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      Clinical outcome of proton therapy for patients with chordomas

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          Abstract

          Purpose

          To investigate the clinical outcome of proton therapy (PT) in patients with chordoma.

          Materials and Methods

          Fifty-eight patients with chordoma treated with PT between June 2007 and December 2015 at the National Cancer Center, Korea, were retrospectively analyzed. The median total dose was 69.6 cobalt gray equivalent (CGE; range, 64.8 to 79.2 CGE). Local progression-free survival (LPFS), distant metastasis-free survival (DMFS), overall survival (OS), and diseasespecific survival (DSS) rates were calculated by the Kaplan–Meier method.

          Results

          With the median follow-up of 42.8 months (range, 4 to 174 months), the 5-year LPFS, DMFS, OS, and DSS rates were 87.9%, 86.7%, 88.3%, and 92.9%, respectively. The tumor location was associated with the patterns of failure: the LPFS rates were lower for cervical tumors (57.1%) than for non-cervical tumors (93.1%) (p = 0.02), and the DMFS rates were lower for sacral tumors (53.5%) than for non-sacral tumors (100%) (p = 0.001). The total dose was associated with both the LPFS rate and DMFS rate. The initial tumor size was associated with the DMFS rate, but was not associated with the LPFS rate. Three patients had grade 3 late toxicity with none ≥grade 4.

          Conclusion

          PT is an effective and safe treatment in patients with chordomas. The tumor location was associated with the patterns of failure: local failure was common in cervical tumors, and distant failure was common in sacral tumors. Further refinement of PT, such as the utilization of intensity modulated PT for cervical tumors, is warranted to improve the outcome.

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          Most cited references15

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          Reporting and analyzing dose distributions: a concept of equivalent uniform dose.

          Modern treatment planning systems for three-dimensional treatment planning provide three-dimensionally accurate dose distributions for each individual patient. These data open up new possibilities for more precise reporting and analysis of doses actually delivered to irradiated organs and volumes of interest. A new method of summarizing and reporting inhomogeneous dose distributions is reported here. The concept of equivalent uniform dose (EUD) assumes that any two dose distributions are equivalent if they cause the same radiobiological effect. In this paper the EUD concept for tumors is presented, for which the probability of local control is assumed to be determined by the expected number of surviving clonogens, according to Poisson statistics. The EUD can be calculated directly from the dose calculation points or, from the corresponding dose-volume distributions (histograms). The fraction of clonogens surviving a dose of 2 Gy (SF2) is chosen to be the primary operational parameter characterizing radiosensitivity of clonogens. The application of the EUD concept is demonstrated on a clinical dataset. The causes of flattening of the observed dose-response curves become apparent since the EUD concept reveals the finer structure of the analyzed group of patients in respect to the irradiated volumes and doses actually received. Extensions of the basic EUD concept to include nonuniform density of clonogens, dose per fraction effects, repopulation of clonogens, and inhomogeneity of patient population are discussed and compared with the basic formula.
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            Chordoma: the nonsarcoma primary bone tumor.

            Chordomas are rare, slowly growing, locally aggressive neoplasms of bone that arise from embryonic remnants of the notochord. These tumors typically occur in the axial skeleton and have a proclivity for the spheno-occipital region of the skull base and sacral regions. In adults, 50% of chordomas involve the sacrococcygeal region, 35% occur at the base of the skull near the spheno-occipital area, and 15% are found in the vertebral column. Craniocervical chordomas most often involve the dorsum sella, clivus, and nasopharynx. Chordomas are divided into conventional, chondroid, and dedifferentiated types. Conventional chordomas are the most common. They are characterized by the absence of cartilaginous or additional mesenchymal components. Chondroid chordomas contain both chordomatous and chondromatous features, and have a predilection for the spheno-occipital region of the skull base. This variant accounts for 5%-15% of all chordomas and up to 33% of cranial chordomas. Dedifferentiation or sarcomatous transformation occurs in 2%-8% of chordomas. This can develop at the onset of the disease or later. Aggressive initial therapy improves overall outcome. Patients who relapse locally have a poor prognosis but both radiation and surgery can be used as salvage therapy. Subtotal resection can result in a stable or improved status in as many as 50% of patients who relapse after primary therapy. Radiation therapy may also salvage some patients with local recurrence. One series reported a 2-year actuarial local control rate of 33% for patients treated with proton beam irradiation.
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              Chordoma: long-term follow-up after radical photon irradiation.

              C. Catton (1996)
              To retrospectively analyze the long term results of treatment and the patterns of failure for patients with chordoma of the sacrum, base of skull and mobile spine treated predominantly with postoperative photon irradiation. Forty-eight adult patients with chordoma of the sacrum (23), base of skull (20) or mobile spine (5), were seen between 1958-1992. Forty-four were referred post operatively with overt disease and 31 of these were irradiated with conventionally fractionated radiation to a median dose of 50 Gy/25 fractions/5 weeks (range 25-60 Gy). Eight received a hyperfractionation protocol of 1 Gy, 4 hourly, 4 times a day (median 40 Gy/44 fractions/14 days), two sacral patients were treated with a hypofractionation protocol and three cases with skull base tumours were referred elsewhere for proton therapy. Endpoints measured were survival from diagnosis, objective response rate, symptomatic response rate and clinical or radiological progression-free survival from radiotherapy. Median survival was 62 months (range 4-240 month) from diagnosis with no difference between clival and non-clival presentations. One complete and no partial responses were identified in 23 assessable patients. A subjective response was recorded for 12/14 (85%) with pain and 10/23 (45%) with neurological signs or symptoms, and the median time to progression for those with overt disease was 35 months (range 5-220 months). There was no survival advantage to patients receiving radiation doses > 50 Gy (median 60 Gy) compared to doses < 50 Gy (median 40 Gy). There was no difference between the conventional or hyperfractionation regimens with respect to the degree or duration of symptomatic response, or in progression-free survival. Fourteen patients who progressed after irradiation were retreated with surgery (6), irradiation (7) or both modalities (1). Median survival after retreatment was 18 months, and the only two symptomatic responses seen were with reirradiation, and after failure of relatively low dose initial therapy. At last follow-up, 35 were dead of or with disease, seven are alive with disease, and two are disease-free. Thirty-eight had local disease persistence as the sole site of failure, and four developed distant metastases initially or subsequently. Overt residual chordoma is rarely cured with conventional external beam irradiation, but treatment does provide useful and prolonged palliation of pain for most patients. Chordoma is a disease with low metastatic potential, and better local control may improve survival. Complete resection rates may be improved for patients with sacral disease by using planned excisions in centres experienced in treating this rare disease. Because radiation therapy may prove to be more successful in controlling microscopic disease, it should be considered as a pre- or postoperative adjuvant to a macroscopically complete resection. Patients with skull base disease should also be resected in centres specializing in this surgery, but complete excision is unlikely. These patients will not obtain local control with conventional photon irradiation, and suitable patients should be considered for irradiation with stereotactic photon or particle beam therapy. For patients who progress after irradiation, there is limited symptomatic benefit to retreatment with surgery or reirradiation, and this should be limited to treating life-threatening complications.
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                Author and article information

                Journal
                Radiat Oncol J
                Radiat Oncol J
                ROJ
                Radiation Oncology Journal
                The Korean Society for Radiation Oncology
                2234-1900
                2234-3164
                September 2018
                30 September 2018
                : 36
                : 3
                : 182-191
                Affiliations
                [1 ]Proton Therapy Center, National Cancer Center Research Institute and Hospital, National Cancer Center, Goyang, Korea
                [2 ]Neuro-Oncology Clinic, National Cancer Center Research Institute and Hospital, National Cancer Center, Goyang, Korea
                [3 ]Department of Radiology, National Cancer Center Research Institute and Hospital, National Cancer Center, Goyang, Korea
                [4 ]Department of Pathology, National Cancer Center Research Institute and Hospital, National Cancer Center, Goyang, Korea
                [5 ]Department of Neurosurgery, Bundang CHA Medical Center, CHA University College of Medicine, Seongnam, Korea
                Author notes
                Correspondence: Kwan Ho Cho, MD, Proton Therapy Center, National Cancer Center Research Institute and Hospital, National Cancer Center, 323 Ilsan-ro, Ilsandong-gu, Goyang 10408, Korea. Tel: +82-31-920-1720, Fax: +82-31-920-0149, E-mail: kwancho@ 123456ncc.re.kr
                Article
                roj-2018-00164
                10.3857/roj.2018.00164
                6226136
                30309209
                7a606f66-c9c9-4157-ae88-0eafa172d87f
                Copyright © 2018 The Korean Society for Radiation Oncology

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 06 April 2018
                : 21 May 2018
                : 11 June 2018
                Categories
                Original Article
                Clinical Investigation

                Oncology & Radiotherapy
                chordoma,proton therapy,treatment outcome,complications
                Oncology & Radiotherapy
                chordoma, proton therapy, treatment outcome, complications

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