The Effect of Beam Energy on the Quality of IMRT Plans for Prostate Conformal Radiotherapy

Three dimensional conformal radiation therapy (3DCRT) for prostate cancer is most commonly delivered with high-energy photons, typically in the range of 10–21 MV. With the advent of Intensity Modulated Radiation Therapy (IMRT), an increase in the number of monitor units (MU) relative to 3DCRT has lead to a concern about secondary malignancies. This risk becomes more relevant at higher photon energies where there is a greater neutron contribution. Subsequently, the majority of IMRT prostate treatments being delivered today are with 6–10 MV photons where neutron production is negligible. However, the absolute risk is small [Hall, E. J. Intensity Modulated Radiation Therapy, Protons, and the Risk of Second Cancers. Int J Radiat Oncol Bio Phys 65, 1–7 (2006); Kry, F. S., Salehpour, M., Followill, D. S., Stovall, M., Kuban, D. A., White, R. A., and Rosen, I. I. The Calculated Risk of Fatal Secondary Malignancies From Intensity Modulated Radiation Therapy. Int J Radiat Oncol Bio Phys 62, 1195–1203 (2005).] and therefore it has been suggested that the use of an 18MV IMRT may achieve better target coverage and normal tissue sparing such that this benefit outweighs the risks. This paper investigates whether 18MV IMRT offer better target coverage and normal tissue sparing. Computed Tomography (CT) image sets of ten prostate cancer patients were acquired and two separate IMRT plans were created for each patient. One plan used 6 MV beams, and the other used 18 MV, both in a coplanar, non-opposed beam geometry. Beam arrangements and optimization constraints were the same for all plans. This work includes a comparison and discussion of the total integral dose, neutron dose conformity index, and total number of MU for plans generated with both energies.

Randomized phase II trial of selenomethionine as a modulator of efficacy and toxicity of chemoradiation in squamous cell carcinoma of the head and neck

AIM: To investigate whether selenomethionine (SLM) reduces mucositis incidence in patients with head and neck squamous cell cancer (HNSCC) undergoing concurrent chemoradiation (CRT).

METHODS: In this multi-institutional, randomized, double-blind phase II trial, patients with Stage III or IV HNSCC received SLM 3600 μg/m² or placebo twice daily for 7 d prior to CRT, once daily during CRT, and daily for 3 wk following CRT. CRT consisted of 70 Gy at 2 Gy per fraction with cisplatin 100 mg/m² IV on days 1, 22, and 43.

RESULTS: Eighteen patients were randomized, 10 received SLM, and there were no differences in baseline factors. There was no difference in mucositis or patient-reported side effects between groups. There was no difference in overall or relapse-free survival at 12 mo.

CONCLUSION: Addition of SLM to CRT for HNSCC was well-tolerated but did not lower the incidence of severe mucositis or improve quality of life or survival outcomes.

Pretreatment nutritional status and locoregional failure of patients with head and neck cancer undergoing definitive concurrent chemoradiation therapy

BACKGROUND

This study was carried out to determine if markers of nutritional status predict for locoregional failure following intensity-modulated radiation therapy (IMRT) with concurrent chemoradiotherapy (CCRT) for squamous cell carcinoma of the head and neck (SCCHN).

METHODS

We performed a retrospective chart review of 78 patients with SCCHN who received definitive CCRT. We compared patient factors, tumor characteristics, and nutritional status indicators between patients with and without locoregional failure.

RESULTS

Fifteen of 78 patients (19%) experienced locoregional failure. Median follow-up for live patients was 38 months. On univariate analysis, pretreatment percentage of ideal body weight (%IBW) (p < .01), pretreatment hemoglobin (p = .04), and treatment duration (p < .01) were significant predictors of failure. On multivariate analysis, pretreatment %IBW (p = .04) and treatment time (p < .01) remained statistically significant.

CONCLUSIONS

Although treatment time is an accepted risk factor for failure, differences in outcome for patients with head and neck cancer undergoing definitive CCRT based on pretreatment %IBW should be examined further.

Variability of marker-based rectal dose evaluation in HDR cervical brachytherapy

In film-based intracavitary brachytherapy for cervical cancer, position of the rectal markers may not accurately represent the anterior rectal wall. This study was aimed at analyzing the variability of rectal dose estimation as a result of interfractional variation of marker placement. A cohort of five patients treated with multiple-fraction tandem and ovoid high-dose-rate (HDR) brachytherapy was studied. The cervical os point and the orientation of the applicators were matched among all fractional plans for each patient. Rectal points obtained from all fractions were then input into each clinical treated plan. New fractional rectal doses were obtained and a new cumulative rectal dose for each patient was calculated. The maximum interfractional variation of distances between rectal dose points and the closest source positions was 1.1 cm. The corresponding maximum variability of fractional rectal dose was 65.5%. The percentage difference in cumulative rectal dose estimation for each patient was 5.4%, 19.6%, 34.6%, 23.4%, and 13.9%, respectively. In conclusion, care should be taken when using rectal markers as reference points for estimating rectal dose in HDR cervical brachytherapy. The best estimate of true rectal dose for each fraction should be determined by the most anterior point among all fractions.

Adjuvant vaginal brachytherapy alone for high risk localized endometrial cancer as defined by the three major randomized trials of adjuvant pelvic radiation

OBJECTIVE

Controversy exists regarding optimal management of high risk localized endometrial cancer. Given that vaginal brachytherapy (VB) alone is used routinely at our institution, we retrospectively reviewed our outcomes among high risk patients defined according to the PORTEC, GOG 99, and/or Aalders randomized trials of pelvic radiation versus observation to determine if acceptable rates of locoregional control could be achieved with vaginal brachytherapy alone in this highest risk patient population.

METHODS

The Roswell Park Cancer Institute hospital tumor registry was used to identify all patients with Stage I or IIA endometrial cancer treated between January 1992 and June 2006. A total of 464 patients were identified. Of 261 patients who received post-operative RT, 225 received VB alone. Of those 225, 87 met the high risk criteria as designated by PORTEC (at least 2 of the following high risk features: age>60, Grade 3, and/or myometrial invasion >or=Occurrences of the mathematical operator' (='were changed to 'OE'. Please check.-->50%), GOG 99 (any age with 3 high risk features: Grade 2-3, >66% myometrial invasion, and/or LVSI; age >or=50 with 2 high risk features; or age >or=70 with 1 high risk feature), and/or Aalders (Stage IC, Grade 3). Descriptive recurrence statistics are provided.

RESULTS

Among 87 high risk patients treated with VB alone, 36, 77, and 14 were high risk per PORTEC, GOG 99, and Aalders respectively. Forty (46%) underwent pelvic lymph node dissection. With a median follow-up of 52 months, 3 (3.4%) pelvic recurrences were observed including 1 vaginal recurrence, 1 pelvic recurrence, and 1 local recurrence involving both the vagina and pelvis. All 3 local recurrences were successfully salvaged with pelvic RT+/-surgery.

CONCLUSIONS

This represents one of the largest known series of high risk localized endometrial cancer treated with VB alone. The observed 3.4% locoregional recurrence compares favorably with the 5% locoregional recurrence noted among the highest risk patients receiving pelvic RT in the PORTEC, GOG 99, and Aalders randomized trials. In this single institution experience, the 3 local recurrences were salvaged. Based on these findings, we will continue to use VB alone in the adjuvant setting for patients with high risk localized endometrial cancer.

Cutaneous head and neck melanoma: the old and the new

The incidence rate of malignant melanoma has shown a rapid worldwide rise in recent years. The staging and management of head and neck melanoma presents some unique challenges. Surgery remains the cornerstone of treatment, while sentinel node biopsy is the most accurate staging modality for regional disease. The complex regional anatomy and lymphovascular drainage of this region may account for the increased biologic aggressiveness and treatment challenges of this disease. Improved understanding of the radiobiology of melanoma has resulted in new adjuvant radiotherapy approaches, yielding improved control rates. The treatment outcomes of metastatic head and neck melanoma remain disappointing but important progress has been made in the understanding of melanoma biology.

Duplicating a tandem and ovoids distribution with intensity-modulated radiotherapy: a feasibility study

Brachytherapy plays an important role in the definitive treatment of cervical cancers by radiotherapy. In the present study, we investigated whether sliding‐window intensity‐modulated radiation therapy (IMRT) can achieve a pear‐shaped distribution with a similar sharp dose falloff identical to that of brachytherapy. The computed tomography scans of a tandem and ovoid patient were pushed to both a high dose rate (HDR) and an IMRT treatment planning system (TPS) after the rectum, bladder, and left and right femoral heads had been outlined, ensuring identical structures in both planning systems. A conventional plan (7 Gy in 5 fractions, defined as the average dose to the left and right point A) was generated for HDR treatment. The 150%, 125%, 100%, 75%, 50%, and 25% isodose curves were drawn on each slice and then transferred to the IMRT TPS. The 100% isodose envelope from the HDR plan was the target for IMRT planning. A 7‐field IMRT plan using 6‐MV X‐ray beams was generated and compared with the HDR plan using isodose conformity to the target and 125% volume, dose– volume histograms, and integral dose. The resulting isodose distribution demonstrated good agreement between the HDR and IMRT plans in the 100% and 125% isodose range. The dose falloff in the HDR plan was much steeper than that in the IMRT plan, but it also had a substantially higher maximum dose. Integral dose for the target, rectum, and bladder were found to be 6.69 J, 1.07 J, and 1.02 J in the HDR plan; the respective values for IMRT were 3.47 J, 1.79 J, and 1.34 J. Our preliminary results indicate that the HDR dose distribution can be replicated using a standard sliding‐window IMRT dose delivery technique for points lying closer to the three‐dimensional isodose envelope surrounding point A. Differences in radiobiology and patient positioning between the two techniques merit further consideration.

PACS: 87.53.Jw

Uterine Cancers Clinical Practice Guidelines

Adenocarcinoma of the endometrium is the most common malignancy of the female genital tract in the United States. Many physicians believe that adenocarcinoma of the endometrium is a relatively benign disease because of the early symptoms of irregular vaginal bleeding in this predominantly postmenopausal patient population, the often-localized nature of the disease, and the generally high survival rate. However, the estimated number of deaths from endometrial cancer continues to increase, indicating the need for a critical reassessment of the guidelines for managing endometrial cancer. Physicians must identify high-risk patients and tailor treatment appropriately to provide the best opportunity for long-term survival.

For the most recent version of the guidelines, please visit NCCN.org

Quantifying IOHDR brachytherapy underdosage resulting from an incomplete scatter environment

PURPOSE

Most brachytherapy planning systems are based on a dose calculation algorithm that assumes an infinite scatter environment surrounding the target volume and applicator. Dosimetric errors from this assumption are negligible. However, in intraoperative high-dose-rate brachytherapy (IOHDR) where treatment catheters are typically laid either directly on a tumor bed or within applicators that may have little or no scatter material above them, the lack of scatter from one side of the applicator can result in underdosage during treatment. This study was carried out to investigate the magnitude of this underdosage.

METHODS

IOHDR treatment geometries were simulated using a solid water phantom beneath an applicator with varying amounts of bolus material on the top and sides of the applicator to account for missing tissue. Treatment plans were developed for 3 different treatment surface areas (4 x 4, 7 x 7, 12 x 12 cm(2)), each with prescription points located at 3 distances (0.5 cm, 1.0 cm, and 1.5 cm) from the source dwell positions. Ionization measurements were made with a liquid-filled ionization chamber linear array with a dedicated electrometer and data acquisition system.

RESULTS

Measurements showed that the magnitude of the underdosage varies from about 8% to 13% of the prescription dose as the prescription depth is increased from 0.5 cm to 1.5 cm. This treatment error was found to be independent of the irradiated area and strongly dependent on the prescription distance. Furthermore, for a given prescription depth, measurements in planes parallel to an applicator at distances up to 4.0 cm from the applicator plane showed that the dose delivery error is equal in magnitude throughout the target volume.

CONCLUSION

This study demonstrates the magnitude of underdosage in IOHDR treatments delivered in a geometry that may not result in a full scatter environment around the applicator. This implies that the target volume and, specifically, the prescription depth (tumor bed) may get a dose significantly less than prescribed. It might be clinically relevant to correct for this inaccuracy.

Adjuvant high dose rate brachytherapy (Ir-192) in the management of keloids which have recurred after surgical excision and external radiation

We describe our experience with adjuvant high dose rate brachytherapy (Ir-192) (HDRB) in patients, who failed surgery and post-operative external radiation therapy. The salvage treatment consisted of excision of the keloid and wound closure followed by HDRB (15 Gy in three fractions given on three consecutive business days beginning the day of surgery). At the time of last follow up, 88% (15/17) of the keloids were without any evidence of recurrence.

Cell lines from the same cervical carcinoma but with different radiosensitivities exhibit different cDNA microarray patterns of gene expression

Combining chemotherapy with radiotherapy has improved the cure rate among patients with cancers of the cervix. Although one-half to two-thirds of the patients can be cured by radiation alone, such patients cannot be identified at present and must therefore suffer the burden of chemotherapy. Our long-range goal is to identify those cervical cancers that are radiosensitive and could be cured by radiotherapy alone. The advent of methods that permit the simultaneous analysis of expression patterns of thousands of genes, make it feasible to attempt to identify the molecular events related to radiosensitivity and the associated regulatory pathways. We hypothesize that the sensitivity of tumor cells to ionizing radiation (IR) is determined by the level of expression of specific genes that may be identified with the aid of cDNA microarrays. As the first step in testing this hypothesis, we determined the gene expression differences between two cell lines exhibiting different degrees of radiosensitivity. These were derived from the same tumor prior to treatment from a patient with squamous cell carcinoma of the cervix. The mRNA from these cells was subjected to cDNA analysis on a microarray of 5,776 known genes and ESTs. The expression of 52 genes of the total of 5,776 was elevated (maximum 4.1 fold) in the radioresistant cells as compared to the radiosensitive cells. Ten of the 52 sequences are known genes while 42 are ESTs. Conversely, the expression of 18 genes was elevated in the sensitive cells as compared to the resistant cells. Seven of these 18 are known genes while eleven are ESTs. Among the genes expressed differentially between the resistant and sensitive cells were several known to be associated with response to IR and many more genes and ESTs that had not previously been reported to be related to radiosensitivity. The genes that showed the greatest overexpression in the radioresistant cell line were metal-regulatory transcription factor-1, cytochrome P450 CYP1B1, adenomatosis polyposis coli, translation elongation factor-1, cytochrome-c oxidase, whereas in the sensitive cell line, transcription factor NF-kappa-B, metalloproteinase inhibitor-1 precursor, superoxide dismutase-2, insulin-like growth factor binding protein-3, guanine nucleotide-binding protein and transforming growth factor beta-induced protein were overexpressed.