Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Peter H. Ahn is active.

Publication


Featured researches published by Peter H. Ahn.


Journal of Clinical Oncology | 2005

Sequence of Radiotherapy With Tamoxifen in Conservatively Managed Breast Cancer Does Not Affect Local Relapse Rates

Peter H. Ahn; Ha Thanh Vu; Donald R. Lannin; Edward Obedian; Michael P. DiGiovanna; Barbara Burtness; Bruce G. Haffty

PURPOSE To evaluate whether the sequencing of tamoxifen (TAM) relative to radiation (RT) affects outcome in breast cancer patients treated with conservative surgery (CS) plus RT (lumpectomy with RT). METHODS Between 1976 and 1999, 1,649 patients with stage I or II breast cancer were treated with CS plus RT at Yale-New Haven Hospital (New Haven, CT). TAM was administered to 500 patients. The timing of TAM relative to RT was documented for each patient. Of the 500 patients, the timing of TAM was unclear in five patients, was administered concurrently with RT in 254 patients (CON-TAM), and was administered sequentially after completion of RT in 241 patients (SEQ-TAM). RESULTS There were no differences between the CON-TAM and SEQ-TAM group in T stage, estrogen and progesterone status, nodal status, histology, or margin status. The CON-TAM group was slightly older than the SEQ-TAM group (62 v 58 years) and received chemotherapy in addition to TAM less frequently (14% v 38%). As of September 2002, with a median follow-up of 10.0 years, there were no significant differences between the CON-TAM and SEQ-TAM groups in overall survival (84% v 82%; hazard ratio [HR], 1.234; 95% CI, 0.42 to 2.05; P = .45), distant-metastasis-free rate (82% v 78%; HR, 1.55; 95% CI, 0.89 to 2.68; P = .12), ipsilateral breast-relapse-free rate (90% v 86%; HR, 0.932; 95% CI, 0.42 to 2.05; P = .86), or contralateral breast-relapse-free rate (95% v 93%; HR, 0.892; 95% CI, 0.53 to 1.48; P = .66). CONCLUSION Although the concurrent use of TAM with RT may theoretically render cancer cells less responsive to RT, this retrospective study suggests that in practical application, concurrent administration of TAM with RT does not compromise local control.


International Journal of Radiation Oncology Biology Physics | 2015

Total Laryngectomy Versus Larynx Preservation for T4a Larynx Cancer: Patterns of Care and Survival Outcomes

Surbhi Grover; Samuel Swisher-McClure; Nandita Mitra; Jiaqi Li; Roger B. Cohen; Peter H. Ahn; John N. Lukens; Ara A. Chalian; Gregory S. Weinstein; Bert W. O'Malley; Alexander Lin

PURPOSE To examine practice patterns and compare survival outcomes between total laryngectomy (TL) and larynx preservation chemoradiation (LP-CRT) in the setting of T4a larynx cancer, using a large national cancer registry. METHODS AND MATERIALS Using the National Cancer Database, we identified 969 patients from 2003 to 2006 with T4a squamous cell larynx cancer receiving definitive treatment with either initial TL plus adjuvant therapy or LP-CRT. Univariate and multivariable logistic regression were used to assess predictors of undergoing surgery. Survival outcomes were compared using Kaplan-Meier and propensity score-adjusted and inverse probability of treatment-weighted Cox proportional hazards methods. Sensitivity analyses were performed to account for unmeasured confounders. RESULTS A total of 616 patients (64%) received LP-CRT, and 353 (36%) received TL. On multivariable logistic regression, patients with advanced nodal disease were less likely to receive TL (N2 vs N0, 26.6% vs 43.4%, odds ratio [OR] 0.52, 95% confidence interval [CI] 0.37-0.73; N3 vs N0, 19.1% vs 43.4%, OR 0.23, 95% CI 0.07-0.77), whereas patients treated in high case-volume facilities were more likely to receive TL (46.1% vs 31.5%, OR 1.78, 95% CI 1.27-2.48). Median survival for TL versus LP was 61 versus 39 months (P<.001). After controlling for potential confounders, LP-CRT had inferior overall survival compared with TL (hazard ratio 1.31, 95% CI 1.10-1.57), and with the inverse probability of treatment-weighted model (hazard ratio 1.25, 95% CI 1.05-1.49). This survival difference was shown to be robust on additional sensitivity analyses. CONCLUSIONS Most patients with T4a larynx cancer receive LP-CRT, despite guidelines suggesting TL as the preferred initial approach. Patients receiving LP-CRT had more advanced nodal disease and worse overall survival. Previous studies of (non-T4a) locally advanced larynx cancer showing no difference in survival between LP-CRT and TL may not apply to T4a disease, and patients should be counseled accordingly.


Head and Neck-journal for The Sciences and Specialties of The Head and Neck | 2016

HPV-related oropharyngeal cancer: Risk factors for treatment failure in patients managed with primary transoral robotic surgery

John Kaczmar; Kay See Tan; Daniel F. Heitjan; Alexander Lin; Peter H. Ahn; Jason G. Newman; Christopher H. Rassekh; Ara A. Chalian; Bert W. O'Malley; Roger B. Cohen; Gregory S. Weinstein

The purpose of this study was to determine clinical factors that predict locoregional recurrence or distant metastasis in patients with human papillomavirus (HPV)‐positive oropharyngeal cancer treated with surgery and guideline‐indicated adjuvant therapy.


Head and Neck-journal for The Sciences and Specialties of The Head and Neck | 2014

Risk of fatal cerebrovascular accidents after external beam radiation therapy for early‐stage glottic laryngeal cancer

Samuel Swisher-McClure; Nandita Mitra; Alexander Lin; Peter H. Ahn; Fei Wan; Bert W. O'Malley; Gregory S. Weinstein; Justin E. Bekelman

This study compared the risk of fatal cerebrovascular accidents (CVAs) in patients with early‐stage glottic laryngeal cancer receiving surgery or external beam radiation therapy (EBRT).


Radiotherapy and Oncology | 2016

Benefit of particle therapy in re-irradiation of head and neck patients. Results of a multicentric in silico ROCOCO trial.

Daniëlle B.P. Eekers; Erik Roelofs; Urszula Jelen; Maura Kirk; Marlies Granzier; Filippo Ammazzalorso; Peter H. Ahn; Geert O. Janssens; Frank Hoebers; Tobias Friedmann; Timothy D. Solberg; Sean Walsh; E.G.C. Troost; Johannes H.A.M. Kaanders; Philippe Lambin

BACKGROUND AND PURPOSE In this multicentric in silico trial we compared photon, proton, and carbon-ion radiotherapy plans for re-irradiation of patients with squamous cell carcinoma of the head and neck (HNSCC) regarding dose to tumour and doses to surrounding organs at risk (OARs). MATERIAL AND METHODS Twenty-five HNSCC patients with a second new or recurrent cancer after previous irradiation (70Gy) were included. Intensity-modulated proton therapy (IMPT) and ion therapy (IMIT) re-irradiation plans to a second subsequent dose of 70Gy were compared to photon therapy delivered with volumetric modulated arc therapy (VMAT). RESULTS When comparing IMIT and IMPT to VMAT, the mean dose to all investigated 22 OARs was significantly reduced for IMIT and to 15 out of 22 OARs (68%) using IMPT. The maximum dose to 2% volume (D2) of the brainstem and spinal cord were significantly reduced using IMPT and IMIT compared to VMAT. The data are available on www.cancerdata.org. CONCLUSIONS In this ROCOCO in silico trial, a reduction in mean dose to OARs was achieved using particle therapy compared to photons in the re-irradiation of HNSCC. There was a dosimetric benefit favouring carbon-ions above proton therapy. These dose reductions may potentially translate into lower severe complication rates related to the re-irradiation.


Journal of Applied Clinical Medical Physics | 2016

Quantitative assessment of anatomical change using a virtual proton depth radiograph for adaptive head and neck proton therapy

Peng Wang; Lingshu Yin; Yawei Zhang; Maura Kirk; Gang Song; Peter H. Ahn; Alexander Lin; James C. Gee; D Dolney; Timothy D. Solberg; Richard L. Maughan; J McDonough; Boon-Keng Kevin Teo

The aim of this work is to demonstrate the feasibility of using water‐equivalent thickness (WET) and virtual proton depth radiographs (PDRs) of intensity corrected cone‐beam computed tomography (CBCT) to detect anatomical change and patient setup error to trigger adaptive head and neck proton therapy. The planning CT (pCT) and linear accelerator (linac) equipped CBCTs acquired weekly during treatment of a head and neck patient were used in this study. Deformable image registration (DIR) was used to register each CBCT with the pCT and map Hounsfield units (HUs) from the planning CT (pCT) onto the daily CBCT. The deformed pCT is referred as the corrected CBCT (cCBCT). Two dimensional virtual lateral PDRs were generated using a ray‐tracing technique to project the cumulative WET from a virtual source through the cCBCT and the pCT onto a virtual plane. The PDRs were used to identify anatomic regions with large variations in the proton range between the cCBCT and pCT using a threshold of 3 mm relative difference of WET and 3 mm search radius criteria. The relationship between PDR differences and dose distribution is established. Due to weight change and tumor response during treatment, large variations in WETs were observed in the relative PDRs which corresponded spatially with an increase in the number of failing points within the GTV, especially in the pharynx area. Failing points were also evident near the posterior neck due to setup variations. Differences in PDRs correlated spatially to differences in the distal dose distribution in the beams eye view. Virtual PDRs generated from volumetric data, such as pCTs or CBCTs, are potentially a useful quantitative tool in proton therapy. PDRs and WET analysis may be used to detect anatomical change from baseline during treatment and trigger further analysis in adaptive proton therapy. PACS number(s): 87.55‐x, 87.55.‐D, 87.57.Q‐The aim of this work is to demonstrate the feasibility of using water-equivalent thickness (WET) and virtual proton depth radiographs (PDRs) of intensity corrected cone-beam computed tomography (CBCT) to detect anatomical change and patient setup error to trigger adaptive head and neck proton therapy. The planning CT (pCT) and linear accelerator (linac) equipped CBCTs acquired weekly during treatment of a head and neck patient were used in this study. Deformable image registration (DIR) was used to register each CBCT with the pCT and map Hounsfield units (HUs) from the planning CT (pCT) onto the daily CBCT. The deformed pCT is referred as the corrected CBCT (cCBCT). Two dimensional virtual lateral PDRs were generated using a ray-tracing technique to project the cumulative WET from a virtual source through the cCBCT and the pCT onto a virtual plane. The PDRs were used to identify anatomic regions with large variations in the proton range between the cCBCT and pCT using a threshold of 3 mm relative difference of WET and 3 mm search radius criteria. The relationship between PDR differences and dose distribution is established. Due to weight change and tumor response during treatment, large variations in WETs were observed in the relative PDRs which corresponded spatially with an increase in the number of failing points within the GTV, especially in the pharynx area. Failing points were also evident near the posterior neck due to setup variations. Differences in PDRs correlated spatially to differences in the distal dose distribution in the beams eye view. Virtual PDRs generated from volumetric data, such as pCTs or CBCTs, are potentially a useful quantitative tool in proton therapy. PDRs and WET analysis may be used to detect anatomical change from baseline during treatment and trigger further analysis in adaptive proton therapy. PACS number(s): 87.55-x, 87.55.-D, 87.57.Q.


British Journal of Radiology | 2016

Nodal metastasis and elective nodal level treatment in sinonasal small-cell and sinonasal undifferentiated carcinoma: a surveillance, epidemiology and end results analysis

Peter H. Ahn; Nandita Mitra; Michelle Alonso-Basanta; Nithin D. Adappa; James N. Palmer; Bert W. O'Malley; Christopher H. Rassekh; Ara A. Chalian; Roger B. Cohen; Alexander Lin

OBJECTIVE Risk of nodal involvement in patients with sinonasal small-cell carcinoma and sinonasal undifferentiated carcinoma (SNUC) has not been well defined because of their rarity. We describe a population-based assessment of specific nodal level involvement in this group of rare neuroectodermal tumours. METHODS The Surveillance, Epidemiology and End Results (SEER) database from 2004 to 2011 identified patients with SNUC and sinonasal small-cell carcinoma. Overall neck involvement and individual nodal level involvement at presentation were assessed, and comparison was made with a contemporaneous cohort of patients with a borderline clinically significant risk of nodal involvement and recurrence. RESULTS Of 141 patients, 31 (22%) had gross nodal involvement at presentation (range 14-33% by site and histology). Non-nasal, non-ethmoid site with SNUC histology has the highest rates of initial nodal involvement, whereas higher stage and size do not predict for higher nodal involvement rates. Bilateral Levels 2-3 for all sinonasal small cell; Levels 2-3 for nasal or ethmoid SNUC; and bilateral Levels 1-3 in non-nasal/non-ethmoid SNUC have the highest rates of involvement compared with a clinical reference standard. CONCLUSION We found high rates of initial nodal involvement in all SNUC and sinonasal small-cell carcinoma. We found higher initial involvement of Levels 2 and 3 and in certain cases to the Level 1 nodal levels, hypothesizing benefit for elective treatment to those levels. ADVANCES IN KNOWLEDGE With small single-institution series reporting conflicting nodal involvement rates, our data support high rates of nodal presentation at diagnosis, hypothesizing benefit for elective nodal treatment in this cohort.


Photochemistry and Photobiology | 2015

Measuring the Physiologic Properties of Oral Lesions Receiving Fractionated Photodynamic Therapy

Shannon M. Gallagher-Colombo; Harry Quon; Kelly M. Malloy; Peter H. Ahn; Keith A. Cengel; Charles B. Simone; Ara A. Chalian; Bert W. O'Malley; Gregory S. Weinstein; Timothy C. Zhu; Mary E. Putt; Jarod C. Finlay; Theresa M. Busch

Photodynamic therapy (PDT) can treat superficial, early‐stage disease with minimal damage to underlying tissues and without cumulative dose‐limiting toxicity. Treatment efficacy is affected by disease physiologic properties, but these properties are not routinely measured. We assessed diffuse reflectance spectroscopy (DRS) for the noninvasive, contact measurement of tissue hemoglobin oxygen saturation (StO2) and total hemoglobin concentration ([tHb]) in the premalignant or superficial microinvasive oral lesions of patients treated with 5‐aminolevulinic acid (ALA)‐PDT. Patients were enrolled on a Phase 1 study of ALA‐PDT that evaluated fluences of 50, 100, 150 or 200 J cm−2 delivered at 100 mW cm−2. To test the feasibility of incorporating DRS measurements within the illumination period, studies were performed in patients who received fractionated (two‐part) illumination that included a dark interval of 90–180 s. Using DRS, tissue oxygenation at different depths within the lesion could also be assessed. DRS could be performed concurrently with contact measurements of photosensitizer levels by fluorescence spectroscopy, but a separate noncontact fluorescence spectroscopy system provided continuous assessment of photobleaching during illumination to greater tissue depths. Results establish that the integration of DRS into PDT of early‐stage oral disease is feasible, and motivates further studies to evaluate its predictive and dosimetric value.


International Journal of Particle Therapy | 2015

The Impact of Anatomic Change on Pencil Beam Scanning in the Treatment of Oropharynx Cancer

David J Thomson; Boon-Keng Kevin Teo; Ashley Ong; Khong Wei Ang; Maura Kirk; Peter H. Ahn; John N. Lukens; Samuel Swisher-McClure; Tom Liptrot; Timothy D. Solberg; N. Slevin; Alexander Lin

Abstract Purpose: To investigate the potential impact of anatomic change in the treatment of locally advanced oropharyngeal cancer with proton pencil beam scanning. Materials and Methods: Ten patients with locally advanced oropharyngeal cancer who previously received intensity-modulated radiation therapy (IMRT) and synchronous chemotherapy underwent replanning by using RapidArc IMRT and proton pencil beam scanning. Deformable image registration deformed the planning computed tomography (CT), target volumes, and organs at risk (OARs) contours onto each weekly cone-beam CT scan. Target and OARs volumes were reviewed and modified. Treatment plans were forward calculated onto each corrected cone-beam CT scan and dose-volume histograms produced for targets and OARs volumes. Results: Proton pencil beam scanning compared with RapidArc IMRT achieved lower mean doses to the contralateral parotid gland (14.8 Gy versus 20.6 Gy, P < .05) and oral cavity (31.5 Gy versus 43.0 Gy, P < .001). For proton pencil beam scann...


Oral Oncology | 2016

Toxicities and early outcomes in a phase 1 trial of photodynamic therapy for premalignant and early stage head and neck tumors.

Peter H. Ahn; Harry Quon; Bert W. O’Malley; Gregory S. Weinstein; Ara A. Chalian; Kelly M. Malloy; Joshua H. Atkins; Thomas P. Sollecito; Martin S. Greenberg; Sally McNulty; Alexander Lin; Timothy C. Zhu; Jarod C. Finlay; Keith A. Cengel; Virginia A. LiVolsi; Michael Feldman; Rosemarie Mick; Theresa M. Busch

OBJECTIVES Management of early superficial lesions in the head and neck remains complex. We performed a phase 1 trial for high-grade premalignant and early superficial lesions of the head and neck using photodynamic therapy (PDT) with Levulan (ALA). MATERIALS AND METHODS Thirty-five subjects with high grade dysplasia, carcinoma in situ, or microinvasive (⩽1.5mm depth) squamous cell carcinoma were enrolled. Cohorts of 3-6 patients were given escalating intraoperative light doses of 50-200J/cm(2) 4-6h after oral administration of 60mg/kg ALA. Light at 629-635nm was delivered in a continuous (unfractionated) or fractionated (two-part) schema. RESULTS PDT was delivered to 30/35 subjects, with 29 evaluable. There was one death possibly due to the treatment. The regimen was otherwise tolerable, with a 52% rate of grade 3 mucositis which healed within several weeks. Other toxicities were generally grade 1 or 2, including odynophagia (one grade 4), voice alteration (one grade 3), and photosensitivity reactions. One patient developed grade 5 sepsis. With a median follow-up of 42months, 10 patients (34%) developed local recurrence; 4 of these received 50J/cm(2) and two each received 100, 150, and 200J/cm(2). Ten (34%) patients developed recurrence adjacent to the treated field. There was a 69% complete response rate at 3months. CONCLUSIONS ALA-PDT is well tolerated. Maximum Tolerated Dose appears to be higher than the highest dose used in this study. Longer followup is required to analyze effect of light dose on local recurrence. High marginal recurrence rates suggest use of larger treatment fields.

Collaboration


Dive into the Peter H. Ahn's collaboration.

Top Co-Authors

Avatar

Alexander Lin

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Ara A. Chalian

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

Bert W. O'Malley

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

Roger B. Cohen

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

John N. Lukens

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

Nandita Mitra

University of Pennsylvania

View shared research outputs
Top Co-Authors

Avatar

Adam P. Dicker

Thomas Jefferson University

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

David Cognetti

Thomas Jefferson University

View shared research outputs
Researchain Logo
Decentralizing Knowledge