Treatment of early vocal cord carcinoma with 60Co gamma rays, 8/10 MV x-rays, or 4 MV x-rays--are the results different?

Prospective Observational Comparative Study of Response and Toxicities in Early Glottic Cancer Using Telecobalt Versus 3D-CRT

The study was performed with 50 patients, 24 patients in Arm A and 26 patients in Arm B. Arm A-Conventional Telecobalt RT 66 Gy/33 fraction in stage T1N0M0 and stage T2N0M0 and Arm B-3D-CRT 66 Gy/33 fraction in T1N0M0 and T2N0M0 used. At the end of RT, 6 weeks, 3 months acute and late toxicities were noted by RTOG/EORTC morbidity scoring criteria for skin reaction, dysphagia and laryngeal toxicity. Fiber optic Laryngoscopy clinical assessment criteria were used to assess response after 6 weeks, 3 months of treatment completion. At 6 weeks of follow-up-Both Arm A and B complete response rate were 83.3% and 88.5% respectively and at 3 months rate were 85.0% and 95.7% respectively. There was no superiority of results with 3D-CRT over 2DRT. At the end of RT dysphagia grade 3 toxicity seen 1 patient (4.2%) but in Arm B (total 26 patients) no grade 3 toxicity found. At the end of 6 week and 3 month, one patient (4.3%) had grade 3 toxicity on Arm B only at 3 month. All these results are comparable. At the end of RT, one patient (3.8%) had incidentally dermatitis grade 3 toxicity in Arm B only. But all the results are comparable. On follow up, 6 week and 3 months, no grade 3 toxicity noted. At the end of RT, grade 3 laryngeal toxicity noted in 3 (12.5%) in Arm A and 2 (7.7%) in Arm B, not statistically significant. At 6 week, grade 3 toxicity found in 3/24 (12.5%) in Arm A and 2/26 (7.7%) in Arm B, at 3 months, 1/26 (4.3%) patient had incidental grade 3 toxicity only in Arm B. As conformal radiotherapy is more time consuming, less available in India and more costly than 2DRT, we can consider Conventional 2D planning for patients in India where most of people belong to low economic profile. Due to limitation in sample size and long-term follow-up further randomized studies are needed to validate the results.

Prognostic Factors in Early Glottic Carcinoma Implications for Treatment

Aim

In this study we aimed to determine the prognostic factors affecting local control (LC) in limited glottic carcinoma treated with definitive radiotherapy (RT).

Material and methods

Between June 1991 and December 2001, 114 patients with early squamous-cell carcinoma of the glottis were treated with definitive RT at our institution. Only four (3.5%) patients were women. The median age was 60 (27-79). Fifteen percent, 72% and 13% of the patients had Tis, T1 and T2 tumors, respectively. Forty-three (37.7%) patients had anterior commissure invasion. Prior to RT 35 (31%) patients had undergone vocal cord stripping and two (2%) cordectomy. A median dose of 66 Gy (50-70.2) was given over a median period of 46 days (20-60). Univariate and multivariate analyses were performed for LC. The prognostic parameters analyzed for LC were T classification, anterior commissure involvement, total RT dose, and overall treatment time.

Results

Five-year local and regional control rates were 84.2% and 97.7%. RTOG grade 3-4 late side effects were observed only in one (0.9%) patient. In 15 patients with local failure, salvage treatment consisted of partial laryngectomy in eight patients and total laryngectomy in five. One of the remaining two patients was medically inoperable, and the other refused salvage surgery. In one of the three patients with regional failure, salvage surgery was applied and the other two were given palliative chemotherapy because of unresectable disease. Following salvage treatments, the ultimate five-year LC rate was 96.9% and the five-year larynx preservation rate was 91.1%. Second primary cancer was diagnosed in 17 (14.9%) patients. Only one patient developed distant metastases and two patients died of laryngeal cancer. While T2 disease and anterior commissure involvement were found to be unfavorable prognostic factors significantly influencing LC in univariate analyses, only T2 disease remained independent in multivariate analysis.

Conclusion

In patients with early glottic carcinoma, T classification proved to be the only independent prognostic factor affecting LC after primary radiotherapy according to the results of this study.

Radiotherapy for T1 Carcinoma of the Glottis

Aims and background

The management of patients with T1 carcinoma of the glottic larynx is controversial, because surgery and radiation therapy are reported to be effective treatments. Several studies have shown radiotherapy to be safe and effective, with a high percentage of voice preservation and minimal complications, but most Italian physicians prefer to surgically treat such patients.

Methods

From 1980 to 1990, 36 patients with stage I squamous cell glottic carcinoma were treated with radiotherapy alone at the Institute of Radiology of University of Rome “La Sapienza”. In all patients the irradiation fields were limited to the larynx, with field size ranging from 4 × 4 cm to 7 × 7 cm. Total tumor doses ranged between 51 and 70 Gy (median 60 Gy) with a mean number of 30 fractions of 2 to 3 Gy per fraction (3 or 5 fractions per week).

Results

After a median follow-up of 98 months, we observed an overall survival rate at 5 years of 91.4% and actuarial 10-year survival of 85.7%. Local control was achieved in 97.1% of cases, with an event-free survival of 94.2% at 5 and 10 years. No major complications like necrosis or persistent edema of the larynx were observed. Minor complications like dysphonia (8%) and dysphagia (5.5%) were temporary; laryngeal function was completely preserved at the end of therapy. Final voice quality ranged from good to excellent.

Conclusions

Our series confirms that radiation therapy has a major role in the management of early glottic cancer, with results comparable to surgical approaches and with better voice preservation.

Radiotherapy for laryngeal cancer-technical aspects and alternate fractionation

Early laryngeal, especially glottic, cancer is a good candidate for radiotherapy because obvious early symptoms (e.g. hoarseness) make earlier treatment possible and with highly successful localized control. This type of cancer is also a good model for exploring the basic principles of radiation oncology and several key findings (e.g. dose, fractionation, field size, patient fixation, and overall treatment time) have been noted. For example, unintended poor outcomes have been reported during transition from 60Cobalt to linear accelerator installation in the 1960s, with usage of higher energy photons causing poor dose distribution. In addition, shell fixation made precise dose delivery possible, but simultaneously elevated toxicity if a larger treatment field was necessary. Of particular interest to the radiation therapy community was altered fractionation gain as a way to improve local tumor control and survival rate. Unfortunately, this interest ceased with advancements in chemotherapeutic agents because alternate fractionation could not improve outcomes in chemoradiotherapy settings. At present, no form of acceleration can potentially compensate fully for the lack of concurrent chemotherapy. In addition, the substantial workload associated with this technique made it difficult to add extra fractionation routinely in busy clinical hospitals. Hypofractionation, on the other hand, uses a larger single fractionation dose (2-3 Gy), making it a reasonable and attractive option for T1-T2 early glottic cancer because it can improve local control without the additional workload. Recently, Japan Clinical Oncology Group study 0701 reprised its role in early T1-T2 glottic cancer research, demonstrating that this strategy could be an optional standard therapy. Herein, we review radiotherapy history from 60Cobalt to modern linear accelerator, with special focus on the role of alternate fractionation.

A multicenter survey of stage T1 glottic cancer treated with radiotherapy delivered in 2.25-Gy fractions in clinical practice: An initial 5-year analysis

The purpose of this study was to evaluate the acute and late toxicity as well as local control (LC) in T1 glottic cancer (GC) patients treated with hypofractionated radiotherapy (RT) in clinical practice. The Tokai Study Group for Therapeutic Radiology and Oncology started RT treatment with a dose of 2.25 Gy for T1 GC in 2011. Ten institutions combined data from 104 patients with T1 squamous cell carcinoma between 2011 and 2015. In total, 104 patients with T1 GC were irradiated with a standard radiation dose of 63 Gy in 28 fractions.The median follow-up duration was 18 (3.7-49.5) months. Acute grade 3 adverse events were observed in 7 patients, with 4 patients (5%) having dermatitis and 3 patients (4%) having mucositis. Late adverse events above grade 3 were not observed. Two patients developed local recurrence. The rates of acute adverse events in the present study were comparable to those in previous studies that have used 2 Gy fractions of RT.

Comparison between 4-MV and 6-MV radiotherapy in T1N0 glottic cancer

OBJECTIVES/HYPOTHESIS

The purpose of this study was to report the outcomes of a retrospective consecutive cohort study of patients with T1N0M0 glottic carcinoma treated with 4-MV or 6-MV radiotherapy.

STUDY DESIGN

Retrospective case-control study.

METHODS

This was a retrospective review of all patients with T1N0M0 glottic carcinoma treated with radiotherapy between January 2000 and December 2012 in the Department of Radiation Oncology at National Cancer Center Singapore. A total of 124 patients were included. Clinical endpoints of interest were: local control (LC), overall survival (OS), and disease-specific survival (DSS). Other prognostic factors for LC were also analyzed: age, gender, smoking status, T substage, dose fraction, field size, anterior commissure involvement, total dose, and overall treatment time.

RESULTS

Six-megavolt photon radiotherapy was used in 73 patients and 4-MV photon radiotherapy in 51 patients. Median follow-up was 4.9 years. The 5-year LC and OS were as follows: 4 MV, 91.6% and 83.4%; 6 MV, 88.8% and 82.8%; and the 5-year LC, OS, and DSS for all patients were 90.4%, 83.3%, and 98.3%. There was no significant difference in LR and OS between 4-MV and 6-MV radiotherapy (P = .92, P = .16, respectively). In the univariate analysis of LC, none of the prognostic factors was statistically significant. Twenty patients (23%) developed second primary cancers, the majority in the lungs.

CONCLUSIONS

Six-megavolt photon radiotherapy yields comparable results to 4-MV photons. Bolus and computed tomographic simulation are useful to ensure adequate dose coverage of target volume. Follow-up postradiotherapy should incorporate chest imaging, smoking cessation advice, and thyroid function test.

LEVEL OF EVIDENCE

4 Laryngoscope, 127:1061-1067, 2017.

Treatment results and prognostic factors of patients undergoing postoperative radiotherapy for laryngeal squamous cell carcinoma

Postoperative radiotherapy (PRT) is widely advocated for patients with squamous cell carcinomas of the head and neck that are considered to be at high risk of recurrence after surgical resection. The aims of this study were to evaluate the treatment outcomes of PRT for patients with laryngeal carcinoma and to identify the value of several prognostic factors. We reviewed the records of 256 patients treated for laryngeal squamous cell carcinoma between January 1993 and December 2005. Disease-free survival (DFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Log-rank test was employed to identify significant prognostic factors for DFS and OS. The Cox proportional hazards model was applied to identify covariates significantly associated with the aforementioned endpoints. Our results showed the 3-, 5-, and 10-year DFS for all patients were 69.9%, 59.5%, and 34.9%, respectively. The 3-, 5-, and 10-year OS rates were 80.8%, 68.6%, and 38.8%, respectively. Significant prognostic factors for both DFS and OS on univariate analysis were grade, primary site, T stage, N stage, overall stage, lymph node metastasis, overall treatment times of radiation, the interval between surgery and radiotherapy, and radiotherapy equipment. Favorable prognostic factors for both DFS and OS on multivariate analysis were lower overall stage, no cervical lymph node metastasis, and using 60Co as radiotherapy equipment. In conclusion, our data suggest that lower overall stage, no cervical lymph node metastasis, and using 60Co as radiotherapy equipment are favorable prognostic factors for DFS and OS and that reducing the overall treatment times of radiation to 6 weeks or less and the interval between surgery and radiotherapy to less than 3 weeks are simple measures to remarkably improve treatment outcome.

Definitive radiotherapy for early stage glottic cancer by 6 MV photons

Purpose

To evaluate the clinical outcome of early glottic cancer (GC) treated by primary radiotherapy (RT) with 6 MV photons.

Methods and materials

We retrospectively reviewed the medical records of 695 consecutive patients with T1N0 and T2N0 GC treated between 1983 and 2005 by RT in our institution. Clinical outcome in terms of local control (LC), overall survival (OS) and cause- specific survival (CSS) rate were evaluated.

Results

The median follow-up time was 10.5 years. The 10-year actuarial LC rates were as follows: T1A, 91%; T1B, 87%; T2, 77%. The 10-year OS were as follows: T1, 74.2%; T2, 70.7%. The 10-year CSS were as follows: T1, 97.7%; T2, 97.1%.

Poorly differentiated histology and tumor biologically effective dose < 65 Gy₁₅ were adverse factors in both LC of T1 and T2 disease. Involvement of anterior commissure was an adverse factor in both LC and CSS of T1 disease. Subglottic extension was associated with poor LC in T2 disease whereas hemoglobin <13.0 was associated with poor LC and CSS of T2 disease.

Conclusion

Primary RT remains an option among the various standard treatments for early GC. Clinical treatment outcome by 6MV photons is similar and comparable to historic data of Cobalt-60 and 2 MV photons.

Long-term observations and salvage operations on patients with T2N0M0 squamous cell carcinoma of the glottic larynx treated with radiation therapy alone

CONCLUSION

A long-term study was carried out on 57 patients treated with radiation alone who had T2N0M0 squamous cell carcinoma of the glottic larynx. The response and survival rates were satisfactory, but the complete response (CR) and the larynx preservation rates showed a need for improvement. Thirty-four patients underwent salvage operations and a safe margin for the partial laryngectomy was evaluated by histopathological examination of serial sections of the surgical specimen.

OBJECTIVE

Although the effectiveness of combined chemoradiation therapy in the treatment of head and neck cancer has been reported, the facts remain unclear. The purpose of this study was to analyze the long-term outcomes of radiation therapy alone for T2N0M0 squamous cell carcinoma of the glottic larynx, i.e. the survival rate, the larynx preservation rate, and the reality of salvage operations. This is expected to contribute to an understanding of the synergistic effects of anticancer drugs used in combined chemoradiation therapy, the use of which will be expanded in the future. The reason for this is that the radiation source, radiation field, and radiation dose are nearly identical for patients with T2N0M0 squamous cell carcinoma of the glottic larynx.

METHODS

The subjects were 57 patients with untreated T2N0M0 squamous cell carcinoma of the glottic larynx. There were 55 males and 2 females. Their ages ranged from 31 to 86 years. The 4 MV Liniac X-ray external beam radiation therapy was carried out via two-dimensional horizontal opposing ports, 2 Gy per dose, five times a week with a total of 66 Gy.

RESULTS

In 57 patients, we observed CR in 33 patients, partial response (PR) in 20 patients, no change (NC) in 4 patients, and progression disease (PD) in none of the patients. The response rate was 93.0% and the CR rate was 57.9%. The survival rates (Kaplan-Meier method) were: 5-year survival rate of 88.5% and 10-year survival rate of 73.5%. The larynx preservation rates (Kaplan-Meier method) were: 5-year larynx preservation rate of 60.4% and 10-year larynx preservation rate of 50.1%. The main side effect of grade 3 or more was only stomatitis in four patients, all of which were reversible changes (CTCAT v3.0 JCOG/JSCO). Salvage operation was required in 34 (59.6%) of 57 patients, 10 patients underwent partial laryngectomy, total laryngectomy was performed in 3 of the 10 patients following the partial laryngectomy, and 27 patients (47.4%) underwent total laryngectomy. The surgical specimens were serially sectioned at a thickness of 4 μm and examined histopathologically and compared to the macroscopic findings at surgery. The safe margin for partial laryngectomy was considered grossly to be 5 mm from the edge of the tumor.

Impact and relationship of anterior commissure and time-dose factor on the local control of T1N0 glottic cancer treated by 6 MV photons

BACKGROUND

To evaluate prognostic factors that may influence local control (LC) of T1N0 glottic cancer treated by primary radiotherapy (RT) with 6 MV photons.

METHODS

We retrospectively reviewed the medical records of 433 consecutive patients with T1N0 glottic cancer treated between 1983 and 2005 by RT in our institution. All patients were treated with 6 MV photons. One hundred and seventy seven (41%) patients received 52.5 Gy in 23 fractions with 2.5 Gy/fraction, and 256 (59%) patients received 66 Gy in 33 fractions with 2 Gy/fraction.

RESULTS

The median follow-up time was 10.5 years. The 10-year LC rates were 91% and 87% for T1a and T1b respectively. Multivariate analysis showed LC rate was adversely affected by poorly differentiated histology (Hazard Ratio [HR]: 7.5, p = 0.035); involvement of anterior commissure (HR: 2.34, p = 0.011); fraction size of 2.0 Gy (HR: 2.17, p = 0.035) and tumor biologically effective dose (BED) < 65 Gy15 (HR: 3.38, p = 0.017).

CONCLUSIONS

The negative impact of anterior commissure involvement could be overcome by delivering a higher tumor BED through using fraction size of > 2.0 Gy. We recommend that fraction size > 2.0 Gy should be utilized, for radiation schedules with five daily fractions each week.

Dose build-up behind air cavities for Co-60, 4, 6 and 8 MV. Measurements and Monte Carlo simulations

It has been shown in several studies that the build-up in photon beams behind air cavities (such as in the head and neck) increases with energy. In this study this effect is investigated over a broad range of energies that have been used for treating head and neck tumours. The study addresses the question of whether an energy lower than 6 MV is desirable and is based on measurements and Monte Carlo (MC) simulations. In a PMMA phantom containing an air cavity (3 x 16 x 3 cm3 at 3 cm depth) an ionization chamber (Capintec PS-033) was used to measure the dose build-up behind the cavity for 4, 6 and 8 MV beam qualities for different field sizes (from 3 x 6 cm2 to 8 x 8 cm2). MC simulations were made using the EGSnrc code for the same geometry and energies as well as for Co-60. Measurements and MC simulations agree well when the fixed-separation plane-parallel chamber measurements have been corrected for the expected over-response in the build-up region. This work demonstrates that the build-up effect of 6 MV is 'closer' to the build-up effect of 8 MV than to that of 4 MV. This suggests that if the build-up effect is of concern when the target volume is in the vicinity of air cavities, 4 MV should be preferred over both 6 MV and 8 MV. This work also shows that the build-up effect for Co-60 is significantly smaller than that of 4 MV. Moreover, the build-up effect increases as the field size decreases. With the increasing use of IMRT (and radiosurgery), small fields are used more frequently making these issues even more relevant. This should be taken into consideration when choosing the accelerator energies for a radiotherapy department.

Does 4MV perform better compared to 6MV in the presence of air cavities in the head and neck region?

BACKGROUND AND PURPOSE

The underdose near air cavities in the head and neck region at photon energies of 4 MV and 6 MV was studied in search for clinical advantages of the 4 MV over 6 MV treatments.

MATERIALS AND METHODS

The on-axis and off-axis dose distributions were measured with a parallel-plate ionization chamber and films in polystyrene phantoms containing an air cavity of appropriate size based on the results of computed tomography scans.

RESULTS

Although most results are similar for both energies, the 4 MV photon beams give a somewhat smaller underdose effect and a faster re-build up than the 6 MV. For both energies a significant underdose effect was observed at the edge of the field in the larynx phantom. This proved to be true for small and large fields, for smaller and larger cavities, for one-beam as well as parallel-opposed beams.

CONCLUSION

For most clinically relevant situations there is no remarkable benefit in the use of either of the two energies.

Three weeks radiotherapy for T1 glottic cancer: the Christie and Royal Marsden Hospital Experience

BACKGROUND AND PURPOSE

Radiotherapy for laryngeal carcinoma is conventionally given over a 6-7-week period. However, in a number of UK centres early lesions are treated over 3 weeks. We review recent results of this policy and discuss the reasons why short treatment times may be advantageous.

MATERIALS AND METHODS

Two hundred patients (100 from each centre) with T1 glottic invasive squamous cell carcinoma treated with definitive radiotherapy between 1989 and 1997 were analysed. The median age was 68 years. All patients received once daily fractionation, 5 days a week to a total tumour dose of 50.0-52.5 Gy in 16 fractions over 21 days; the fraction size ranged from 3.12 to 3.28 Gy. The median follow-up period was 5 years and 10 months.

RESULTS

The 5-year local control rates with radiotherapy for the whole group was 93%; there were 14 recurrences of which seven were salvaged by laryngectomy giving an ultimate local control of 96%. The 5-year overall survival was 80% and cause specific survival at 5 years was 97%. Univariate analysis revealed that T1 substaging (P=0.82) and anterior commissure involvement (P=0.47) did not significantly influence local control. A severe late radiation complication was seen in only one patient who continued to smoke heavily after treatment. There were no severe acute complications.

CONCLUSIONS

Once daily radiotherapy over 3 weeks gives excellent local control in patients with T1 glottic squamous-cell carcinoma and has a low rate of severe complications. The short overall treatment time and large fraction size may be advantageous in radiotherapy of these well-differentiated tumours.

Treatment of early and moderately advanced vocal cord carcinoma with 6-MV X-rays

PURPOSE

Whereas there are many reports regarding treatment of early vocal cord cancer with cobalt 60 or 2-4-MV X-rays, there are still few reports on the results of treatment with 6-MV X-rays. Theoretically, 6-MV X-rays result in greater underdosage of tumor at the air-tissue interface and at the anterior commissure. This paper analyzes the results of irradiation of early and moderately advanced squamous cell carcinoma of the true vocal cord treated exclusively with 6-MV X-rays in a community hospital. The literature pertinent to the issue is reviewed.

METHODS AND MATERIALS

Eighty-three patients with Tis, T1, T2, or T3 squamous cell carcinoma of the true vocal cord were treated with curative intent at Bethesda Memorial Hospital in Boynton Beach, Florida between April 1986 and April 1998. The dose schedules most commonly used were 63 Gy in 28 fractions (2.25 Gy per fraction once a day) for T1 tumors or 74.40 Gy in 62 fractions (1.2 Gy per fraction twice a day) for T2 and T3 tumors. All patients have minimum 2-year follow-up; 63 (76%) have 5-year minimum follow-up.

RESULTS

Local control was achieved in 6 of 6 Tis, 53 of 54 (98%) T1, 8 of 8 T2, and 6 of 6 T3 lesions. No complications were encountered.

CONCLUSIONS

A recent literature review indicates that the treatment of early vocal cord cancer with 6-MV X-rays remains controversial. The dose schedules used in the present paper produced a high rate of local control, a finding that is consistent with reports of other investigators who used dose schedules similar to those used in the present series. However, several other investigators have reported significantly lower rates of local control for T1 or T2 glottic cancer treated with 6-MV X-rays when compared to results obtained with cobalt 60 or 4 MV at their own institution. The latter institutions used lower total doses and/or lower dose per fraction than those institutions reporting high rates of local control with 6 MV. Data from the literature, as well as our own data, are consistent with the following hypotheses: (1) the lower rates of local control reported by several institutions when using 6 MV compared with cobalt or 2-4 MV, using the same radiation dose schedules for each beam energy, indicate that underdosage of mucosal surfaces in the laryngeal air cavity may be a clinically important phenomenon, and (2) time-dose factors, although certainly important for lower energy beams, may be even more important when using 6 MV.

Radiotherapy with 6-megavolt photons for early glottic carcinoma: potential impact of extension to the posterior vocal cord

PURPOSE

Radiation therapy has a high success rate in the treatment of early glottic carcinoma. Excellent outcomes have been reported from centers using cobalt-60 or relatively low-energy (< or = 4 MV) radiation therapy to achieve these results. Whether similar outcomes can be achieved with a 6 MV linear accelerator has been less rigorously evaluated. This study assesses the efficacy of 6 MV radiation therapy for early stage glottic cancer and identifies prognostic factors for local control and overall survival in this common disease.

MATERIALS AND METHODS

One hundred twenty-eight consecutive cases of Tis, T1, and T2 squamous cell carcinomas of the glottis from 1982 to 1996 were retrospectively analyzed with regard to local control and survival. All patients were treated with definitive radiation therapy with a 6-MV linear accelerator. Potential prognostic factors for local control and survival were evaluated with univariate and multivariate models. Median follow-up of locally controlled patients was 65 months.

RESULTS

The overall 3-year actuarial local control rates for T1 and T2 carcinomas were 86% and 68%, respectively. Patients with lesions involving the posterior third of the vocal cord had significantly worse 3-year local control (76% vs. 86%, P =.038). Radiation therapy technique and overall treatment time did not significantly affect local control. For patients with Tis and T1 lesions, factors associated with significantly worse local control included cordectomy-ineligible disease (P =.024), dose less than 6,600 cGy (P =.024), and lesions limited to the posterior third of the vocal cord (P =.004). Three-year local control was 76%, with doses less than 6,600 cGy and 90% with higher doses. High rates of second primary malignancies were observed and represented the major cause of death. Five-year overall survival was 84%.

CONCLUSIONS

The use of 6-MV photons for treatment of early glottic cancer seems to achieve local control similar to that reported with lower-energy photons. However, patients with posterior third involvement had a poorer local control rate with standard radiation therapy, thereby suggesting that alternative approaches be considered.

The impact of treatment time and smoking on local control and complications in T1 glottic cancer

PURPOSE

To define the optimal treatment regimen, patients with T1N0M0 glottic larynx carcinoma were treated with six different radiotherapy (RT) schedules. To assess the influence of patient characteristics, complication rates, and to evaluate the overall larynx preservation.

METHODS AND MATERIALS

Out of a consecutive series of 383 patients treated for T1N0M0 glottic larynx carcinoma between 1965 and 1992, 352 evaluable patients were treated with six different "standard" fractionation schedules: 65 Gy (20 x 3.25 Gy), 62 Gy (20 x 3.1 Gy), 61.6 Gy (22 x 2.8 Gy), 60 Gy (25 x 2.4 Gy), 66 Gy (33 x 2 Gy) and 60 Gy (30 x 2 Gy). The median follow-up of all patients was 89 months. Patient factors analyzed included: age, sex, concurrent illness, smoking habits, tumor localization and extension, tumor differentiation, the effect of tumor biopsy or stripping of the vocal cord, and the presence of visible tumor at the start of radiotherapy. Treatment parameters evaluated were: year of treatment, beam energy, treatment planning, field size, fractionation schedule, fraction size, number of fractions, total dose, treatment time and treatment gap, the use of wedges, and neck diameter.

RESULTS

The overall 5-year actuarial locoregional control was 89%, varying between 83 and 93% for the different schedules. Univariately, local control decreased with increasing treatment time. This could not be explained by the confounding variables sex, tumor extension, and field length (p = 0.0065). Adjusted for these variables, 5-year local control percentage decreased from 95% (SE 2%) for 22-29 days to 79% (SE 6%) for treatment time > or = 40 days. The overall complication rate (grade I-IV) at 5 years was 15.3%, and varied between the different schedules, from 7 to 17%. No relation was found between complications and treatment factors. Patients who continued smoking had a higher complication rate than those who never smoked or stopped smoking, univariately as well as adjusted for tumor extension, macroscopic tumor, and neck diameter (p = 0.0038). Twenty-eight percent (SE 6%) of the patients who continued smoking had complications at 10 years, compared to about 13% (SE 4%) of those who stopped before or after RT. No evidence was found for any other relation between complications and patient or tumor factors. Severe edema and necrosis (grade III and IV) were not observed in the 2 Gy fraction schedules. A laryngectomy was performed in 36 patients: 30 for recurrence, 3 for complications (at 40, 161, and 272 months), and 3 for a second primary. The overall larynx preservation was 90% at 10 years, and for the different schedules it was 20 x 3.25 Gy: 97%; 20 x 3.1 Gy: 96%; 22 x 2.8 Gy: 92%; 25 x 2.4 Gy: 89%; 33 x 2 Gy: 78%; and 30 x 2 Gy: 80%.

CONCLUSION

Overall treatment time is the most significant factor for locoregional control of T1 glottic cancer. A schedule of 25 x 2.4 Gy appeared to be the optimal treatment schedule considering both tumor control and long term toxicity. The complication rate was increased in patients who continued smoking.

Impact of radiation therapy fraction size on local control of early glottic carcinoma

PURPOSE

Different radiotherapy fractionation schedules were used over a 10-year period to treat patients with early squamous cell carcinoma of the vocal cords at McGill University. A retrospective analysis was performed to study the effect of fraction size on local control in this group of patients.

METHODS AND MATERIALS

A total of 126 previously untreated patients with T1 invasive squamous cell carcinoma of the true vocal cords were irradiated between January 1978 and December 1988 in the Department of Radiation Oncology at McGill University. All patients received megavoltage irradiation, 94 patients received daily fractions > 2 Gy (64 patients received 50 Gy with once-daily 2.5-Gy fractions, and 30 received 65.25 Gy in 29 fractions of 2.25 Gy each), and 32 patients were treated to a dose of 66 Gy in 33 fractions with 2 Gy/fraction. Patients' characteristics of prognostic importance were equally distributed between the two fractionation groups.

RESULTS

At a median follow-up of 84 months, the 10-year disease-free survival and overall survival were 76% and 93%, respectively. Local control for patients treated with > 2 Gy fraction was 84%, compared to 65.6% for those treated with 2-Gy fractions (p = 0.026). Among the prognostic factors tested, such as gender, age, stage, anterior and posterior commissure involvement, smoking history, and fraction size, the latter was the only significant predictor of local control for the whole group of patients in univariate (p = 0.041) and multivariate (p = 0.023) analysis. There was no observed difference in the incidence of complications between the two fractionation groups.

CONCLUSIONS

From the results of this retrospective review of patients treated with radiotherapy for T1 true vocal cord cancer, and within the range of total doses and overall treatment times used in our patients, it was found that fractionation schedules using daily fraction size > 2 Gy are associated with a better local control than schedules delivering 2 Gy/fraction, with no increase in toxicity.

Assessment of mucosal underdosing in larynx irradiation

PURPOSE

Mucosal underdosing as a result of electron disequilibrium at the air cavity may affect local recurrence rates for T1 and T2 larynx cancers. Secondary build-up properties of high-energy beams have been demonstrated in a slab phantom. It was the aim of this investigation to determine whether significant surface underdosing exists for the mucosa under clinical conditions.

METHODS AND MATERIALS

Measurements were made using a thermoluminescent dosimetry (TLD) extrapolation technique in an anatomic larynx phantom. The larynx phantom was constructed using tissue and cartilage equivalent material, based on patient cross-sectional anatomy. Three different thicknesses of LiF ribbons, 0.14, 0.39, and 0.89 mm, were placed reproducibly at 12 different positions at the anterior, posterior, and lateral walls on the endolarynx surface. Measured doses were plotted and an extrapolation was made back to the mucosal depth to obtain the dose received at each of the positions. Results were obtained for two different field configurations, opposed laterals and oblique fields, for 6-MV X rays and opposed lateral fields from a telecesium unit. In addition, the larynx surface doses of field sizes from 4 x 6 cm2 to 7 x 6 cm2 were investigated.

RESULTS

Surface underdosing was observed owing to the secondary build-up and build-down effect of the air cavity, and the dose measured for the three extrapolation TLDs at any position varied by up to 18%. An average variation of 6% was observed. The surface underdosing was most apparent for the 6-MV opposed lateral beam technique, where mucosa doses down to 76% of the prescribed dose were observed. Mucosal underdosing at the measurement positions was less marked with oblique techniques, telecesium treatment, and increasing field size.

CONCLUSION

Because of underdosing, some surface positions receive < 80% of the prescribed dose. This may contribute to the potential for higher recurrence rates observed with high-energy photons.

Radiotherapy for early vocal cord cancer: a dosimetric analysis of 60CO versus 6 MV photons

BACKGROUND

Currently, many patients with early vocal cord cancers are treated with 6 MV photons, but almost all the published radiotherapy data are based on patients treated with 60Co, 2-MV, or 4-MV X-rays. A theoretical risk of underdosage exists with higher energy beams due to lack of dose build-up. This dosimetric study compares 6-MV photons with 60Co.

METHODS

A tissue-equivalent phantom was constructed of a stack of 0.5-cm-thick acrylic plates. With a male subject in treatment position as the model, the external surfaces of the phantom were machined to match the contour of the neck. To precisely represent the internal contour of the airway, computed tomography (CT) was performed on the subject in treatment position, with images at 0.5-cm intervals, and the airway shown on the CT was cut out of each corresponding acrylic plate. Thermoluminescent dosimetry (TLD) rods were inserted into the phantom. For each measurement, a calculated tumor dose of 10 Gy was delivered to the volume specified as the entire right true vocal cord in the phantom, with either 60Co or 6-MV photons (15 measurements were made with each). In a second series of eight experiments with each modality, TLD minichips were used to measure the dose received by the immediate surface of the vocal cords with delivery of a calculated tumor dose of 0.5 Gy.

RESULTS

The doses received at the vocal cords, as well as a point 6 mm beneath the anterior skin surface, did not differ significantly for the two energies compared. The dose delivered to the skin and a point 3 mm beneath the anterior skin surface was significantly lower with the use of 6-MV photons.

CONCLUSION

Although there is no difference in the dose received by the vocal cords, underdosage of the anterior tissues may occur with the use of 6-MV photons.

Radiation therapy for glottic cancer using 6-MV photons

BACKGROUND

It has been recommended that cobalt-60 or 4-MV photons be used when treating glottic cancer with radiation therapy. Underdosing may occur when using higher energy photons, particularly when the anterior commissure is involved. The authors report their experience using higher energy photons (6 MV) for the treatment of glottic cancer.

METHODS

Between January 1975 and July 1991, 73 patients with Tis, T1, T2, or T3 glottic tumors underwent radiation therapy with curative intent. Cobalt-60 or 4-MV photons were used to treat the cancers of 30 patients, and 6-MV photons were used to treat 43 patients. Clinical records were reviewed retrospectively to determine patterns of treatment failure, cancer deaths, and local tumor control in the 43 patients receiving treatment with 6-MV photons. Patients were followed until death or for a minimum of two years.

RESULTS

Treatment failures were: local recurrence, one patient; local recurrence and distant metastasis, one patient; delayed neck metastasis, two patients; and delayed neck metastasis with distant metastasis, one patient. Three patients who had treatment failure are alive and free of cancer after salvage treatment. Two patients died of neck and distant metastases. The 2-year initial local tumor control rate was 94.8%.

CONCLUSIONS

Glottic cancer can be treated successfully with 6-MV photons. Local tumor control is similar to that reported using cobalt-60 or 4-MV photons.

Head and neck cancer

This synthesis of the literature on radiotherapy for head and neck cancer is based on 424 scientific articles, including 3 meta-analyses, 38 randomized studies, 45 prospective studies, and 246 retrospective studies. These studies involve 79174 patients. The literature review shows that radiotherapy, either alone or in combination with surgery, plays an essential role in treating head and neck cancers. When tumors are localized, many tumor patients can be cured by radiotherapy alone and thereby maintain full organ function (1, 2). Current technical advancements in radiotherapy offer the potential for better local tumor control with lower morbidity (3). This, however, will require more sophisticated dose planning resources. To further improve treatment results for advanced tumors, other fractionation schedules, mainly hyperfractionation, should be introduced (5). This mainly increases the demands on staff resources for radiotherapy. The combination of radiotherapy and chemotherapy should be subjected to further controlled studies involving a sufficiently large number of patients (4, 5). Interstitial treatment (in the hands of experienced radiotherapists) yields good results for selected cancers. The method should be more generally accessible in Sweden. Intraoperative radiotherapy should be targeted for further study and development.

The influence of air cavities on interface doses for photon beams

PURPOSE

As the quantification of dose in homogeneous media is now better understood, it is necessary to further quantify effects from heterogeneous media. The most extreme case is related to air cavities. Although dose corrections at large distances beyond a cavity are accountable by attenuation differences, perturbations at air-tissue interfaces are complex to measure or calculate. These measurements helps understand the physical processes that govern these perturbations.

METHODS AND MATERIALS

A thin window parallel-plate chamber and a special diode were used for measurements with various air cavity geometries (layer, channel, cubic cavity, triangle) in x-ray beams of 4 and 15 MV.

RESULTS

Underdosing effects occur at both the distal and proximal air cavity interfaces. The magnitude depends on geometry, energy, and field sizes. As the cavity thickness increases, the central axis dose at the distal interface decreases. Increasing field size remedied the underdosing, as did the introduction of lateral walls. Following a 2.0 cm wide air channel for a 4 MV, 4 x 4 cm2 field there was an 11% underdose at the distal interface, while a 2.0 cm cubic cavity yielded only a 3% loss. Measurements at the proximal interface showed losses of 5% to 8%. For a 4 MV parallel opposed beam irradiation the losses at the interfaces were 10% for a channel cavity (in comparison with the homogeneous case) and 1% for a cube. The losses were slightly larger for the 15 MV beam. Underdosage at the lateral interface was 4% and 8% for the 4 MV and 15 MV beams, respectively.

CONCLUSION

Although reports suggest better clinical results using lower photon energies with the presence of air cavities, there is no reliable dose calculation algorithm to predict interface doses accurately. The measurements reported here can be used to guide the development of new calculation models under nonequilibrium conditions. This situation is of clinical concern when lesions such as larynx carcinoma beyond air cavities are irradiated.

Prognostic factors for local control and survival in T1 squamous cell carcinoma of the glottis

PURPOSE

To evaluate the effect of host, tumor, and treatment-related variables on local control and survival in patients with T1N0M0 squamous cell carcinoma of the glottis.

MATERIALS AND METHODS

Ninety-one patients with T1N0M0 squamous cell carcinoma of the glottic larynx were analyzed. Median follow-up was 9 years (range 2-25). Patients were treated with daily fractions of 180 cGy to 220 cGy to doses of 5925-7000 cGy (median 6400). The following factors were analyzed: age, sex, histologic grade, disease extent, beam energy, field size, total dose, dose per fraction, and elapsed treatment days.

RESULTS

The 5-year actuarial local control was 80%. On univariate analysis, only elapsed treatment days and dose per fraction were significant factors for local control. Local control was 100% if treatment was completed within 42 days, 91% for 43-46 days, 74% for 47-50 days, 65% for 51-54 days, and 50% for 55-66 days (p = 0.0001). In patients treated at < 200 cGy per fraction, local control was 62% as compared to 87% for > or = 200 cGy per fraction (p = 0.006). On multivariate analysis, only elapsed treatment days was a significant factor for local control (p = 0.0001). The 5-year actuarial survival for the whole group was 92%. Elapsed treatment days was the only variable affecting survival. Survival was 100% if treatment was delivered within 42 days, 96% for 43-46 days, 94% for 47-50 days, 91% for 51-54 days, and 67% for 55-66 days (p = 0.02). The 5-year actuarial disease-specific survival was 95%, with treatment duration again being the only significant prognostic factor. Disease-specific survival was 97% for treatment completed within 39-54 days versus 80% for 55-66 days (p = 0.02). Only three (3.3%) patients experienced moderate or severe complications. None of the evaluated parameters impacted significantly on complications.

CONCLUSION

We conclude that elapsed days is the most prognostically significant factor for local control and survival in patients treated with radiotherapy for T1 squamous cell carcinoma of the glottis. We recommend that these patients be treated with 210 cGy daily fractions to 6300 cGy.