- Email: [email protected]
In response to Dr. Harari
I. J. Radiation
912
Oncology
0 Biology
0 Physics
IN RESPONSE TO DR. HARARI To the Editor: Our intention was to present another method for treating head and neck cancer that uses a single isocenter and asymmetric collimators. The potential advantages of this technique include reproducibility of field set up, decreased set up time, and dose uniformity at the field junction. Dr. Harari has offered constructive commentary and our responses are as follows: We agree that the true absence of “any hot spots” in the treatment of head and neck cancer would require complex 3D dose compensation. The “hot spots” refers to the field junction as verified by film dosimetry and does not include any dose inhomogeneity caused by missing tissue. Dr. Harari is correct that older 4-MV machine with 80-cm sourceto-isocenter distance can have large lateral dose, or “horns,” at D mai relative to central axis dose. We recommend the reported technique (2) for use with modem 6-MV machines. We prescribe dose to the center of the treated field rather than the central axis. Prescribing at this reference point makes the ratio (maximal dose at “horn” position/prescribed dose) less than would be expected from quoted dosimetric “horn” that is referenced to the central axis. Using parallel opposed fields with a maximal dose at the horn position found at 1.5-cm depth, this ratio becomes about 1.05. Many modem accelerators have asymmetric collimators and dual energy capabilities, with 6 MV and higher energy beams. Although the 6-MV beam has a lower dose in the build-up region compared with the 4 MV or Cow, clinically this does not appear to be a problem because many institutions, including our own, treat definitive and postoperative cases using the 6-MV machine with no evidence of inferior results. In terms of toxicity, local regional control or survival, a recent abstract by Schwade et al. ( 1) did not find any discernible difference for patients with advanced head and neck cancer treated with Co” and 4 MV as opposed to 6-MV photons. Authors agree with Dr. Harari. We do not advocate the omission of a spinal cord “cheater block” as this would require extreme accuracy of the three-field set up. In rare instances where this block may compromise tumor/nodal coverage, this set up may provide a more uniform dose at the junction compared to the traditional threefield technique. We appreciate
Dr. Harari’s
comments. JASON W. SOHN, M.D. JOHN H. SUH, M.D.
Department Cleveland Cleveland,
of Radiation Oncology Clinic OH 44195 SURJ POHAR, M.D. Department of Radiation Oncology Saint Francis Regional Cancer Center Cranberry Twp., PA 16066
1. Schwade, J. G.; Farnan, N. C.; Ares, A.; Schuller, D. E.; Oken, M. M.; Ervin, T. J.; Jacobs, C.; Wheeler, R. H.; Laramore, G. Lack of outcome difference by beam energy in head and neck cancer patients treated with cobalt-66 and 4 MV rather than 6 MV photons. Presented at the 1994 American Radium Society Meeting in Bermuda. 2. Sohn, J. W.; Suh, J. H.; Pohar, S. A method for delivering accurate and uniform radiation dosages to the head and neck with asymmetric collimators and a single isocenter. lnt. J. Radiat. Oncol. Biol. Phys. 32:809-813; 1995.
Volume
33. Number
4, 1995
NONREPRESENTATIVE SUBSETS OF PATIENTS: REGARDING STAMEY, ZJROBP
33:967-968;
1995
To rhe Editor: Dr. Stamey’s broad range of comments are always challenging. However, there are some specifics that can be addressed. I hope the percent of Grade 4/5 tumor will someday show a direct correlation with outcome that is stronger on multivatiate analysis than the presence of Grade 4/5 tumor. Until that occurs the correlation with volume at prostatectomy is interesting but the presence of Grade 4/5 will have more operational value. The series of “every irradiated patient who had serial PSA, etc.” is so highly selected that the terrible results are not confirmed by results from the Massachusetts General Hospital, MD Anderson, Fox Chase, or even the Stanford radiation series of every patient treated in the same time interval. The overall biochemical freedom from disease rates are 40-55% at 5 years in these diverse institutions. All of these refutations of the Stamey series of nonrepresentative data (including the PSA doubling time comments) are now published or in press ( l-4). The radiation treatment of patients with pretreatment PSA > 20 ngm/ ml shows an outcome close to but not quite as bad as the Stamey group, and that high PSA patient population now represents only 19% of our patients. Hopefully, the “20% non-rising PSA” observation will come to rest in the same grave as the uro-oncology randomized trial of prostatectomy versus irradiation. Unfortunately, like the uro-oncology study, it has adversely influenced the availability of radiation treatment to patients in the United States and other countries. 3. Despite Dr. Stamey’s years of effort to prove that the radiation treatment of prostate cancer is ineffective, there is an increasing body of data (including series reporting all patients treated by pretreatment PSA groupings) that demonstrate identical results of radiation and prostatectomy in early (low PSA) disease. Perhaps someday we will see some positive outcome data from Stanford urology that might include every patient treated by prostatectomy, and would show the outcome effectiveness of cancer control from prostatectomy performed at Stanford to compare to results with irradiation. GERALD
E. HANKS,
M.D.
Radiation Oncology Fox Chase Cancer Center Philadelphia, PA 19111
1. Hancock, S. L.; Cox, R. S.; Bagshaw, M. A. Prostate specific antigen after radiotherapy for prostate cancer. A re-evaluation of long-term biochemical control and the kinetics of recurrence in patients treated at Stanford. J. Urol. (in press) 1995. 2. Hanks, G. E.; Lee, W. R.; Schultheiss, T. E. Clinical and biochemical evidence of control of prostate cancer at five years after external beam radiation. J. Urol. 154:456-459; 1995. 3. Zagars, G. K.; Pollack, A. Radiation therapy for Tl and T2 prostate cancer: prostate-specific antigen and disease outcome. Urol. 45: 476-483; 1995. 4. Zeitman, A. L.; Coen, J. J.; Dallow, K. C.; Shipley, W. U. The treatment of prostate cancer by conventional radiation therapy: An analysis of long-term outcome. lnt. J. Radiat. Oncol. Biol. Phys. 32:287-292; 1995.
912
Oncology
0 Biology
0 Physics
IN RESPONSE TO DR. HARARI To the Editor: Our intention was to present another method for treating head and neck cancer that uses a single isocenter and asymmetric collimators. The potential advantages of this technique include reproducibility of field set up, decreased set up time, and dose uniformity at the field junction. Dr. Harari has offered constructive commentary and our responses are as follows: We agree that the true absence of “any hot spots” in the treatment of head and neck cancer would require complex 3D dose compensation. The “hot spots” refers to the field junction as verified by film dosimetry and does not include any dose inhomogeneity caused by missing tissue. Dr. Harari is correct that older 4-MV machine with 80-cm sourceto-isocenter distance can have large lateral dose, or “horns,” at D mai relative to central axis dose. We recommend the reported technique (2) for use with modem 6-MV machines. We prescribe dose to the center of the treated field rather than the central axis. Prescribing at this reference point makes the ratio (maximal dose at “horn” position/prescribed dose) less than would be expected from quoted dosimetric “horn” that is referenced to the central axis. Using parallel opposed fields with a maximal dose at the horn position found at 1.5-cm depth, this ratio becomes about 1.05. Many modem accelerators have asymmetric collimators and dual energy capabilities, with 6 MV and higher energy beams. Although the 6-MV beam has a lower dose in the build-up region compared with the 4 MV or Cow, clinically this does not appear to be a problem because many institutions, including our own, treat definitive and postoperative cases using the 6-MV machine with no evidence of inferior results. In terms of toxicity, local regional control or survival, a recent abstract by Schwade et al. ( 1) did not find any discernible difference for patients with advanced head and neck cancer treated with Co” and 4 MV as opposed to 6-MV photons. Authors agree with Dr. Harari. We do not advocate the omission of a spinal cord “cheater block” as this would require extreme accuracy of the three-field set up. In rare instances where this block may compromise tumor/nodal coverage, this set up may provide a more uniform dose at the junction compared to the traditional threefield technique. We appreciate
Dr. Harari’s
comments. JASON W. SOHN, M.D. JOHN H. SUH, M.D.
Department Cleveland Cleveland,
of Radiation Oncology Clinic OH 44195 SURJ POHAR, M.D. Department of Radiation Oncology Saint Francis Regional Cancer Center Cranberry Twp., PA 16066
1. Schwade, J. G.; Farnan, N. C.; Ares, A.; Schuller, D. E.; Oken, M. M.; Ervin, T. J.; Jacobs, C.; Wheeler, R. H.; Laramore, G. Lack of outcome difference by beam energy in head and neck cancer patients treated with cobalt-66 and 4 MV rather than 6 MV photons. Presented at the 1994 American Radium Society Meeting in Bermuda. 2. Sohn, J. W.; Suh, J. H.; Pohar, S. A method for delivering accurate and uniform radiation dosages to the head and neck with asymmetric collimators and a single isocenter. lnt. J. Radiat. Oncol. Biol. Phys. 32:809-813; 1995.
Volume
33. Number
4, 1995
NONREPRESENTATIVE SUBSETS OF PATIENTS: REGARDING STAMEY, ZJROBP
33:967-968;
1995
To rhe Editor: Dr. Stamey’s broad range of comments are always challenging. However, there are some specifics that can be addressed. I hope the percent of Grade 4/5 tumor will someday show a direct correlation with outcome that is stronger on multivatiate analysis than the presence of Grade 4/5 tumor. Until that occurs the correlation with volume at prostatectomy is interesting but the presence of Grade 4/5 will have more operational value. The series of “every irradiated patient who had serial PSA, etc.” is so highly selected that the terrible results are not confirmed by results from the Massachusetts General Hospital, MD Anderson, Fox Chase, or even the Stanford radiation series of every patient treated in the same time interval. The overall biochemical freedom from disease rates are 40-55% at 5 years in these diverse institutions. All of these refutations of the Stamey series of nonrepresentative data (including the PSA doubling time comments) are now published or in press ( l-4). The radiation treatment of patients with pretreatment PSA > 20 ngm/ ml shows an outcome close to but not quite as bad as the Stamey group, and that high PSA patient population now represents only 19% of our patients. Hopefully, the “20% non-rising PSA” observation will come to rest in the same grave as the uro-oncology randomized trial of prostatectomy versus irradiation. Unfortunately, like the uro-oncology study, it has adversely influenced the availability of radiation treatment to patients in the United States and other countries. 3. Despite Dr. Stamey’s years of effort to prove that the radiation treatment of prostate cancer is ineffective, there is an increasing body of data (including series reporting all patients treated by pretreatment PSA groupings) that demonstrate identical results of radiation and prostatectomy in early (low PSA) disease. Perhaps someday we will see some positive outcome data from Stanford urology that might include every patient treated by prostatectomy, and would show the outcome effectiveness of cancer control from prostatectomy performed at Stanford to compare to results with irradiation. GERALD
E. HANKS,
M.D.
Radiation Oncology Fox Chase Cancer Center Philadelphia, PA 19111
1. Hancock, S. L.; Cox, R. S.; Bagshaw, M. A. Prostate specific antigen after radiotherapy for prostate cancer. A re-evaluation of long-term biochemical control and the kinetics of recurrence in patients treated at Stanford. J. Urol. (in press) 1995. 2. Hanks, G. E.; Lee, W. R.; Schultheiss, T. E. Clinical and biochemical evidence of control of prostate cancer at five years after external beam radiation. J. Urol. 154:456-459; 1995. 3. Zagars, G. K.; Pollack, A. Radiation therapy for Tl and T2 prostate cancer: prostate-specific antigen and disease outcome. Urol. 45: 476-483; 1995. 4. Zeitman, A. L.; Coen, J. J.; Dallow, K. C.; Shipley, W. U. The treatment of prostate cancer by conventional radiation therapy: An analysis of long-term outcome. lnt. J. Radiat. Oncol. Biol. Phys. 32:287-292; 1995.