The predictive role of bioeffect dose models in radiation-induced late effects in glottic cancers.

Late radiation-induced laryngeal oedema for different doses per fraction was analyzed in 208 cases with squamous cell carcinoma of the vocal cord. The series comprised 156 cases with T1N0M0 and 52 cases with T2N0M0 lesions. Radical radiotherapy was given with three different regimens delivering 3.33 Gy, 2.5 Gy, and 2.25 Gy per fraction. There were 52 cases of late radiation-induced laryngeal oedema. A strong correlation (p less than 0.015) between the dose per fraction and the risk of the late complication in the vocal cord has been demonstrated. The analysis suggests that the empirical models like Nominal Standard Dose (NSD) or Time-Dose Factors (TDF) do not predict correctly the late normal tissue reactions for different dose fractionations. The analysis with extrapolated response dose (ERD) values of the linear-quadratic (L-Q) model also fail to correlate with the late complications (p greater than 0.5). Care should be exercised when using these bioeffect dose models to calculate regimens iso-effective for late damage, even when modest changes in fraction size from 2 to 3 Gy are contemplated.

Influence of dose-rate and dose per fraction on clinical outcome of breast cancer treated by external beam irradiation plus iridium-192 implants: analysis of 289 cases.

PURPOSE: To study the influence of Iridium 192 implant dose-rate and dose per fraction of external irradiation on clinical outcome, the results in 289 patients with early breast cancer were analyzed retrospectively. METHODS AND MATERIALS: From 1980 to 1990, 118 T1 and 171 T2 lesions of breast were treated definitively by radiotherapy, following conservative surgery. External irradiation dose of 45 Gy was delivered either with 2.5 Gy or 1.8 Gy per fraction to the entire target volume, plus boost to the primary tumor. Boost dose of 15 to 30 Gy was given to the primary tumor either with iridium-192 implants or electrons. The implant dose-rate varied between 20 cGy/hr to 160 cGy/hr. RESULTS: The minimum follow-up was of 12 months and maximum of 11 years (median: 56 months). Out of 273 tumors boosted with implants, the 270 patients were divided into five groups according to dose-rate as, groups 1 (20-29 cGy/hr, n = 17), group 2 (30-49 cGy/hr, n = 144), group 3 (50-69 cGy/hr, n = 69), group 4 (70-99 cGy/hr, n = 27) and group 5 (100-160 cGy/hr, n = 13). The local failure rate was significantly increased in the group of patients treated with implant dose-rate < 30 cGy/hr (p < 0.05). While the incidence of late normal tissue complications and poor cosmetic outcome was significantly higher in the group of patients treated with implant dose-rate > 100 cGy/hr (p < 0.05). CONCLUSION: The present analysis indicate that the implant dose-rate should be maintained between 30-70 cGy/hr to maximize local control and reduce the late normal tissue injury. Also the increase in dose per fraction of external irradiation while not influencing local control rate was crucial for incidence of late complications and cosmetic outcome.

Predictive role of TDF values in late rectal recto-sigmoid complications in irradiation treatment of cervix cancer.

Radiation-induced late rectal and recto-sigmoid complications for different doses per fraction were analyzed retrospectively in 203 cases of Stage IIIB carcinoma of the uterine cervix. The patients were treated with a combination of external irradiation and a single intracavitary insertion during January 1979 to December 1983. The external irradiation was randomised to deliver by four different fractionation regimens having dose per fraction of 2 Gy, 3 Gy, 4 Gy and 5.4 Gy. The doses for various fractionations were matched with the daily regimen using the time-dose factors (TDF) model. A single intracavitary insertion delivered a dose of 22 to 24 Gy to point A using Fletcher-Suit applicator. All patients had a minimum follow-up of 30 months. Thirty nine cases of late radiation induced rectal and recto-sigmoid complications were observed. The complication rate of 8.2% for daily treatment regimen delivering 2 Gy per fraction was increased to 33.3% for once weekly treatment regimen delivering 5.4 Gy per fraction (p = 0.041). Despite similar Time-Dose Factors (TDF) values in four different treatment regimens, the complication rate increased significantly in the once weekly regimen. The analysis suggest that the Time-Dose Factors (TDF) values do not predict correctly the late normal tissue reactions for different dose fractionation schedules.

Therapeutic factors influencing the cosmetic outcome and late complications in the conservative management of early breast cancer.

PURPOSE: To investigate the impact of clinical and physical parameters on the cosmetic result and complications, in cancer breast treated with conservative surgery and definitive irradiation. METHODS AND MATERIALS: Between October 1980 and December 1990, 289 patients were treated with lumpectomy and/or axillary dissection, radical irradiation with or without adjuvant therapy. The radiation therapy technique consisted of external beam therapy followed by an Ir-192 implant or electron beam boost. Univariate and multivariate analysis were used to evaluate the correlation between multiple factors affecting the cosmetic outcome and the complications. RESULTS: Of 289 patients, cosmesis was evaluable in 285 and recorded as excellent to good in 226 (79%), fair in 35 (12%), and poor in 24 (9%). On multivariate analysis of these results, a high dose per fraction (p = .0018), and use of electrons as boost to the tumor bed (p = .001) were found to be significant. When patients boosted with electrons were excluded, a high boost dose (p = .0433) was also found significant. Fifteen (5%) patients developed severe late radiation sequelae and 14 (5%) moderate or severe arm edema. On multivariate analysis only dose per fraction of 2.5 Gy (p < .0001) and higher boost doses (p = .017) were significant. CONCLUSION: In 289 patients of early breast cancer treated with conservative surgery and radical irradiation, multivariate analysis suggests that higher dose per fraction with teletherapy and higher brachytherapy boost dose adversely affect cosmesis and contribute to the late complications.

Close or positive margins after surgical resection for the head and neck cancer patient: the addition of brachytherapy improves local control.

PURPOSE: Microscopically positive or close margins after surgical resection results in an approximately 21-26% local failure rate despite excellent postoperative external radiation therapy. We sought to demonstrate improved local control in head and neck cancer patients who had a resection with curative intent, and had unexpected, microscopically positive or close surgical margins. METHODS AND MATERIALS: Twenty-nine patients with microscopically close or positive margins after curative surgery were given definitive, adjuvant external radiation therapy and 125I brachytherapy. All 29 patients had squamous cell cancer and tonsil was the most common subsite within the head and neck region. After external radiation therapy and thorough discussions with the attending surgeon and pathologists, the slides, gross specimens, and appropriate radiographs were reviewed and a target volume was determined. The target volume was the region of the margin in question and varied in size based on the surgery and pathologic results. Once the target volume was identified the patient was taken back to the operating room for insertion of 125I seeds. Activity implanted (range 2.9-21.5 millicuries) was designed to administer a cumulative lifetime dose of 120-160 Gy. RESULTS: Twenty-nine patients were followed for a median of 26 months (range 5-86 months). Two-year actuarial local control was 92%. CONCLUSION: 125I, after external radiation therapy, is an excellent method to improve local control in the subset of patients with unexpectedly unsatisfactory margins.

Late radiation induced laryngeal oedema in the treatment of vocal cord cancer: analysis using the linear quadratic model.

The incidence of late complications for different size of dose per fraction is analysed in 208 cases with squamous cell carcinoma of the vocal cord. The series comprised 156 cases with T1 and 52 cases with T2 lesions. Radical radiotherapy was given with three different regimens having dose per fraction as 3.33, 2.5 and 2.25 Gy. There were 46 cases with persisting radiation induced laryngeal oedema. Using two different statistical methods, an alpha/beta value of 2.38 Gy of linear quadratic model was estimated for late complications of vocal cord. The analysis indicate the increased incidence of late complications with size of dose per fraction. Relevance of linear quadratic model for the prediction of late complication is demonstrated in the present study.

Importance of dose per fraction and estimation of an alpha/beta value for the late complications of the vocal cord.

The incidence of late complications for different sizes of dose per fraction is analysed in 208 cases with squamous cell carcinoma of the vocal cord. The series comprised 156 cases with T1N0M0 and 52 cases with T2N0M0 lesions. Radical radiotherapy was given with three different regimens having dose per fraction of 3.33 Gy, 2.5 Gy and 2.25 Gy. There were 46 cases of late radiation induced laryngeal oedema. Using this clinical data an alpha/beta value of 2.35 +/- 0.13 Gy was estimated for late complications of the vocal cord. It was found that there is strong correlation between size of dose per fraction and the risk of late complication in the vocal cord.

The severity of late rectal and recto-sigmoid complications related to fraction size in irradiation treatment of carcinoma cervix stage III B.

A retrospective analysis of late rectal and recto-sigmoid complications was carried out of the 203 patients with stage III B carcinoma of uterine cervix, treated using radiation therapy alone during January 1979 to December 1983. The patients were treated with a combination of external irradiation and single intracavitary insertion. External irradiation was randomised to one of the four different fractionation regimens having dose per fraction of 2 Gy, 3 Gy, 4 Gy and 5.4 Gy, delivering with five fractions/week, three fractions/week, two fractions/week and one fraction/week, respectively. The total doses in four different regimens were adjusted using the TDF model. There were 39 cases of late radiation induced rectal and recto-sigmoid complications. The complication rate was correlated with the dose per fraction and TDFs delivered in each regimen. The complication rate of 8.2% for 2 Gy per fraction was increased to 33.33% for 5.4 Gy per fraction. It was found that there is strong correlation (P less than 0.05) between size of dose per fraction and the risk of late complications. Present analysis shows that the empirical models as the NSD and TDF do not predict correctly, the late normal tissue damage for different dose fractionations.

Alpha/beta value and importance of dose per fraction for the late rectal and recto-sigmoid complications.

A total of 203 patients with cancer of cervix stage IIIB, treated by radiation alone were analysed retrospectively for the incidence of late rectal and recto-sigmoid complications. The patients were treated with a combination of external irradiation and a single intracavitary insertion during January 1979 to December 1983. The external irradiation was randomised to deliver by four different fractionation regimens having dose per fraction of 2 Gy, 3 Gy, 4 Gy and 5.4 Gy. The doses for various fractionation regimens were matched using the time dose factors (TDF) model. 39 cases of late radiation induced rectal and recto-sigmoid complications were observed. The complication rate increased significantly (p < 0.05) with the size of dose per fraction. Using this clinical data an alpha/beta value of 3.87 +/- 0.74 Gy was estimated for late rectal and recto-sigmoid complications.