Significance of prone positioning in planning treatment for esophageal cancer

Respiratory motion tracking of spine stereotactic radiotherapy in prone position

PURPOSE

The CyberKnife system is a specialized device for non-coplanar irradiation; however, it possesses the geometric restriction that the beam cannot be irradiated from under the treatment couch. Prone positioning is expected to reduce the dose to normal lung tissue in spinal stereotactic body radiotherapy (SBRT) owing to the efficiency of beam arrangement; however, respiratory motion occurs. Therefore, the Xsight spine prone tracking (XSPT) system is used to reduce the effects of respiratory motion. The purpose of this study was to evaluate the motion-tracking error of the spine in the prone position.

MATERIALS AND METHODS

Data from all 25 patients who underwent spinal SBRT at our institution between April 2020 and February 2022 using CyberKnife (VSI, version 11.1.0) with the XSPT tracking system were retrospectively analyzed using log files. The tumor motion, correlation, and prediction errors for each patient were examined. Furthermore, to assess the potential relationships between the parameters, the relationships between the tumor-motion amplitudes and correlation or prediction errors were investigated using linear regression.

RESULTS

The tumor-motion amplitudes in each direction were as follows: superior-inferior (SI), 0.51 ± 0.39 mm; left-right (LR), 0.37 ± 0.29 mm; and anterior-posterior (AP), 3.43 ± 1.63 mm. The overall mean correlation and prediction errors were 0.66 ± 0.48 mm and 0.06 ± 0.07 mm, respectively. The prediction errors were strongly correlated with the tumor-motion amplitudes, whereas the correlation errors were not.

CONCLUSIONS

This study demonstrated that the correlation error of spinal SBRT in the prone position is sufficiently small to be independent of the tumor-motion amplitude. Furthermore, the prediction error is small, contributing only slightly to the tracking error. These findings will improve the understanding of how to compensate for respiratory-motion uncertainty in the prone position.

Characterization of Respiration-Induced Motion in Prone Versus Supine Patient Positioning for Thoracic Radiation Therapy

Purpose

Variations in the breathing characteristics, both on short term (intrafraction) and long term (interfraction) time scales, may adversely affect the radiation therapy process at all stages when treating lung tumors. Prone position has been shown to improve consistency (ie, reduced intrafraction variability) and reproducibility (ie, reduced interfraction variability) of the respiratory pattern with respect to breathing amplitude and period as a result of natural abdominal compression, with no active involvement required from the patient. The next natural step in investigating breathing-induced changes is to evaluate motion amplitude changes between prone and supine targets or organs at risk, which is the purpose of the present study.

Methods and Materials

Patients with lung cancer received repeat helical 4-dimensional computed tomography scans, one prone and one supine, during the same radiation therapy simulation session. In the maximum-inhale and maximum-exhale phases, all thoracic structures were delineated by an expert radiation oncologist. Geometric centroid trajectories of delineated structures were compared between patient orientations. Motion amplitude was measured as the magnitude of difference in structure centroid position between inhale and exhale.

Results

Amplitude of organ motion was larger when the patient was in the prone position compared with supine for all structures except the lower left lobe and left lung as a whole. Across all 12 patients, significant differences in mean motion amplitude between orientations were identified for the right lung (3.0 mm, P = .01), T2 (0.5 mm, P = .01) and T12 (2.1 mm, P < .001) vertebrae, the middle third of the esophagus (4.0 mm, P = .03), and the lung tumor (1.7 mm, P = .02).

Conclusions

Respiration-induced thoracic organ motion was quantified in the prone position and compared with that of the supine position for 12 patients with thoracic lesions. The prone position induced larger organ motion compared with supine, particularly for the lung tumor, likely requiring increases in planning margins compared with supine.

Technical considerations in radiation therapy for gastroesophageal junction cancer

Contemporary randomized trials have demonstrated that radiation therapy combined with chemotherapy and surgery improves survival in both the neoadjuvant and adjuvant treatment of gastroesophageal cancers. Consequently, radiation treatment planning and administration have taken on an added importance to ensure optimal outcomes as well as minimize treatment-related morbidity. This article highlights recent technical advances and considerations for radiation therapy planning for gastroesophageal junction tumors.

Chemoradiation in conservation therapy for esophageal cancer

Irradiation alone can be highly beneficial for patients with advanced or metastatic esophageal cancer, but external beam irradiation alone is now usually reserved for patients only requiring palliation. Higher cure rates are achieved with irradiation delivered with radiosensitizing chemotherapy based on clinical trials performed over the last decade. Chemoradiation programs based on the modest success with infusional 5-FU, cisplatin, and 50 Gy are justified for either palliative or curative treatment as long as the toxicity is acceptable. One challenge is to increase the incidence of pathologic complete response rates without incurring unacceptable acute toxicity, which is the major dose-limiting factor in current trials. Newer methods that may ameliorate acute injury are different dose schedules for chemoradiation and different methods of dose delivery. Infusional administration of chemotherapy and new dose planning and delivery systems for irradiation (conformal irradiation) are currently under study. Organ preservation for larger numbers of patients may be possible if any of these methods hold up to the early indications of success.

Combined modality therapy for esophageal cancer

Whereas many patients with esophageal carcinoma present with what appears to be localized disease, cure rates with surgical resection alone remain low. Although surgical resection, where feasible, affords patients the best chance of cure, the primary tumor has often invaded local tissues or structures, and occult micrometastases often exist at the time of presentation. In an effort to improve treatment results, various combinations of surgery, radiotherapy, and chemotherapy have been used. The results of combined modality therapy are reviewed in this article. The importance of accurate pretreatment staging is discussed, and ongoing prospective randomized trials are reviewed.

A quantitative treatment planning study evaluating the potential of dose escalation in conformal radiotherapy of the oesophagus

BACKGROUND AND PURPOSE

This study aims to evaluate the reduction in radiation dose to normal thoracic structures through the use of conformal radiotherapy techniques in the treatment of oesophageal cancer, and to quantify the resultant potential for dose escalation.

MATERIALS AND METHODS

Three different CT-derived treatment plans were created and compared for each of ten patients. A two-phase treatment with conventional straight-edged fields and standard blocks (CV2), a two-phase conformal plan (CF2), and a three-phase conformal plan where the third phase was delivered to the gross tumour only (CF3), were considered for each patient. Escalated dose levels were determined for techniques CF2 and CF3, which by virtue of the conformal field shaping, did not increase the mean lung dose. The resulting increase in tumour control probability (TCP) was estimated.

RESULTS

A two-phase conformal technique (CF2) reduced the volume of lung irradiated to 18 Gy from 19.7+/-11.8 (1 SD) to 17.1+/-12.3% (P=0.004), and reduced the normal tissue complication probability (NTCP) from 2.4+/-4.0 to 0.7+/-1.6% (P=0.02) for a standard prescribed dose of 55 Gy. Consequently, technique CF2 permitted a target dose of 59.1+/-3.2 Gy without increasing the mean lung dose. Technique CF3 facilitated a prescribed dose of 60.7+/-4.3 Gy to the target, the additional 5 Gy increasing the TCP from 53. 1+/-5.5 to 68.9+/-4.1%. When the spinal cord tolerance was raised from 45 to 48 Gy, technique CF3 allowed 63.6+/-4.l Gy to be delivered to the target, thereby increasing the TCP to 78.1+/-3.2%.

CONCLUSIONS

Conformal radiotherapy techniques offer the potential for a 5-10 Gy escalation in dose delivered to the oesophagus, without increasing the mean lung dose. This is expected to increase local tumour control by 15-25%.

Localization of the apex of the vagina: implications for radiation therapy planning

PURPOSE

To evaluate (a) the displacement of the vaginal apex by a rod during radiation therapy simulation for gynecologic malignancy and (b) apical localization with implanted radiopaque markers.

MATERIALS AND METHODS

Metallic markers were implanted in the cervix or vaginal cuff in nine patients with cervical or endometrial carcinoma who underwent irradiation. In all but one patient, radiographs were obtained with and then without the vaginal rod. Displacement of the markers relative to bone landmarks was measured. The total displacement was the square root of the sum of the squares of displacement in each axial direction.

RESULTS

All patients showed displacement of the cervical markers by the vaginal rod (mean total displacement, 1.9 cm; range, 0.6-3.6 cm). The greatest displacement was cephalic (mean, 1.5 cm; range, 0.5-2.4 cm). Anteroposterior displacement occurred in all patients but was not as predictable as cephalic displacement. Displacement was anterior in five of the eight patients, posterior in three patients, and lateral in four patients.

CONCLUSION

Displacement of the vaginal apex and/or cervix with placement of the vaginal rod during simulation was marked in all patients. Use of implanted cervical markers to localize the vaginal apex or the cervix during simulation is more accurate than use of a vaginal rod.

Comparative treatment planning between proton and x-ray therapy in esophageal cancer

PURPOSE

Conformal treatment planning with megavoltage x-rays and protons for five patients with esophageal cancer has been studied in an attempt to determine if there are advantages of using protons instead of x-rays.

METHODS AND MATERIALS

For each of the five patients, two different proton plans, one x-ray plan, and one mixed plan with x-rays and protons were made. A three-dimensional treatment planning system, TMS, was used. The evaluation of the different plans was made by applying the tumor control probability (TCP) model proposed by Nahum and Webb and the normal tissue complication (NTCP) model proposed by Lyman on the dose distributions in terms of dose-volume histograms (DVHs).

RESULTS

The comparison shows advantages of using protons instead of x-rays for all five patients. The dose-limiting organs at risk are the spinal cord, the lungs, and the heart, but the proton plans also spare the kidneys better than the x-ray plan does. At 5% NTCP in any risk organ, the calculated mean TCP value for the five patients is increased by an average of 20%-units (from 2 to 23%-units) with the best proton plan compared with x-rays only. However, if we assume maximally a 1% risk in the spinal cord and a total NTCP for the two lungs of 100%, the mean TCP value for the five patients is increased from 6 to 49% with the best proton plan compared with x-rays only. The corresponding figure for the mixed plan is 27%. These gains are relatively insensitive to variations within reasonable limits in the biological parameters.

CONCLUSIONS

Protons appear to have clear therapeutic advantages over conventional external radiotherapy when treating esophageal carcinoma.

Management of adenocarcinoma of the esophagus with chemoradiation alone or chemoradiation followed by esophagectomy: results of sequential nonrandomized phase II studies

PURPOSE

The incidence of adenocarcinoma of the esophagus is increasing, but the optimal treatment for this disease is unknown. We evaluated the efficacy of chemoradiation and chemoradiation followed by esophagectomy as treatment for adenocarcinoma of the esophagus in sequential prospective nonrandomized phase II studies.

METHODS AND MATERIALS

Between May 1981 and June 1992, all previously untreated patients (N = 35) with potentially resectable adenocarcinoma of the esophagus (clinical Stage I or II) were treated with curative intent in sequential prospective Phase II studies. From May 1981 to August 1987, 11 patients (median age 66) were treated with concurrent chemotherapy [mitomycin C, and 5-fluorouracil (5-FU)] and radiotherapy to a median dose of 60 Gy (CRT group). From September 1987 to June 1992, 24 patients (median age 65) were treated with the same regimen of chemoradiation followed by planned esophagectomy (CRT+PE group). Of these, 12 patients (median age 62) actually underwent esophagectomy (CRT+E subgroup).

RESULTS

The median overall survival was 19 months for the CRT group and 15 months for the CRT+PE group. For the CRT+E subgroup, the median overall survival was 33 months. The 3-year actuarial overall survival for the CRT and the CRT+PE groups were 36 and 28% (p = 0.949). The subset of patients treated with chemoradiation followed by esophagectomy had a 3-year actuarial overall survival of 33% (p = 0.274). The 3-year actuarial freedom from local failure rates were similar: 62% in the CRT group vs. 58% in the CRT+PE group. Of the 12 patients who underwent esophagectomy (CRT+E group), 9 (75%) were free of local failure. Four of 12 (33%) patients had no pathologic evidence of malignancy in their surgical specimen. Six of 11 patients (55%) in the CRT group were free of local failure at the time of analysis. Two of five patients in this group who had local recurrence at 2 and 10 months underwent surgical salvage with subsequent survivals of 20 and 100 months, respectively. Treatment-related mortality was 0 out of 11 in the CRT group and 2 out of 24 in the CRT+PE group. Dysphagia relief was similar in the CRT group vs. the CRT+E subgroup; however, a greater percentage of patients treated with chemoradiation alone had normal long-term swallowing function when compared to those patients also undergoing esophagectomy (100% vs. 73%).

CONCLUSION

High-dose chemoradiation alone appears to provide similar survival and relief of dysphagia compared with high-dose chemoradiation followed by esophagectomy for patients with potentially resectable esophageal adenocarcinoma. Local failure may be higher in patients undergoing chemoradiation compared to chemoradiation followed by esophagectomy, but surgical salvage is possible, thus providing similar overall local control. However, because of the small number of patients in each group, these treatment modalities need to be further evaluated in a prospective randomized Phase III study.

Esophageal cancer

Esophageal cancer is an important problem in the United States. It results in more deaths (over 10,000 annually) than rectal cancer. Furthermore, the incidence of esophageal adenocarcinoma is increasing at a rate faster than that of nearly any other cancer and the reasons for the increase are not well understood. A variety of tumor-suppressor genes (including p53, APC, DCC and Rb) and proto-oncogenes (including prad1, EGFR, c-erb-2 and TGF alpha) may be involved in the development and progression of esophageal cancer. Clinical prognostic factors include stage, Karnofsky performance status, sex, age, anatomic location of the tumor, and degree of weight loss. A new staging system based on depth of wall penetration and lymph node involvement correlates well with prognosis for patients undergoing esophagectomy. Newer staging procedures including endoscopic ultrasound as well as the use of minimally invasive surgery, such as thoracoscopy and laparoscopy, may allow accurate staging without esophagectomy. Surgical resection provides excellent palliation; however, the chance for cure with esophagectomy alone is only 10% to 20%. Adjuvant treatment with pre- or postesophagectomy radiation may improve local-regional control but does not improve survival. Nor has preoperative chemotherapy been shown to improve survival; however, it remains an active area of investigation. Multimodality therapy, namely, chemotherapy and radiation (chemoradiation), given concurrently prior to surgical resection shows promise, with one study indicating a 5-year survival of 34%. A complete pathologic response to chemoradiation correlates with improved survival. Chemoradiation has been shown to be superior to radiation as primary management of esophageal cancer. There has been no successfully completed randomized trial of surgery versus definitive radiation or chemoradiation. However, chemoradiation represents a reasonable alternative to esophagectomy in the primary management of squamous cell carcinoma of the esophagus and chemoradiation also appears to be effective in the treatment of patients with adenocarcinoma of the esophagus, offering significant palliation and a chance for long-term survival as well. Randomized studies of preoperative chemoradiation versus surgery or versus chemoradiation alone are needed. The treatment of advanced esophageal cancer must be directed toward palliation of symptoms. Newer endoscopic techniques, including the use of expansile metal stents, laser ablation, intraluminal high-dose rate brachytherapy, BICAP tumor probe, or photodynamic therapy, offer selected patients short-term palliation.(ABSTRACT TRUNCATED AT 400 WORDS)

Swallowing function in patients with esophageal cancer treated with concurrent radiation and chemotherapy

BACKGROUND

Major goals of concurrent radiation and chemotherapy in the treatment of esophageal cancer are the early restoration and long-term maintenance of swallowing function. The purpose of this study was to determine the impact of concurrent radiation and chemotherapy on swallowing function.

METHODS

Between September 1980 and September 1990, 120 patients with esophageal cancer were treated at the Fox Chase Cancer Center on the basis of one of three prospective nonrandomized protocols using concurrent chemotherapy and radiation. Swallowing function was retrospectively assessed in these patients by use of a swallowing-function scoring system. In addition, patients who had long-term control of their esophageal cancer underwent a more detailed analysis of swallowing function.

RESULTS

Initial improvement in dysphagia occurred in 88% of the 102 assessable patients, with a median time to improvement of 2 weeks. There was no difference in overall percentage of initial improvement for patients with adenocarcinoma versus squamous cell carcinoma. Patients with distal tumors, however, showed both earlier and higher frequency of initial improvement than did patients with tumors in the upper two-thirds of the thoracic esophagus (95% versus 79%). Local relapse-free survival of definitively treated patients at 3 years was 60% and was significantly better for patients with Stage I (76%) versus Stage II cancers (55%) (P < 0.05). All 25 patients treated with curative intent who survived for more than 1 year without evidence of disease were able to eat soft or solid foods and had a benign stricture rate of only 12%. Even in patients with advanced disease who were treated with palliative intent, 91% had an initial improvement in swallowing function and 67% had improvement in swallowing function that lasted until death.

CONCLUSIONS

High-dose concurrent radiation and chemotherapy provides rapid improvement in dysphagia, and this improvement results in normal or near-normal swallowing function of long duration.