for reliable node coverage, setup simplicity, and zero risk of overdose at field junctions.

Irradiation of the inguinal lymph nodes in patients of differing body habitus: A comparison of techniques and resulting normal tissue complication probabilities

The treatment of the inguinal lymph nodes with radiotherapy is strongly influenced by the body habitus of the patient. The effect of 7 radiotherapy techniques on femoral head doses was studied. Three female patients of differing body habitus (ectomorph, mesomorph, endomorph) were selected. Radiation fields included the pelvis and contiguous inguinal regions and were representative of fields used in the treatment of cancers of the lower pelvis. Seven treatment techniques were compared. In the ectomorph and mesomorph, normal tissue complication probability (NTCP) for the femoral heads was lowest with use of anteroposterior (AP) and modified posteroanterior (PA) field with inguinal electron field supplements (technique 1). In the endomorph, NTCP was lowest with use of AP and modified PA field without electron field supplements (technique 2) or a 4-field approach (technique 6). Technique 1 for ectomorphs and mesomorphs and techniques 2 and 6 for endomorphs were optimal techniques for providing relatively homogeneous dose distributions within the target area while minimizing the dose to the femoral heads.

Improved treatment of pelvis and inguinal nodes using modified segmental boost technique: dosimetric evaluation

PURPOSE

To describe a novel, yet simple, modified segmental boost technique (MSBT) and to compare the dosimetry of our method with that of other traditional methods of treatment for the pelvis and inguinal nodes.

METHODS AND MATERIALS

We developed a radiotherapy technique that uses linear accelerators with multileaf collimators to treat the pelvis and sequentially boost the inguinal regions, while minimizing "hot spots" across the match-line. This was achieved by angling the gantry for the inguinal fields so that their medial borders aligned with the divergence of the posterior pelvic field. Film dosimetry was performed to compare the MSBT with the traditional segmental boost technique, partial transmission block, and photon/electron combination techniques. These treatment techniques were scored on the basis of the dose homogeneity index, defined as the ratio of match-line maximum dose to the average dose at a given depth in the groin treatment area.

RESULTS

The values of the dose homogeneity index were the same (1.04) for MSBT and partial transmission block, and 1.21, 1.39, and 1.18 for the segmental boost technique, photon pelvis with electron tags, and photon pelvis with electron boost, respectively.

CONCLUSION

The MSBT proved to be technically simple while optimizing dose homogeneity compared with the other techniques and allows for maximum use of the features of modern linear accelerators.

A technique for inguinal node boost using photon fields defined by asymmetric collimator jaws

A technique is described for treating inguinal nodes when using radiotherapy in the control of pelvic malignancies. A posterior photon field treats the pelvis. A wider anterior photon field treats pelvis and inguinal nodes. An anterior photon boost to nodes is delivered using asymmetric collimator jaws moved across center line. Advantages of this technique include simplicity of setup and treatment (a single isocenter is retained, and no transmission block is needed), minimal dose inhomogeneity, reduced dose to femoral necks reducing the risk of femoral fracture, low risk of nodal underdose, and elimination of dosimetric difficulties inherent in electron beam boosts.

Tratamento do carcinoma do canal anal com radioterapia e quimioterapia concomitantes: resultados preliminares do Hospital do Câncer A. C. Camargo

OBJETIVO: Reportar os resultados preliminares do tratamento do carcinoma do canal anal com radioterapia e quimioterapia concomitantes. MÉTODOS: De janeiro de 1992 a maio de 1998, foram tratados 24 pacientes com diagnóstico histológico de carcinoma do canal anal, sendo 18 pacientes do sexo feminino e seis do sexo masculino (3:1). A idade dos mesmos variou de 35 a 74 anos e a média foi de 59 anos. A distribuição do número de pacientes por estádio clínico foi: I - 1, II - 13, III - 9 e IV - 1. A radioterapia foi realizada com dose de 45 Gy na pelve no Acelerador Linear de 4 MV, seguida de complementação de dose no canal anal até 55 Gy através de campo direto no cobalto. A quimioterapia foi realizada com 5-FU (1.000mg/m²) em infusão contínua e mitomicina C (10mg/m²) em bólus durante os cinco primeiros e os cinco últimos dias da radioterapia. RESULTADOS: O seguimento médio foi de 34 meses. Resposta completa ao tratamento foi obtida em 23 (95,8%) pacientes. Quatorze (58,3%) estão vivos sem doença, três (12%) vivos com doença, cinco (20,8%) mortos pelo câncer e um (4,2%) morreu sem câncer. Recidivas locais ocorreram em cinco (20,8%) pacientes e metástase a distância em quatro (16,6%). A função esfincteriana foi preservada em 18 (75%) pacientes. Complicações agudas e crônicas foram observadas em 19 (79,2%) e em nove (37,5%) pacientes respectivamente. CONCLUSÕES: O tratamento foi efetivo em termos de controle local e preservação esfincteriana, porém com toxicidade aguda e tardia elevadas. Diminuição da dose de radioterapia em toda pelve representa uma estratégia razoável para diminuir os efeitos colaterais agudos e crônicos. Um maior número de pacientes e seguimento mais longo trarão mais informações sobre esta abordagem terapêutica.

Chemoradiation as primary or adjuvant treatment for locally advanced carcinoma of the vulva

PURPOSE

To determine the impact of primary or adjuvant chemotherapy and radiation (CRT) on the survival rates of patients with locally advanced vulvar carcinoma.

METHODS AND MATERIALS

Between 1973 and 1998, 54 patients with vulvar cancer were treated with radiation therapy, among which 20 received CRT, while 34 patients received radiation therapy (RT) alone. Of the 20 patients, 14 were treated for primary or recurrent disease (pCRT), and 6 after radical vulvectomy for high-risk disease (aCRT). Of the 34 patients, 12 were treated primarily (pRT) and 22 received adjuvant treatment (aRT). Chemotherapy consisted of 2 courses of 5-fluorouracil (5-FU) and mitomycin C administered during RT. Six patients received cisplatin in place of mitomycin C. In CRT groups, radiation was administered to the vulva, pelvic, and inguinal lymph nodes to a median dose of 45 Gy with additional 6-17 Gy to gross disease. In RT groups, the median dose to the microscopic diseases was 45 Gy. Nine patients received external beam boost and 16 patients received supplementary brachytherapy in the forms of (226)Ra or (241)Am plaques to sites of macroscopic disease.

RESULTS

Overall survival was superior in the patients treated with pCRT versus pRT with statistical significance (p = 0.04). There was also a statistically significant improvement in disease-specific (p = 0.03) and relapse-free survival (p = 0.01) favoring pCRT. No statistically significant trends of improved survival rates favoring aCRT over aRT were observed.

CONCLUSION

Concurrent radiation therapy and chemotherapy decreases local relapse rate, improves disease-specific and overall survival over RT alone as primary treatment for locally advanced vulvar cancer.

Transmission blocks for lower neck and inguinal lymph node radiotherapy

We evaluate techniques for radiotherapy to low neck and inguinal lymph nodes. Partial transmission blocks (PTBs) simplify treatment planning, daily setup, and improve reproducibility and dose homogeneity. PTBs minimize the risk for dose misadministration to critical organs. Disadvantages include doses that are potentially lower to the medial cervical lymphatics and higher to the femur. PTBs can surmount common treatment planning problems.

Adjuvant radiation for vulvar carcinoma: improved local control

PURPOSE

Local recurrence is a significant problem following primary surgery for advanced vulva carcinoma. The objectives of this study were to evaluate the impact of adjuvant vulvar radiation on local control in high risk patients and the impact of local recurrence on overall survival.

METHODS AND MATERIALS

From 1980-1994, 62 patients with invasive vulva carcinoma and either positive or close (less 8 mm) margins of excision were retrospectively studied. Thirty-one patients were treated with adjuvant radiation therapy to the vulva and 31 patients were observed after surgery. Kaplan-Meier estimates and the Cox proportional hazard regression model were used to evaluate the effect of adjuvant radiation therapy on local recurrence and overall survival. Independent prognostic factors for local recurrence and survival were also assessed.

RESULTS

Local recurrence occurred in 58% of observed patients and 16% in patients treated with adjuvant radiation therapy. Adjuvant radiation therapy significantly reduced local recurrence rates in both the close margin and positive margin groups (p = 0.036, p = 0.0048). On both univariate and multivariate analysis adjuvant radiation and margins of excision were significant prognostic predictors for local control. Significant determinants of actuarial survival included International Federation of Gynecologists and Obstetricians (FIGO) stage, percentage of pathologically positive inguinal nodes and margins of excision. The positive margin observed group had a significantly poorer actuarial 5 year survival than the other groups (p = 0.0016) and adjuvant radiation significantly improved survival for this group. The 2 year actuarial survival after developing local recurrence was 25%. Local recurrence was a significant predictor for death from vulva carcinoma (risk ratio 3.54).

CONCLUSION

Local recurrence is a common occurrence in high risk patients. In this study adjuvant radiation therapy significantly reduced local recurrence rates and may improve overall survival in certain subgroups. As salvage rates after developing local recurrence are poor adjuvant vulvar radiation should be considered for patients at risk after primary surgery.

Topographic distribution of inguinal lymph nodes metastasis: significance in determination of treatment margin for elective inguinal lymph nodes irradiation of low pelvic tumors

PURPOSE

To study the distribution of gross inguinal lymph node metastasis and, in particular, its correlation with major pelvic bony structures on a simulation film.

METHODS AND MATERIALS

Thirty-seven cases of low pelvic tumors having gross inguinal lymph node metastasis that were treated with radiation therapy between November 1987 and December 1992 were segregated for study. The patient's nodes were palpated and marked with lead wire before the simulation film was assumed to be the origin of the previously uninfested node. A total of 84 such labeled nodes was taken. The geometric center of the usually round or elliptical node on the film was obtained from these 37 cases. These centers were transferred to and mapped collectively on a new simulation film showing major pelvic bony structures of left hemipelvis and upper femur.

RESULTS

Distribution of gross inguinal lymph nodes was found confined to the following area, as related to major pelvic bony structure: laterally, just abutting the tangential line that passes through lateral border of the femoral head; medially: 3 cm away from the body's midline axis; superiorly: 1 cm below the line that joins both upper borders of the femoral head; inferiorly: 2.5 cm below the low borders of ischial tuberosity. According to this rectangular boundary, three nodes were out of the field, nine nodes near the border less than 1 cm margin. This area adequately covered 86% (72 of 84) of the studied nodes.

CONCLUSION

Distribution study is important in determining the treatment margin. In general, an additional 1-2 cm beyond the area described above is the recommended treatment margin for elective inguinal lymph nodes irradiation with high confidence level of coverage.

A simple technique for fabrication of transmission block for concomitant treatment of bilateral anterior inguinal lymphatics and pelvic/perineal structures

The efficacy of transmission block technique with contiguous photon irradiation of inguinal as well as pelvic and perineal structures has been reported in literature. In this paper, a simple and accurate method for the proper fabrication of transmission block has been described and also demonstrated to be effective and useful. The procedures for a precise geometrical alignment and dose verification are also detailed.

Femoral neck fracture following groin irradiation

PURPOSE

The incidence and risk factors are evaluated for femoral neck fracture following groin irradiation for gynecologic malignancies.

METHODS AND MATERIALS

The radiation therapy records of 1313 patients with advanced and recurrent cancer of the vagina, vulva, cervix, and endometrium, treated at the Mallinckrodt Institute of Radiology from 1954 to 1992, were reviewed. Median follow-up was 12.7 years. From this group, 207 patients were identified who received irradiation to the pelvis and groins with anterposterior-posterior anterior (AP-PA), 18 MV photons. Data were reviewed regarding irradiation dose to the femoral neck and other presumed risk factors including age, primary site, stage, groin node status, menopausal status, estrogen use, cigarette use, alcohol consumption, and osteoporosis.

RESULTS

The per-patient incidence of femoral neck fracture was 4.8% (10 out of 207). Four patients developed bilateral fractures. However, the cumulative actuarial incidence of fracture was 11% at 5 years and 15% at 10 years. Cox multivariate analysis of age, weight, and irradiation dose showed that only irradiation dose may be important to developing fracture. Step-wise logistic regression of presumed prognostic factors revealed that only cigarette use and x-ray evidence of osteoporosis prior to irradiation treatment were predictive of fracture.

CONCLUSION

Femoral head fracture is a common complication of groin irradiation for gynecologic malignancies. Fracture in our database appears to be related to irradiation dose, cigarette use, and x-ray evidence of osteoporosis. Special attention should be given in treatment planning (i.e., shielding of femoral head/neck and use of appropriate electron beam energies for a portion of treatment) to reduce the incidence of this complication.

Femoral vessel depth and the implications for groin node radiation

PURPOSE

To quantify, based on pretreatment computer tomographic measurements, potential groin node depths, which will aid in optimal treatment planning for patients requiring groin node radiation.

METHODS AND MATERIALS

The pretreatment computer tomographic scans of 50 gynecologic cancer patients were reviewed to determine the distance of each femoral vessel beneath the overlying skin surface, as an indicator of potential groin node depth. Correlative data regarding height and weight were obtained from patient medical records, and were used to calculate the Quetelet index, defined as (weight in kg)/(height in m)2. Treatment parameters of 5 patients who failed prophylactic groin radiation in a recently published study were assessed to determine if underdosage represented a possible cause of failure.

RESULTS

Individual femoral vessel depths ranged from 2.0 to 18.5 cm. When the depths of all four femoral vessels were averaged in each patient, the mean "4-vessel average" depth for this patient population was 6.1 cm. The median Quetelet index for the group was 25.6, and there was a strong correlation between femoral vessel depth and patient Quetelet index. Recalculation of doses provided to the 5 patients failing prophylactic groin radiation in the Gynecologic Oncology Group study showed that all had received potential tumor doses < 4700 cGy, with 3 patients being underdosed by > 30%.

CONCLUSION

While surgery is often indicated in the management of patients with potential groin node metastases, the role of prophylactic groin radiation should not be rejected. Data from this study may aid in the optimal design and implementation of groin node radiotherapy.

Transmission block technique for the treatment of the pelvis and perineum including the inguinal lymph nodes: dosimetric considerations

Radical radiotherapy of pelvic malignancies (e.g., vulva, anus) includes therapeutic dosage to the inguinal nodes. To minimize the dosage to the femoral head, the transmission block technique has been developed to fully irradiate the central pelvis midplane and inguinal nodes. Originally, this technique compensated for dose inhomogeneity in the transverse plane only. In some patients, however, we have observed a significant dose variation along the sagittal plane. The authors have developed a lead compensation technique to homogenize the sagittal dose variations due to the longitudinal sloping in the patient, along with further refinements in this technique. Dosimetric and technical details are also discussed.