Brachytherapy training in India: Results from the GEC-ESTRO-India survey.

INTRODUCTION: Brachytherapy (BT) is integral in treatment of gynecological malignancies and is also an option for many other cancers. Data on training and proficiency levels of early career oncologists is limited. Like other continents a survey was conducted for early career oncologists in India. METHODS AND MATERIALS: An online survey was conducted from November 2019 to February 2020, through Association of Radiation Oncologists of India (AROI) for early career radiation oncologists expected to be within 6 years of training. The survey used a 22 item questionnaire that was also used for European survey. Responses to individual statements were recorded on a 1-5 Likert-type scale. Descriptive statistics were used to describe proportions. RESULTS: One-hundred twenty-four (17%) of 700 recipients responded to the survey. Majority of the respondents (88%) stated that being able to perform BT at the end of their training was important. Two-thirds of the respondents (81/124) had performed >10 intracavitary procedure and 22.5% had performed >10 intracavitary-interstitial implants. Many respondents had not performed nongynecological procedure- breast (64%), prostate(82%), gastro-intestinal (47%). Respondents predicted that in next 10 years, the role of BT is likely to increase. Lack of dedicated curriculum and training was perceived as the greatest barriers to achieving independence in BT (58%). Respondents suggested that BT training should be prioritized during conferences (73%) and online teaching modules (56%), along with development of BT skills labs (65%). CONCLUSION: This survey identified a lack of proficiency in gynecological intracavitary-interstitial brachytherapy and non-gynecological brachytherapy, despite BT training being regarded as highly important. Dedicated programs, including standardized curriculum and assessment need to be developed for training early- career radiation oncologists in BT.

Serial Bone Density Changes in Women Undergoing Pelvic (Chemo) Radiation: Results From the PARCER Trial.

PURPOSE: Pelvic irradiation leads to substantial dose to the pelvic girdle. However, bone density loss as a function of radiation therapy dose and time has not been investigated. This study was undertaken to evaluate such a dose-response relationship. METHODS AND MATERIALS: Women undergoing pelvic radiation therapy for cervix cancer within a phase 3 trial were included. The study necessitated 2 computed tomography imaging sets acquired at least 12 months apart in patients with no evidence of relapse. All images were transferred to the treatment planning system to determine radiation dose and Hounsfield unit (HU). Across the entire lumbopelvic region (lumbar 1-5 [L1-5] vertebrae, pubic symphysis, femur, acetabulum, greater trochanter, and anterior-superior iliac spine) multiple regions were defined to measure radiation therapy dose and HU. Bone health was categorized as normal if >130 HU, osteopenic at 110 to 130 HU, and osteoporotic <110 HU at baseline and follow-up. Univariate analysis was performed to test the effect of various factors on HU. Further interaction among radiation therapy dose, time, and HU was assessed using a linear mixed model. RESULTS: Overall, 132 of 300 patients were eligible. The median age was 49 (42-56) years. With a prescription dose of 50 Gy, the L1 and L2 vertebrae received a median dose of 1.2 and 4 Gy, respectively, and L3-5 received 10 to 50 Gy. At 24 months, median HU loss at L4-5 was 45 HU (interquartile range, 34-77 HU). Out of the 132 patients, at baseline 96% had normal bone health. However, at the last follow-up, 3% of patients had normal bone health, 12% developed osteopenia, and 85% developed osteoporosis (P < .001). There were no patient- or treatment-related factors predicted for HU loss on univariate analysis. HU loss >60 to 70 was observed at >45 Gy at L5 vertebra (60-70 HU, P < .02) and >15 Gy at L4 vertebra (33 HU; P = .04). CONCLUSIONS: Dose-response relationship is observed between radiation dose and bone mineral density loss. Prospective studies are needed to corroborate these observations and design future interventions.

Recurrence pattern with respect to two different dose fractionations in patients with locally advanced head and neck cancer treated with chemoradiation using image-guided volumetric arc therapy.

BACKGROUND: Patients with head and neck cancer were treated with either 70 Gy in 35 fractions (Arm A) or 66 Gy in 30 fractions (Arm B). MATERIALS AND METHODS: Total 168 patients of carcinoma oropharynx, larynx, and hypopharynx treated with radical chemoradiation in two Arm A versus B (65 vs. 103 patients). RESULTS: With a median follow-up of 16 months (0-67), 2 year disease-free survival (DFS) and overall survival (OS) was 56.3% versus 62.1% (p = 0.64) and 44.5% versus 53.0% (p = 0.51) in Arm A versus B. Total 22 (33.8%) versus 28 (27.2%) failed locoregionally. Majority of failures were infield for both primary (17 vs. 23 cases) and nodes (13 vs. 12) in Arm A versus B. Ten (71.4%) vs. 10 (76.9%) had nodal failure in index nodal level only. CONCLUSION: Commonly seen failure in head-neck radical chemoradiation is within infield high-risk volume, nodal failure being most common in index nodal level.

Patterns of Relapse After Adjuvant Chemoradiation for Cervical Cancer in a Phase 3 Clinical Trial (PARCER): An Evaluation of Updated NRG Oncology/RTOG Target Delineation Guidelines.

PURPOSE: The Radiation Therapy Oncology Group (RTOG) under NRG Oncology recently published updated contouring guidelines for intensity modulated radiation therapy in postoperative treatment for endometrial and cervical cancer. The present study was designed to evaluate the implications of newly published guidelines. METHODS AND MATERIALS: We recruited 300 patients in a phase 3 randomized controlled trial of adjuvant chemoradiation therapy for cervical cancer (NCT01279135) to understand patterns of relapse. For those patients with pelvic relapse, we imported radiation therapy structure sets, treatment plans, and diagnostic images at relapse on the treatment planning system. We performed rigid registration with treatment planning images that contained the delineated planning target volume and radiation dose information. We delineated gross tumor volume at time of relapse on the diagnostic scans and superimposed it on the radiation therapy treatment scans. We categorized the site of pelvic relapse as "within field of old RTOG/[Postoperative Adjuvant Radiation in Cervical Cancer (PARCER)] target delineation guidelines" or "within field of new NRG/RTOG guidelines," or both, and compared proportions of recurrences contained within the 2 guidelines. We consider a P value of <.05 statistically significant. Additionally, we generated intensity modulated radiation therapy treatment plans based on the new guidelines for a limited set of patients to see if these new guidelines increased the organ at risk doses. RESULTS: Most common form of relapse was distant metastasis (15%). Pelvic relapse rate in our study was 8%. Overall, 9 out of 19 relapses were encompassed in the contouring guidelines of the old RTOG/ Postoperative Adjuvant Radiation in Cervical Cancer (PARCER) trial, and 12 out of 19 were encompassed within the new RTOG 2021 contouring guidelines. This corresponded to a further 1% reduction in local relapses (P = .007). Dose to rectum was marginally increased with the new contouring, with no difference in other organs at risk. Salvage treatment was offered in 25 out of 60 patients who relapsed. Patients who received local treatment after relapse had a mean survival after relapse of 27.2 months compared with 8 months among those who received supportive care alone. CONCLUSIONS: Our study supports the use of newly published NRG/RTOG contouring guidelines in patients with cervical cancer who have undergone hysterectomy. Further data are needed to ascertain if anterior extension of the clinical target volume is needed as in the Postoperative Adjuvant Radiation in Cervical Cancer trial.

Outcomes of locally advanced cervical cancer presenting with obstructive uropathy: An institutional audit.

BACKGROUND: There is paucity of outcome data of patients with cervical cancer presenting with malignant obstructive uropathy. The present retrospective study describes outcomes of patients with cervical cancer who presented with obstructive uropathy at the time of diagnosis and underwent urinary diversion with percutaneous nephrostomy (PCN) before/during treatment. METHODS: Patients who underwent PCN from January 2010 to June 2015 were included. Intent of treatment (radical or palliative) was decided within multidisciplinary team depending on disease stage, Karnofsky performance status (KPS), and degree of renal derangement. Treatment and outcome details were retrieved from electronic records. Time to normalization of creatinine, feasibility of delivering planned treatment, and overall survival (OS) were determined. Impact of various prognostic factors on outcomes was determined using univariate or multivariate analysis. RESULTS: After PCN and double-J stenting, 50% were eligible for (chemo) radiation. All radically treated patients (26/52) received brachytherapy. The median EQD2 to point A was 78 Gy (72-84 Gy). The median OS was 10 (0.5-60) months. Patients who completed chemoradiation had median OS of 31 months. Those receiving radical radiation and palliative radiation had median OS of 11 and 6 months, respectively. On univariate analysis, smaller tumor size (p = 0.03), high KPS (P = 0.04), and radical intent of treatment (P = 0.05) predicted for OS. CONCLUSION: Patients presenting with obstructive uropathy have median OS less than a year despite urinary diversion. Select cohort with good performance status, small tumor size, and serum creatinine of ≤3 mg/dL may be selected for diversion procedures and potential radical treatment.

Standard Chemoradiation and Conventional Brachytherapy for Locally Advanced Cervical Cancer: Is It Still Applicable in the Era of Magnetic Resonance-Based Brachytherapy?

Purpose Recent guidelines recommend magnetic resonance imaging-based brachytherapy (MRBT) for locally advanced cervical cancer. However, its implementation is challenging within the developing world. This article reports the outcomes of patients with locally advanced cervical cancer treated with chemoradiation and point A-based brachytherapy (BT) using x-ray- or computed tomography-based planning. Methods Patients treated between January 2014 and December 2015 were included. Patients underwent x-ray- or computed tomography-based BT planning with an aim to deliver equivalent doses in 2 Gy (EQD2) > 84 Gy10 to point A while minimizing maximum dose received by rectum or bladder to a point or 2 cc volume to < 75 Gy EQD2 and < 90 Gy EQD2, respectively. The impact of known prognostic factors was evaluated. Results A total of 339 patients were evaluated. Median age was 52 (32 to 81) years; 52% of patients had stage IB2 to IIB and 48% had stage III to IVA disease. There was 85% compliance with chemoradiation, and 87% of patients received four or more cycles. Median point A dose was 84 (64.8 to 89.7) Gy. The median rectal and bladder doses were 73.5 (69.6 to 78.4) Gy3 and 83 (73.2 to 90.0) Gy3, respectively. At a median follow-up of 28 (4 to 45) months, the 3-year local, disease-free, and overall survival for stage IB to IIB disease was 94.1%, 83.3%, and 82.7%, respectively. The corresponding rates for stage III to IVA were 85.1%, 60.7%, and 69.6%. Grade III to IV proctitis and cystitis were observed in 4.7% and 0% of patients, respectively. Conclusion This audit demonstrates good 3-year outcomes that are comparable to published MRBT series. Conventional BT with selective use of interstitial needles and MRBT should continue as standard procedures until level-I evidence for MRBT becomes available.

Cancer cervix: Establishing an evidence-based strategy, an experience of a tertiary care centre in India.

Carcinoma cervix is a common cancer among Indian women. Evidence based management is essential for best practice in treatment of carcinoma cervix for its effective control. The current imaging system like CT, MRI and PET CT scans have contributed in identifying the patients for optimal treatment and delivering treatment accurately. For stages IB2 to IV, concurrent chemoradiation is advocated with improvement in overall survival proven with randomized trials. Brachytherapy is an integral part in the radiation treatment. Imaged-guided brachytherapy using MRI is desirable, however less expensive imaging modalities such as CT and ultrasonography has been evaluated. In special situation such as for HIV positive patients and patients with neuroendocrine tumors have role of radiotherapy. For further improvement in control of cancer, it is required to integrate basic research to answer clinically relevant questions.

Impact of HPV 16/18 infection on clinical outcomes in locally advanced cervical cancers treated with radical radio (chemo) therapy - A prospective observational study.

OBJECTIVE: With an aim to investigate the impact of Human Papilloma Virus (HPV) 16/18 infection on clinical outcomes in locally advanced cervical cancers treated with radical radio (chemo) therapy, we undertook this prospective study. METHODS: Between May 2010 and April 2012, 150 histologically proven cervical cancer patients treated with radio (chemo) therapy were accrued. Cervical biopsies/brushings were collected at pre-treatment, end of treatment and at 3 monthly intervals up to 24months. Quantitative estimation of HPV 16/18 was done using real-time polymerase chain reaction (RT-PCR) and correlated with various clinical end-points. RESULTS: Out of 150 patients accrued, 135 patients were considered for final analysis. Pre-treatment HPV16/18 DNA was detected in 126 (93%) patients, with HPV-16 present in 91%. The mean log (±SD) HPV-16 and HPV-18 viral load at pre-treatment was 4.76 (±2.5) and 0.14 (±2.1) copies/10ng of DNA, respectively. Though significant decline in viral load was observed on follow-ups (p<0.0001); by 9-month follow-up, 89 (66%) patients had persistence of HPV infection. Patients with persistent HPV 16/18 infection had a significantly higher overall and loco-regional relapses [44/89 (49%) and 29/89 (32%)] as compared to HPV clearance by 9months [12/43 (28%) and 5/43 (11%)] with p=0.024 and p=0.02, respectively. Also, persistent HPV infection by 24-month showed a significant impact on loco-regional control (LRC) and recurrence-free survival (RFS). CONCLUSION: In locally advanced cervical cancers treated with radical radio (chemo) therapy, persistent HPV 16/18 infection is significantly high in immediate post-treatment period and correlated with higher loco-regional, overall relapses and was also associated with early relapses.

Income generated by women treated with magnetic resonance imaging-based brachytherapy: A simulation study evaluating the macroeconomic benefits of implementing a high-end technology in a public sector healthcare setting.

PURPOSE: To estimate the difference in income generated if all women presenting in our institute over a 5-year period were treated with MRI-based image-guided brachytherapy (MR-IGBT) instead of conventional radiograph-based brachytherapy (CR-BT). METHODS AND MATERIALS: Outcome data from 463 patients (94 treated with MR-IGBT) treated in our institute was used to simulate cumulative women-days of work and cumulative income over 5 years for 5526 patients expected to be treated in this period. The average daily income for a woman was derived from the National Sample Survey Organization (NSSO) survey data. Outcomes from both unmatched and propensity score-matched data sets were simulated. RESULTS: The cumulative income in 5 years ranged between Rs 101-168 million if all patients presenting at our institute underwent MR-IGBT. The simulated excess income ranged from Rs 4-45 million after 5 years, which represented 6-66% of the expenditure incurred for acquiring the required equipment and manpower for practicing exclusive MR-IGBT. CONCLUSIONS: Using outcome data from a prospective cohort of patients treated with MR-IGBT in our institute, we demonstrated that significant economic gains may be realized if MR-IGBT was used instead of CR-BT.

High dose chemoradiation for unresectable hilar cholangiocarcinomas using intensity modulated external beam radiotherapy: a single tertiary care centre experience.

BACKGROUND: We present results of patients diagnosed with unresectable hilar cholangiocarcinomas treated with high dose radiotherapy and concurrent chemotherapy. METHODS: From Aug 2005 to Dec 2012, 68 consecutive patients were treated. Fifty patients (group 1) presenting to us with obstructive jaundice were planned for endobiliary brachytherapy (EBBT 14 Gy) followed external beam radiotherapy (EBRT 45 Gy). Twenty-two patients (group 2) who had previously undergone biliary drainage underwent EBRT (57 Gy). All patients received injection Gemcitabine 300 mg/m2/weekly along with EBRT. RESULTS: Twenty-nine patients in group 1 and 22 patients in group 2 completed the treatment. Twenty-six (55%) patients achieved complete radiological response, 16 (64%) belonging to group 1 and 8 (44%) of group 2 (P=0.05). The median overall survival (MOS) was 17.5 and 16 months for group 1 and 2 respectively (P=0.07). The 1- and 2-year survival was 63%, and 18% for group I and 61% and 22% for group II respectively. The MOS was 5 months and 1 year survival was 14% for patients receiving EBBT only. MOS was significantly better after complete response (P=0.001). CONCLUSIONS: Intensity modulated radiotherapy (IMRT) modulated high dose radiotherapy used either alone or with brachytherapy demonstrates potential to prolonged overall survival in unresectable hilar cholangiocarcinomas.

Radiation Oncology in India: Challenges and Opportunities.

Rising cancer incidence and mortality in India emphasize the need to address the increasing burden of this disease and the stark inequities in access to radiotherapy and other essential medical treatments. State-of-the-art technology is available within the private sector and a few hospitals in the public sector, but 75% of patients in the public sector in India do not have access to timely radiotherapy. This inequity in access to radiotherapy in the public sector is amplified in rural areas, where most of India׳s population lives. A long-term government commitment to machine purchase and human resource development in the public sector is needed to improve access. A number of innovative initiatives to improve cancer treatment and access have emerged that could support such an investment. These include local production of equipment, twinning programs between institutions in high- and low-income countries to exchange knowledge and expertise, and nongovernmental and state-sponsored schemes to sponsor and support patients in their cancer journey. Strengthening of cancer registries and regulatory bodies with authority to enforce minimum standards is also required to improve care. The more uniform and frequent availability of high-quality radiotherapy can improve cancer outcomes and may be regarded as a marker of a comprehensive and equitable system of health care delivery.

Incidental Dose to Pelvic Nodes in Bladder-Only Radiotherapy: Is It Clinically Relevant?

BACKGROUND AND PURPOSE: Although there is a strong biological rationale to electively treat the pelvic nodes during bladder preservation, its clinical benefit is uncertain. This may be explained by the incidental dose received by the nodal regions when treating the bladder alone. This study was conducted to investigate the doses received by the different pelvic nodal regions when the bladder alone is treated by standard conformal radiotherapy. METHODS AND MATERIALS: The computed tomography data sets of 20 patients with node-negative muscle-invasive bladder cancer treated in a bladder preservation protocol were studied. Patients were originally treated with conformal radiotherapy to the bladder alone. Replanning was done with additional delineation of the pelvic nodal regions namely common iliac (upper and lower), presacral, internal iliac, obturator, and external iliac. Dose volume parameters such as Dmean, Dmax, D100%, D66%, D33%, V40, and V50 to each of the nodal regions were estimated for all patients. RESULTS: The obturator nodes received the highest dose among all nodal regions. The mean dose received by obturator, external iliac, and internal iliac regions was 59, 45, and 36 Gy, respectively. The dose received by these 3 regions in the full bladder state was 63, 52, and 47 Gy, respectively. The dose received by all other pelvic nodal regions was low and not clinically relevant. CONCLUSION: The incidental dose received by obturator and external iliac nodes is clinically significant in bladder-only radiation, possibly enough to influence micrometastatic disease. This may be a reason for the lack of clear benefit seen with nodal irradiation in bladder cancer. Advances in Knowledge: This study highlights that the incidental dose received by obturator and external iliac nodes is clinically significant in bladder-only radiation. The obturator nodes received the highest dose among all nodal regions with mean dose of 59 Gy.

Clinical outcome of high-dose-rate interstitial brachytherapy in vulvar cancer: A single institutional experience.

PURPOSE: With an aim to evaluate and report high dose date interstitial brachytherapy (HDR-ISBT) in vulvar cancers, we undertook this retrospective analysis. METHODS AND MATERIALS: Histologically proven vulvar cancers treated with HDR-ISBT between 2001 and 2016 were analyzed. Radiotherapy details, clinical outcome in terms of local control rates, survivals, and toxicities were evaluated. RESULTS: A total of 38 patients received HDR-ISBT, with definitive radiation in 29 (76.3%), adjuvant postoperative in six (15.8%) and salvage radiation in three (7.9%) patients. Of them, 29 patients received brachytherapy boost and nine patients ISBT alone. BT procedure included freehand plastic tube technique in 23 (single [n = 5] or multiple plane [n = 18]), 13 patients with template based and two patients combined approach. Patients with brachytherapy alone received median EQD2 of 38.4 Gy10 (35.5-46.7 Gy10), as boost received median 23.3 Gy10 (13-37.3 Gy10). At 3-month post-treatment response evaluation, 30 patients achieved clinically complete response, two patients partial response and six maintained postoperative status. With a median follow-up of 30 months, 29 (76.3%) were disease free, and 9 (23.7%) patients had relapsed disease with four patients expired due to disease and two died of other causes. The 5-year overall survival, disease free survival, and local control rates were 82%, 51%, and 77%, respectively. CONCLUSIONS: HDR-ISBT in vulvar cancer is a feasible and a viable option with acceptable and comparable outcomes.

Incidental Dose to Pelvic Nodal Regions in Prostate-Only Radiotherapy.

OBJECTIVES: Pelvic lymph nodal regions receive an incidental dose from conformal treatment of the prostate. This study was conducted to investigate the doses received by the different pelvic nodal regions with varying techniques used for prostate radiotherapy. METHODS AND MATERIALS: Twenty patients of high-risk node-negative prostate cancer treated with intensity-modulated radiotherapy to the prostate alone were studied. Replanning was done for intensity-modulated radiotherapy, 3-dimensional conformal treatment, and 2-dimensional conventional radiotherapy with additional delineation of the pelvic nodal regions, namely, common iliac (upper and lower), presacral, internal iliac, obturator, and external iliac. Dose-volume parameters such as Dmean, D100%, D66%, D33%, V40, and V50 to each of the nodal regions were estimated for all patients. RESULTS: The obturator nodes received the highest dose among all nodal regions. The mean dose received by obturator nodal region was 44, 29, and 22 Gy from 2-dimensional conventional radiotherapy, 3-dimensional conformal treatment, and intensity-modulated radiotherapy, respectively. The mean dose was significantly higher when compared between 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment ( P < .001), 2-dimensional conventional radiotherapy and intensity-modulated radiotherapy ( P < .001), and 3-dimensional conformal treatment and intensity-modulated radiotherapy ( P < .001). The D33% of the obturator region was 64, 39, and 37 Gy from 2-dimensional conventional radiotherapy, 3-dimensional conformal treatment, and intensity-modulated radiotherapy, respectively. The dose received by all other pelvic nodal regions was low and not clinically relevant. CONCLUSION: The incidental dose received by obturator regions is significant especially with 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment techniques as used in the trials studying elective pelvic nodal irradiation. However, with intensity-modulated radiotherapy, this dose is lower, making elective pelvic irradiation more relevant. Advances in Knowledge: This study highlights that incidental dose received by obturator regions is significant especially with 2-dimensional conventional radiotherapy and 3-dimensional conformal treatment techniques.

Cardiac metastasis in cervical cancer.

Metastasis of cervical carcinoma to the heart is uncommon. Most cases are found during autopsy. These type of metastasis occur mostly in epicardium and myocardium. We present a case report of a patient with carcinoma cervix stage IIIB who presented to the hospital with pitting edema of right lower limb, post 1 year of completion of treatment. PET-CT scan showed FDG avid inguinal, iliac and retroperitoneal lymph nodes, which were bulky on right side causing pedal edema. There was FDG avid uptake seen in right atrial wall and in the atrioventricular groove indicative of metastasis to the heart. Patient refused biopsy or further treatment and hence received best supportive care only. She had a disease free survival of 12 months, and survived for 11 months after being diagnosed with recurrence. Overall survival was 23 months.

Intensity modulated radiation therapy (IMRT) is not superior to three-dimensional conformal radiation (3DCRT) for adjuvant gastric radiation: A matched pair analysis.

AIMS: To compare three-dimensional conformal radiation (3DCRT) and Intensity Modulated Radiation Therapy (IG-IMRT) for adjuvant gastric irradiation. SUBJECTS AND METHODS: From Jan 2010-Aug 2013, all patients undergoing 3DCRT and IG-IMRT were included. Systemic chemotherapy included 1 cycle before and 2 cycles after chemoradiation. Planning Target Volume (PTV) received 45 Gy/25 fractions/5 weeks with concurrent capcetabine 825 mg/m2 bid. Matched pair analysis was performed to evaluate imbalance in two cohorts if any. Common Toxicity Criteria for Adverse Event (CTCAE) vs 3.0 was used to record gastrointestinal (GI), hematological (HL), and renal toxicity during treatment and follow-up. Patterns of recurrence were documented. Mann-Whitney U test was used for statistical comparison. RESULTS: Of the 51 patients, 26 received 3DCRT and 25 IMRT. IMRT led to decrease in dose received by right and left kidney (12.4 Gy and 7.1 Gy and 29 Gy vs 8.2 Gy; P<0.001). Overall, 17.6% and 19.6% patients had grade II GI and HL toxicity and 3.9% and 5.9% had grade III GI and HL toxicity. No difference was observed in acute grade II-V GI or HL toxicity (11.5% vs 24%, P=0.07; 7.6% vs 20% P=0.20) or late GI, HL, or renal toxicity between 3DCRT and IMRT. No difference was observed in patterns of local relapse (11.5% vs 12%, P=0.14) or overall survival (39% and 38% (P=0.97)) between 3DCRT and IMRT. CONCLUSIONS: 3DCRT and IMRT are equivalent in terms of toxicity and local control.

Late rectal toxicity after image-based high-dose-rate interstitial brachytherapy for postoperative recurrent and/or residual cervical cancers: EQD2 predictors for Grade ≥II toxicity.

PURPOSE: To investigate the correlation of rectal dose volume metrics with late rectal toxicity after high-dose-rate pelvic interstitial brachytherapy. METHODS AND MATERIALS: From October 2009 to November 2012, 50 patients with residual or recurrent cervical cancer were included. Patients received external radiation 50 Gy in 25 fractions over 5 weeks with weekly cisplatin. Rectum and rectal mucosal (RM) contours were delineated retrospectively. RM was defined as the outer surface of the flatus tube inserted at brachytherapy. The dose received by 0.1, 1, 2, 5 cc of rectum, RM, and sigmoid was recorded. Cumulative equivalent dose in 2 Gy (EQD2) for organs at risk was calculated assuming α/ß of 3. Univariate analysis was performed to identify predictors of rectal toxicity. RESULTS: At a median follow-up of 34 months (12-51 months), Grade II and III late rectal toxicity was observed in 9 (18%) and 2 (4%) patients, respectively. On univariate analysis, rectal doses were not significant predictors; however, D 0.1-cc RM dose >72 Gy (p = 0.04), D 1-cc RM dose >65 Gy (p = 0.004), D 2-cc RM dose >62.3 Gy (p = 0.004), and D 5-cc RM dose >60 Gy (p = 0.007) correlated with Grade ≥II toxicity. On probit analysis, the estimated dose in EQD2 for a 10% and 20% risk of rectal toxicity was D 2-cc rectum of 55 and 66 Gy, and RM <55 and 63 Gy, respectively. CONCLUSIONS: Limiting 2-cc RM and rectal doses within the proposed thresholds can minimize Grade ≥II toxicity for gynecologic high-dose-rate interstitial brachytherapy.